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Research Article Effect of NaNO 2 and C 6 H 15 NO 3 Synergistic Admixtures on Steel-Rebar Corrosion in Concrete Immersed in Aggressive Environments Joshua Olusegun Okeniyi, 1 Abimbola Patricia Idowu Popoola, 2 Cleophas Akintoye Loto, 1,2 Olugbenga Adeshola Omotosho, 1 Stanley Okechukwu Okpala, 1 and Idemudia Joshua Ambrose 1 1 Mechanical Engineering Department, Covenant University, Ota 112001, Nigeria 2 Chemical and Metallurgical Engineering Department, Tshwane University of Technology, Pretoria 0001, South Africa Correspondence should be addressed to Joshua Olusegun Okeniyi; [email protected] Received 5 October 2014; Accepted 2 March 2015 Academic Editor: Richard Hennig Copyright © 2015 Joshua Olusegun Okeniyi et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. is paper studies effect of different combinations of NaNO 2 (sodium nitrite) and C 6 H 15 NO 3 (triethanolamine (TEA)), as synergistic admixtures in concrete immersed in NaCl and in H 2 SO 4 test environments, on the corrosion of the concrete reinforcing steel (rebar). Although statistically analysed electrochemical test results confirmed NaNO 2 effectiveness, synergistic combinations of 4 g NaNO 2 +4gC 6 H 15 NO 3 in NaCl medium and of 2 g NaNO 2 +6gC 6 H 15 NO 3 in H 2 SO 4 medium were also highly effective at inhibiting rebar corrosion. Synergistic parameter analyses showed that the effective synergistic admixtures that inhibited concrete steel-rebar corrosion in their respective medium were the NaNO 2 and C 6 H 15 NO 3 combinations that exhibited synergistic interactions of cooperative adsorption on steel-rebar. ese support the suitability of requisite concentration of triethanolamine as additive admixture with sodium nitrite for steel-rebar corrosion mitigation, which is potent with reduced environmental effects, in concrete immersed in NaCl and in H 2 SO 4 corrosive media. 1. Introduction Concrete is the most widely used cement-based construction materials for buildings structures and infrastructures [1– 3]. However, corrosion degradation of the reinforcing steel (steel-rebar) in concrete is affecting sustainability and service performance of concrete building and infrastructures and generating safety and economic concerns among construc- tion stakeholders, globally [3–6]. Normally, steel embedded in concrete is protected from corrosion attack by a passive layer of thin oxide film from the highly alkaline, pH of about 12.5∼13, cement hydration products [3, 7, 8]. Steel- rebar corrodes in concrete due to breakdown of the protective oxide film by aggressive agents of the environments, in the form of chloride ingress, from natural marine or artificial saline (deicing salts) [8, 9], or sulphate attack, from microbial or industrial environments [7, 10–12]. Corroded products from these are expansive within concrete leading to cracks, spalling, delamination, and loss of structural integrity of the reinforced concrete [8, 9, 13]. Among many methods [1], the use of corrosion inhibitors had been identified as an easy, effective, and economi- cal approach for mitigating steel-rebar corrosion and for improving durability of steel-reinforced concrete structures in aggressive environments [2, 5, 14, 15]. However, important criteria for achieving acceptable mitigation of corrosion rate in a corrosive environment include responsible application of the inhibiting substance at a suitable concentration in the corrosive system [2, 16]. at the presence of an inhibiting substance at an unsuitable concentration in the corrosive sys- tem could aggravate, instead of inhibiting, corrosion [16, 17] necessitates studies of suitable concentrations of admixture Hindawi Publishing Corporation Advances in Materials Science and Engineering Volume 2015, Article ID 540395, 11 pages http://dx.doi.org/10.1155/2015/540395

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Page 1: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

Research ArticleEffect of NaNO

2and C

6H15

NO3

SynergisticAdmixtures on Steel-Rebar Corrosion in ConcreteImmersed in Aggressive Environments

Joshua Olusegun Okeniyi1 Abimbola Patricia Idowu Popoola2

Cleophas Akintoye Loto12 Olugbenga Adeshola Omotosho1

Stanley Okechukwu Okpala1 and Idemudia Joshua Ambrose1

1Mechanical Engineering Department Covenant University Ota 112001 Nigeria2Chemical and Metallurgical Engineering Department Tshwane University of Technology Pretoria 0001 South Africa

Correspondence should be addressed to Joshua Olusegun Okeniyi joshuaokeniyicovenantuniversityedung

Received 5 October 2014 Accepted 2 March 2015

Academic Editor Richard Hennig

Copyright copy 2015 Joshua Olusegun Okeniyi et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

This paper studies effect of different combinations of NaNO2(sodium nitrite) and C

6H15NO3(triethanolamine (TEA)) as

synergistic admixtures in concrete immersed in NaCl and in H2SO4test environments on the corrosion of the concrete reinforcing

steel (rebar) Although statistically analysed electrochemical test results confirmed NaNO2effectiveness synergistic combinations

of 4 g NaNO2+ 4 g C

6H15NO3in NaCl medium and of 2 g NaNO

2+ 6 g C

6H15NO3in H2SO4medium were also highly effective

at inhibiting rebar corrosion Synergistic parameter analyses showed that the effective synergistic admixtures that inhibitedconcrete steel-rebar corrosion in their respective medium were the NaNO

2and C

6H15NO3combinations that exhibited synergistic

interactions of cooperative adsorption on steel-rebar These support the suitability of requisite concentration of triethanolamine asadditive admixture with sodium nitrite for steel-rebar corrosion mitigation which is potent with reduced environmental effects inconcrete immersed in NaCl and in H

2SO4corrosive media

1 Introduction

Concrete is the most widely used cement-based constructionmaterials for buildings structures and infrastructures [1ndash3] However corrosion degradation of the reinforcing steel(steel-rebar) in concrete is affecting sustainability and serviceperformance of concrete building and infrastructures andgenerating safety and economic concerns among construc-tion stakeholders globally [3ndash6] Normally steel embeddedin concrete is protected from corrosion attack by a passivelayer of thin oxide film from the highly alkaline pH ofabout 125sim13 cement hydration products [3 7 8] Steel-rebar corrodes in concrete due to breakdown of the protectiveoxide film by aggressive agents of the environments in theform of chloride ingress from natural marine or artificialsaline (deicing salts) [8 9] or sulphate attack frommicrobial

or industrial environments [7 10ndash12] Corroded productsfrom these are expansive within concrete leading to cracksspalling delamination and loss of structural integrity of thereinforced concrete [8 9 13]

Amongmanymethods [1] the use of corrosion inhibitorshad been identified as an easy effective and economi-cal approach for mitigating steel-rebar corrosion and forimproving durability of steel-reinforced concrete structuresin aggressive environments [2 5 14 15] However importantcriteria for achieving acceptable mitigation of corrosion ratein a corrosive environment include responsible applicationof the inhibiting substance at a suitable concentration in thecorrosive system [2 16] That the presence of an inhibitingsubstance at an unsuitable concentration in the corrosive sys-tem could aggravate instead of inhibiting corrosion [16 17]necessitates studies of suitable concentrations of admixture

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 540395 11 pageshttpdxdoiorg1011552015540395

2 Advances in Materials Science and Engineering

OH

OH

N

HO

(a) (b)

Figure 1 Triethanolamine (C6H15NO3 TEA) (a) molecular structure and (b) optimized ball and stick model

for mitigating steel-rebar corrosion in their corrosive serviceenvironments

Nitrites are well-known corrosion inhibiting substance[2 5 15 18] although they suffer the setback that their use isbeing restricted in many countries due to their toxicity andhazardousness to the environmental ecosystems [1 19 20]This is fostering research deliberations on the search formoreenvironmentally friendly substances for totally or partiallyreplacing the traditional but toxic inhibitor However suchsearch had been difficult due to the high effectiveness ofnitrites at inhibiting steel-rebar corrosion Triethanolamine(C6H15NO3 TEA) is an organic chemical with the molec-

ular structure shown in Figure 1 that is nontoxic to theenvironment and which had been employed for mitigatingchloride-induced carbon steel corrosion in simulated alkalinepore solution [21] Yet there is paucity of studies on thesuitability of triethanolamine as an environmentally benignalternative for synergistic partial replacement of the highlyeffective but toxic nitrite admixture as inhibitor of steel-rebar corrosion in concrete slab immersed in aggressivemedia Specific motivation for this paper was especiallydrawn from [22] that showed that inhibition effectiveness ofnitrites could be improved by requisite addition of anotherchemical This is because such additional model channeledusing nontoxic chemical is potent with reduction in environ-mental effects from the consequently lower usage of the toxicNaNO

2inhibitor quantity required for adequate corrosion

inhibition This paper therefore investigates the effect ofsynergistic combinations of different sodiumnitrite (NaNO

2)

and triethanolamine (C6H15NO3 TEA) concentrations as

synergistic admixtures on the corrosion of steel-rebar inconcrete immersed in NaCl and in H

2SO4media

2 Materials and Methods

21 Reinforcing Steel and Reinforced Concrete Block SpecimensSteel reinforcement used in the study was obtained from theFederated Steel Rolling Mills Ota Ogun State Nigeria The12mmdeformed rebar has composition in of 027 C 040Si 078 Mn 004 P 004 S 014 Cr 011 Ni 002 Mo 024 Cu001 Co 001 Nb 001 Sn and the balance Fe The steel-rebarwas cut into specimen rods each of which was 190mm long

Surface preparation was then maintained uniformly for eachof these rods Each rod of rebar was ground with coarse andfine abrasive papers pickled for 10 minutes in 10 H

2SO4

[23] rinsed and cleaned in ultrasonic cleaner degreased withacetone dried with warm air stream and kept in desiccatorprior to being used for the experiment [24 25]

Forty steel-reinforced concrete samples used for theexperiment were produced as replicated blocks [26] fourblocks per batch and each of size 100mm times 100mm times200mm such as volume of each concrete block = 2 times 103m3In each of these blocks 150mm length of the 12mm steel-rebar was embedded which was symmetrically placed acrossthe width of each of the blocks implying 44mm concretecover thickness with the remaining length of the rebarprotruding for electrochemical connections This protrudedrebar from the concrete was painted with glossy paintDrinkable water was used for mixing the concrete blocksEach block was formulated using ordinary Portland cementclean natural sand and granite stones The formulation usedfor the mixing of each steel-reinforced concrete specimenincludes cement = 3000 kgm3 sand = 8906 kgm3 granitestones = 11063 kgm3 and mixing water of 1497 kgm3 thusmaking the watercement (wc) ratio = 0499 [14 23]

22 Inhibitor Admixture The admixture concentrations ofNaNO

2and C

6H15NO3by mass in synergistic combinations

and individual admixtures in each 100mm times 100mm times200mm concrete specimen and in each of the corrosivemedia of specimen immersion were as presented in Table 1These in duplicate samples (tagged as ldquo Duprdquo) include blankconcretes without admixture followed by concretes admixedwith different combinations of NaNO

2and C

6H15NO3con-

centrations and then concretes with individual concentra-tions of the NaNO

2and of the C

6H15NO3 This was designed

for facilitating synergistic parameter modelling [27 28]Addition of the admixtures to the cast concrete samples wasas prescribed by ASTM C192192M-02 [29] For admixing inconcrete sample the admixture was weighed on analyticalweighing balance mixed thoroughly with concrete mixingwater that was made up to the required water volume for thewater-cement ratio of the concrete sample for the casting ofthe concrete sample

Advances in Materials Science and Engineering 3

Table 1 Inhibitor admixtures by mass in the steel reinforced concrete samples

Serialnumber Inhibitor admixture by mass Serialnumber Inhibitor admixture by mass1 0 g admixture (blank or control in NaCl) 2 0 g admixture (blank or control in H2SO4)3 0 g admixture (blank or control in NaCl Dup) 4 0 g admixture (blank or control in H2SO4 Dup)5 6 g NaNO2 + 2 g C6H15NO3 in NaCl 6 6 g NaNO2 + 2 g C6H15NO3 in H2SO4

7 6 g NaNO2 + 2 g C6H15NO3 in NaCl Dup 8 6 g NaNO2 + 2 g C6H15NO3 in H2SO4 Dup9 4 g NaNO2 + 4 g C6H15NO3 in NaCl 10 4 g NaNO2 + 4 g C6H15NO3 in H2SO4

11 4 g NaNO2 + 4 g C6H15NO3 in NaCl Dup 12 4 g NaNO2 + 4 g C6H15NO3 in H2SO4 Dup13 2 g NaNO2 + 6 g C6H15NO3 in NaCl 14 2 g NaNO2 + 6 g C6H15NO3 in H2SO4

15 2 g NaNO2 + 6 g C6H15NO3 in NaCl Dup 16 2 g NaNO2 + 6 g C6H15NO3 in H2SO4 Dup17 6 g NaNO2 in NaCl 18 6 g NaNO2 in H2SO4

19 6 g NaNO2 in NaCl Dup 20 6 g NaNO2 in H2SO4 Dup21 4 g NaNO2 in NaCl 22 4 g NaNO2 in H2SO4

23 4 g NaNO2 in NaCl Dup 24 4 g NaNO2 in H2SO4 Dup25 2 g NaNO2 in NaCl 26 2 g NaNO2 in H2SO4

27 2 g NaNO2 in NaCl Dup 28 2 g NaNO2 in H2SO4 Dup29 2 g C6H15NO3 in NaCl 30 2 g C6H15NO3 in H2SO4

31 2 g C6H15NO3 in NaCl Dup 32 2 g C6H15NO3 in H2SO4 Dup33 4 g C6H15NO3 in NaCl 34 4 g C6H15NO3 in H2SO4

35 4 g C6H15NO3 in NaCl Dup 36 4 g C6H15NO3 in H2SO4 Dup37 6 g C6H15NO3 in NaCl 38 6 g C6H15NO3 in H2SO4

