effectofcapillarywaterabsorptiononelectricalresistivityof ... · 2021. 5. 3. · according to astm...

Research ArticleEffect of Capillary Water Absorption on Electrical Resistivity ofConcrete with Coal Gangue Ceramsite as Coarse Aggregates

Dong Li Shi Liu and Haiqing Liu

College of Civil Engineering Liaoning Technical University Fuxin Liaoning China

Correspondence should be addressed to Shi Liu liushilntueducn

Received 6 December 2020 Revised 12 April 2021 Accepted 22 April 2021 Published 3 May 2021

Academic Editor Hailing Kong

Copyright copy 2021Dong Li et alampis is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

ampis study intends to access the influence of the capillary action on electrical property of the concrete containing the coal gangueceramsite For this purpose four kinds of concrete samples were prepared the coal gangue ceramsite was adopted at four volumeratios of 0 30 60 and 100 respectivelyampe resistivity of the samples was explored using the two-electrode method duringthe capillary action ampe effects of the coal gangue ceramsite contents on capillary water absorption capacity and resistivity of thematrix were verifiedampe variation of the resistivity of the matrix under the influence of capillary water transmission was analyzedampe results demonstrated that for the unsaturated concrete the resistivity of the matrix increased with the increment of the coalgangue ceramsite dosageampe electrical properties of the concrete were affected noticeably by the capillary water absorption of thematrix the resistivity of the matrix dropped significantly under the capillary suction which may be attributed to the formation ofthe new conductive channels caused by the absorbed water ampe variation of the resistivity of the concrete under the capillarysuction sustained the two-stage reduction curve ampe ability of the capillary water absorption of concrete was enhanced with theaddition of coal gangue ceramsite compared to the traditional aggregates concrete the initial sorptivity and secondary sorptivityof the matrix increased by 47 and 16 with the 100 content of coal gangue ceramsite However during the process of thecapillary suction the resistivity of the coal gangue ceramic concrete was always greater than that of the concrete with traditionalcrushed aggregates

1 Introduction

ampe electrical resistivity of the concrete is generally in therange of 1times 101ndash1times 106Ωmiddotm [1ndash3] In a completely dry statethe concrete can be attributed to insulating material [4]However due to the hydrophilicity of the cement-basedmaterial the water in the surrounding circumstance cantransport to the concrete through capillary action at theserviceability stage [5] ampe ingress of moisture greatly en-hances the electrical properties of the concrete which mayinfluence the progress of corrosion of embedded steel rebarand produce a negative effect on the durability of thestructures [6ndash8] For example the stray current generated bysubways can flow through reinforced concrete and producean alteration of the potential distribution inside the matrixwhich can accelerate the corrosion of the reinforcing bars[9ndash11] In a humid environment the electrical resistivity of

the concrete may decrease due to the capillary water ab-sorption and the negative impact of stray current will beexacerbated Some signaling systems are also affected by theinadequate electrical resistivity of the concrete in the tunnel[12] amperefore the electrical properties of cementitiousmaterials are concerned by some investigators [13ndash17]Noort et al [18] studied the effect of water to cement ratio onthe electrical property of concrete and the results showedthat the electrical conductivity of the matrix increased withthe increase of water to cement ratio Sengul [19] investi-gated the electrical resistivity of concrete with limestoneaggregate and gravel the results showed that the electricalperformance of the matrix was also affected by the type ofaggregates Hussain et al [20] studied the influence of the flyash on the electrical resistivity of the concrete the resultsdemonstrated that the electrical resistivity of the matrixcould be enhanced by 120 with 30 (by mass) of the

HindawiAdvances in Civil EngineeringVolume 2021 Article ID 6623808 12 pageshttpsdoiorg10115520216623808

cement replaced by the fly ash Liang et al [21] suggested anew model for the electrical conductivity of cementitiousmaterial by regarding the pore size distribution Capillarysuction is one of the main ways of water penetration intoconcrete [22ndash27] amperefore the capillary water absorptioncapacity of concrete is an important factor regarding thechanges in the electrical resistivity of the matrix Howeverthe investigations considering the effect of capillary waterabsorption on the electrical resistivity of concrete are stillrare

Coal gangues are solid wastes obtained during coalmining and processing [28 29] A large amount of coalgangue was stored around the coaling areas and there wasabout 5 billion tons of coal gangue stored in Fuxin ChinaMany investigators and engineers focused on the resourceutilization of the coal gangue As an important aspect of theutilization coal gangue ceramsite demonstrates the char-acteristics of light weight and high strength ampe coal gangueceramsite are used as coarse aggregates in concrete for re-ducing the mining of the traditional aggregates [30]Compared with traditional aggregates the coal gangueceramsite has larger porosity and stronger water absorptioncapacityampe addition of coal gangue ceramsite may enhancethe capillary transportability of concrete while from anotherperspective due to the porosity of the coal gangue ceramsitethe resistivity of the matrix may be higher compared totraditional aggregate concrete the higher resistivity of theconcrete contributes to the durability of the structuresamperefore it is necessary to explore the influence of coalgangue ceramsite on the resistivity of concrete in humidenvironment the results may provide a meaningful expe-rience for effectively reducing the negative influence of thestray current in subway

In this paper the capillary water absorption capacity ofthe concrete with the coal gangue ceramsite was studiedaccording to ASTM C1585 [31] the effect of the coal gangueceramsite on sorptivity of the matrix was explored ampeelectrical resistance of the coal gangue ceramsite concretespecimens was measured by the two-electrode method andthe variation of the resistivity of the samples during thecapillary water absorption process was analyzed ampe in-fluence of coal gangue ceramsite on concrete resistivity wasinvestigated ampe combined effects of coal gangue ceramsiteon the capillary water absorption capacity and the electricalresistivity of the concrete were compared

2 Experimental Investigations

21 Materials and Mixture Design In this study OrdinaryPortland cement 425R was used Limestone aggregates withamaximum size of 20mmwere adopted as traditional coarseaggregates and the river sand with fineness modulus of 26was used as fine aggregates ampe specimens with traditionalcoarse aggregates were recorded as PC For coal gangueceramsite concrete the limestone aggregates were replacedby the coal gangue ceramsite (see Figure 1(a)) with 3060 and 100 by volume and the specimens were recordedas CGC30 CGC60 and CGC100 respectively ampe coalgangue ceramsite adopted in the experiment was the

commercial product supplied by the factory in Fuxin China(see Figure 1(b))ampe properties of the coal gangue ceramsiteand the traditional coarse aggregates were illustrated inTable 1 ampe mix proportions of the concrete were shown inTable 2

