investigation on residual compressive … on residual compressive strength of self compacting ......

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Int. J. Struct. & Civil Engg. Res. 2013 A S Patharwat and H S Jadhav, 2013

INVESTIGATION ON RESIDUAL COMPRESSIVESTRENGTH OF SELF COMPACTING CONCRETE

USING FIBERS UNDER ELEVATED TEMPERATURE

H S Jadhav1 and A S Patharwat1*

1 Associate Professor & Head Department of Civil Engineering, Rajarambapu Institute of Technology, Rajaramnagar.

*Corresponding Author: A S Patharwat,[email protected]

ISSN 2319 – 6009 www.ijscer.comVol. 2, No. 3, August 2013

© 2013 IJSCER. All Rights Reserved

Int. J. Struct. & Civil Engg. Res. 2013

Research Paper

INTRODUCTIONNow a day’s high-strength and high-performance concrete are widely usedthroughout the world. To produce them it isnecessary to reduce the water and binder ratioand increase the binder content. Superplasticisers are used in these concretes to

achieve the required workability. Differentkinds of cement replacement materials areusually added to because of desirable porosityand permeability. Behavior of concrete underelevated temperature has recently increased.These studies are very useful for the design ofspecial concrete structures subjected to

Fiber reinforced concrete is geometry made of steel, glass or natural fiber. In recent years, Self-Compacting Concrete (SCC) has gained wide use for placement in congested reinforcedconcrete structures with difficult casting conditions. SCC is basically developed to solve problemsof pouring and setting concrete in high rebar densities structures. Now days, it is need to checkthe safety of structure against fire. It is a challenge to build fire resistant structure in an economicalway. For a newly developing material like Glass fiber or Steel fiber SCC studies is of paramountimportance for instilling confidence amongst the engineers and builders. The main aim of thisexperimental is to find out the residual compressive strength of fiber reinforced Self compactingconcrete by using two aspect ratio of an Alkali-Resistance glass fiber and crimped type steelfiber. The specimens were heated to different elevated temperature 200oC, 350oC and 500oCand different duration 3 h, 6 h and 9 h for each temperature. From this experimental studyconcluded that the significant improvement in compressive strength is observed with the inclusionof fibers. The residual compressive strength remains more for AR High Desperation Glass fiberSelf Compacting Concrete. Also percentage decrease in compressive strength is less for HighDesperation Glass fiber Self Compacting Concrete which is 25% at 500oC for 9 h.

Keywords: Glass fiber, Steel fiber, Self compacting concrete, Elevated temperature, ResidualCompressive Strength

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elevated temperatures such as thermalshielding for nuclear reactors, metallurgical andchemical industries, runways, etc. Exposureto elevated temperatures causes physicalchanges. The physical changes including largevolume changes owing to thermal shrinkageand creep related to water loss. The changesin volume will result in large internal stressesthus leading to micro cracking. Elevatedtemperatures also bring in some chemical andmicro-structural changes such as migration ofwater, increase in dehydration and thermalincompatibility of the interface betweencement paste and aggregates. All of thesechanges will have a bearing on the decreaseof the strength and stiffness of concrete.Concrete is an inorganic material and hightemperature and its duration decreases theconcrete strength and its durability. Fireresistance of concrete is primarily affected byfactors like the temperature, duration andcondition of the fire. Self CompactingConcrete (SCC) is a high performanceconcrete that can flow under its own weight tocompletely fi l l the form work and selfconsolidates without any mechanical vibration.Such concrete an accelerate the placement,reduce the labor requirements needed forconsolidation, f inishing and eliminateenvironmental pollution. The SCC is also usedmainly for repair application and for castingconcrete in restricted areas, including sectionsthat present limited access to vibrate. Suchvalue added construction material has beenused in applications justifying the highermaterial and quality control cost whenconsidering the simplified placement andhandling requirements of the concrete. The

glass fibers are among the most versatileindustrial materials known today. They arereadily produced from raw materials, whichare available in virtually unlimited supply. Theglass fibers are derived from compositioncontaining silica. They exhibit useful bulkproperties such as hardness, resistance tochemical attack, stability and inertness as wellas desirable fiber properties such as strength,flexibility and stiffness. The uses of Steel FiberReinforced Concrete (SFRC) over the past 30years have been so varied and so widespread,that it is difficult to categorize them. The mostcommon applications are tunnel linings,pavements and slabs. There has also beensome recent experimental work on roller-compacted concrete reinforced with steelfibers.