39 6 g C6H15NO3 in NaCl Dup 40 6 g C6H15NO3 in H2SO4 Dup

23 Experimental Procedures

231 Corrosion Test Setup Steel reinforced concrete speci-mens were divided into two sets Each of the specimens ineach set was partially immersed longitudinally in plasticbowl containing corrosive test environment A duplicatedset of twenty samples was partially immersed in 35 NaClsolution [30 31] for simulating salinemarine environmentwhile the second duplicated set was partially immersed in05M H

2SO4solution [2 10 32 33] for simulating micro-

bialindustrial environment In each bowl the test mediumwas made up to just below the concrete steel-rebar but wasnot touching it Also according to the practice describedin [24] the test medium in each bowl was replenishedevery three weeks to prevent dryness and induce continuoussystem of corrosive environment through the ninety-six-day immersion of the steel-reinforced concrete samples Allchemicals used for both chemical admixtures and corrosivetest environments are analytical grade

232 Electrochemical Measurements Nondestructive elec-trochemical measurements [14 32ndash35] were taken from theexperimental setup first in five-day interval for forty daysand thereafter in seven-day interval for the following eightweeks This totalled 17 measurements within the experimen-tal period of ninety-six days for the studyThe nondestructiveelectrochemical test methods used for evaluating corrosioninhibition performance of theNaNO

2andC

6H15NO3admix-

tures in concrete include the following

(i) Half-cell potential (HCP) measurements thesewere taken through the experimental period versusCuCuSO

4electrode (CSE) Model 8-A (Tinker amp

Rasor) using high impedance digital multimeterModel DT-9205A according to ASTM C876-91 R99[36]

(ii) Electrochemical cell current (ECC) measurementsthese were taken versus the CSE using zero resistanceammeter (ZRA) Model ZM3P (corrosion service)[14 37 38]Thiswas done for themeasurementmodelof the reinforcing steel dissolution activity [14 39] inthe aggressive test solution systems sharing porouspartitioning with the CuCuSO

4

(iii) Corrosion rate (CR) measurements these wereobtained through direct instrument conversion tompy [14] using the three-electrode LPR Data LoggerModel MS1500L (metal samples) [40]

24 Data Analyses

241 Statistical Distributions and Goodness-of-Fit AnalysesAs prescribed in [41 42] measurements of electrochemicaltest data from the corrosion test setup were subjected tothe statistical analysis of the Weibull probability distributionfunction [2 14 32 33 42] This statistical modelling tool hasprobability distribution function given by

119891 (119909)

119882= (

119896

119888

) (

119909

119888

)

119896minus1

exp [minus(119909119888

)

119896

] (1)

where 119909 is corrosion test data from the requisite corrosionvariable which could be the half-cell potential the cellcurrent or the corrosion rate Also 119896 is the Weibull shapeparameter and 119888 is theWeibull scale parameter both of whichare estimated from the 119899 = 17 test data of corrosion test

4 Advances in Materials Science and Engineering

variable from each sample from the solution of simultaneousmaximum likelihood equations [43 44]

119899

119896

minus 119899 log (119888) +119899

sum

119894=1

log119909119894minus

119899

sum

119894=1

(

119909

119894

119888

)

log(119909

119894

119888

) = 0

119888 minus

1

119899

119899

sum

119894=1

119909

119894

1

= 0

(2)

The unbiased estimates of 119888 and 119896 from these equations findusefulness for computing Weibull mean 120583

119882 through

120583

119882= 119888Γ (1 +

1

119896

) (3)

Compatibility of the electrochemical test data to each ofthe Weibull distributions was ascertained by subjecting eachvariable of measured data to the Kolmogorov-Smirnov (K-S) goodness-of-fit (GoF) test criteria [42 43 45 46] ThisK-S GoF measures the absolute difference between empiri-cal distribution function 119865lowast(119909) and theoretical distributionfunction 119865(119909) [45 47 48] through the statistics

119863

119899= 119863 (119909

1 119909

119899) = supminusinfinlt119909ltinfin

1003816

1003816

1003816

1003816

119865

lowast(119909) minus 119865 (119909)

1003816

1003816

1003816

1003816

(4)

where 119899 = 17 data points obtained from the days ofmeasurements for each electrochemical test variable The 119863value evaluation from (4) was used for direct computationof the K-S 119875 value using the procedures from [45] By thiscriteria were set such that for 120572 = 005 significant level K-S 119875 value lt 120572 for a probability distribution of corrosion testdata indicates that such data did not follow that distributionwhile K-S 119875 value ge 120572 showed that the test data followed thedistribution

242 Inhibition Efficiency and Synergistic Parameter AnalysesThe mean corrosion rate performance 120583 obtained fromthe Weibull analysis of corrosion rate data finds usefulnessfor evaluating inhibition efficiency 120578 for each admixtureconcentration employed relative to that of the blank samplefrom the formula [14 27 30 37]

120578 =

120583blank minus 120583inh120583blank

times 100 (5)

Also these mean performances were employed for investi-gating synergistic effect of the partial NaNO

2replacement by

C6H15NO3admixtures on the inhibition of concrete steel-

rebar This entails evaluating synergistic parameter 119878 foreach combination of the NaNO

2+ C6H15NO3admixture

concentrations using the formula [27 28]

119878 =

120583NaNO2conc times 120583C

6H15NO3conc

120583

(NaNO2conc+C

6H15NO3conc) (6)

3 Results and Discussions

31 StatisticalModelling of Corrosion Test DataMeasurementsPlots of the Weibull mean of variables of corrosion test data

measurements the half-cell potential cell current and corro-sion rate are shown in Figure 2 for NaNO

2and TEA admixed

steel reinforced concretes samples Figure 2(a) showed addi-tional horizontal parallel lines as specified in ASTMC876-91R99 [36] delineating probability of corrosion risks for directinterpretation of the Weibull mean performance of half-cell potential in each of the reinforced concrete samples Inthe plots the electrochemical monitoringmethods employedshowed good agreements among many of the duplicatedsamples Also the test methods revealed higher prevalence ofcorrosive activities in the samples immersed in the chloridetest environments compared to those in the sulphate testenvironments For instance (see Figure 2(a)) the Weibullmean performance of corrosion potential obtained fromthe reinforced concrete samples immersed in the salinesimulating medium highly overshot the corrosion potentialperformance of samples immersed in the acidic mediumThis according to interpretations from ASTM C876-91 R99[36] which are shown by the horizontal lines in Figure 2(a)implies existence of higher probability of corrosion risk inthe concrete samples in NaCl medium compared to thesamples in H

2SO4medium In Figure 2(b) also the trends

of corrosion cell currents in the samples in chloride mediumovershot the trends of cell currents of samples immersed inthe sulphuric acid medium thus suggesting higher dissolu-tion activity in the NaCl-immersed concrete samples

The corrosion rate performance in Figure 2(c) tends tofollow these trends of the other corrosion test variablesBy this the mitigated corrosion rates of the NaNO

2and

C6H15NO3(TEA) admixed samples relative to the overshot

of corrosion rates obtained from the duplicates of controlsamples in NaCl were still generally higher compared to thecorrosion rates samples immersed in the H

2SO4medium

Common to all these plots are the identifiable mitigationsand in some other cases peaks denoting aggravations ofcorrosion activities by the concentrations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced concrete

samples immersed in aggressive media According to inter-pretation of ASTM C876-91 R99 [36] Figure 2(a) reaffirmedthat the HCP of the blank samples in the saline media wasmore negative than the ldquosevere corrosionrdquo condition range ofthe ASTM standard Also the HCP of the blank samples inthe acidic media is classified to the ldquohigh (gt90) corrosionriskrdquo region These suggest the inference that the media ofconcrete immersions employed in the study were aggressiveto the embedded steel-rebar in the reinforced concretes notcontaining admixtures It is based on these that mitigationsof corrosion rate relative to the blank concrete samples by thesynergistic partial NaNO

2replacement by C

6H15NO3(TEA)

admixtures in the reinforced concrete samples especially inthe severe saline media (see Figure 2(c)) could be noted

The plots of the K-S 119875 values from the application ofthe K-S GoF test statistics to the measurements of corrosiontest variables from the steel-reinforced concrete samples inaggressive media are presented in Figure 3 Each of theseplots includes the delineating line plot of the significantlevel 120572 = 005 for directly ascertaining from the figuredataset of test variable that followed or did not follow theWeibull probability distribution function From this it could

Advances in Materials Science and Engineering 5

Blan

kBl

ank_

Dup

Admixtures in concrete

Low (lt10)IntermediateSevere

0

200

400

600

800

NaCl

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

upPote

ntia

l (minus

mV

vers

us C

SE)

H2SO4

(a)

Admixtures in concreteNaCl

0

200

400

600

800

1000

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Curr

ent (minus120583

A)

H2SO4

(b)

Admixtures in concreteNaCl

0

2

4

6

8

10

12

Cor

rosio

n ra

te (m

my

)

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(c)

Figure 2Weibullmeanmodels of the electrochemical test data of steel-reinforced concrete samples immersed in aggressivemedia for ninety-six days of experimental period (a) half-cell potential (with corrosion risk levels as per ASTM C876-91 R99 [36]) (b) cell current and (c)corrosion rate

be deduced that all datasets of the half-cell potential fromthe duplicated concrete samples studied scattered like theWeibull probability distribution function see Figure 3(a)However the cell current datasets of the 4 g TEA the 2 gTEA and the synergistic 2 gNaNO

2+ 6 gTEA admixed steel-

reinforced concrete samples in the H2SO4medium were not

distributed like the Weibull fitting function see Figure 3(b)All the other datasets of measured test variables from the

reinforced concrete samples follow the Weibull probability

distribution function By this the entire corrosion ratedatasets measured from the duplicated samples of steel-reinforced concretes considered in the study also followed theWeibull probability distribution function according to the K-S GoF test criteria (see Figure 3(c))These in line with ASTMG16-95 R04 [41] support the use of the Weibull analysesof the mean of the corrosion rate test data from the steelreinforced concrete samples for representing the prevailingcorrosion conditions in each of the corrosive test systems

6 Advances in Materials Science and Engineering

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(a)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Kolm

ogor

ov-S

mirn

ovP

val

ue

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(b)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(c)

Figure 3 K-S goodness of fit test of measured corrosion test variables from concrete samples (a) half-cell potential (b) cell current and (c)corrosion rate

The choice of corrosion rate for detailing corrosion conditionin the samples instead of corrosion potential that the test dataalso followed theWeibull model was due to the identificationfrom [49] that the corrosion potential gives poor indicationof absolute corrosion activity

32 Admixture Performance and Inhibition Efficiency Esti-mations The Weibull mean corrosion rate was employedfor interpreting levels of corrosion degree as per [16 3550] and estimating averaged inhibition efficiency of theduplicated samples of admixed reinforced concrete relativeto the duplicated blank samples in each test medium Theresults of admixture performance from these are presented in

Figure 4 in ranking order of effectiveness of the admixturesat inhibiting concrete steel-rebar corrosion in each of theaggressive test environments The use of delineating linesof requisite levels of corrosion degree interpretations from[16 35 50] was employed in the parts of the plots in Figure 4involving rankings of the corrosion rate performance of thestudied admixture concentrations The results of admixtureperformance ranking in Figure 4(a) showed that the blanksamples without admixture in the NaCl medium exhibitedcorrosion rate that was higher than the upper bound of ldquoveryhighrdquo degree of corrosion rate 01 le CR (mmy) lt 1 as per[16 35 50] This supports the inference that the degree ofcorrosion rate in these blank samples in NaCl medium was

Advances in Materials Science and Engineering 7

Very high

0

1

2

3

4

5

6

7

8

9

10C

orro

sion

rate

(mm

y)

Admixture

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(a)

Admixture

946 922 909 894 894849

765717 708

00

minus10

0

10

20

30

40

50

60

70

80

90

100

Inhi

bitio

n effi

cien

cy120578

()

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(b)

Admixture

Low ormoderate

High

0

005

01

015

02

025

03

035

04

Cor

rosio

n ra

te (m

my

)

2g

NaN

O2+6

gTE

A

4g

TEA

4g

NaN

O2

2g

TEA

Blan

k

2g

NaN

O2

6g

NaN

O2+2

gTE

A

4g

NaN

O2+4

gTE

A

6g

TEA

6g

NaN

O2

(c)

Admixture

647

322308 302

minus351

minus490minus543

minus555

minus80

minus60

minus40

minus20

0

20

40

60

80

Inhi

bitio

n effi

cien

cy120578

()

minus03minus116

2g

NaN

O2+6

gTE

A4

gTE

A4

gN

aNO

2

2g

TEA

Blan

k2

gN

aNO

2

6g

NaN

O2+2

gTE

A4

gN

aNO

2+4

gTE

A6

gTE

A6

gN

aNO

2

(d)

Figure 4 Performance effectiveness ranking of admixtures at inhibiting concrete steel-rebar corrosion in concrete immersed in aggressivemedia for ninety-six days of experimental period (a) corrosion rate ranking in NaCl medium (b) inhibition efficiency ranking in NaClmedium (c) corrosion rate ranking in H

2SO4medium and (d) inhibition efficiency ranking in H

2SO4medium

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 2: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

2 Advances in Materials Science and Engineering

OH

OH

N

HO

(a) (b)

Figure 1 Triethanolamine (C6H15NO3 TEA) (a) molecular structure and (b) optimized ball and stick model

for mitigating steel-rebar corrosion in their corrosive serviceenvironments

Nitrites are well-known corrosion inhibiting substance[2 5 15 18] although they suffer the setback that their use isbeing restricted in many countries due to their toxicity andhazardousness to the environmental ecosystems [1 19 20]This is fostering research deliberations on the search formoreenvironmentally friendly substances for totally or partiallyreplacing the traditional but toxic inhibitor However suchsearch had been difficult due to the high effectiveness ofnitrites at inhibiting steel-rebar corrosion Triethanolamine(C6H15NO3 TEA) is an organic chemical with the molec-

ular structure shown in Figure 1 that is nontoxic to theenvironment and which had been employed for mitigatingchloride-induced carbon steel corrosion in simulated alkalinepore solution [21] Yet there is paucity of studies on thesuitability of triethanolamine as an environmentally benignalternative for synergistic partial replacement of the highlyeffective but toxic nitrite admixture as inhibitor of steel-rebar corrosion in concrete slab immersed in aggressivemedia Specific motivation for this paper was especiallydrawn from [22] that showed that inhibition effectiveness ofnitrites could be improved by requisite addition of anotherchemical This is because such additional model channeledusing nontoxic chemical is potent with reduction in environ-mental effects from the consequently lower usage of the toxicNaNO