22 Experimental Procedures For each mixture six cubicspecimens of 100times100times100mm were made ampree of thesamples were prepared for the compressive strength testampecopper meshes were arranged on two sides of the other threesamples during pouring the samples were prepared for thecapillary absorption and electrical resistance experimentsAll the samples were cured for 28 d in the curing room

ampe test equipment included a capillary water absorptiondevice as shown in Figure 2(a) and a two-electrode resis-tance measuring systemampe resistance was measured by theLCR meter (at 100 kHz 4V) as shown in Figure 2(b) ampespecific test steps were as follows (1) all the specimens weredried at 105degC in the thermostatic drying chamber toconstant mass (2) the four sides around the water ab-sorption face of the samples were sealed with epoxy (3) themass and the resistance of the sample were measured in thedry state (4) the sample was placed in the tank with a waterimmersion depth of 2ndash5mm and kept in point contact withthe supports (5) the cumulative water absorbed and theresistance were recorded at different time intervals afterremoving the surface water by a dampened tissue

ampe resistivity of the sample can be obtained by

ρ RA

l (1)

where ρ means the resistivity of the matrix kΩmiddotm R meansthe resistance of the matrix kΩ Ameans the cross-sectionalarea of the sample m2 l means the length of the sample m

3 Results and Discussion

31Compressive Strength In order to verify the effect of coalgangue ceramsite on the compressive strength of concretethe uniaxial compression experiment was conductedaccording to the guidelines [32] ampe values of the com-pressive strength of the specimens at 28 d are shown inFigure 3 For each type the result is the average value of threesamples

From Figure 3 it can be seen that the compressivestrength of the concrete is affected by the coal gangueceramsite ampe values of the PC CGC30 CGC60 andCGC100 are 339MPa 336MPa 321MPa and 305MParespectively Compared to the value of PC the values of theCGC30 CGC60 and CGC100 decrease by 1 5 and 10respectively ampe phenomenon is also observed for theconcrete with untreated coal gangue as coarse aggregates andthe variation trend for the influence of coal gangue oncompressive strength of the concrete agrees with the pre-vious investigation performed by Li et al [33] Zhou et al[34] and Gao et al [35] It means that the compressivestrength of the matrix is not obviously affected with coalgangue ceramsite replacement below 60 the decreasing of

2 Advances in Civil Engineering

(a) (b)

Figure 1 Coal gangue recycling (a) coal gangue ceramsite (b) production workshop

Table 1 Properties of the coarse aggregates

Types Bulk density(kgm3)

Rushing strength(MPa)

Crushed value()

24 h water absorption()

Coefficient ofsoftening LOIa

Coal gangue ceramsite 844 62 mdash 84 098 003Traditional coarseaggregate 1450 mdash 98 08 mdash mdash

aLoss on ignition

Table 2 Mix proportion of the concrete

Types Cement(kgm3)

Limestoneaggregates (kgm3)

Coal gangueceramsite (kgm3)

Fine aggregates(kgm3)

Fly ash(kgm3)

Wateradditionalwater (kgm3)

Superplasticizer(kgm3)

PC 390 850 mdash 850 155 2730 55CGC30 390 595 148 850 155 273124 55CGC60 390 340 297 850 155 273249 55CGC100 390 mdash 495 850 155 273416 55

Concrete

Support

Embedded electrode

Distilled water

(a)

LCR

(b)

Figure 2 Experimental device (a) schematic diagram of water absorption test (b) schematic diagram of electrical resistance test

Advances in Civil Engineering 3

the compressive strength of the matrix is significant with thecoal gangue ceramsite replacement above 60

32CumulativeWaterAbsorptionof Concrete ampe results ofthe cumulative water absorption are illustrated in Figure 4In the plots each curve is the average result of three samples

From Figure 4 it can be seen that the cumulative waterabsorption of the specimens increases with the extension oftime ampe increment rate of the cumulative water absorptionof the matrix is rapid at the initial stage and then slowsgradually In order to compare the influence of coal gangueceramsite on the capillary water absorption performance ofconcrete the cumulative water absorption corresponding tothe time t of 0 360 and 10080min is taken as examples forcomparative analysis ampe cumulative water absorption ofthe specimens is shown in Figure 5

From Figure 5 it can be seen that the cumulative waterabsorption of concrete specimens increases with the increaseof coal gangue ceramsite dosage When the time t is 360minthe cumulative water absorption of PC CGC30 CGC60 andCGC100 is 90 g 106 g 119 g and 118 g Compared to thevalue of PC the cumulative water absorption of CGC30CGC60 and CGC100 increases by 18 32 and 31respectively When the time t is 10080min the cumulativewater absorption of PC CGC30 CGC60 and CGC100 is123 g 137 g 149 g and 162 g Compared to the value ofPC the cumulative water absorption of CGC30 CGC60 andCGC100 increases by 11 21 and 32 respectively ampisphenomenon may be attributed to the micropump functionof the coal gangue ceramsiteampe coal gangue ceramsite has alarge porosity and relatively strong water absorption ca-pacity therefore the coal gangue ceramsite may demon-strate a positive effect on the capillary water transmission

33 Sorptivity of the Concrete ampe cumulative volume ofwater absorbed per unit inflow area i increases with thesquare root of elapsed time [26] As a result from the pointof view of data fitting the relationship between i and t12 isoften given as

i a + St12

(2)

where a means a correction term S means the sorptivitymmmiddotminminus12 t means the exposure time min ampe cumu-lative capillary water absorption height i is calculated as

i Δm

Acρw

(3)

where Δm is the weight of absorbed water regarding thegiven time g Ac is the cross-section area of the specimencorresponding to the capillary water absorption mm2 ρw isthe density of water gcm3

ampe relationship between water absorption height of thesamples and square root of exposure time is shown inFigure 6

From Figure 6 it can be seen that the relationship be-tween the cumulative water absorption height and thesquare root of time demonstrates a two-stage change ruleampe changing trend is in accordance with the guidelines [31]

ndash10

40

35

30

25

Com

pres

sive s

treng

th f c

u (M

Pa)

PC CGC30 CGC60 CGC100

339 336 321

305

Figure 3 Comparison of the compressive strength

18

16

14

12

10

8

6

4

2

0 2000 4000 6000 8000 10000Time (min)

Calc

ulat

ive w

ater

abso

rptio

n (g

)

16141210

8642

00 500 1000 1500

PCCGC30

CGC60CGC100

Figure 4 Cumulative water absorption of different specimens

18

16

14

12

10

8

6

4

2

0

Cum

ulat

ive w

ater

abso

rptio

n (g

)


t = 0t = 360t = 10080

Figure 5 Effect of coal gangue ceramsite on cumulative waterabsorption of concrete


and the results investigated by Yang et al [36] and Ding et al[37] for the concrete with traditional coarse aggregates ampeslopes of the two-liner portions of the plots are defined as theinitial sorptivity S1 and secondary sorptivity S2 By usingleast-squares linear regression the values of S1 and S2 of thesamples can be obtained as listed in Table 3

From Table 3 the following can be seen

ampe standard deviation corresponding to the fittingparameters is small ampe coefficient values (R2 1 R2 2)of six groups are larger than 0950 the coefficient values(R2 1 R2 2) of two groups are larger than 0900 ampe R2

values of all the samples are greater than 0900 whichsustained the existence of the linear relationship be-tween the absorption and the square root of timeampe initial sorptivity S1 of PC CGC30 CGC60 andCGC100 is 00393mmmiddotminminus12 00454mmmiddotminminus1200523mmmiddotminminus12 and 00576mmmiddotminminus12 Com-pared to the value of PC the initial sorptivity of CGC30CGC60 and CGC100 increases by 16 33 and 47respectivelyampe secondary sorptivity S2 of PC CGC30CGC60 and CGC100 is 000184mmmiddotminminus12000194mmmiddotminminus12 000202mmmiddotminminus12 and000213mmmiddotminminus12 Compared to the value of PC thesecondary sorptivity of CGC30 CGC60 and CGC100increases by 5 10 and 16 respectively It meansthat the initial sorptivity S1 and the secondary sorptivityS2 of the concrete increase with the increase of coalgangue ceramsite dosage

