1. INTRODUCTION
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 12 | Dec 2021 www.irjet.net p ISSN: 2395 0072 © 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page149 An Experimental Investigation on Mechanical and Durable Properties of High Strength Fiber Reinforced Concrete by Partial Replacement of Cement with Silica Fumes and Fly Ash T Venkat Ravi Bharath1 , V Lokesh2
2. MATERIALS Silica Fume
The main difference between normal strength concrete NSC and high strength concrete HSC is that the compressive strength that shows highest resistance to concretesamplefortheappliedpressure.Eventhoughthere is no specific point of division between normal strength concreteandhighstrengthconcretetheAmericanConcrete Institute (ACI) explains that high strength concrete as concretewithcompressivestrengthgreaterthan60N/mm2
Silicafumeisaby productintheproductionofsiliconand silicon alloys. Silica fume is available in various forms of whichthemostusuallyusedisindandifiedform.AsperIS: 1331(PART 1)1992andASTMC(1240 2000)Silicafumeis beingused Itisalsoreferredasmicrosilicaorascondensed silicafumewhichisaby productmaterialthatisbeingused aspozzolanic.Thisby productisaresultofreductionofhigh purity quartz with coal as an electric arc furnace in manufacturingofsiliconorferro siliconalloy. Fly Ash AsperASTMC618
This type of fly ash is produced in the process of burning harder and older anthracite and bituminous coal. Class F is usually low calcium fly ash which has carbon contentlessthan5%butoccasionallyit’scarboncontentis ashighas10%.Thistypeofflyashispozzolanicinnature andlimeCaOcontent isless than20% Having pozzolanic propertiesalumina,glassysilicaofClassFflyashrequirea cementing agent like Portland cement, hydrated lime, quicklime with water in to react and form cementations compounds. Class F ashes will only react with the by productsproducedwhencementreactswithwater.Instead ofthis,whenchemicalactivatorlikesodium(waterglass)is addedtoClassFflyashthatleadstotheformationofHigh strengthconcrete
The usage of fine Pozzolanic materials in high strengthconcretelikeflyash,silicafume leadtoreduction in crystalline compounds mostly calcium hydroxide. Also therewillbereductioninthicknessofinterfacialtransition zoneofhigh strengthconcrete.Usageofmineraladmixtures like silica fume SF, fly ash FA in concrete is effective to increaseinthestrengthandmakedurableforhighstrength concrete in future. Addition of admixtures to concrete mixturewillincreasethestrengthofconcretebypozzolanic actionandfillsthevoidsthatarecreatedbetweencement particles.
A) Class F fly ash
2Asst.Professor, Department of Civil Engineering, Sree Rama Engineering College, Tirupati, Andhra Pradesh, India ***
B) Class C fly ash Class Cflyashisproducedbyburningofsubbituminous coaloryoungerlignite.Inadditionto pozzolanicproperties, ClassCasheswillalsopossessself cementingproperties.In the presence of water ClassC ashes will react and harden sameascementandalsogainsstrengthovertime.ClassCfly ashusuallycontainscarboncontentlessthan2%withmore than20%lime(CaO).Self cementingClassCflyashdoesnot requireanactivatorincontrasttoClassF.InClassCflyashes sulphate(SO4)andAlkalicontentsaregenerallyhigher.
1M.Tech Structures Student, Department of Civil Engineering, Sree Rama Engineering College, Tirupati, Andhra Pradesh, India
Key Words: Highstrengthconcrete,silicafume,flyash,Steel fibres,Concretestrength
1.1 Economic Benefit Cement representsthemostexpensivecomponent ofa concretemixture.Asitisahighlyenergyintensivematerial, theincreasingenergycostsreflectonhigherCementcosts. Most of the pozzolanic and cementitious materials in use today are industrial by products, which require no expenditureofenergyforuseasmineraladmixtures.When usedaspartialCementreplacement,upto70%Cementby mass, mineral admixtures can result in substantial energy andcostsavings
Abstract In this study, the various types of admixtures were used to study individual and as well as combined effects on the concrete strength in addition to the effects on durability, workability and compressive strength by replacement of admixtures by 10 %, 15 %ofsilica fumeand 10 %, 20 % and 30 % of fly ash by weight of cement with a fixed amount of 0.5 % steel hook fibers that are added by volume of concrete throughout the study.