2inhibitor quantity required for adequate corrosion

inhibition This paper therefore investigates the effect ofsynergistic combinations of different sodiumnitrite (NaNO

2)

and triethanolamine (C6H15NO3 TEA) concentrations as

synergistic admixtures on the corrosion of steel-rebar inconcrete immersed in NaCl and in H

2SO4media

2 Materials and Methods

21 Reinforcing Steel and Reinforced Concrete Block SpecimensSteel reinforcement used in the study was obtained from theFederated Steel Rolling Mills Ota Ogun State Nigeria The12mmdeformed rebar has composition in of 027 C 040Si 078 Mn 004 P 004 S 014 Cr 011 Ni 002 Mo 024 Cu001 Co 001 Nb 001 Sn and the balance Fe The steel-rebarwas cut into specimen rods each of which was 190mm long

Surface preparation was then maintained uniformly for eachof these rods Each rod of rebar was ground with coarse andfine abrasive papers pickled for 10 minutes in 10 H

2SO4

[23] rinsed and cleaned in ultrasonic cleaner degreased withacetone dried with warm air stream and kept in desiccatorprior to being used for the experiment [24 25]

Forty steel-reinforced concrete samples used for theexperiment were produced as replicated blocks [26] fourblocks per batch and each of size 100mm times 100mm times200mm such as volume of each concrete block = 2 times 103m3In each of these blocks 150mm length of the 12mm steel-rebar was embedded which was symmetrically placed acrossthe width of each of the blocks implying 44mm concretecover thickness with the remaining length of the rebarprotruding for electrochemical connections This protrudedrebar from the concrete was painted with glossy paintDrinkable water was used for mixing the concrete blocksEach block was formulated using ordinary Portland cementclean natural sand and granite stones The formulation usedfor the mixing of each steel-reinforced concrete specimenincludes cement = 3000 kgm3 sand = 8906 kgm3 granitestones = 11063 kgm3 and mixing water of 1497 kgm3 thusmaking the watercement (wc) ratio = 0499 [14 23]

22 Inhibitor Admixture The admixture concentrations ofNaNO

2and C

6H15NO3by mass in synergistic combinations

and individual admixtures in each 100mm times 100mm times200mm concrete specimen and in each of the corrosivemedia of specimen immersion were as presented in Table 1These in duplicate samples (tagged as ldquo Duprdquo) include blankconcretes without admixture followed by concretes admixedwith different combinations of NaNO

2and C

6H15NO3con-

centrations and then concretes with individual concentra-tions of the NaNO

2and of the C

6H15NO3 This was designed

for facilitating synergistic parameter modelling [27 28]Addition of the admixtures to the cast concrete samples wasas prescribed by ASTM C192192M-02 [29] For admixing inconcrete sample the admixture was weighed on analyticalweighing balance mixed thoroughly with concrete mixingwater that was made up to the required water volume for thewater-cement ratio of the concrete sample for the casting ofthe concrete sample

Advances in Materials Science and Engineering 3

Table 1 Inhibitor admixtures by mass in the steel reinforced concrete samples

Serialnumber Inhibitor admixture by mass Serialnumber Inhibitor admixture by mass1 0 g admixture (blank or control in NaCl) 2 0 g admixture (blank or control in H2SO4)3 0 g admixture (blank or control in NaCl Dup) 4 0 g admixture (blank or control in H2SO4 Dup)5 6 g NaNO2 + 2 g C6H15NO3 in NaCl 6 6 g NaNO2 + 2 g C6H15NO3 in H2SO4

7 6 g NaNO2 + 2 g C6H15NO3 in NaCl Dup 8 6 g NaNO2 + 2 g C6H15NO3 in H2SO4 Dup9 4 g NaNO2 + 4 g C6H15NO3 in NaCl 10 4 g NaNO2 + 4 g C6H15NO3 in H2SO4

11 4 g NaNO2 + 4 g C6H15NO3 in NaCl Dup 12 4 g NaNO2 + 4 g C6H15NO3 in H2SO4 Dup13 2 g NaNO2 + 6 g C6H15NO3 in NaCl 14 2 g NaNO2 + 6 g C6H15NO3 in H2SO4

15 2 g NaNO2 + 6 g C6H15NO3 in NaCl Dup 16 2 g NaNO2 + 6 g C6H15NO3 in H2SO4 Dup17 6 g NaNO2 in NaCl 18 6 g NaNO2 in H2SO4

19 6 g NaNO2 in NaCl Dup 20 6 g NaNO2 in H2SO4 Dup21 4 g NaNO2 in NaCl 22 4 g NaNO2 in H2SO4

23 4 g NaNO2 in NaCl Dup 24 4 g NaNO2 in H2SO4 Dup25 2 g NaNO2 in NaCl 26 2 g NaNO2 in H2SO4

27 2 g NaNO2 in NaCl Dup 28 2 g NaNO2 in H2SO4 Dup29 2 g C6H15NO3 in NaCl 30 2 g C6H15NO3 in H2SO4

31 2 g C6H15NO3 in NaCl Dup 32 2 g C6H15NO3 in H2SO4 Dup33 4 g C6H15NO3 in NaCl 34 4 g C6H15NO3 in H2SO4

35 4 g C6H15NO3 in NaCl Dup 36 4 g C6H15NO3 in H2SO4 Dup37 6 g C6H15NO3 in NaCl 38 6 g C6H15NO3 in H2SO4

39 6 g C6H15NO3 in NaCl Dup 40 6 g C6H15NO3 in H2SO4 Dup

23 Experimental Procedures

231 Corrosion Test Setup Steel reinforced concrete speci-mens were divided into two sets Each of the specimens ineach set was partially immersed longitudinally in plasticbowl containing corrosive test environment A duplicatedset of twenty samples was partially immersed in 35 NaClsolution [30 31] for simulating salinemarine environmentwhile the second duplicated set was partially immersed in05M H

2SO4solution [2 10 32 33] for simulating micro-

bialindustrial environment In each bowl the test mediumwas made up to just below the concrete steel-rebar but wasnot touching it Also according to the practice describedin [24] the test medium in each bowl was replenishedevery three weeks to prevent dryness and induce continuoussystem of corrosive environment through the ninety-six-day immersion of the steel-reinforced concrete samples Allchemicals used for both chemical admixtures and corrosivetest environments are analytical grade

232 Electrochemical Measurements Nondestructive elec-trochemical measurements [14 32ndash35] were taken from theexperimental setup first in five-day interval for forty daysand thereafter in seven-day interval for the following eightweeks This totalled 17 measurements within the experimen-tal period of ninety-six days for the studyThe nondestructiveelectrochemical test methods used for evaluating corrosioninhibition performance of theNaNO

2andC

6H15NO3admix-

tures in concrete include the following

(i) Half-cell potential (HCP) measurements thesewere taken through the experimental period versusCuCuSO

4electrode (CSE) Model 8-A (Tinker amp

Rasor) using high impedance digital multimeterModel DT-9205A according to ASTM C876-91 R99[36]

(ii) Electrochemical cell current (ECC) measurementsthese were taken versus the CSE using zero resistanceammeter (ZRA) Model ZM3P (corrosion service)[14 37 38]Thiswas done for themeasurementmodelof the reinforcing steel dissolution activity [14 39] inthe aggressive test solution systems sharing porouspartitioning with the CuCuSO

4

(iii) Corrosion rate (CR) measurements these wereobtained through direct instrument conversion tompy [14] using the three-electrode LPR Data LoggerModel MS1500L (metal samples) [40]

24 Data Analyses

241 Statistical Distributions and Goodness-of-Fit AnalysesAs prescribed in [41 42] measurements of electrochemicaltest data from the corrosion test setup were subjected tothe statistical analysis of the Weibull probability distributionfunction [2 14 32 33 42] This statistical modelling tool hasprobability distribution function given by

119891 (119909)

119882= (

119896

119888

) (

119909

119888

)

119896minus1

exp [minus(119909119888

)

119896

] (1)

where 119909 is corrosion test data from the requisite corrosionvariable which could be the half-cell potential the cellcurrent or the corrosion rate Also 119896 is the Weibull shapeparameter and 119888 is theWeibull scale parameter both of whichare estimated from the 119899 = 17 test data of corrosion test

4 Advances in Materials Science and Engineering

variable from each sample from the solution of simultaneousmaximum likelihood equations [43 44]

119899

119896

minus 119899 log (119888) +119899

sum

119894=1

log119909119894minus

119899

sum

119894=1

(

119909

119894

119888

)

log(119909

119894

119888

) = 0

119888 minus

1

119899

119899

sum

119894=1

119909

119894

1

= 0

(2)

The unbiased estimates of 119888 and 119896 from these equations findusefulness for computing Weibull mean 120583

119882 through

120583

119882= 119888Γ (1 +

1

119896

) (3)

Compatibility of the electrochemical test data to each ofthe Weibull distributions was ascertained by subjecting eachvariable of measured data to the Kolmogorov-Smirnov (K-S) goodness-of-fit (GoF) test criteria [42 43 45 46] ThisK-S GoF measures the absolute difference between empiri-cal distribution function 119865lowast(119909) and theoretical distributionfunction 119865(119909) [45 47 48] through the statistics

119863

119899= 119863 (119909

1 119909

119899) = supminusinfinlt119909ltinfin

1003816

1003816

1003816

1003816

119865

lowast(119909) minus 119865 (119909)

1003816

1003816

1003816

1003816

(4)

where 119899 = 17 data points obtained from the days ofmeasurements for each electrochemical test variable The 119863value evaluation from (4) was used for direct computationof the K-S 119875 value using the procedures from [45] By thiscriteria were set such that for 120572 = 005 significant level K-S 119875 value lt 120572 for a probability distribution of corrosion testdata indicates that such data did not follow that distributionwhile K-S 119875 value ge 120572 showed that the test data followed thedistribution

242 Inhibition Efficiency and Synergistic Parameter AnalysesThe mean corrosion rate performance 120583 obtained fromthe Weibull analysis of corrosion rate data finds usefulnessfor evaluating inhibition efficiency 120578 for each admixtureconcentration employed relative to that of the blank samplefrom the formula [14 27 30 37]

120578 =

120583blank minus 120583inh120583blank

times 100 (5)

Also these mean performances were employed for investi-gating synergistic effect of the partial NaNO

2replacement by

C6H15NO3admixtures on the inhibition of concrete steel-

rebar This entails evaluating synergistic parameter 119878 foreach combination of the NaNO

2+ C6H15NO3admixture

concentrations using the formula [27 28]

119878 =

120583NaNO2conc times 120583C

6H15NO3conc

120583

(NaNO2conc+C

6H15NO3conc) (6)

3 Results and Discussions

31 StatisticalModelling of Corrosion Test DataMeasurementsPlots of the Weibull mean of variables of corrosion test data

measurements the half-cell potential cell current and corro-sion rate are shown in Figure 2 for NaNO

2and TEA admixed

steel reinforced concretes samples Figure 2(a) showed addi-tional horizontal parallel lines as specified in ASTMC876-91R99 [36] delineating probability of corrosion risks for directinterpretation of the Weibull mean performance of half-cell potential in each of the reinforced concrete samples Inthe plots the electrochemical monitoringmethods employedshowed good agreements among many of the duplicatedsamples Also the test methods revealed higher prevalence ofcorrosive activities in the samples immersed in the chloridetest environments compared to those in the sulphate testenvironments For instance (see Figure 2(a)) the Weibullmean performance of corrosion potential obtained fromthe reinforced concrete samples immersed in the salinesimulating medium highly overshot the corrosion potentialperformance of samples immersed in the acidic mediumThis according to interpretations from ASTM C876-91 R99[36] which are shown by the horizontal lines in Figure 2(a)implies existence of higher probability of corrosion risk inthe concrete samples in NaCl medium compared to thesamples in H

2SO4medium In Figure 2(b) also the trends

of corrosion cell currents in the samples in chloride mediumovershot the trends of cell currents of samples immersed inthe sulphuric acid medium thus suggesting higher dissolu-tion activity in the NaCl-immersed concrete samples

The corrosion rate performance in Figure 2(c) tends tofollow these trends of the other corrosion test variablesBy this the mitigated corrosion rates of the NaNO

2and

C6H15NO3(TEA) admixed samples relative to the overshot

of corrosion rates obtained from the duplicates of controlsamples in NaCl were still generally higher compared to thecorrosion rates samples immersed in the H

2SO4medium

Common to all these plots are the identifiable mitigationsand in some other cases peaks denoting aggravations ofcorrosion activities by the concentrations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced concrete

samples immersed in aggressive media According to inter-pretation of ASTM C876-91 R99 [36] Figure 2(a) reaffirmedthat the HCP of the blank samples in the saline media wasmore negative than the ldquosevere corrosionrdquo condition range ofthe ASTM standard Also the HCP of the blank samples inthe acidic media is classified to the ldquohigh (gt90) corrosionriskrdquo region These suggest the inference that the media ofconcrete immersions employed in the study were aggressiveto the embedded steel-rebar in the reinforced concretes notcontaining admixtures It is based on these that mitigationsof corrosion rate relative to the blank concrete samples by thesynergistic partial NaNO

2replacement by C

6H15NO3(TEA)

admixtures in the reinforced concrete samples especially inthe severe saline media (see Figure 2(c)) could be noted