34 Prediction of Water Content Distribution ampe capillarywater absorption capacity of cementitious materials isusually described by Darcyrsquos unsaturated fluid theory[2426]

q minusK(θ)nablaΨ (4)

where q means the flow velocity vector Ψ means the cap-illary potential energy K(θ) means the function of hydraulic

conductivity and θ means the relative water content of thematrix as follows

θ Θ minus Θi

Θs minus Θi

(5)

Here Θ denotes the moisture content of the matrix Θidenotes the moisture content of the matrix before contactwith water and Θs denotes the moisture content of thematrix under the saturated condition

Assuming that only one exposed surface of the sample isin contact with water and the influence of gravity is alsoignored the one-dimensional capillary water absorptionequation in concrete is obtained [38]

zθzt

z

zxD(θ)

zθzx

1113888 1113889 (6)

whereD(θ) means the hydraulic diffusivity while its physicalmeaning is different from the diffusion process of ions insolution under a concentration gradient [39] ampe boundarycondition θ 1 at x 0 and the initial condition θ 0 at xgt 0

Using the Boltzmann transform ϕ xt12 equation (6)is rewritten as the ordinary differential equation

minus12ϕ

dθdϕ

1113888 1113889 ddθ

D(θ)dθdϕ

1113888 1113889 (7)

ampe approximate analytical solution of equation (7) wasgiven by Parlange et al [40] as

211139461

θ

D(a)

ada sϕ +

B

2ϕ2 (8)

Here s means the relative sorptivity given by

s S

Θs minus Θi

11139461

0(1 + θ)D(θ)dθ1113888 1113889

12

(9)

And B is given by

B 2 minuss2

111393810 D(θ)dθ

(10)

Set

λ(θ) 11139461

0D(θ)dθ (11)

Equation (7) becomes

Bϕ2 + 2sϕ minus 4λ(θ) 0 (12)

Finally the water penetration depth can be obtained as

x ϕt12

minuss + s

2+ 4Bλ(θ)1113960 1113961

12

Bt12

(13)

In order to verify the relationship between the waterpenetration depth x and water content θ at the given timeboth the relative sorptivity s and hydraulic diffusivity D(θ)are required ampe parameters B and λ(θ) can be obtained interms of D(θ) and the sorptivity S can be obtained by theexperiment ampe functional relationship between D and θ is

PCCGC30

CGC60CGC100

20

18

16

14

12

10

08

06

04

02

00

i (m

m)

0 20 40 60 80 100t12 (min12)

Figure 6 Relationship between water absorption height and squareroot of exposure time


strongly nonlinear and is commonly approximated by thepower function [26 41 42]

D(θ) D0θn (14)

Here D0 and n are the fitted constants and n is generallytaken as 4 Expression for D0 and B has been derived basedon the expression law of D(θ) as

D0 (1 + n)(2 + n)s

2

3 + 2n (15)

B 1

2(2 + n) (16)

Subsequently λ(θ) can be written as

λ(θ) D0

n1 minus θn

( 1113857 (17)

With equations (13)ndash(17) and the sorptivity obtained byexperiment into equation (2) the water content distributionof the matrix can be predicted for any exposure time of awater resource

Figure 7 shows the predictions of water content distri-bution after a series of time intervals for the matrix of PCCGC30 CGC60 and CGC100

From Figure 7 it can be seen that the water distributionof the concrete is affected by the addition of the coal gangueceramsite In order to analyze the influence of the coalgangue ceramsite on water penetration depth of the matrixquantitatively take the case of 100min exposure as an ex-ample (see Figure 8) the penetration depths of the PCCGC30 CGC60 and CGC100 are 3912mm 4313mm4826mm and 5014mm respectively Compared to thevalue of PC the penetration depths of the CGC30 CGC60and CGC100 increase by 10 23 and 28 respectively

35 Electrical Resistivity of the Concrete ampe results of theelectrical resistivity of the specimens are illustrated inFigure 9

From Figure 9 we can see that due to the capillary waterabsorption the resistivity of each group of specimensgradually decreases and the curve shows a two-stage vari-ation trend that is the curvature rapidly decreases in theinitial stage and then slows down gradually In order tocompare the influence of coal gangue ceramsite on the re-sistivity property of concrete the resistivity regarding thetime t of 0 360 and 10080min is taken as examples forcomparative analysis ampe resistivity of the specimens cor-responding to the time t of 0 360 and 10080min is shown inFigure 10

From Figure 10 it can be seen that when the time t is0min (completely dry state) the electrical resistivity of PCCGC30 CGC60 and CGC100 is 0331 kΩmiddotm 0378 kΩm0402 kΩm and 0425 kΩm Compared to the value of PCthe electrical resistivity of CGC30 CGC60 and CGC100increases by 14 21 and 28 respectively When thetime t is 360min the electrical resistivity of PC CGC30CGC60 and CGC100 is 0233 kΩmiddotm 0243 kΩm0244 kΩm and 0250 kΩm Compared to the value of PCthe electrical resistivity of CGC30 CGC60 and CGC100increases by 4 5 and 7 respectively When the time tis 10080min the electrical resistivity of PC CGC30CGC60 and CGC100 is 0196 kΩmiddotm 0218 kΩm0220 kΩm and 0214 kΩm Compared to the value of PCthe electrical resistivity of CGC30 CGC60 and CGC100increases by 11 12 and 9 respectively It means thatthe electrical resistivity of the concrete is affected by thecoal gangue ceramsite the influence of aggregate type onelectrical resistivity of the matrix is also observed by otherresearchers [3 43ndash45] ampe electrical resistivity of theunsaturated matrix has increased noticeably with the in-crease of coal gangue ceramsite dosage Under the influenceof capillary water suction the electrical resistivity of coalgangue ceramsite concrete decreases significantly while thevalues of the electrical resistivity of the concrete with coalgangue ceramsite are still greater than that of the traditionalaggregate concrete specimens In addition according to theEuropean Concrete Committee (CEB 192) [46ndash48] theconcrete with the matrix resistivity below 0200 kΩm isattributed to be under corrosion risk During the experi-ment only the electrical resistivity of the samples with thetraditional coarse aggregates is below the specific valuetherefore the addition of the coal gangue ceramsite canreduce the corrosion risk of the concrete structures at theserviceability stage

36 Relationship between the Variation of Water AbsorptionCapacity and Electrical Resistivity ampe variation of cumu-lative capillary water absorption height-resistivity-timesquare root of each group of specimens is shown inFigure 11

From Figure 11 it can be seen that the relationshipbetween the changes of electrical resistivity of each group ofspecimens and the square root of time also demonstrates atwo-stage change rule With reference to the form of thesorptivity of the matrix the initial change rate of electricalresistivity C1 and the secondary change rate of electricalresistivity C2 of the test samples can be obtained ampe resultsare shown in Table 4