RESEARCH SIGNIFICANCEFor a newly developing material like Glass fiber

Self Compacting Concrete and Steel fiber Self

Compacting Concrete, studies on residualcompressive strength is of paramount

importance for instilling confidence amongstthe engineers and builders. The literature

indicates that while some studies are available

on the normal concrete, a comprehensive studywhich involves strength that is not available on

Glass fiber Self Compacting Concrete andSteel fiber Self Compacting Concrete. Hence

considering the gap in the existing literature,an attempt has been made to study the

residual compressive strength of Glass fiber

Self Compacting Concrete and Steel fiber SelfCompacting Concrete subjected to

temperature 200oC, 350oC and 500oC for M30grade concrete.

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LITERATURE REVIEWPhan et al.(2001) describes results on effectsof elevated temperature exposure on residualmechanical properties of HPC. Residualmechanical properties were measured byheating the 102 mm X 204 mm cylinders tosteady state thermal conditions at a targettemperature. The specimens were heated toa maximum core temperature of 4000C, atheating rate of 50C/min. An examination of thespecimens heating characteristics indicatethat the HPC mixtures which experiencedexplosive spalling had a more restrictiveprocess of capillary pore and chemicallybound water loss than those which did notexperience spalling.

Chen and Liu (2004) investigated residualstrengths of High-Strength Concrete (HSC)and hybrid-fiber-reinforced high-strengthconcrete (HFRHSC) after exposure to hightemperatures. The results shows that normalHSC is prone to spalling after exposure to hightemperatures and Mixing high melting pointfiber (i.e., carbon or steel fiber) with low meltingpoint fiber (i.e., PP fiber) HSC greatly improvesthe properties of HSC after exposure to hightemperatures.

Lau and Anson(2006) investigated differentelevated heating temperatures rangingbetween 105°C and 1200°C the compressivestrength, flexural strength, elastic modulus andporosity of concrete reinforced with 1% steelfiber (SFRC) and changes of color to theheated concrete. The results show a loss ofconcrete strength with increased maximumheating temperature and with increased initialsaturation percentage before firing.

Sekhar et al. (2011) says that damage in

concrete structures due to fire depends to agreat extent on the intensity and duration offire. This work presents an experimentalinvestigation on the residual compressivestrength of glass fiber reinforced selfcompacting concrete using Alkali-Resistanceglass fibers subjected to elevatedtemperature at 4 h, 8 h and12 h duration for various grades of concreteof mixes M 30 to M 65.

OBJECTIVES OF STUDY1. To study effect of different fibers on

compressive strength self compactingconcrete.

2. To determine residual compressivestrength of self compacting concrete byusing glass fiber under different elevatedtemperature (200oC, 350oC and 500oC)and different durations (3 h, 6 h and 9 h) foreach temperature.

3. To determine residual compressivestrength of self compacting concrete byusing steel fiber under different elevatedtemperature (200oC, 350oC and 500oC)and different duration (3 h, 6 h and 9 h) foreach temperature.

4. To compare the result when self compactingconcrete subjected to elevated temperaturewith and without fiber

PROPOSED WORK ANDMATERIAL PROPERTIESThe main aim is to study residual compressivestrength of Self Compacting Concrete usingfibers under elevated temperature 200oC,350oC and 500oC for M30 grade concrete.

Cement: Ordinary Portland Cement of 53

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grade used. The specific gravity of cement is3.15.

Coarse Aggregates: The maximum size ofaggregate of 12.5 mm size was used. Thespecific gravity was found to be 2.96 andfineness modulus of coarse aggregate was7.49.

Fine Aggregate: Locally available NaturalRiver sand of zone I with specific gravity 2.66,water absorption 1.1%, and fineness modulus2.57 .Conforming to IS 383-1970.

Water

Clean potable water was used for mixing.

Admixture: Superplasticisers

BASF GELLNIUM SKY 784 is used with aproportion of 1.2% with respect to weight ofpowder content was used to achieve thedesired slump flow value for SCC sinceaddition of fibers adversely affects theworkability of self compacting concrete.