The plots of the K-S 119875 values from the application ofthe K-S GoF test statistics to the measurements of corrosiontest variables from the steel-reinforced concrete samples inaggressive media are presented in Figure 3 Each of theseplots includes the delineating line plot of the significantlevel 120572 = 005 for directly ascertaining from the figuredataset of test variable that followed or did not follow theWeibull probability distribution function From this it could

Advances in Materials Science and Engineering 5

Blan

kBl

ank_

Dup

Admixtures in concrete

Low (lt10)IntermediateSevere

0

200

400

600

800

NaCl

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

upPote

ntia

l (minus

mV

vers

us C

SE)

H2SO4

(a)

Admixtures in concreteNaCl

0

200

400

600

800

1000

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Curr

ent (minus120583

A)

H2SO4

(b)

Admixtures in concreteNaCl

0

2

4

6

8

10

12

Cor

rosio

n ra

te (m

my

)

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(c)

Figure 2Weibullmeanmodels of the electrochemical test data of steel-reinforced concrete samples immersed in aggressivemedia for ninety-six days of experimental period (a) half-cell potential (with corrosion risk levels as per ASTM C876-91 R99 [36]) (b) cell current and (c)corrosion rate

be deduced that all datasets of the half-cell potential fromthe duplicated concrete samples studied scattered like theWeibull probability distribution function see Figure 3(a)However the cell current datasets of the 4 g TEA the 2 gTEA and the synergistic 2 gNaNO

2+ 6 gTEA admixed steel-

reinforced concrete samples in the H2SO4medium were not

distributed like the Weibull fitting function see Figure 3(b)All the other datasets of measured test variables from the

reinforced concrete samples follow the Weibull probability

distribution function By this the entire corrosion ratedatasets measured from the duplicated samples of steel-reinforced concretes considered in the study also followed theWeibull probability distribution function according to the K-S GoF test criteria (see Figure 3(c))These in line with ASTMG16-95 R04 [41] support the use of the Weibull analysesof the mean of the corrosion rate test data from the steelreinforced concrete samples for representing the prevailingcorrosion conditions in each of the corrosive test systems

6 Advances in Materials Science and Engineering

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(a)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Kolm

ogor

ov-S

mirn

ovP

val

ue

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(b)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(c)

Figure 3 K-S goodness of fit test of measured corrosion test variables from concrete samples (a) half-cell potential (b) cell current and (c)corrosion rate

The choice of corrosion rate for detailing corrosion conditionin the samples instead of corrosion potential that the test dataalso followed theWeibull model was due to the identificationfrom [49] that the corrosion potential gives poor indicationof absolute corrosion activity

32 Admixture Performance and Inhibition Efficiency Esti-mations The Weibull mean corrosion rate was employedfor interpreting levels of corrosion degree as per [16 3550] and estimating averaged inhibition efficiency of theduplicated samples of admixed reinforced concrete relativeto the duplicated blank samples in each test medium Theresults of admixture performance from these are presented in

Figure 4 in ranking order of effectiveness of the admixturesat inhibiting concrete steel-rebar corrosion in each of theaggressive test environments The use of delineating linesof requisite levels of corrosion degree interpretations from[16 35 50] was employed in the parts of the plots in Figure 4involving rankings of the corrosion rate performance of thestudied admixture concentrations The results of admixtureperformance ranking in Figure 4(a) showed that the blanksamples without admixture in the NaCl medium exhibitedcorrosion rate that was higher than the upper bound of ldquoveryhighrdquo degree of corrosion rate 01 le CR (mmy) lt 1 as per[16 35 50] This supports the inference that the degree ofcorrosion rate in these blank samples in NaCl medium was

Advances in Materials Science and Engineering 7

Very high

0

1

2

3

4

5

6

7

8

9

10C

orro

sion

rate

(mm

y)

Admixture

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(a)

Admixture

946 922 909 894 894849

765717 708

00

minus10

0

10

20

30

40

50

60

70

80

90

100

Inhi

bitio

n effi

cien

cy120578

()

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(b)

Admixture

Low ormoderate

High

0

005

01

015

02

025

03

035

04

Cor

rosio

n ra

te (m

my

)

2g

NaN

O2+6

gTE

A

4g

TEA

4g

NaN

O2

2g

TEA

Blan

k

2g

NaN

O2

6g

NaN

O2+2

gTE

A

4g

NaN

O2+4

gTE

A

6g

TEA

6g

NaN

O2

(c)

Admixture

647

322308 302

minus351

minus490minus543

minus555

minus80

minus60

minus40

minus20

0

20

40

60

80

Inhi

bitio

n effi

cien

cy120578

()

minus03minus116

2g

NaN

O2+6

gTE

A4

gTE

A4

gN

aNO

2

2g

TEA

Blan

k2

gN

aNO

2

6g

NaN

O2+2

gTE

A4

gN

aNO

2+4

gTE

A6

gTE

A6

gN

aNO

2

(d)

Figure 4 Performance effectiveness ranking of admixtures at inhibiting concrete steel-rebar corrosion in concrete immersed in aggressivemedia for ninety-six days of experimental period (a) corrosion rate ranking in NaCl medium (b) inhibition efficiency ranking in NaClmedium (c) corrosion rate ranking in H

2SO4medium and (d) inhibition efficiency ranking in H

2SO4medium

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 3: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

Advances in Materials Science and Engineering 3

Table 1 Inhibitor admixtures by mass in the steel reinforced concrete samples

Serialnumber Inhibitor admixture by mass Serialnumber Inhibitor admixture by mass1 0 g admixture (blank or control in NaCl) 2 0 g admixture (blank or control in H2SO4)3 0 g admixture (blank or control in NaCl Dup) 4 0 g admixture (blank or control in H2SO4 Dup)5 6 g NaNO2 + 2 g C6H15NO3 in NaCl 6 6 g NaNO2 + 2 g C6H15NO3 in H2SO4

7 6 g NaNO2 + 2 g C6H15NO3 in NaCl Dup 8 6 g NaNO2 + 2 g C6H15NO3 in H2SO4 Dup9 4 g NaNO2 + 4 g C6H15NO3 in NaCl 10 4 g NaNO2 + 4 g C6H15NO3 in H2SO4

11 4 g NaNO2 + 4 g C6H15NO3 in NaCl Dup 12 4 g NaNO2 + 4 g C6H15NO3 in H2SO4 Dup13 2 g NaNO2 + 6 g C6H15NO3 in NaCl 14 2 g NaNO2 + 6 g C6H15NO3 in H2SO4

15 2 g NaNO2 + 6 g C6H15NO3 in NaCl Dup 16 2 g NaNO2 + 6 g C6H15NO3 in H2SO4 Dup17 6 g NaNO2 in NaCl 18 6 g NaNO2 in H2SO4

19 6 g NaNO2 in NaCl Dup 20 6 g NaNO2 in H2SO4 Dup21 4 g NaNO2 in NaCl 22 4 g NaNO2 in H2SO4

23 4 g NaNO2 in NaCl Dup 24 4 g NaNO2 in H2SO4 Dup25 2 g NaNO2 in NaCl 26 2 g NaNO2 in H2SO4

27 2 g NaNO2 in NaCl Dup 28 2 g NaNO2 in H2SO4 Dup29 2 g C6H15NO3 in NaCl 30 2 g C6H15NO3 in H2SO4

31 2 g C6H15NO3 in NaCl Dup 32 2 g C6H15NO3 in H2SO4 Dup33 4 g C6H15NO3 in NaCl 34 4 g C6H15NO3 in H2SO4

35 4 g C6H15NO3 in NaCl Dup 36 4 g C6H15NO3 in H2SO4 Dup37 6 g C6H15NO3 in NaCl 38 6 g C6H15NO3 in H2SO4

39 6 g C6H15NO3 in NaCl Dup 40 6 g C6H15NO3 in H2SO4 Dup

23 Experimental Procedures

231 Corrosion Test Setup Steel reinforced concrete speci-mens were divided into two sets Each of the specimens ineach set was partially immersed longitudinally in plasticbowl containing corrosive test environment A duplicatedset of twenty samples was partially immersed in 35 NaClsolution [30 31] for simulating salinemarine environmentwhile the second duplicated set was partially immersed in05M H

2SO4solution [2 10 32 33] for simulating micro-

bialindustrial environment In each bowl the test mediumwas made up to just below the concrete steel-rebar but wasnot touching it Also according to the practice describedin [24] the test medium in each bowl was replenishedevery three weeks to prevent dryness and induce continuoussystem of corrosive environment through the ninety-six-day immersion of the steel-reinforced concrete samples Allchemicals used for both chemical admixtures and corrosivetest environments are analytical grade

232 Electrochemical Measurements Nondestructive elec-trochemical measurements [14 32ndash35] were taken from theexperimental setup first in five-day interval for forty daysand thereafter in seven-day interval for the following eightweeks This totalled 17 measurements within the experimen-tal period of ninety-six days for the studyThe nondestructiveelectrochemical test methods used for evaluating corrosioninhibition performance of theNaNO

2andC

6H15NO3admix-

tures in concrete include the following

(i) Half-cell potential (HCP) measurements thesewere taken through the experimental period versusCuCuSO

4electrode (CSE) Model 8-A (Tinker amp

Rasor) using high impedance digital multimeterModel DT-9205A according to ASTM C876-91 R99[36]

(ii) Electrochemical cell current (ECC) measurementsthese were taken versus the CSE using zero resistanceammeter (ZRA) Model ZM3P (corrosion service)[14 37 38]Thiswas done for themeasurementmodelof the reinforcing steel dissolution activity [14 39] inthe aggressive test solution systems sharing porouspartitioning with the CuCuSO

4

(iii) Corrosion rate (CR) measurements these wereobtained through direct instrument conversion tompy [14] using the three-electrode LPR Data LoggerModel MS1500L (metal samples) [40]

24 Data Analyses

241 Statistical Distributions and Goodness-of-Fit AnalysesAs prescribed in [41 42] measurements of electrochemicaltest data from the corrosion test setup were subjected tothe statistical analysis of the Weibull probability distributionfunction [2 14 32 33 42] This statistical modelling tool hasprobability distribution function given by

119891 (119909)

119882= (

119896

119888

) (

119909

119888

)

119896minus1

exp [minus(119909119888

)

119896

] (1)

where 119909 is corrosion test data from the requisite corrosionvariable which could be the half-cell potential the cellcurrent or the corrosion rate Also 119896 is the Weibull shapeparameter and 119888 is theWeibull scale parameter both of whichare estimated from the 119899 = 17 test data of corrosion test

4 Advances in Materials Science and Engineering

variable from each sample from the solution of simultaneousmaximum likelihood equations [43 44]

119899

119896

minus 119899 log (119888) +119899

sum

119894=1

log119909119894minus

119899

sum

119894=1

(

119909

119894

119888

)

log(119909

119894

119888

) = 0

119888 minus

1

119899

119899

sum

119894=1

119909

119894

1

= 0

(2)

The unbiased estimates of 119888 and 119896 from these equations findusefulness for computing Weibull mean 120583

119882 through

120583

119882= 119888Γ (1 +

1

119896

) (3)

Compatibility of the electrochemical test data to each ofthe Weibull distributions was ascertained by subjecting eachvariable of measured data to the Kolmogorov-Smirnov (K-S) goodness-of-fit (GoF) test criteria [42 43 45 46] ThisK-S GoF measures the absolute difference between empiri-cal distribution function 119865lowast(119909) and theoretical distributionfunction 119865(119909) [45 47 48] through the statistics

119863

119899= 119863 (119909

1 119909

119899) = supminusinfinlt119909ltinfin

1003816

1003816

1003816

1003816

119865

lowast(119909) minus 119865 (119909)

1003816

1003816

1003816

1003816

(4)

where 119899 = 17 data points obtained from the days ofmeasurements for each electrochemical test variable The 119863value evaluation from (4) was used for direct computationof the K-S 119875 value using the procedures from [45] By thiscriteria were set such that for 120572 = 005 significant level K-S 119875 value lt 120572 for a probability distribution of corrosion testdata indicates that such data did not follow that distributionwhile K-S 119875 value ge 120572 showed that the test data followed thedistribution

242 Inhibition Efficiency and Synergistic Parameter AnalysesThe mean corrosion rate performance 120583 obtained fromthe Weibull analysis of corrosion rate data finds usefulnessfor evaluating inhibition efficiency 120578 for each admixtureconcentration employed relative to that of the blank samplefrom the formula [14 27 30 37]

120578 =

120583blank minus 120583inh120583blank

times 100 (5)

Also these mean performances were employed for investi-gating synergistic effect of the partial NaNO

2replacement by

C6H15NO3admixtures on the inhibition of concrete steel-

rebar This entails evaluating synergistic parameter 119878 foreach combination of the NaNO

2+ C6H15NO3admixture

concentrations using the formula [27 28]

119878 =

120583NaNO2conc times 120583C

6H15NO3conc

120583

(NaNO2conc+C

6H15NO3conc) (6)

3 Results and Discussions

31 StatisticalModelling of Corrosion Test DataMeasurementsPlots of the Weibull mean of variables of corrosion test data

measurements the half-cell potential cell current and corro-sion rate are shown in Figure 2 for NaNO

2and TEA admixed

steel reinforced concretes samples Figure 2(a) showed addi-tional horizontal parallel lines as specified in ASTMC876-91R99 [36] delineating probability of corrosion risks for directinterpretation of the Weibull mean performance of half-cell potential in each of the reinforced concrete samples Inthe plots the electrochemical monitoringmethods employedshowed good agreements among many of the duplicatedsamples Also the test methods revealed higher prevalence ofcorrosive activities in the samples immersed in the chloridetest environments compared to those in the sulphate testenvironments For instance (see Figure 2(a)) the Weibullmean performance of corrosion potential obtained fromthe reinforced concrete samples immersed in the salinesimulating medium highly overshot the corrosion potentialperformance of samples immersed in the acidic mediumThis according to interpretations from ASTM C876-91 R99[36] which are shown by the horizontal lines in Figure 2(a)implies existence of higher probability of corrosion risk inthe concrete samples in NaCl medium compared to thesamples in H