Table 3 Fitting results of the sorptivity

Types S1 (mmmiddotminminus12) Standard deviation σS1 R21 S2 (mmmiddotminminus12) Standard deviation σS2 R2

2

PC 00393 00033 0941 000184 000017 0959CGC30 00454 00032 0956 000194 000020 0947CGC60 00523 00036 0959 000202 000008 0992CGC100 00576 00039 0960 000213 000011 0986


10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)

t = 20mint = 40mint = 80min

t = 100mint = 160min

PC

(a)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



CGC30

(b)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC60

(c)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC100

(d)

Figure 7 Prediction of water distribution of matrix at different times (a) PC (b) CGC30 (c) CGC60 (d) CGC100

10

08

06

04

02

Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5Depth x (mm)

PCCGC30

CGC60CGC100

t = 100min

Figure 8 Influence of coal gangue ceramsite dosage on waterpenetration depth

06

05

04

03

02

010 2000 4000 6000 8000 10000

Time (min)

Resis

tivity

(kΩ

middotm)

040035030025020015

045

0 500 1000 1500

PCCGC30

CGC60CGC100

Figure 9 Resistivity of different specimens


06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080

Figure 10 Influence of coal gangue ceramsite on electrical resistivity of concrete

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)

Figure 11 Cumulative water absorption height-resistivity-time curves (a) PC (b) CGC30 (c) CGC60 (d) CGC100


ampe standard deviation regarding the fitting parameters isreally smallampe coefficient values (Rprime2 1 and Rprime2 2) of sixgroups are larger than 0900 the coefficient values (Rprime2 1and Rprime2 2) of only two groups are greater than 0700 Itmeans that the curve of the electrical resistivity-squareroot of time substantiates the two-stage variation trendsampe initial change rate of electrical resistivity C1 of PCCGC30 CGC60 and CGC100 is minus000512 (kΩm)middotminminus12 minus000727 (kΩm)middotminminus12 minus000885 (kΩm)middotminminus12 and minus001018 (kΩm)middotminminus12 Compared tothe value of PC the absolute initial change rate ofelectrical resistivity of CGC30 CGC60 and CGC100increases by 42 73 and 99 respectively ampesecondary change rate of electrical resistivity D2 of PCCGC30 CGC60 and CGC100 is minus0000536(kΩmiddotm)middotminminus12 minus0000350 (kΩm)middotminminus12 minus0000352 (kΩm)middotminminus12 and minus0000369 (kΩm)middotminminus12 Compared tothe value of PC the absolute secondary change rate ofelectrical resistivity of CGC30 CGC60 and CGC100decreases by 35 34 and 31 respectively It meansthat the initial change rate of electrical resistivity C1would increase significantly with the increase of thecoal gangue ceramsite content while the secondarychange rate of electrically resistivity C2 reduces with theincrease of the coal gangue ceramsite dosage

37 Relationship between Cumulative Water Absorption andElectrical Resistivity ampe electrical resistivity of the samplesunder capillary water absorption can be simplified as aparallel connection of two resistors as shown in Figure 12

With parallel form the equivalent electrical resistancecan be obtained by [49]

1R

1

R1+

1R2

(18)

whereRmeans the equivalent electrical resistance kΩR1meansthe electrical resistance of the matrix without the influence ofcapillary water absorption kΩ R2 means the electrical resistanceof the matrix under capillary water absorption kΩ

By considering equation (1) equation (18) can be re-written as

A

ρl

A1

ρ1l+

A2

ρ2l (19)

where A1 means the cross-sectional area of the matrixwithout the influence of capillary water absorption m2 ρ1means the electrical resistivity of the matrix without theinfluence of capillary water absorption kΩmiddotm A2 means thecross-sectional area of the matrix under capillary water

absorption m2 ρ2 means the electrical resistivity of thematrix under capillary water absorption kΩmiddotm

A1 and A2 are given by

A1 l(l minus i) (20)

A2 li (21)

Subsequently equation (19) can be written as

l

ρ

l minus i

ρ1+

i

ρ2 (22)

Finally equation (22) is obtained as

ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)

ampe relationship between cumulative water absorptionheight and variation of the specimen resistivity with differentcoal gangue ceramsite dosage is shown in Figure 13

From Figure 13 we can see that the resistivity of eachgroup of specimens gradually decreases with the increase ofthe cumulative water absorption height ampe curve can bedivided into three stages (take the curve of CGC100 as anexample as shown in Figure 13)

Stage I the electrical resistivity of the concrete de-creases slowly It may be attributed to the fact that atthe initial stage of capillary water suction the cumu-lative water absorption height is very small and thecontribution of the capillary water to the electricalresistivity of the matrix is limitedStage II the electrical resistivity of the matrix decreasessignificantly As the capillary water absorption thecumulative water absorption height of the matrix in-creasesampe water entering the matrix begins to overlapand form a conductive network When the watercontent inside the material increases to the percolationthreshold the local conductive networks contact eachother and the interconnected conductive channels areformed inside the matrix ampereby the electrical re-sistivity of the concrete reduces notably ampe phe-nomenon can also be explained according to equation(23) ampe relationship between i and ρ is inverselyproportional With the increase of i the electrical re-sistivity ρ drops noticeablyStage III the electrical resistivity demonstrates a certaindegree of reductionampis may be due to the fact that thecapillary water absorption rate is quite small at thisstage the water distribution in the matrix is morehomogeneous which further reduces the resistivity ofthe matrix

Table 4 Fitting results of the electrical resistivity rate

Types C1(kΩmiddotm)middotminminus12 Standard deviation σC1 Rprime21 C2(kΩmiddotm)middotminminus12 Standard deviation σC2 Rprime22PC minus000512 000039 0944 minus0000536 0000153 0710CGC30 minus000727 000035 0977 minus0000350 0000039 0939CGC60 minus000885 000062 0953 minus0000352 0000030 0965CGC100 minus001018 000048 0978 minus0000369 0000069 0850


In addition we can see that with the addition of coalgangue ceramsite the electrical resistivity of the matrixdemonstrates an advantage than the concrete with tradi-tional aggregates under the action of capillary water suc-tion It means that the coal gangue ceramsite demonstratespositive effects on the electrical resistivity of concrete eventhough the addition of coal gangue ceramsite may con-tribute to the capillary water absorption capacity of theconcrete

4 Conclusions

ampe following conclusions can be obtained according to theexperimental and analytical exploration

(1) ampe electrical resistivity of the unsaturated concreteincreases obviously with the increment of coalgangue ceramsite dosage

(2) ampe addition of the coal gangue ceramsite demon-strates a significant influence on the capillary waterabsorption capacity of concrete With the increase ofthe coal gangue ceramsite content the water ab-sorption capacity of the matrix increases ampe waterabsorption rate of the coal gangue ceramsite concreteconforms to the two-stage change law ampe initialwater absorption rate and the secondary water ab-sorption rate increase with the increment of coalgangue ceramsite content

(3) Due to the capillary action more conductivechannels are formed inside the concrete and theelectrical resistivity of the matrix drops dramatically