Table2givestheresultofinitialandfinalsettingtimefor different replacement percentages of Cement with Silica fume. Initial setting time test results shows very slight increaseininitialsettingtimeofCementfordifferentdosages 0%, 10% and 15% of Silica fume in Ordinary Portland Cement. Final setting time test results shows very slight decreaseinfinalsettingtimeofCementfordifferentdosages 0%, 10% and 15% of Silica fume in Ordinary Portland Cement.
1.Planesectionsremainplaneafterbending 2.Thecompressiveforceisequaltothetensileforce.
B) Steel Fiber Reinforced Concrete (SFRC) Concrete is most extensively used structural material aroundtheglobewithproductionofmorethansevenbillion tons per year. For various reasons in concrete cracks are usually observed. The main cause for concrete to develop cracks is may be due to structural, economic, or environmentalfactorsbutmostlythecracksareformeddue totheweaknessofmaterialtoresisttensileforces.
Initial(minutes)TimeSetting Final(minutes)TimeSetting 1 100%OPCand0%FA 40 350 2 90%OPCand10%FA 60 320 3 80%OPCand20%FA 70 280 4 70%OPCand30%FA 80 250
Initialandfinalsettingtimefordifferent percentagesofcementwithsilicafume S.NO Mix Proportion Initial(minutes)TimeSetting Final(minutes)TimeSetting 1 100%OPCand0%SF 40 350 2 90%OPCand10%SF 45 340 3 85%OPCand15%SF 50 330
3. The internal moment is equal to the applied bending moment.Split tensile test as per IS specifications IS 5816:1999istobeconducted.Thesizeofcylinderis150mm diameterandlengthof300mmlengthisconsidered.“The cylindersareplacedhorizontallybetweentheloadingplate surfacesofcompressiontestingmachine.Alignthesample such that the lines are marked on the ends is vertical and centeredoverthebottomplateoftheapparatus Putother plywood strip over the specimen and bring down upper S.NO Mix Proportion
TABLE 2
o To control plastic shrinkage and drying shrinkage cracks. o Toreducepermeabilityofconcreteinwhichitfurther reducesbleedingofwatercanbereduced.
2. EFFECT ON INITIAL AND FINAL SETTING TIME
3. TESTS ON CONCRETE 3.1 Tests for hardened concrete Compressive Strength Testing Machine is used for the determination of compressive strength for cubes and cylinders.Thespecimensaftersubjectedtocuringdryingfor 1dayareloadedincompressivestrengthtestingmachine. Basedonusualcompatibilityandequilibriumconditions usedfornormalreinforcedconcreteexcept thecontribution of the fibers in the tension is recognized and the ultimate flexuralstrengthanalysisisbeingpresentedinthispaper
Followingassumptionsareconsideredintheanalysis
Steel Fibres Steel fibres make significant improvement in impact, flexuralandfatiguestrengthofconcrete.Thesefibresused ascrackarresterforconcreteandalsosignificantlyimproves
staticanddynamicpropertiesofconcrete Withincreasein steelfibrescontentinconcretetheCompressivestrengthof fibrereinforcedconcreteincreasedsignificantly.