2SO4medium In Figure 2(b) also the trends

of corrosion cell currents in the samples in chloride mediumovershot the trends of cell currents of samples immersed inthe sulphuric acid medium thus suggesting higher dissolu-tion activity in the NaCl-immersed concrete samples

The corrosion rate performance in Figure 2(c) tends tofollow these trends of the other corrosion test variablesBy this the mitigated corrosion rates of the NaNO

2and

C6H15NO3(TEA) admixed samples relative to the overshot

of corrosion rates obtained from the duplicates of controlsamples in NaCl were still generally higher compared to thecorrosion rates samples immersed in the H

2SO4medium

Common to all these plots are the identifiable mitigationsand in some other cases peaks denoting aggravations ofcorrosion activities by the concentrations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced concrete

samples immersed in aggressive media According to inter-pretation of ASTM C876-91 R99 [36] Figure 2(a) reaffirmedthat the HCP of the blank samples in the saline media wasmore negative than the ldquosevere corrosionrdquo condition range ofthe ASTM standard Also the HCP of the blank samples inthe acidic media is classified to the ldquohigh (gt90) corrosionriskrdquo region These suggest the inference that the media ofconcrete immersions employed in the study were aggressiveto the embedded steel-rebar in the reinforced concretes notcontaining admixtures It is based on these that mitigationsof corrosion rate relative to the blank concrete samples by thesynergistic partial NaNO

2replacement by C

6H15NO3(TEA)

admixtures in the reinforced concrete samples especially inthe severe saline media (see Figure 2(c)) could be noted

The plots of the K-S 119875 values from the application ofthe K-S GoF test statistics to the measurements of corrosiontest variables from the steel-reinforced concrete samples inaggressive media are presented in Figure 3 Each of theseplots includes the delineating line plot of the significantlevel 120572 = 005 for directly ascertaining from the figuredataset of test variable that followed or did not follow theWeibull probability distribution function From this it could

Advances in Materials Science and Engineering 5

Blan

kBl

ank_

Dup

Admixtures in concrete

Low (lt10)IntermediateSevere

0

200

400

600

800

NaCl

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

upPote

ntia

l (minus

mV

vers

us C

SE)

H2SO4

(a)

Admixtures in concreteNaCl

0

200

400

600

800

1000

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Curr

ent (minus120583

A)

H2SO4

(b)

Admixtures in concreteNaCl

0

2

4

6

8

10

12

Cor

rosio

n ra

te (m

my

)

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(c)

Figure 2Weibullmeanmodels of the electrochemical test data of steel-reinforced concrete samples immersed in aggressivemedia for ninety-six days of experimental period (a) half-cell potential (with corrosion risk levels as per ASTM C876-91 R99 [36]) (b) cell current and (c)corrosion rate

be deduced that all datasets of the half-cell potential fromthe duplicated concrete samples studied scattered like theWeibull probability distribution function see Figure 3(a)However the cell current datasets of the 4 g TEA the 2 gTEA and the synergistic 2 gNaNO

2+ 6 gTEA admixed steel-

reinforced concrete samples in the H2SO4medium were not

distributed like the Weibull fitting function see Figure 3(b)All the other datasets of measured test variables from the

reinforced concrete samples follow the Weibull probability

distribution function By this the entire corrosion ratedatasets measured from the duplicated samples of steel-reinforced concretes considered in the study also followed theWeibull probability distribution function according to the K-S GoF test criteria (see Figure 3(c))These in line with ASTMG16-95 R04 [41] support the use of the Weibull analysesof the mean of the corrosion rate test data from the steelreinforced concrete samples for representing the prevailingcorrosion conditions in each of the corrosive test systems

6 Advances in Materials Science and Engineering

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(a)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Kolm

ogor

ov-S

mirn

ovP

val

ue

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(b)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(c)

Figure 3 K-S goodness of fit test of measured corrosion test variables from concrete samples (a) half-cell potential (b) cell current and (c)corrosion rate

The choice of corrosion rate for detailing corrosion conditionin the samples instead of corrosion potential that the test dataalso followed theWeibull model was due to the identificationfrom [49] that the corrosion potential gives poor indicationof absolute corrosion activity

32 Admixture Performance and Inhibition Efficiency Esti-mations The Weibull mean corrosion rate was employedfor interpreting levels of corrosion degree as per [16 3550] and estimating averaged inhibition efficiency of theduplicated samples of admixed reinforced concrete relativeto the duplicated blank samples in each test medium Theresults of admixture performance from these are presented in

Figure 4 in ranking order of effectiveness of the admixturesat inhibiting concrete steel-rebar corrosion in each of theaggressive test environments The use of delineating linesof requisite levels of corrosion degree interpretations from[16 35 50] was employed in the parts of the plots in Figure 4involving rankings of the corrosion rate performance of thestudied admixture concentrations The results of admixtureperformance ranking in Figure 4(a) showed that the blanksamples without admixture in the NaCl medium exhibitedcorrosion rate that was higher than the upper bound of ldquoveryhighrdquo degree of corrosion rate 01 le CR (mmy) lt 1 as per[16 35 50] This supports the inference that the degree ofcorrosion rate in these blank samples in NaCl medium was

Advances in Materials Science and Engineering 7

Very high

0

1

2

3

4

5

6

7

8

9

10C

orro

sion

rate

(mm

y)

Admixture

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(a)

Admixture

946 922 909 894 894849

765717 708

00

minus10

0

10

20

30

40

50

60

70

80

90

100

Inhi

bitio

n effi

cien

cy120578

()

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(b)

Admixture

Low ormoderate

High

0

005

01

015

02

025

03

035

04

Cor

rosio

n ra

te (m

my

)

2g

NaN

O2+6

gTE

A

4g

TEA

4g

NaN

O2

2g

TEA

Blan

k

2g

NaN

O2

6g

NaN

O2+2

gTE

A

4g

NaN

O2+4

gTE

A

6g

TEA

6g

NaN

O2

(c)

Admixture

647

322308 302

minus351

minus490minus543

minus555

minus80

minus60

minus40

minus20

0

20

40

60

80

Inhi

bitio

n effi

cien

cy120578

()

minus03minus116

2g

NaN

O2+6

gTE

A4

gTE

A4

gN

aNO

2

2g

TEA

Blan

k2

gN

aNO

2

6g

NaN

O2+2

gTE

A4

gN

aNO

2+4

gTE

A6

gTE

A6

gN

aNO

2

(d)

Figure 4 Performance effectiveness ranking of admixtures at inhibiting concrete steel-rebar corrosion in concrete immersed in aggressivemedia for ninety-six days of experimental period (a) corrosion rate ranking in NaCl medium (b) inhibition efficiency ranking in NaClmedium (c) corrosion rate ranking in H

2SO4medium and (d) inhibition efficiency ranking in H

2SO4medium

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 4: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

4 Advances in Materials Science and Engineering

variable from each sample from the solution of simultaneousmaximum likelihood equations [43 44]

119899

119896

minus 119899 log (119888) +119899

sum

119894=1

log119909119894minus

119899

sum

119894=1

(

119909

119894

119888

)

log(119909

119894

119888

) = 0

119888 minus

1

119899

119899

sum

119894=1

119909

119894

1

= 0

(2)

The unbiased estimates of 119888 and 119896 from these equations findusefulness for computing Weibull mean 120583

119882 through

120583

119882= 119888Γ (1 +

1

119896

) (3)

Compatibility of the electrochemical test data to each ofthe Weibull distributions was ascertained by subjecting eachvariable of measured data to the Kolmogorov-Smirnov (K-S) goodness-of-fit (GoF) test criteria [42 43 45 46] ThisK-S GoF measures the absolute difference between empiri-cal distribution function 119865lowast(119909) and theoretical distributionfunction 119865(119909) [45 47 48] through the statistics

119863

119899= 119863 (119909

1 119909

119899) = supminusinfinlt119909ltinfin

1003816

1003816

1003816

1003816

119865

lowast(119909) minus 119865 (119909)

1003816

1003816

1003816

1003816

(4)

where 119899 = 17 data points obtained from the days ofmeasurements for each electrochemical test variable The 119863value evaluation from (4) was used for direct computationof the K-S 119875 value using the procedures from [45] By thiscriteria were set such that for 120572 = 005 significant level K-S 119875 value lt 120572 for a probability distribution of corrosion testdata indicates that such data did not follow that distributionwhile K-S 119875 value ge 120572 showed that the test data followed thedistribution

242 Inhibition Efficiency and Synergistic Parameter AnalysesThe mean corrosion rate performance 120583 obtained fromthe Weibull analysis of corrosion rate data finds usefulnessfor evaluating inhibition efficiency 120578 for each admixtureconcentration employed relative to that of the blank samplefrom the formula [14 27 30 37]

120578 =

120583blank minus 120583inh120583blank

times 100 (5)

Also these mean performances were employed for investi-gating synergistic effect of the partial NaNO

2replacement by

C6H15NO3admixtures on the inhibition of concrete steel-

rebar This entails evaluating synergistic parameter 119878 foreach combination of the NaNO

2+ C6H15NO3admixture

concentrations using the formula [27 28]

119878 =

120583NaNO2conc times 120583C

6H15NO3conc

120583

(NaNO2conc+C

6H15NO3conc) (6)

3 Results and Discussions

31 StatisticalModelling of Corrosion Test DataMeasurementsPlots of the Weibull mean of variables of corrosion test data

measurements the half-cell potential cell current and corro-sion rate are shown in Figure 2 for NaNO

2and TEA admixed

steel reinforced concretes samples Figure 2(a) showed addi-tional horizontal parallel lines as specified in ASTMC876-91R99 [36] delineating probability of corrosion risks for directinterpretation of the Weibull mean performance of half-cell potential in each of the reinforced concrete samples Inthe plots the electrochemical monitoringmethods employedshowed good agreements among many of the duplicatedsamples Also the test methods revealed higher prevalence ofcorrosive activities in the samples immersed in the chloridetest environments compared to those in the sulphate testenvironments For instance (see Figure 2(a)) the Weibullmean performance of corrosion potential obtained fromthe reinforced concrete samples immersed in the salinesimulating medium highly overshot the corrosion potentialperformance of samples immersed in the acidic mediumThis according to interpretations from ASTM C876-91 R99[36] which are shown by the horizontal lines in Figure 2(a)implies existence of higher probability of corrosion risk inthe concrete samples in NaCl medium compared to thesamples in H

2SO4medium In Figure 2(b) also the trends

of corrosion cell currents in the samples in chloride mediumovershot the trends of cell currents of samples immersed inthe sulphuric acid medium thus suggesting higher dissolu-tion activity in the NaCl-immersed concrete samples

The corrosion rate performance in Figure 2(c) tends tofollow these trends of the other corrosion test variablesBy this the mitigated corrosion rates of the NaNO

2and

C6H15NO3(TEA) admixed samples relative to the overshot

of corrosion rates obtained from the duplicates of controlsamples in NaCl were still generally higher compared to thecorrosion rates samples immersed in the H

2SO4medium

Common to all these plots are the identifiable mitigationsand in some other cases peaks denoting aggravations ofcorrosion activities by the concentrations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced concrete

samples immersed in aggressive media According to inter-pretation of ASTM C876-91 R99 [36] Figure 2(a) reaffirmedthat the HCP of the blank samples in the saline media wasmore negative than the ldquosevere corrosionrdquo condition range ofthe ASTM standard Also the HCP of the blank samples inthe acidic media is classified to the ldquohigh (gt90) corrosionriskrdquo region These suggest the inference that the media ofconcrete immersions employed in the study were aggressiveto the embedded steel-rebar in the reinforced concretes notcontaining admixtures It is based on these that mitigationsof corrosion rate relative to the blank concrete samples by thesynergistic partial NaNO

2replacement by C

6H15NO3(TEA)

admixtures in the reinforced concrete samples especially inthe severe saline media (see Figure 2(c)) could be noted

The plots of the K-S 119875 values from the application ofthe K-S GoF test statistics to the measurements of corrosiontest variables from the steel-reinforced concrete samples inaggressive media are presented in Figure 3 Each of theseplots includes the delineating line plot of the significantlevel 120572 = 005 for directly ascertaining from the figuredataset of test variable that followed or did not follow theWeibull probability distribution function From this it could

Advances in Materials Science and Engineering 5

Blan

kBl

ank_

Dup

Admixtures in concrete

Low (lt10)IntermediateSevere

0

200

400

600

800

NaCl

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

upPote

ntia

l (minus

mV

vers

us C

SE)

H2SO4

(a)

Admixtures in concreteNaCl

0

200

400

600

800

1000

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Curr

ent (minus120583

A)

H2SO4

(b)

Admixtures in concreteNaCl

0

2

4

6

8

10

12

Cor

rosio

n ra

te (m

my

)

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(c)

Figure 2Weibullmeanmodels of the electrochemical test data of steel-reinforced concrete samples immersed in aggressivemedia for ninety-six days of experimental period (a) half-cell potential (with corrosion risk levels as per ASTM C876-91 R99 [36]) (b) cell current and (c)corrosion rate

be deduced that all datasets of the half-cell potential fromthe duplicated concrete samples studied scattered like theWeibull probability distribution function see Figure 3(a)However the cell current datasets of the 4 g TEA the 2 gTEA and the synergistic 2 gNaNO

2+ 6 gTEA admixed steel-

reinforced concrete samples in the H2SO4medium were not

distributed like the Weibull fitting function see Figure 3(b)All the other datasets of measured test variables from the

reinforced concrete samples follow the Weibull probability

distribution function By this the entire corrosion ratedatasets measured from the duplicated samples of steel-reinforced concretes considered in the study also followed theWeibull probability distribution function according to the K-S GoF test criteria (see Figure 3(c))These in line with ASTMG16-95 R04 [41] support the use of the Weibull analysesof the mean of the corrosion rate test data from the steelreinforced concrete samples for representing the prevailingcorrosion conditions in each of the corrosive test systems