(4) Under the capillary action the variation of theelectrical resistivity of the concrete is affected by thedosage of coal gangue ceramsite ampe incorporationof coal gangue ceramsite can enhance the watertransmission capacity of the matrix to a certainextent and reduce its electrical resistivity but theelectrical resistivity of the matrix is still greater thanthat of the corresponding traditional aggregateconcrete

(5) In a humid environment the coal gangue ceramsiteconcrete can maintain a relatively high electricalresistivity which may reduce the negative influenceof stray current and improve the durability of thestructures

Data Availability

ampe data used to support the investigations of this study areavailable from the corresponding author upon request

Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III

Figure 13 Relationship between resistivity and cumulative waterabsorption height

i

l

l

l

(a)

Current R1

R2

(b)

Figure 12 Schematic diagram of the electrical resistivity of the matrix under capillary water absorption (a) capillary water absorptionprocess (b) parallel connection of two resistors


Conflicts of Interest

ampe authors declare that they have no conflicts of interestregarding the publication of this paper

Acknowledgments

ampe authors gratefully acknowledge the Educational De-partment of Liaoning Province China (GrantLJ2019QL010) National Natural Science Foundation ofChina (Grant 52074144) and Liaoning Technical UniversityChina (Grant LNTU20TD-12)

References

[1] D Maguire and M Olen ldquoReport on an investigation into theelectrical properties of concreterdquo Transactions of the SouthAfrican Institute of Electrical Engineers vol 31 no 11pp 301ndash313 1940

[2] X Zeng C Ling Z Pan et al ldquoInfluence of capillary waterabsorption on resistivity of cement mortarrdquo Journal ofBuilding Materials vol 21 no 5 pp 714ndash719 2018 inChinese

[3] A Pejman and G Rishi ldquoElectrical resistivity of concrete fordurability evaluation a reviewrdquo Advances in Materials Scienceand Engineering vol 2017 Article ID 8453095 30 pages 2017

[4] H W Whittington J Mccarter and M C Forde ldquoampeconduction of electricity through concreterdquo Magazine ofConcrete Research vol 33 no 114 pp 48ndash60 1981

[5] C Hall and W D Hoff Water Transport in Brick Stone andConcrete CRC Press Boca Raton FL USA 2011

[6] A M Neville Properties of Concrete Longman LondonLondon UK 1995

[7] R Spragg C Villani K Snyder D Bentz J W Bullard andJ Weiss ldquoFactors that influence electrical resistivity mea-surements in cementitious systemsrdquo Transportation ResearchRecord Journal of the Transportation Research Boardvol 2342 no 1 pp 90ndash98 2013

[8] K Hornbostel C K Larsen and M R Geiker ldquoRelationshipbetween concrete resistivity and corrosion rate - a literaturereviewrdquo Cement and Concrete Composites vol 39 pp 60ndash722013

[9] B Luca E Bernhard P Pietro et al Corrosion of Steel inConcrete Prevention Diagnosis Repair WileymdashVCHHoboken NJ USA 2004

[10] L Bertolini M Carsana and P Pedeferri ldquoCorrosion be-haviour of steel in concrete in the presence of stray currentrdquoCorrosion Science vol 49 no 3 pp 1056ndash1068 2007

[11] A O S Solgaard M Carsana M R Geiker A Kuter andL Bertolini ldquoExperimental observations of stray current ef-fects on steel fibres embedded in mortarrdquo Corrosion Sciencevol 74 pp 1ndash12 2013

[12] C-H Lee and H-MWang ldquoEffects of grounding schemes onrail potential and stray currents in Taipei rail transit systemsrdquoIEE Proceedings - Electric Power Applications vol 148 no 2pp 148ndash154 2001

[13] J F Lataste C Sirieix D Breysse and M Frappa ldquoElectricalresistivity measurement applied to cracking assessment onreinforced concrete structures in civil engineeringrdquo NDT amp EInternational vol 36 no 6 pp 383ndash394 2003

[14] C-T Chen J-J Chang and W-C Yeih ldquoampe effects ofspecimen parameters on the resistivity of concreterdquo Con-struction and Building Materials vol 71 pp 35ndash43 2014

[15] Y-C Lim T Noguchi and C-G Cho ldquoA quantitativeanalysis of the geometric effects of reinforcement in concreteresistivity measurement above reinforcementrdquo Constructionand Building Materials vol 83 pp 189ndash193 2015

[16] A Lubeck A L G Gastaldini D S Barin and H C SiqueiraldquoCompressive strength and electrical properties of concretewith white Portland cement and blast-furnace slagrdquo Cementand Concrete Composites vol 34 no 3 pp 392ndash399 2012

[17] J Sanchez C Andrade J Torres et al ldquoDetermination ofreinforced concrete durability with on-site resistivity mea-surementsrdquo Materials and Structures vol 50 no 1 pp 1ndash92017

[18] R Noort M Hunger and P Spiesz ldquoLong-term chloridemigration coefficient in slag cement-based concrete and re-sistivity as an alternative test methodrdquo Construction andBuilding Materials vol 43 2016

[19] O Sengul ldquoUse of electrical resistivity as an indicator fordurabilityrdquo Construction and Building Materials vol 73pp 434ndash441 2014

[20] S E Hussain ldquoCorrosion resistance performance of fly ashblended cement concreterdquo ACI Materials Journal vol 91no 3 pp 264ndash272 1994

[21] K Liang X Zeng X Zhou F Qu and P Wang ldquoA newmodel for the electrical conductivity of cement-basedmaterialby considering pore size distributionrdquo Magazine of ConcreteResearch vol 69 no 20 pp 1067ndash1078 2017

[22] J Bao S Li P Zhang et al ldquoInfluence of the incorporation ofrecycled coarse aggregate on water absorption and chloridepenetration into concreterdquo Construction and Building Ma-terials vol 239 Article ID 117845 2020

[23] J Bao S Xue P Zhang et al ldquoCoupled effects of sustainedcompressive loading and freezendashthaw cycles on water pene-tration into concreterdquo in Structural ConcreteWiley HobokenNJ USA 2020

[24] L Wang and S Li ldquoCapillary absorption of concrete aftermechanical loadingrdquo Magazine of Concrete Research vol 66no 8 pp 420ndash431 2014

[25] N S Martys and C F Ferraris ldquoCapillary transport inmortars and concreterdquoCement and Concrete Research vol 27no 5 pp 747ndash760 1997

[26] C Hall ldquoWater sorptivity of mortars and concretes a reviewrdquoMagazine of Concrete Research vol 41 no 147 pp 51ndash611989

[27] P Zhang F H Wittmann M Vogel H S Muller andT Zhao ldquoInfluence of freeze-thaw cycles on capillary ab-sorption and chloride penetration into concreterdquo Cement andConcrete Research vol 100 pp 60ndash67 2017

[28] X Y Cong S Lu Y Yao and Z Wang ldquoFabrication andcharacterization of self-ignition coal gangue autoclaved aer-ated concreterdquoMaterials amp Design vol 97 pp 155ndash162 2016