Fly Ash

Fly ash added to improve the quality anddurability of SCC. In the present investigationwork, the fly ash used is obtained from Devgadthermal power station in Maharashtra. Thespecific surface of fly ash is found to be 4250cm2/g by blaines permeability apparatus andits specific gravity is 2.3.

Fibers

Shaktiman Steel Fibers flat Crimped in shapeof 30 mm and 50 mm in length as shown inFigure 1 are supplied by the Stewols India Pvt.(Ltd.) Nagpur. AR Glass fibers High Dispersion(AR-GFHD) and AR Glass fibers HighPerformance (AR-GFHP) as shown in Figure2 are manufactured by Owens Corning, Goa

are used. Properties of fibers are given inTable 1.

Figure 1: Steel Fibers(Aspect ratio 30 & 50)

Figure 2: AR Glass Fibers

Concrete Mix Proportion

The Nan-Su et al. (2001)method is used formix proportion of SCC. In this method initialmix proportions were calculated using mixdesign method of conventional concrete givenby Indian Standard method instead of simplyassuming the contents of Cement, CoarseAggregate and Fine Aggregate as given by

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the literature. These contents were comparedwith the EFNARC Specifications (2005) andsmall modifications were done to the contentsthat arrived in the Indian Standard method tosatisfy the SCC mix composition criteria. Thequantities of materials required for M30 gradper 1 cum of SCC with and without fiber aregiven in Table 2.

EXPERIMENTAL PROGRAMCasting of Specimens

The cube specimens were casted of size 150mm X 150 mm X 150 mm. Ingredients of the mixwere taken as per the mix proportion. Concretewas filled in mould without compaction. The topsurface of the specimens was hand trowelled.The moulds were stripped after 24 h. Thespecimens were casted as shown in Figure 3and cured for 28 days in curing pond.

Heating Exposure Technique

Electric furnace of maximum temperature of1200°C was used. The specimens were keptin furnace as shown in Figure 4 at requiredtemperature 200oC, 350oC and 500oC for 3 h,6 h and 9 h at each temperature. After heatingthe specimens were taken out and cooled inair.

Testing of Cube Specimens

Then specimens of each mix type were testedfor their compressive strength at roomtemperature. All the cubes were tested onCompression Testing Machine of capacity2000 kN compressive load as shown inFigure 5.

RESULTS AND DISCUSSIONCompressive Strength of Self Compacting

Table 1: Properties of fibers

Fiber Type Shape Len-gthMm Equiv-alent Dia.mm Tensile Strengt-h MPa Densi-tyKg/m3

Steel Fibers Flat Crimped 30 1 1100 7850

Steel Fibers Flat Crimped 50 1 1100 7850

AR-Gass Fibers Flat Fibrillated 12 0.014 1700 2600

Table 2: Quantities of Materials RequiredFor M30 Grade Per 1 cum of SCC With and Without Fiber

Mix Cement Fly Ash Sand Coarse Aggregate Water SP Fibers

Kg/m3 Kg/m3 Kg/m3 Kg/m3 Kg/m3 Kg/m3 Kg/m3

Plain SCC 325 140 874 806 170 5.11 -

GFSCC-HD 325 140 874 806 170 5.58 2.32

GFSCC-HP 325 140 874 806 170 5.58 3.48

SFSCC-30 325 140 874 806 170 5.58 23.21

SFSCC-50 325 140 874 806 170 5.58 23.21

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Concrete with and without fibers at roomtemperature

Table 3 gives the overall results ofCompressive Strength of Self CompactingConcrete with and without fibers at roomtemperature. The compressive strength ofGFSCC-HD at the level of 0.1% volume offibers is 38.42 MPa which is improved by15.62% and for GFSCC-HP at the level of0.15% volume of fibers is 39.55 MPa whichTable 3 Compressive strength for differentconcrete mix is improved by 19.00% ascompared to plain SCC. The compressivestrength of SFSCC-30 at the level of 1%volume of fibers is 44.16 MPa which isimproved by 32.89% and for SFSCC-50 at thelevel of 1% volume of fibers is 41.78 MPa whichis improved by 25.72% as compared to plainSCC. The variation of compressive strengthof different concrete mix at room temperatureis plotted in the graph as shown in theFigure 6.