6 Advances in Materials Science and Engineering

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(a)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Kolm

ogor

ov-S

mirn

ovP

val

ue

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(b)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(c)

Figure 3 K-S goodness of fit test of measured corrosion test variables from concrete samples (a) half-cell potential (b) cell current and (c)corrosion rate

The choice of corrosion rate for detailing corrosion conditionin the samples instead of corrosion potential that the test dataalso followed theWeibull model was due to the identificationfrom [49] that the corrosion potential gives poor indicationof absolute corrosion activity

32 Admixture Performance and Inhibition Efficiency Esti-mations The Weibull mean corrosion rate was employedfor interpreting levels of corrosion degree as per [16 3550] and estimating averaged inhibition efficiency of theduplicated samples of admixed reinforced concrete relativeto the duplicated blank samples in each test medium Theresults of admixture performance from these are presented in

Figure 4 in ranking order of effectiveness of the admixturesat inhibiting concrete steel-rebar corrosion in each of theaggressive test environments The use of delineating linesof requisite levels of corrosion degree interpretations from[16 35 50] was employed in the parts of the plots in Figure 4involving rankings of the corrosion rate performance of thestudied admixture concentrations The results of admixtureperformance ranking in Figure 4(a) showed that the blanksamples without admixture in the NaCl medium exhibitedcorrosion rate that was higher than the upper bound of ldquoveryhighrdquo degree of corrosion rate 01 le CR (mmy) lt 1 as per[16 35 50] This supports the inference that the degree ofcorrosion rate in these blank samples in NaCl medium was

Advances in Materials Science and Engineering 7

Very high

0

1

2

3

4

5

6

7

8

9

10C

orro

sion

rate

(mm

y)

Admixture

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(a)

Admixture

946 922 909 894 894849

765717 708

00

minus10

0

10

20

30

40

50

60

70

80

90

100

Inhi

bitio

n effi

cien

cy120578

()

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(b)

Admixture

Low ormoderate

High

0

005

01

015

02

025

03

035

04

Cor

rosio

n ra

te (m

my

)

2g

NaN

O2+6

gTE

A

4g

TEA

4g

NaN

O2

2g

TEA

Blan

k

2g

NaN

O2

6g

NaN

O2+2

gTE

A

4g

NaN

O2+4

gTE

A

6g

TEA

6g

NaN

O2

(c)

Admixture

647

322308 302

minus351

minus490minus543

minus555

minus80

minus60

minus40

minus20

0

20

40

60

80

Inhi

bitio

n effi

cien

cy120578

()

minus03minus116

2g

NaN

O2+6

gTE

A4

gTE

A4

gN

aNO

2

2g

TEA

Blan

k2

gN

aNO

2

6g

NaN

O2+2

gTE

A4

gN

aNO

2+4

gTE

A6

gTE

A6

gN

aNO

2

(d)

Figure 4 Performance effectiveness ranking of admixtures at inhibiting concrete steel-rebar corrosion in concrete immersed in aggressivemedia for ninety-six days of experimental period (a) corrosion rate ranking in NaCl medium (b) inhibition efficiency ranking in NaClmedium (c) corrosion rate ranking in H

2SO4medium and (d) inhibition efficiency ranking in H

2SO4medium

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 5: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

Advances in Materials Science and Engineering 5

Blan

kBl

ank_

Dup

Admixtures in concrete

Low (lt10)IntermediateSevere

0

200

400

600

800

NaCl

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

upPote

ntia

l (minus

mV

vers

us C

SE)

H2SO4

(a)

Admixtures in concreteNaCl

0

200

400

600

800

1000

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Curr

ent (minus120583

A)

H2SO4

(b)

Admixtures in concreteNaCl

0

2

4

6

8

10

12

Cor

rosio

n ra

te (m

my

)

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

2

6g

NaN

O2_D

up4

gN

aNO

2

4g

NaN

O2_D

up2

gN

aNO

2

2g

NaN

O2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(c)

Figure 2Weibullmeanmodels of the electrochemical test data of steel-reinforced concrete samples immersed in aggressivemedia for ninety-six days of experimental period (a) half-cell potential (with corrosion risk levels as per ASTM C876-91 R99 [36]) (b) cell current and (c)corrosion rate

be deduced that all datasets of the half-cell potential fromthe duplicated concrete samples studied scattered like theWeibull probability distribution function see Figure 3(a)However the cell current datasets of the 4 g TEA the 2 gTEA and the synergistic 2 gNaNO

2+ 6 gTEA admixed steel-

reinforced concrete samples in the H2SO4medium were not

distributed like the Weibull fitting function see Figure 3(b)All the other datasets of measured test variables from the

reinforced concrete samples follow the Weibull probability

distribution function By this the entire corrosion ratedatasets measured from the duplicated samples of steel-reinforced concretes considered in the study also followed theWeibull probability distribution function according to the K-S GoF test criteria (see Figure 3(c))These in line with ASTMG16-95 R04 [41] support the use of the Weibull analysesof the mean of the corrosion rate test data from the steelreinforced concrete samples for representing the prevailingcorrosion conditions in each of the corrosive test systems

6 Advances in Materials Science and Engineering

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(a)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Kolm

ogor

ov-S

mirn

ovP

val

ue

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(b)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(c)

Figure 3 K-S goodness of fit test of measured corrosion test variables from concrete samples (a) half-cell potential (b) cell current and (c)corrosion rate

The choice of corrosion rate for detailing corrosion conditionin the samples instead of corrosion potential that the test dataalso followed theWeibull model was due to the identificationfrom [49] that the corrosion potential gives poor indicationof absolute corrosion activity

32 Admixture Performance and Inhibition Efficiency Esti-mations The Weibull mean corrosion rate was employedfor interpreting levels of corrosion degree as per [16 3550] and estimating averaged inhibition efficiency of theduplicated samples of admixed reinforced concrete relativeto the duplicated blank samples in each test medium Theresults of admixture performance from these are presented in

Figure 4 in ranking order of effectiveness of the admixturesat inhibiting concrete steel-rebar corrosion in each of theaggressive test environments The use of delineating linesof requisite levels of corrosion degree interpretations from[16 35 50] was employed in the parts of the plots in Figure 4involving rankings of the corrosion rate performance of thestudied admixture concentrations The results of admixtureperformance ranking in Figure 4(a) showed that the blanksamples without admixture in the NaCl medium exhibitedcorrosion rate that was higher than the upper bound of ldquoveryhighrdquo degree of corrosion rate 01 le CR (mmy) lt 1 as per[16 35 50] This supports the inference that the degree ofcorrosion rate in these blank samples in NaCl medium was

Advances in Materials Science and Engineering 7

Very high

0

1

2

3

4

5

6

7

8

9

10C

orro

sion

rate

(mm

y)

Admixture

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(a)

Admixture

946 922 909 894 894849

765717 708

00

minus10

0

10

20

30

40

50

60

70

80

90

100

Inhi

bitio

n effi

cien

cy120578

()

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(b)

Admixture

Low ormoderate

High

0

005

01

015

02

025

03

035

04

Cor

rosio

n ra

te (m

my

)

2g

NaN

O2+6

gTE

A

4g

TEA

4g

NaN

O2

2g

TEA

Blan

k

2g

NaN

O2

6g

NaN

O2+2

gTE

A

4g

NaN

O2+4

gTE

A

6g

TEA

6g

NaN

O2

(c)

Admixture

647

322308 302

minus351

minus490minus543

minus555

minus80

minus60

minus40

minus20

0

20

40

60

80

Inhi

bitio

n effi

cien

cy120578

()

minus03minus116

2g

NaN

O2+6

gTE

A4

gTE

A4

gN

aNO

2

2g

TEA

Blan

k2

gN

aNO

2

6g

NaN

O2+2

gTE

A4

gN

aNO

2+4

gTE

A6

gTE

A6

gN

aNO

2

(d)

Figure 4 Performance effectiveness ranking of admixtures at inhibiting concrete steel-rebar corrosion in concrete immersed in aggressivemedia for ninety-six days of experimental period (a) corrosion rate ranking in NaCl medium (b) inhibition efficiency ranking in NaClmedium (c) corrosion rate ranking in H

2SO4medium and (d) inhibition efficiency ranking in H

2SO4medium

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 6: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

6 Advances in Materials Science and Engineering

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(a)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Kolm

ogor

ov-S

mirn

ovP

val

ue

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

H2SO4

(b)

Admixtures in concreteNaCl

120572 = 0050

0102030405060708091

Blan

kBl

ank_

Dup

6g

NaN

O2+2

g TE

A6

gN

aNO

2+2

gTE

A_D

up4

gN

aNO

2+4

gTE

A4

gN

aNO

2+4

gTE

A_D

up2

gN

aNO

2+6

gTE

A2

gN

aNO

2+6

gTE

A_D

up6

gN

aNO

26

gN

aNO

2_D

up4

gN

aNO

24

gN

aNO

2_D

up2

gN

aNO

22

gN

aNO

2_D

up2

gTE

A2

gTE

A_D

up4

gTE

A4

gTE

A_D

up6

gTE

A6

gTE

A_D

up

Kolm

ogor

ov-S

mirn

ovP

val

ue

H2SO4

(c)

Figure 3 K-S goodness of fit test of measured corrosion test variables from concrete samples (a) half-cell potential (b) cell current and (c)corrosion rate

The choice of corrosion rate for detailing corrosion conditionin the samples instead of corrosion potential that the test dataalso followed theWeibull model was due to the identificationfrom [49] that the corrosion potential gives poor indicationof absolute corrosion activity

32 Admixture Performance and Inhibition Efficiency Esti-mations The Weibull mean corrosion rate was employedfor interpreting levels of corrosion degree as per [16 3550] and estimating averaged inhibition efficiency of theduplicated samples of admixed reinforced concrete relativeto the duplicated blank samples in each test medium Theresults of admixture performance from these are presented in

Figure 4 in ranking order of effectiveness of the admixturesat inhibiting concrete steel-rebar corrosion in each of theaggressive test environments The use of delineating linesof requisite levels of corrosion degree interpretations from[16 35 50] was employed in the parts of the plots in Figure 4involving rankings of the corrosion rate performance of thestudied admixture concentrations The results of admixtureperformance ranking in Figure 4(a) showed that the blanksamples without admixture in the NaCl medium exhibitedcorrosion rate that was higher than the upper bound of ldquoveryhighrdquo degree of corrosion rate 01 le CR (mmy) lt 1 as per[16 35 50] This supports the inference that the degree ofcorrosion rate in these blank samples in NaCl medium was

Advances in Materials Science and Engineering 7

Very high

0

1

2

3

4

5

6

7

8

9

10C

orro

sion

rate

(mm

y)

Admixture

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(a)

Admixture

946 922 909 894 894849

765717 708

00

minus10

0

10

20

30

40

50

60

70

80

90

100

Inhi

bitio

n effi

cien

cy120578

()

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(b)

Admixture

Low ormoderate

High

0

005

01

015

02

025

03

035

04

Cor

rosio

n ra

te (m

my

)

2g

NaN

O2+6

gTE

A

4g

TEA

4g

NaN

O2

2g

TEA

Blan

k

2g

NaN

O2

6g

NaN

O2+2

gTE

A

4g

NaN

O2+4

gTE

A

6g

TEA

6g

NaN

O2

(c)

Admixture

647

322308 302

minus351

minus490minus543

minus555

minus80

minus60

minus40

minus20

0

20

40

60

80

Inhi

bitio

n effi

cien

cy120578

()

minus03minus116

2g

NaN

O2+6

gTE

A4

gTE

A4

gN

aNO

2

2g

TEA

Blan

k2

gN

aNO

2

6g

NaN

O2+2

gTE

A4

gN

aNO

2+4

gTE

A6

gTE

A6

gN

aNO

2

(d)

Figure 4 Performance effectiveness ranking of admixtures at inhibiting concrete steel-rebar corrosion in concrete immersed in aggressivemedia for ninety-six days of experimental period (a) corrosion rate ranking in NaCl medium (b) inhibition efficiency ranking in NaClmedium (c) corrosion rate ranking in H

2SO4medium and (d) inhibition efficiency ranking in H

2SO4medium

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 7: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

Advances in Materials Science and Engineering 7

Very high

0

1

2

3

4

5

6

7

8

9

10C

orro

sion

rate

(mm

y)

Admixture

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(a)

Admixture

946 922 909 894 894849

765717 708

00

minus10

0

10

20

30

40

50

60

70

80

90

100

Inhi

bitio

n effi

cien

cy120578

()

6g

NaN

O2

4g

NaN

O2+4

gTE

A

2g

NaN

O2

4g

NaN

O2

2g

NaN

O2+6

gTE

A

2g

TEA

6g

NaN

O2+2

gTE

A

6g

TEA

4g

TEA

Blan

k

(b)

Admixture

Low ormoderate

High

0

005

01

015

02

025

03

035

04

Cor

rosio

n ra

te (m

my

)

2g

NaN

O2+6

gTE

A

4g

TEA

4g

NaN

O2

2g

TEA

Blan

k

2g

NaN

O2

6g

NaN

O2+2

gTE

A

4g

NaN

O2+4

gTE

A

6g

TEA

6g

NaN

O2

(c)

Admixture

647

322308 302

minus351

minus490minus543

minus555

minus80

minus60

minus40

minus20

0

20

40

60

80

Inhi

bitio

n effi

cien

cy120578

()

minus03minus116

2g

NaN

O2+6

gTE

A4

gTE

A4

gN

aNO

2

2g

TEA

Blan

k2

gN

aNO

2

6g

NaN

O2+2

gTE

A4

gN

aNO

2+4

gTE

A6

gTE

A6

gN

aNO

2

(d)

Figure 4 Performance effectiveness ranking of admixtures at inhibiting concrete steel-rebar corrosion in concrete immersed in aggressivemedia for ninety-six days of experimental period (a) corrosion rate ranking in NaCl medium (b) inhibition efficiency ranking in NaClmedium (c) corrosion rate ranking in H