[29] Y Z Zhang Q H Wang M Zhou et al ldquoMechanicalproperties of concrete with coarse spontaneous combustiongangue aggregate (SCGA) experimental investigation andprediction methodologyrdquo Construction and Building Mate-rials vol 255 pp 1ndash15 2012

[30] H Li Comprehensive Utilization of Coal Gangue ChemicalIndustry Press Beijing China 2010 in Chinese

[31] ASTM International Standard Test Method for Measurementof Rate of Absorption of Water by Hydraulic-Cement Con-cretes ASTM International West Conshohocken PA USA1585

[32] Natioinal Standards of the Peoplersquos Republic of China (GBT50082) Standard for Test Methods of Long-Term Performance


and Durability of Ordinary Concrete China Architecture ampBuilding Press Beijing China 2009

[33] G Li B Wang and M Zhou ldquoStudy on flexural properties ofreinforced spontaneous combustion gangue concrete beamsrdquoPeriodica Polytechnica Civil Engineering vol 62 no 1pp 206ndash218 2018

[34] M Zhou Y Dou Y Zhang Y Zhang and B Zhang ldquoEffectsof the variety and content of coal gangue coarse aggregate onthe mechanical properties of concreterdquo Construction andBuilding Materials vol 220 pp 386ndash395 2019

[35] S Gao G Zhao L Guo L Zhou and K Yuan ldquoUtilization ofcoal gangue as coarse aggregates in structural concreterdquoConstruction and Building Materials vol 268 Article ID121212 2021

[36] L Yang G Liu D Gao and C Zhang ldquoExperimental studyon water absorption of unsaturated concrete wc ratio coarseaggregate and saturation degreerdquo Construction and BuildingMaterials vol 272 Article ID 121945 2021

[37] X Ding X Liang Y Zhang Y Fang J Zhou and T KangldquoCapillary water absorption and micro pore connectivity ofconcrete with fractal analysisrdquo Crystals vol 10 no 10 p 8922020

[38] D Lockington J-Y Parlange and P Dux ldquoSorptivity and theestimation of water penetration into unsaturated concreterdquoMaterials and Structures vol 32 no 5 pp 342ndash347 1999

[39] C Hall ldquoAnomalous diffusion in unsaturated flow fact orfictionrdquo Cement and Concrete Research vol 37 no 3pp 378ndash385 2007

[40] J-Y Parlange I G Lisle S N Prasad and M J M RomkensldquoWetting front analysis of the nonlinear diffusion equationrdquoWater Resources Research vol 20 no 5 pp 636ndash638 1984

[41] C Leech D Lockington and P Dux ldquoUnsaturated diffusivityfunctions for concrete derived from NMR imagesrdquo Materialsand Structures vol 36 no 6 pp 413ndash418 2003

[42] J Bao and L Wang ldquoEffect of short-term sustained uniaxialloadings on water absorption of concreterdquo Journal of Mate-rials in Civil Engineering vol 29 no 3 Article ID 040162342017

[43] W Morris E I Moreno and A A Sagues ldquoPractical eval-uation of resistivity of concrete in test cylinders using aWenner array proberdquo Cement and Concrete Research vol 26no 12 pp 1779ndash1787 1996

[44] Y Liu and F Presuelmoreno ldquoEffect of elevated temperaturecuring on compressive strength and electrical resistivity ofconcrete with fly ash and GGBSrdquo ACI Materials Journalvol 111 no 5 pp 531ndash542 2014

[45] N Singh and S P Singh ldquoElectrical resistivity of self con-solidating concretes prepared with reused concrete aggregatesand blended cementsrdquo Journal of Building Engineeringvol 25 Article ID 100780 2019

[46] CEB-FIP ldquoDiagnosis and assessment of concrete structur-esmdashstate of the art reportrdquo CEB Bulletins vol 192 1989

[47] P K Mehta and P J M Monteiro Concrete MicrostructureProperties and Materials McGraw-Hill Education NewYork NY USA 2014

[48] D V Ribeiro J A Labrincha andM R Morelli ldquoEffect of theaddition of red mud on the corrosion parameters of rein-forced concreterdquo Cement and Concrete Research vol 42 no 1pp 124ndash133 2012

[49] W Bauer and G D Westfall University Physics with ModernPhysics McGraw-Hill New York NY USA 2011


cement replaced by the fly ash Liang et al [21] suggested anew model for the electrical conductivity of cementitiousmaterial by regarding the pore size distribution Capillarysuction is one of the main ways of water penetration intoconcrete [22ndash27] amperefore the capillary water absorptioncapacity of concrete is an important factor regarding thechanges in the electrical resistivity of the matrix Howeverthe investigations considering the effect of capillary waterabsorption on the electrical resistivity of concrete are stillrare

Coal gangues are solid wastes obtained during coalmining and processing [28 29] A large amount of coalgangue was stored around the coaling areas and there wasabout 5 billion tons of coal gangue stored in Fuxin ChinaMany investigators and engineers focused on the resourceutilization of the coal gangue As an important aspect of theutilization coal gangue ceramsite demonstrates the char-acteristics of light weight and high strength ampe coal gangueceramsite are used as coarse aggregates in concrete for re-ducing the mining of the traditional aggregates [30]Compared with traditional aggregates the coal gangueceramsite has larger porosity and stronger water absorptioncapacityampe addition of coal gangue ceramsite may enhancethe capillary transportability of concrete while from anotherperspective due to the porosity of the coal gangue ceramsitethe resistivity of the matrix may be higher compared totraditional aggregate concrete the higher resistivity of theconcrete contributes to the durability of the structuresamperefore it is necessary to explore the influence of coalgangue ceramsite on the resistivity of concrete in humidenvironment the results may provide a meaningful expe-rience for effectively reducing the negative influence of thestray current in subway

In this paper the capillary water absorption capacity ofthe concrete with the coal gangue ceramsite was studiedaccording to ASTM C1585 [31] the effect of the coal gangueceramsite on sorptivity of the matrix was explored ampeelectrical resistance of the coal gangue ceramsite concretespecimens was measured by the two-electrode method andthe variation of the resistivity of the samples during thecapillary water absorption process was analyzed ampe in-fluence of coal gangue ceramsite on concrete resistivity wasinvestigated ampe combined effects of coal gangue ceramsiteon the capillary water absorption capacity and the electricalresistivity of the concrete were compared

2 Experimental Investigations

21 Materials and Mixture Design In this study OrdinaryPortland cement 425R was used Limestone aggregates withamaximum size of 20mmwere adopted as traditional coarseaggregates and the river sand with fineness modulus of 26was used as fine aggregates ampe specimens with traditionalcoarse aggregates were recorded as PC For coal gangueceramsite concrete the limestone aggregates were replacedby the coal gangue ceramsite (see Figure 1(a)) with 3060 and 100 by volume and the specimens were recordedas CGC30 CGC60 and CGC100 respectively ampe coalgangue ceramsite adopted in the experiment was the

commercial product supplied by the factory in Fuxin China(see Figure 1(b))ampe properties of the coal gangue ceramsiteand the traditional coarse aggregates were illustrated inTable 1 ampe mix proportions of the concrete were shown inTable 2