Overall results of Residual compressivestrength of self compacting concrete with andwithout fibers are subjected to differentelevated temperature

Exposure to high temperature resulted inloss of strength for SCC and fiber reinforcedSCC. Figure 7 shows the residualcompressive strength of SCC mixes afterexposure to different high temperature anddifferent duration for each temperature. Within2000C, the changes of residual compressivestrength values within the temperature for alltypes of SCC mixes were changed suddenly.However, when temperature was higher than2000C, their strength values were changedlinearly. For normal SCC, the strength values

Figure 3: Concrete Curingin Air After Prepartion

Figure 4: Concrete Specimens Ready forElevated Temperature in Furnace

Figure 5: Compressive Test for Cube

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Table 3: Compressive Strength for Different Concrete Mix

Concrete Mixes Plain GFSCC-HD GFSCC-HP SFSCC-30 SFSCC-50

SCC (0.1%) (0.15%) (1%) (1%)

Compressive 33.23 38.42 39.55 44.16 41.78

Strength (MPa)

Figure 6: Compressive Test for Cube

33.23

38.42 39.55

44.1641.78

25

30

35

40

45

50

Plain SCC GFSCC-HD GFSCC-HP SFSCC-30 SFSCC-50

Concrete Mix

Co

mpr

essi

ve S

tren

gth

(M

Pa

)

decreased significantly. When temperaturereached at 5000C for 9 h, its residualcompressive strength was 68.31% of original

strength. Because high elastic modulus fiberssuch as Steel and Glass fibers resist crackinginside the concrete, they can control volume

Figure 7: Overall Results OfResidual Compressive Strength

of Self Compacting Concrete Withand Without Fibers are Subjected to

Different Elevated Temperature

2 0

2 5

3 0

3 5

4 0

4 5

50

Ro omtemp .

2 00 °C 3 50°C 500 °C

Temperaure (oC)

Res

idua

l C

omp

ress

ive

stre

ng

th

(MP

a)

S CC-3hr

S CC-6hr

S CC-9hr

GFS CC(HD) -3hr

GFS CC(HD) -6hr

GFS CC(HD) -9hr

GFS CC(HP ) -3hr

GFS CC(HP ) -6hr

GFS CC(HP ) -9hr

S FS CC(30)-3hr

S FS CC(30)-6hr

S FS CC(30)-9hr

S FS CC(50)-3hr

S FS CC(50)-6hr

S FS CC(50)-9hrTemperaure (oC)

Figure 8: Overall Results OfPercentage Decrement In CompressiveStrength of Concrete Cube Specimenare Subjected to Different Elevated

Temperature

5

10

15

20

25

30

35

500°C 350°C 200°C

% D

ecre

ase

in C

ompr

essi

ve S

tren

gth(

MP

a)

SCC-3hr

SCC-6hr

SCC-9hr

GFSCC(HD)-3hrGFSCC(HD)-6hrGFSCC(HD)-9hrGFSCC(HP)-3hrGFSCC(HP)-6hrGFSCC(HP)-9hrSFSCC(30)-3hr

SFSCC(30)-6hr

SFSCC(30)-9hr

SFSCC(50)-3hr

SFSCC(50)-6hr

SFSCC(50)-9hr

Temperaure (oC)

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Table 3: Overall results of Residual compressive strength of self compacting concretewith and without fibers are subjected to different elevated temperature

Concrete Mixes Temperatures(ºC) Residual compressive strength for different exposure time (MPa)

0 h 3 h 6 h 9 h

SCC Room temp. 33.23 - - -

200ºC - 28.01 27.05 25.11

350ºC - 26.40 25.12 23.51

500ºC - 25.76 24.12 22.70

GFSCC-HD Room temp. 38.42 - - -

200ºC - 34.58 33.43 31.12

350ºC - 32.66 31.12 29.20

500ºC - 30.74 29.97 28.82

GFSCC-HP Room temp. 39.55 - - -

200ºC - 35.20 33.22 31.24

350ºC - 33.22 31.64 30.00

500ºC - 31.64 30.00 28.87

SFSCC-30 Room temp. 44.16 - - -

200ºC - 38.42 37.54 36.21

350ºC - 36.21 34.44 32.12

500ºC - 34.88 33.56 31.80

SFSCC-50 Room temp. 41.78 - - -

200ºC - 35.93 34.68 33.42

350ºC - 33.84 32.17 30.92

500ºC - 32.17 31.34 29.25

Table 4: Overall Results Of Percentage Decrement In Compressive Strength OfConcrete Cube Specimen Are Subjected To Different Elevated Temperature