2SO4medium and (d) inhibition efficiency ranking in H

2SO4medium

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 8: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

8 Advances in Materials Science and Engineering

in the very severe level which is an important requirementprescribed by [42] even as this finds agreements with theHCP interpretation as per ASTM C876-91 R99 [36] for theseblank samples in Figure 2(a) Also the admixture perfor-mance rankings in Figure 4(a) and Figure 4(b) reaffirmedhigh effectiveness of the NaNO

2admixtures at inhibiting

steel-rebar corrosion in concrete immersed in the aggressivesalinemarine simulating environments However in thishighly corrosive NaCl medium the effective 6 g NaNO

2

admixture with inhibition efficiency 120578 = 946 was fol-lowed closely in ranking order by the equal-mass synergisticcombination of the 4 g NaNO

2+ 4 g C

6H15NO3admixture

This synergistic admixture has inhibition efficiency 120578 =922 which compares well with that obtained from the6 g NaNO

2admixture and which surpasses other NaNO

2

admixtures studied in effectiveness By corrosion rate inter-pretations from [16 35 50] in Figure 4(a) both the 6 gNaNO

2

and the 4 g NaNO2+ 4 g C

6H15NO3admixtures mitigated

steel-rebar corrosion from the very severe corrosion in theblank samples to well below the upper bound of ldquoveryhighrdquo corrosion Also consideration of the half-cell potentialtrends in Figure 2(a) showed that duplicate concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture exhibited lower

probability of corrosion risks than the duplicate concretesamples with 6 g NaNO

2admixtures Also the cell current

trends in Figure 2(b) showed that the concrete sampleswith 4 g NaNO

2+ 4 g C

6H15NO3admixture find better

agreements in lowered trends of reinforcing steel dissolutionactivities than those obtained from concrete samples with 6 gNaNO

2admixture These agreements from electrochemical

test results by different instruments strongly suggest suitabil-ity of this synergistic combination of NaNO

2and C

6H15NO3

for reducing environmental effects due to lower usage ofNaNO

2as inhibitor of steel-rebar corrosion inNaClmedium

From the consideration of the admixture performancein this study it could also be inferred that multiplica-tive NaNO

2-mass amount would be required for suitable

C6H15NO3-mass that would synergistically combine with

NaNO2admixture in order to attain inhibition performance

that compares with that of the individual NaNO2that was

initially reduced for the synergistic combination model Aspecific example from this study includes the 4 g NaNO

2

(a 2 g NaNO2+ 2 g NaNO

2amount) which was modelled

with the same inhibition efficiency 120578 = 894 as that ofthe synergistic 2 g NaNO

2+ 6 g C

6H15NO3in the NaCl

medium see Figure 4(a) This constitutes triplication of the2 g NaNO

2part as the 6 g C

6H15NO3part for attaining

the same inhibition effectiveness as the individual NaNO2

that was initially reduced for the synergy in the NaCl testmedium

The admixture performance ranking in Figure 4(c)showed that the blank samples without admixture in theH2SO4medium exhibited corrosion rate that was higher

than the upper bound of ldquohighrdquo degree of corrosion rate001 le CR (mmy) lt 01 according to [16 35 50] Thiscorrosion rate classification also finds agreements with theHCP interpretation for the blank samples in H

2SO4medium

that was also in the ldquohigh (gt90) corrosion riskrdquo region asper ASTMC876-91 R99 [36] in Figure 2(a) In furtherance of

this the admixture performance rankings in Figure 4(c) andFigure 4(d) also identified many of the NaNO

2admixtures

with good effectiveness at mitigating steel-rebar corrosion inthe H

2SO4medium However the NaNO

2admixtures were

all surpassed in effectiveness at inhibiting concrete steel-rebarcorrosion by the 2 g NaNO

2+ 6 g C

6H15NO3synergistic

admixture In this medium it is only the corrosion rate of the2 g NaNO

2+ 6 g C

6H15NO3synergistic admixture that was

classified as below the upper bound of the ldquohighrdquo degree ofcorrosion rate as per [16 35 50] in Figure 4(c)This evaluatedto the inhibition efficiency of 120578 = 647 by the 2 g NaNO

2

+ 6 g C6H15NO3synergistic admixture which indicated that

the 2 g NaNO2and the 6 g C

6H15NO3combined to improve

effectiveness of one another at inhibiting rebar corrosion inH2SO4 Also other trends of electrochemical test variables

identified the 2 g NaNO2+ 6 g C

6H15NO3admixed concrete

with lower probability of corrosion risk in Figure 2(a) andlesser steel-rebar dissolution activity in Figure 2(b) thanthose of the blank samples in the acidic medium Theadmixture of proximate effectiveness to the 2 g NaNO

2+

6 g C6H15NO3synergistic admixture at inhibiting steel-rebar

corrosion includes the 4 g C6H15NO3(120578 = 322) followed by

the 4 g NaNO2(120578 = 308) But these individual admixtures

exhibited much higher corrosion rates which translated tomuch lower corrosion inhibition effectiveness than the 120578 =647 inhibition effectiveness performance by the 2 gNaNO

2

+ 6 g C6H15NO3synergistic admixtureThese considerations

support the suitability of the 2 g NaNO2+ 6 g C

6H15NO3

admixture as optimal admixture and synergistic combinationof NaNO

2and C

6H15NO3for inhibiting steel-rebar corro-

sion in acidic microbialindustrial simulating environmentstudied And by this also the synergistic 2 g NaNO

2+ 6 g

C6H15NO3admixture exhibits potency of higher reduction

of NaNO2admixture usage in concretes immersed in H

2SO4

medium However the other synergistic admixtures exhib-ited aggravations of concrete steel-rebar corrosion in theacidic medium instead of corrosion inhibition This fostersinterests on the mode of synergistic interactions betweenthe NaNO

2and C

6H15NO3combinations constituting these

synergistic partial NaNO2replacement admixtures

33 Synergistic Parameter Modelling Results of synergisticparameter modelling of the combinations of NaNO

2and

C6H15NO3(TEA) admixtures in the steel reinforced con-

cretes studied are plotted in Figure 5 This figure identifiedthe 4 g NaNO

2+ 4 g C

6H15NO3and the 2 g NaNO

2+

6 g C6H15NO3admixtures with optimal performance of

synergistic parameter in their respective NaCl and H2SO4

media It could also be noted from the figure that the 2 gNaNO

2+ 6 g C

6H15NO3also exhibited high synergistic

parameter performance in the NaCl medium Interpretationsfrom [27 28] showed that the 4 g NaNO

2+ 4 g C

6H15NO3

with synergistic parameter S = 397 and the 2 g NaNO2+ 6 g

C6H15NO3with S= 242 exhibited prevalent synergistic inter-

action S gt 1 between NaNO2and C

6H15NO3admixtures in

the NaCl medium Also application of similar interpretationshowed that the 2 g NaNO

2+ 6 g C

6H15NO3with S =

119 exhibited prevalent synergistic interaction in the H2SO4

medium According to [27 28] these prevalent synergistic

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 9: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

Advances in Materials Science and Engineering 9

S = 1

0

05

1

15

2

25

3

35

4

45

Syne

rgist

ic p

aram

eter

S

AdmixtureNaCl mediumH2SO4 medium

2g

NaN

O2+6

gTE

A

4g

NaN

O2+4

gTE

A

6g

NaN

O2+2

gTE

A

Figure 5 Synergistic interaction modelling NaNO2and C

6H15NO3

(TEA) admixtures on steel-rebar corrosion

interactions indicate cooperative adsorption of the NaNO2

and C6H15NO3on the steel-rebar especially according to the

schematic representation presented in [27] That schematicsynergisticmechanism in [27] suggested the adsorption of thehighly effective NaNO

2on the steel-rebar surface while the

C6H15NO3adsorbed on the layer of the NaNO

2adsorption

at the same sites of the embedded steel-rebar in concreteIt is especially worth noting that the synergistic admixturesthat exhibited the mechanism of cooperative adsorption astheir prevalent synergistic interaction in this study were theadmixtures that were found suitable for reducing NaNO

2

usage as inhibitor in their testmediaThe improved inhibitionefficiency from the 4 g NaNO

2+ 4 g C

6H15NO3admixture

in the NaCl medium and the 2 g NaNO2+ 6 g C

6H15NO3

admixture in the NaCl and H2SO4media relative to their

individual admixtureswere due to the synergistic interactionsbetween these admixtures

The other remaining synergistic admixtures in bothmedia exhibited the synergistic mechanism of antagonisticinteractions by their synergistic parameter S lt 1 betweenthe NaNO

2and C

6H15NO3admixtures in their respective

environments According to [27 28] these synergistic mech-anisms of antagonistic interactions are due to competitiveadsorption of the NaNO

2and C

6H15NO3on the steel-

rebar This synergistic interaction of competitive adsorptionindicates that the NaNO

2and the C

6H15NO3admixtures

adsorb at different sites on the steel-rebar surface It is alsoworth noting that the admixture combinations exhibitingthis kind of antagonistic interaction in this study were notalso found suitable for inhibiting steel-rebar corrosion intheir admixed concretes immersed in their respective testmedia The comparatively low inhibition efficiency from the4 g NaNO

2+ 4 g C

6H15NO3in the H

2SO4and the 6 g

NaNO2

+ 2 g C6H15NO3

admixture in the NaCl and

the H2SO4relative to their individual admixtures were due

to the antagonistic interaction between the admixtures

4 Conclusions

The effect of NaNO2and C

6H15NO3synergistic admixtures

in concrete slab immersed in the aggressive NaCl and H2SO4

environments on the corrosion of the embedded concretesteel-rebar had been studied in this work Conclusions thatcould be drawn from these include the following

(i) The statistical analyses of electrochemical test resultsidentified in agreements the prevalence of corrosiveactivities in the sodium chloride medium above thatoccurring in the sulphuric acid test medium acrossall the concentrations of admixtures studied theseelectrochemical test results also showed that both ofthe NaCl and H

2SO4test media employed constitute

aggressive environments especially to concrete steel-rebar in blank concrete samples not having inhibitoradmixture

(ii) Although many of the NaNO2admixtures exhibited

good effectiveness at inhibiting steel-rebar corrosionin both media inhibition efficiency (120578) modellingsupports the combined usage of 4 g NaNO

2+ 4 g

C6H15NO3admixture with 120578 = 922 as effective

synergistic inhibitor of steel-rebar corrosion in steel-reinforced concrete immersed in the NaCl mediumwhile the combination of 2 g NaNO

2+ 6 g C

6H15NO3

admixture with inhibition efficiency 120578 = 647was found suitable as effective synergistic inhibitorof steel-rebar corrosion in steel-reinforced concreteimmersed in H

2SO4medium

(iii) Synergistic parameter modelling identified the 4 gNaNO

2+ 4 g C

6H15NO3admixture 119878 = 397

and the 2 g NaNO2+ 6 g C

6H15NO3admixture

S = 242 with prevalent synergistic interaction ofcooperative adsorption on steel-rebar between theNaNO

2and C

6H15NO3synergistic admixtures in the

NaCl medium while the 2 g NaNO2+ 6 g C

6H15NO3

admixture exhibited this kind of prevalent synergisticinteraction of cooperative adsorption on steel-rebarS = 119 in the H

2SO4medium

(iv) All the synergistic admixtures exhibiting prevalentsynergistic interaction of cooperative adsorption onsteel-rebar in the study were also highly effec-tive at inhibiting concrete steel-rebar corrosion intheir corrosive media of test immersions Thesestrongly support suitability of requisite concentrationof C6H15NO3as additive admixture with sodium

nitrite for inhibiting steel-rebar corrosion in concreteimmersed in NaCl and H

2SO4corrosive media This

is potent with the additional advantage of reducedenvironmental effects due to lower NaNO

2usage as

corrosion inhibitor admixture in concrete designedfor the aggressive service environments studied

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 10: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

10 Advances in Materials Science and Engineering

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] F-L Fei J Hu J-X Wei Q-J Yu and Z-S Chen ldquoCorrosionperformance of steel reinforcement in simulated concrete poresolutions in the presence of imidazoline quaternary ammoniumsalt corrosion inhibitorrdquo Construction and Building Materialsvol 70 pp 43ndash53 2014

[2] J O Okeniyi O A Omotosho O O Ajayi and C A LotoldquoEffect of potassium-chromate and sodium-nitrite on concretesteel-rebar degradation in sulphate and salinemediardquoConstruc-tion and Building Materials vol 50 pp 448ndash456 2014

[3] S L Rodrıguez Reyna J M Miranda Vidales C GaonaTiburcio L Narvaez Hernandez and L S Hernandez ldquoStateof corrosion of rebars embedded in mortar specimens after anelectrochemical chloride removalrdquo Portugaliae ElectrochimicaActa vol 28 no 3 pp 153ndash164 2010

[4] L Sadowski ldquoMethodology for assessing the probability of cor-rosion in concrete structures on the basis of half-cell potentialand concrete resistivity measurementsrdquo The Scientific WorldJournal vol 2013 Article ID 714501 8 pages 2013

[5] A Krolikowski and J Kuziak ldquoImpedance study on calciumnitrite as a penetrating corrosion inhibitor for steel in concreterdquoElectrochimica Acta vol 56 no 23 pp 7845ndash7853 2011

[6] L Bertolini ldquoSteel corrosion and service life of reinforcedconcrete structuresrdquo Structure and Infrastructure Engineeringvol 4 no 2 pp 123ndash137 2008

[7] Z Cao M Hibino and H Goda ldquoEffect of nitrite ions on steelcorrosion induced by chloride or sulfate ionsrdquo InternationalJournal of Corrosion vol 2013 Article ID 853730 16 pages 2013

[8] L Adelaide B Richard F Ragueneau and C Cremona ldquoAsimplified numerical approach of global behaviour of RC beamsdegraded by corrosionrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 414ndash439 2012