22 Experimental Procedures For each mixture six cubicspecimens of 100times100times100mm were made ampree of thesamples were prepared for the compressive strength testampecopper meshes were arranged on two sides of the other threesamples during pouring the samples were prepared for thecapillary absorption and electrical resistance experimentsAll the samples were cured for 28 d in the curing room

ampe test equipment included a capillary water absorptiondevice as shown in Figure 2(a) and a two-electrode resis-tance measuring systemampe resistance was measured by theLCR meter (at 100 kHz 4V) as shown in Figure 2(b) ampespecific test steps were as follows (1) all the specimens weredried at 105degC in the thermostatic drying chamber toconstant mass (2) the four sides around the water ab-sorption face of the samples were sealed with epoxy (3) themass and the resistance of the sample were measured in thedry state (4) the sample was placed in the tank with a waterimmersion depth of 2ndash5mm and kept in point contact withthe supports (5) the cumulative water absorbed and theresistance were recorded at different time intervals afterremoving the surface water by a dampened tissue

ampe resistivity of the sample can be obtained by

ρ RA

l (1)

where ρ means the resistivity of the matrix kΩmiddotm R meansthe resistance of the matrix kΩ Ameans the cross-sectionalarea of the sample m2 l means the length of the sample m

3 Results and Discussion

31Compressive Strength In order to verify the effect of coalgangue ceramsite on the compressive strength of concretethe uniaxial compression experiment was conductedaccording to the guidelines [32] ampe values of the com-pressive strength of the specimens at 28 d are shown inFigure 3 For each type the result is the average value of threesamples

From Figure 3 it can be seen that the compressivestrength of the concrete is affected by the coal gangueceramsite ampe values of the PC CGC30 CGC60 andCGC100 are 339MPa 336MPa 321MPa and 305MParespectively Compared to the value of PC the values of theCGC30 CGC60 and CGC100 decrease by 1 5 and 10respectively ampe phenomenon is also observed for theconcrete with untreated coal gangue as coarse aggregates andthe variation trend for the influence of coal gangue oncompressive strength of the concrete agrees with the pre-vious investigation performed by Li et al [33] Zhou et al[34] and Gao et al [35] It means that the compressivestrength of the matrix is not obviously affected with coalgangue ceramsite replacement below 60 the decreasing of


(a) (b)





Crushed value()




aLoss on ignition


Types Cement(kgm3)




Fly ash(kgm3)




Concrete

Support

Embedded electrode

Distilled water

(a)

LCR

(b)








i a + St12

(2)


i Δm

Acρw

(3)




ndash10

40

35

30

25

Com

pres

sive s

treng

th f c

u (M

Pa)


339 336 321

305


18

16

14

12

10

8

6

4

2

0 2000 4000 6000 8000 10000Time (min)

Calc

ulat

ive w

ater

abso

rptio

n (g

)

16141210

8642

00 500 1000 1500

PCCGC30

CGC60CGC100


18

16

14

12

10

8

6

4

2

0

Cum

ulat

ive w

ater

abso

rptio

n (g

)


t = 0t = 360t = 10080











θ Θ minus Θi

Θs minus Θi

(5)



zθzt

z

zxD(θ)

zθzx

1113888 1113889 (6)



minus12ϕ

dθdϕ

1113888 1113889 ddθ

D(θ)dθdϕ

1113888 1113889 (7)


211139461

θ

D(a)

ada sϕ +

B

2ϕ2 (8)


s S

Θs minus Θi

11139461

0(1 + θ)D(θ)dθ1113888 1113889

12

(9)

And B is given by

B 2 minuss2

111393810 D(θ)dθ

(10)

Set

λ(θ) 11139461

0D(θ)dθ (11)


Bϕ2 + 2sϕ minus 4λ(θ) 0 (12)


x ϕt12

minuss + s

2+ 4Bλ(θ)1113960 1113961

12

Bt12

(13)


PCCGC30

CGC60CGC100

20

18

16

14

12

10

08

06

04

02

00

i (m

m)

0 20 40 60 80 100t12 (min12)




D(θ) D0θn (14)


D0 (1 + n)(2 + n)s

2

3 + 2n (15)

B 1

2(2 + n) (16)


λ(θ) D0

n1 minus θn

( 1113857 (17)












2

PC 00393 00033 0941 000184 000017 0959CGC30 00454 00032 0956 000194 000020 0947CGC60 00523 00036 0959 000202 000008 0992CGC100 00576 00039 0960 000213 000011 0986


10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



PC

(a)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



CGC30

(b)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC60

(c)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC100

(d)


10

08

06

04

02

Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5Depth x (mm)

PCCGC30

CGC60CGC100

t = 100min


06

05

04

03

02

010 2000 4000 6000 8000 10000

Time (min)

Resis

tivity

(kΩ

middotm)

040035030025020015

045

0 500 1000 1500

PCCGC30

CGC60CGC100



06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080


20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)






1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References





















































(a) (b)





Crushed value()




aLoss on ignition


Types Cement(kgm3)




Fly ash(kgm3)




Concrete

Support

Embedded electrode

Distilled water

(a)

LCR

(b)








i a + St12

(2)


i Δm

Acρw

(3)




ndash10

40

35

30

25

Com

pres

sive s

treng

th f c

u (M

Pa)


339 336 321

305


18

16

14

12

10

8

6

4

2

0 2000 4000 6000 8000 10000Time (min)

Calc

ulat

ive w

ater

abso

rptio

n (g

)

16141210

8642

00 500 1000 1500

PCCGC30

CGC60CGC100


18

16

14

12

10

8

6

4

2

0

Cum

ulat

ive w

ater

abso

rptio

n (g

)


t = 0t = 360t = 10080











θ Θ minus Θi

Θs minus Θi

(5)



zθzt

z

zxD(θ)

zθzx

1113888 1113889 (6)



minus12ϕ

dθdϕ

1113888 1113889 ddθ

D(θ)dθdϕ

1113888 1113889 (7)


211139461

θ

D(a)

ada sϕ +

B

2ϕ2 (8)


s S

Θs minus Θi

11139461

0(1 + θ)D(θ)dθ1113888 1113889

12

(9)

And B is given by

B 2 minuss2

111393810 D(θ)dθ

(10)

Set

λ(θ) 11139461

0D(θ)dθ (11)


Bϕ2 + 2sϕ minus 4λ(θ) 0 (12)


x ϕt12

minuss + s

2+ 4Bλ(θ)1113960 1113961

12

Bt12

(13)


PCCGC30

CGC60CGC100

20

18

16

14

12

10

08

06

04

02

00

i (m

m)

0 20 40 60 80 100t12 (min12)




D(θ) D0θn (14)


D0 (1 + n)(2 + n)s

2

3 + 2n (15)

B 1

2(2 + n) (16)


λ(θ) D0

n1 minus θn

( 1113857 (17)












2

PC 00393 00033 0941 000184 000017 0959CGC30 00454 00032 0956 000194 000020 0947CGC60 00523 00036 0959 000202 000008 0992CGC100 00576 00039 0960 000213 000011 0986


10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



PC

(a)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



CGC30

(b)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC60

(c)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC100

(d)


10

08

06

04

02

Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5Depth x (mm)