Concrete Temperatures Percentage decrease in compressive strength for Different Exposure Time (%)

Mixes (ºC) 3 h 6 h 9 h

SCC 200ºC 16 19 24

350ºC 20 24 29500ºC 22 27 32

GFSCC-HD 200ºC 10 13 19350ºC 15 18 23500ºC 20 22 25

GFSCC-HP 200ºC 11 16 21350ºC 16 20 24500ºC 20 24 27

SFSCC-30 200ºC 13 15 18350ºC 18 22 25500ºC 21 24 28

SFSCC-50 200ºC 14 17 20350ºC 19 23 26500ºC 23 25 30

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change of concrete due to rapid change ofenvironmental and large temperature gradient.Also it controls initiation and expansion of innermicrodefects of concrete. For concrete withGF-HD, the loss of strength is not significant,for temperature at 5000C kept for 9 h; itsresidual compressive strength was 75% oforiginal strength. Also for GF-HP, fortemperature at 5000C kept for 9 h, its residualcompressive strength was 73% of originalstrength. Adding steel fibers to SCC, thesignificant decrease in strength occurred. Forconcrete with SF-30, for temperature at 5000Ckept for 9hr, its residual compressive strengthwas 70% of original strength. Table 3 showsthe Overall results of Residual compressivestrength of self compacting concrete with andwithout fibers are subjected to differentelevated temperature.

Overall Results of Percentage Decrementin Compressive Strength of ConcreteCube Specimen are Subjected to DifferentElevated Temperature

For concrete with fiber, especially GF-HD, theirproperties exposed to high temperatureimproved significantly. As shown in Figure 8their residual compressive strength around75% of original strength, when it exposed at5000C for 9 h. It may be because during therapid temperature increasing process, GF-HDfibers melts and vaporize due to the relativelylower melting point, which resul ts inmicrochannels in the concrete. Thus, gratervapor tension in capillaries can be released.In addition, GF-HP or SF can to some degree,restrict the initiation and expansion of crackingin the concrete due to their tensile resistancewhich maintain higher residual strengths ofconcretes after exposure to high temperature.

CONCLUSION1. The signi ficant improvement in

compressive strength is observed with theinclusion of fibers.

2. The percentage decrease in compressivestrength is less for GFSCC-HD is 25% andfor GFSCC-HP is 27% at 5000C for 9 h incomparison with room temperature.

3. The percentage decrease in compressivestrength for SFSCC-30 is 28% and forSFSCC-50 is 30% at 5000C for 9 h incomparison with room temperature.

4. The percentage decrease in compressivestrength for SCC with and without fiberspecimens will be higher for higherexposure time and temperature.

5. The loss of compressive strength in SCCis more than SCC with inclusion of fibersdue to elevated temperature.

REFERENCES1. Chen B and Liu J (2004), “Residual

Strength of Hybrid-Fiber-ReinforcedHigh-Strength Concrete after Exposure toHigh Temperatures”, Journal of Cementand Concrete Research, Vol. 34, pp.1065-1069.

2. EFNARC (2005), “The EuropeanGuidelines for Self Compacting ConcreteSpecification, Production and Use”, May.

3. Lau A and Anson M (2006), “Effect of HighTemperatures on High PerformanceSteel Fiber Reinforced Concrete”,Journal of Cement and ConcreteResearch, Vol. 36, pp. 1698-1707.

4. Nan Su, Kung- Chung Hsu and His-WenChai (2001), “A simple mix design

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method for Self Compacting Concrete”,Journal of Cement and ConcreteResearch, Vol. 31, pp. 1799-1807.

5. Phan L T, Lawson J R and David F L(2001), “Effects of Elevated TemperatureExposure on Heating Characteristics,Spalling, and Residual Properties of HighPerformance Concrete”, Journal of

Materials and Structures Constructions,Vol. 34, pp. 83-91.

6. Sekhar T S, Rao P S and Sravana P(2011), “Investigation on ResidualCompressive Strength of Glass FiberSelf Compacting Concrete”, Journal ofthe Institution of Engineers (India), Vol.92, pp. 36-41.

investigation on residual compressive … on residual compressive strength of self compacting ......

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