[9] N Ukrainczyk I B Pecur andN Bolf ldquoEvaluating rebar corro-sion damage in RC structures exposed to marine environmentusing neural networkrdquo Civil Engineering and EnvironmentalSystems vol 24 no 1 pp 15ndash32 2007

[10] H Gerengi Y Kocak A Jazdzewska M Kurtay and HDurgun ldquoElectrochemical investigations on the corrosionbehaviour of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sulphuric acidrdquo Constructionand Building Materials vol 49 pp 471ndash477 2013

[11] M A G Tommaselli N A Mariano and S E Kuri ldquoEffec-tiveness of corrosion inhibitors in saturated calcium hydroxidesolutions acidified by acid rain componentsrdquo Construction andBuilding Materials vol 23 no 1 pp 328ndash333 2009

[12] E Hewayde M L Nehdi E Allouche and G Nakhla ldquoUsingconcrete admixtures for sulphuric acid resistancerdquo Proceedingsof the Institution of Civil EngineersmdashConstructionMaterials vol160 no 1 pp 25ndash35 2007

[13] B Richard M Quiertant V Bouteiller L Adelaide J-L Tail-han and C Cremona ldquoInfluence of accelerated corrosion onthe reinforced cover concrete cracking behavior experimentaland numerical studyrdquo European Journal of Environmental andCivil Engineering vol 16 no 3-4 pp 450ndash459 2012

[14] J O Okeniyi I O Oladele I J Ambrose et al ldquoAnalysisof inhibition of concrete steel-rebar corrosion by Na

2Cr2O7

concentrations implications for conflicting reports on inhibitoreffectivenessrdquo Journal of Central South University vol 20 no 12pp 3697ndash3714 2013

[15] M B Valcarce and M Vazquez ldquoCarbon steel passivity exam-ined in alkaline solutions the effect of chloride and nitrite ionsrdquoElectrochimica Acta vol 53 no 15 pp 5007ndash5015 2008

[16] T A Soylev and M G Richardson ldquoCorrosion inhibitorsfor steel in concrete state-of-the-art reportrdquo Construction andBuilding Materials vol 22 no 4 pp 609ndash622 2008

[17] A M Vaysburd and P H Emmons ldquoCorrosion inhibitorsand other protective systems in concrete repair concepts ormisconceptsrdquo Cement and Concrete Composites vol 26 no 3pp 255ndash263 2004

[18] M Aoyama S Miyazato and M Kawamura ldquoProtection ofsteel corrosion in concrete members by the combination ofgalvanic anode and nitrite penetrationrdquo International Journal ofCorrosion vol 2014 Article ID 618280 11 pages 2014

[19] J O Okeniyi C A Loto and A P I Popoola ldquoRhizophoramangle L effects on steel-reinforced concrete in 05M H

2SO4

implications for corrosion-degradation of wind-energy struc-tures in industrial environmentsrdquo Energy Procedia vol 50 pp429ndash436 2014

[20] L Feng H Yang and F Wang ldquoExperimental and theoreticalstudies for corrosion inhibition of carbon steel by imida-zoline derivative in 5 NaCl saturated Ca(OH)

2solutionrdquo

Electrochimica Acta vol 58 no 1 pp 427ndash436 2011[21] M Ormellese L Lazzari S Goidanich G Fumagalli and

A Brenna ldquoA study of organic substances as inhibitors forchloride-induced corrosion in concreterdquo Corrosion Science vol51 no 12 pp 2959ndash2968 2009

[22] I Carrillo B Valdez R ZlatevM StoychevaM Schorr andMCarrillo ldquoCorrosion inhibition of the galvanic couple copper-carbon steel in reverse osmosis waterrdquo International Journal ofCorrosion vol 2011 Article ID 856415 7 pages 2011

[23] ASTM G109-99a Standard Test Method for Determining theEffects of Chemical Admixtures on the Corrosion of EmbeddedSteel Reinforcement in Concrete Exposed to Chloride Environ-ments ASTM International West Conshohocken Pa USA2004

[24] S Muralidharan V Saraswathy S P M Nima and NPalaniswamy ldquoEvaluation of a composite corrosion inhibitingadmixtures and its performance in Portland pozzolana cementrdquoMaterials Chemistry and Physics vol 86 no 2-3 pp 298ndash3062004

[25] A K Singh S K Shukla M A Quraishi and E EEbenso ldquoInvestigation of adsorption characteristics of NN1015840-[(methylimino)dimethylidyne]di-24-xylidine as corrosioninhibitor at mild steelsulphuric acid interfacerdquo Journal ofthe Taiwan Institute of Chemical Engineers vol 43 no 3 pp463ndash472 2012

[26] F H Haynie ldquoStatistical treatment of data data interpretationand reliabilityrdquo in Corrosion Tests and Standards Applicationand Interpretation R Baboian Ed pp 83ndash88 ASTM Interna-tional West Conshohocken Pa USA 2nd edition 2005

[27] A S Fouda M Abdallah and A A Attia ldquoInhibition of carbonsteel corrosion by some cyanoacetohydrazide derivatives inHCL solutionrdquo Chemical Engineering Communications vol 197no 8 pp 1091ndash1108 2010

[28] Q Qu S Jiang W Bai and L Li ldquoEffect of ethylenediaminetetraacetic acid disodium on the corrosion of cold rolledsteel in the presence of benzotriazole in hydrochloric acidrdquoElectrochimica Acta vol 52 no 24 pp 6811ndash6820 2007

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 11: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

Advances in Materials Science and Engineering 11

[29] ASTM International ASTM C192192M-02 Standard Practicefor Naking and Curing Concrete Test Specimens in the Labora-tory ASTM International West Conshohocken Pa USA 2005

[30] X Zhou H Yang and FWang ldquoInvestigation on the inhibitionbehavior of a pentaerythritol glycoside for carbon steel in 35NaCl saturated Ca(OH)

2solutionrdquo Corrosion Science vol 54

no 1 pp 193ndash200 2012[31] M M Mennucci E P Banczek P R P Rodrigues and I

Costa ldquoEvaluation of benzotriazole as corrosion inhibitor forcarbon steel in simulated pore solutionrdquo Cement amp ConcreteComposites vol 31 no 6 pp 418ndash424 2009

[32] J O Okeniyi O A Omotosho O O Ajayi O O Jamesand C A Loto ldquoModelling the performance of sodium nitriteand aniline as inhibitors in the corrosion of steel-reinforcedconcreterdquoAsian Journal of Applied Sciences vol 5 no 3 pp 132ndash143 2012

[33] O A Omotosho C A Loto O O Ajayi and J O OkeniyildquoAniline effect on concrete steel rebar degradation in salineand sulfatemediardquoAgricultural Engineering International CIGRJournal vol 13 no 2 Manuscript no 1830 17 pages 2011

[34] H-W Song and V Saraswathy ldquoCorrosion monitoring ofreinforced concrete structures a reviewrdquo International Journalof Electrochemical Science vol 2 no 1 pp 1ndash28 2007

[35] S G Millard D Law J H Bungey and J Cairns ldquoEnvi-ronmental influences on linear polarisation corrosion ratemeasurement in reinforced concreterdquo NDT amp E Internationalvol 34 no 6 pp 409ndash417 2001

[36] ASTM ldquoStandard test method for half-cell potentials ofuncoated reinforcing steel in concreterdquo ASTM C876-91 R99ASTM International Conshohocken Pa USA 2004

[37] G E Abdelaziz A M K Abdelalim and Y A Fawzy ldquoEvalua-tion of the short and long-term efficiencies of electro-chemicalchloride extractionrdquo Cement amp Concrete Research vol 39 no 8pp 727ndash732 2009

[38] S Jaggi H Bohni and B Elsener ldquoMacrocell corrosion ofsteel in concrete-experimental and numerical modellingrdquo inProceedings of the Eurocorr Riva di Garda Italy 2001

[39] W J McCarter and Oslash Vennesland ldquoSensor systems for usein reinforced concrete structuresrdquo Construction and BuildingMaterials vol 18 no 6 pp 351ndash358 2004

[40] V S SastriGreenCorrosion InhibitorsTheory andPractice JohnWiley amp Sons Hoboken NJ USA 2011

[41] ASTM International ldquoStandard guide for applying statisticsto analysis of corrosion datardquo ASTM G16-95 R04 ASTMInternational West Conshohocken Pa USA 2005

[42] P R Roberge ldquoStatistical interpretation of corrosion testresultsrdquo in Corrosion Fundamentals Testing and Protection SD Cramer and B S Covino Jr Eds vol 13A ofASMHandbookpp 425ndash429 ASM International Materials Park Ohio USA2003

[43] J O Okeniyi ldquoC10H18N2Na2O10

inhibition and adsorptionmechanism on concrete steel-reinforcement corrosion in cor-rosive environmentsrdquo Journal of the Association of Arab Univer-sities for Basic and Applied Sciences 2014

[44] R-D Reiss and M Thomas Statistical Analysis of ExtremeValues Birkhauser Basel Switzerland 3rd edition 2007

[45] J O Okeniyi and E T Okeniyi ldquoImplementation ofKolmogorov-Smirnov p-value computation in Visual Basicimplication for Microsoft Excel library functionrdquo Journal ofStatistical Computation and Simulation vol 82 pp 1727ndash17412012

[46] D Izquierdo C Alonso C Andrade andM Castellote ldquoPoten-tiostatic determination of chloride threshold values for rebardepassivation experimental and statistical studyrdquo Electrochim-ica Acta vol 49 no 17-18 pp 2731ndash2739 2004

[47] J O Okeniyi C A Loto and A P I Popoola ldquoElectrochemicalperformance of Anthocleista djalonensis on steel reinforcementcorrosion in concrete immersed in salinemarine simulatingenvironmentrdquo Transactions of the Indian Institute of Metals vol67 no 6 pp 959ndash969 2014

[48] J O Okeniyi S O Okpala O M Omoniyi I O Oladele C ALoto and A P I Popoola ldquoMethods of ASTMG16 and conflictsin corrosion test data case study of NaNO

2effectiveness on

steel-rebar corrosionrdquo Canadian Journal of Pure and ApliedSciences vol 7 no 13 pp 2589ndash2597 2013

[49] N S Berke and M C Hicks ldquoPredicting long-term durabilityof steel reinforced concrete with calcium nitrite corrosioninhibitorrdquoCementampConcrete Composites vol 26 no 3 pp 191ndash198 2004

[50] J H Bungey S G Millard and M G Grantham Testing ofConcrete in Structures Taylor amp Francis New York NY USA4th edition 2006

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Page 12: Effect of NaNO H NO Synergistic Admixtures on Steel-Rebar

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials


Admixtures Final Report

REBAR TYING MACHINES REBAR BENDERS REBAR CUTTERS

Admixtures Presentation1

Concrete Admixtures - libvolume3.xyzlibvolume3.xyz/civil/btech/semester8/advancedconcretetechnology/... · Concrete Admixtures Team Members: ... Chemical Admixtures ... • Shotcrete

7314245 Admixtures

phl.sika.com · PDF fileWater Reducing Admixtures Set Controlling Admixtures Durability Enhancing Admixtures Additives for Grinding Process SIKA

สารผสมเพิ่ม (Admixtures)

Cement Admixtures

Mineral Admixtures

Admixtures for Concrete - College of · PDF fileAir-entraining admixtures Water-reducing admixtures Plasticizers Accelerating admixtures Retarding admixtures ... ASTM C 260 or AASHTO

Product-Catalogue Rebar&Wire-Rod 19May · PRODUCT CATALOGUE | 4 PRODUCT Rebar Rebar In Coil* Rebar Rebar Rebar CS2:20112 BS 4449: 2005 NOTE: * Rebar in coil for BS 4449:2005 specification

Concrete - Additives & Admixtures

Essence of admixtures in concrete - The i-Capital · PDF filecontrolling retarders) used ... While a wide variety of admixtures available to the industry, air admixtures, with set-admixtures

An Overview of Chemical Admixtures for Concreteemail.concrete.org/Education/April/AprilHandout.pdf · An Overview of Chemical Admixtures for Concrete ... •Admixtures for Shotcrete

212.3R-91 Chemical Admixtures for Concrete · 6.4-Bonding admixtures 6.5-Pumping aids 6.6-Coloring admixtures 6.7-Flocculating admixtures 6.8-Fungicidal, germicidal, and insecticidal

Rebar Splicing - Construction Suppliesrichformconstructionsupply.com/.../Rebar-splicing-DS_Bridge_Deck_H… · injuries from rebar protruding from the concrete. ... Rebar Splicing

Sterile Products & admixtures

LECT Admixtures

Concret Admixtures

Admixtures in concrete

2.8 Admixtures

ACI 212.3R-16: Report on Chemical Admixtures for Concrete · PDF fileCHAPTER 7—ACCELERATING ADMIXTURES, p. 19 ... 16.8—Shotcrete admixtures, ... Report on Chemical Admixtures for

New Generation Admixtures

49258386 Admixtures

Cement & Admixtures

Admixtures 8

Iv admixtures PPT

Admixtures Brochure - Euclid Chemicaleuclidchemical.com/fileshare/ELit/Brochures/Admixtures Brochure... · HIGH PERFORMANCE CONCRETE ADMIXTURES AIR ENTRAINERS (ASTM C260) Designed

Chemical Admixtures for Concrete - Egeinsaat.ege.edu.tr/uploads/d399_435_water_reducers.pdfChemical Admixtures for Concrete WATER-REDUCING ADMIXTURES Özge Andiç Çakır, PhD.

Rebar to Rebar Connection for Thermit Welding

Rebar to Rebar Connection for Thermite Welding

apps.web.maine.gov...ANCHOR BOLT CAGE REBAR Hoops PAGE 10 TYING REBAR HOOPS TO INSIDE AND OUTSIDE ANCHOR BOLT CIRCLES REBAR HOOP PLACEMENT PAGE PLACING REBAR HOOPS REBAR HOOPS PAGE

Admixtures for Concrete

4 Chemical Admixtures

Admixtures Olek