PCCGC30

CGC60CGC100

t = 100min


06

05

04

03

02

010 2000 4000 6000 8000 10000

Time (min)

Resis

tivity

(kΩ

middotm)

040035030025020015

045

0 500 1000 1500

PCCGC30

CGC60CGC100



06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080


20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)






1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References


























































i a + St12

(2)


i Δm

Acρw

(3)




ndash10

40

35

30

25

Com

pres

sive s

treng

th f c

u (M

Pa)


339 336 321

305


18

16

14

12

10

8

6

4

2

0 2000 4000 6000 8000 10000Time (min)

Calc

ulat

ive w

ater

abso

rptio

n (g

)

16141210

8642

00 500 1000 1500

PCCGC30

CGC60CGC100


18

16

14

12

10

8

6

4

2

0

Cum

ulat

ive w

ater

abso

rptio

n (g

)


t = 0t = 360t = 10080











θ Θ minus Θi

Θs minus Θi

(5)



zθzt

z

zxD(θ)

zθzx

1113888 1113889 (6)



minus12ϕ

dθdϕ

1113888 1113889 ddθ

D(θ)dθdϕ

1113888 1113889 (7)


211139461

θ

D(a)

ada sϕ +

B

2ϕ2 (8)


s S

Θs minus Θi

11139461

0(1 + θ)D(θ)dθ1113888 1113889

12

(9)

And B is given by

B 2 minuss2

111393810 D(θ)dθ

(10)

Set

λ(θ) 11139461

0D(θ)dθ (11)


Bϕ2 + 2sϕ minus 4λ(θ) 0 (12)


x ϕt12

minuss + s

2+ 4Bλ(θ)1113960 1113961

12

Bt12

(13)


PCCGC30

CGC60CGC100

20

18

16

14

12

10

08

06

04

02

00

i (m

m)

0 20 40 60 80 100t12 (min12)




D(θ) D0θn (14)


D0 (1 + n)(2 + n)s

2

3 + 2n (15)

B 1

2(2 + n) (16)


λ(θ) D0

n1 minus θn

( 1113857 (17)












2

PC 00393 00033 0941 000184 000017 0959CGC30 00454 00032 0956 000194 000020 0947CGC60 00523 00036 0959 000202 000008 0992CGC100 00576 00039 0960 000213 000011 0986


10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



PC

(a)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



CGC30

(b)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC60

(c)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC100

(d)


10

08

06

04

02

Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5Depth x (mm)

PCCGC30

CGC60CGC100

t = 100min


06

05

04

03

02

010 2000 4000 6000 8000 10000

Time (min)

Resis

tivity

(kΩ

middotm)

040035030025020015

045

0 500 1000 1500

PCCGC30

CGC60CGC100



06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080


20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)






1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References





























































θ Θ minus Θi

Θs minus Θi

(5)



zθzt

z

zxD(θ)

zθzx

1113888 1113889 (6)



minus12ϕ

dθdϕ

1113888 1113889 ddθ

D(θ)dθdϕ

1113888 1113889 (7)


211139461

θ

D(a)

ada sϕ +

B

2ϕ2 (8)


s S

Θs minus Θi

11139461

0(1 + θ)D(θ)dθ1113888 1113889

12

(9)

And B is given by

B 2 minuss2

111393810 D(θ)dθ

(10)

Set

λ(θ) 11139461

0D(θ)dθ (11)


Bϕ2 + 2sϕ minus 4λ(θ) 0 (12)


x ϕt12

minuss + s

2+ 4Bλ(θ)1113960 1113961

12

Bt12

(13)


PCCGC30

CGC60CGC100

20

18

16

14

12

10

08

06

04

02

00

i (m

m)

0 20 40 60 80 100t12 (min12)




D(θ) D0θn (14)


D0 (1 + n)(2 + n)s

2

3 + 2n (15)

B 1

2(2 + n) (16)


λ(θ) D0

n1 minus θn

( 1113857 (17)












2

PC 00393 00033 0941 000184 000017 0959CGC30 00454 00032 0956 000194 000020 0947CGC60 00523 00036 0959 000202 000008 0992CGC100 00576 00039 0960 000213 000011 0986


10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



PC

(a)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



CGC30

(b)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC60

(c)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC100

(d)


10

08

06

04

02

Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5Depth x (mm)

PCCGC30

CGC60CGC100

t = 100min


06

05

04

03

02

010 2000 4000 6000 8000 10000

Time (min)

Resis

tivity

(kΩ

middotm)

040035030025020015

045

0 500 1000 1500

PCCGC30

CGC60CGC100



06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080


20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)






1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References






















































D(θ) D0θn (14)


D0 (1 + n)(2 + n)s

2

3 + 2n (15)

B 1

2(2 + n) (16)


λ(θ) D0

n1 minus θn

( 1113857 (17)












2

PC 00393 00033 0941 000184 000017 0959CGC30 00454 00032 0956 000194 000020 0947CGC60 00523 00036 0959 000202 000008 0992CGC100 00576 00039 0960 000213 000011 0986


10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



PC

(a)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



CGC30

(b)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC60

(c)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC100

(d)


10

08

06

04

02

Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5Depth x (mm)

PCCGC30

CGC60CGC100

t = 100min


06

05

04

03

02

010 2000 4000 6000 8000 10000

Time (min)

Resis

tivity

(kΩ

middotm)

040035030025020015

045

0 500 1000 1500

PCCGC30

CGC60CGC100



06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080


20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)






1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References





















































10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



PC

(a)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 6Depth x (mm)



CGC30

(b)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC60

(c)

10

08

06

04

02Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5 76Depth x (mm)



CGC100

(d)


10

08

06

04

02

Relat

ive w

ater

cont

ent θ

0 1 2 3 4 5Depth x (mm)

PCCGC30

CGC60CGC100

t = 100min


06

05

04

03

02

010 2000 4000 6000 8000 10000

Time (min)

Resis

tivity

(kΩ

middotm)

040035030025020015

045

0 500 1000 1500

PCCGC30

CGC60CGC100



06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080


20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)






1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References





















































06

05

04

03

02

01

Resis

tivity

(kΩ

middotm)


t = 0t = 360t = 10080


20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

PC

(a)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC30

(b)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC60

(c)

20

18

16

14

12

10

08

06

04

02

00

i (m

in)

0 20 40 60 80 100Time (min12)

04

03

02

01

00

Resis

tivity

(kΩ

middotm)

CGC100

(d)






1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References
























































1R

1

R1+

1R2

(18)



A

ρl

A1

ρ1l+

A2

ρ2l (19)





A2 li (21)


l

ρ

l minus i

ρ1+

i

ρ2 (22)


ρ 1

1 + ρ1 minus ρ2( 1113857ρ2l)iρ1((23)








4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References






















































4 Conclusions







Data Availability


Resis

tivity

(kΩ

middotm)

PCCGC30

CGC60CGC100

050

045

040

035

030

025

020

00 02 04 06 08 10 12 14 16 18 20i (mm)

I

II

III


i

l

l

l

(a)

Current R1

R2

(b)





Acknowledgments


References























































Acknowledgments


References





















































effectofcapillarywaterabsorptiononelectricalresistivityof ... · 2021. 5. 3. · according to astm...

Documents