TABLE 1 Initialandfinalsettingtimefordifferent percentagesofcementwithflyash
Table1givestheresultsofinitialandfinalsettingtime for different replacement percentages of Cement with Fly ash. Initial setting time test results shows very slight increase in initial setting time of Cement for different dosages 0%, 10%, 20% and 30% of Fly ash in Ordinary PortlandCement.Finalsettingtimetestresultsshowsvery slightdecreaseinfinalsettingtimeofCementfordifferent dosages 0%, 10%, 20% and 30% of Fly ash in Ordinary PortlandCement
A) Uses of steel fibers in concrete InconcreteSteelFibersareusuallyusedforthefollowing reasons:
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 12 | Dec 2021 www.irjet.net p ISSN: 2395 0072 © 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page150
CompactionFactor=(P1 P2/P2 P)
3.3 Strength of concrete for different types of tests
Slump cone test apparatus was made according to IS: 7320 1974andusedforcalculatingnormalconsistencyof concreteFreshconcretewasfilledinslumpconebytamping eachlayerfor25timeswithatampingrod.Lateronmetal coneisraisedslowlyintheverticaldirection.Assoonasthe settlementofconcreteslumpoftheconcretemeasuredby scale. Compaction factor test “Place the concrete sample in the upper hopper to its edgebyusingthehandscoopandlevelit.Coverthecylinder and open the trap door at bottom of the upper hopper so thatconcretefallsintothelowerhopper Pushtheconcrete stickingonitssidesgentlywiththeroad.Openthetrapdoor oflowerhopperandallowtheconcretesothatitwillfallinto thecylinderbelow”.[2] Removeexcessconcreteabovethetoplevelofcylinder withthehelpoftrowelandlevelit.Cleantheoutsideofthe cylinder.Weightthecylinderwithconcreteroundingoffto the nearest 10 gm. This weight is known as weight of partiallycompactedconcrete(P1).Emptythecylinderand thenfillitagainwithsameconcretemixtureintothreelayers approximately5cmdeepandeachlayerhastobeheavily rammedtoobtainfullcompaction.Levelthetopsurfaceand weigh the cylinder with fully compacted concrete. The weight we get is known as the weight of fully compacted concrete(P2).Tofindtheweightofemptycylinder(P)
Fromtheabovegraphitisobservedthatforevery10%, 20% and 30% of fly ash replacement the difference in compressivestrengthreachestoamaximumat10%ofsilica fume.Withtheincreasingsilicafumereplacementto15%it showsdecreasingcompressivestrengthvaluesofconcrete. Henceitisconcludedthat at10%silica fumeand20%fly ash replacement the mix gives maximum 28 days compressive strength as 81.92 N/mm2. Therefore this replacement percentage (S10F20) can be considered as optimummix Split tensile strength of concrete Chart 2: Tensilestrengthat28daysforvarious percentagesofSilicaFumeandFlyAsh
3.2 Tests carried out on fresh concrete
Compressive strength of concrete increases with the usage of mineral admixtures. Considering the proportion (S15F20)thecompressivestrengthsfor3,7,28,56and90 daysare36.41,47.33,71.55,73.55and78N/mm2 Byusing this proportion the compressive strength of concrete has beenincreasedby5.11%. 75.33 81.92 76.6 74.08 74.67 71.55 65 7570 8580
From the above chart 2 it can be seen that the comparisonofsplittensilestrength resultsofconcretefor differentreplacementsofsilicafumeandflyashwith0.5% ofsteelhookfibersasadmixture.At10%ofsilicafumeand 20% of fly ash the mix gives the maximum 28 days split tensilestrengthas5.2N/mm2
Slump cone test
Compressive strength of concrete
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 12 | Dec 2021 www.irjet.net p ISSN: 2395 0072 © 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page151 platetotouchtheplywoodstrip.Applytheloaduniformly untilwereachthebreakingload(P)” .[1]
10% flyash 20% fly ash 30% fly ash 10% silica fume 15% silica fume
The compressive strength of concrete for different replacementsofcementwith10%and20%ofsilicafume and10%,20%and30%offlyashwith0.5%steelhook fibersbyvolumeofconcreteistestedfor3,7,28,56and90 daysbyusingcompressivetestmachine(CTM).Thewaterto cementratioinconcretemixwastakenas0.35.Threecubes were casted for each proportion and the average of three test samples was taken for the accuracy of results. At the roomtemperatureandimmersingthecubesinwatertankor sumptheconcretecubeswerecured.
Chart 1: 28dayscompressivestrengthvariationfor10% and15%silicafumeforevery10%,20%and30%offly ashreplacement.
REFERENCES
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1. Additionofsteelhookfibersinconcretewillresultin increaseofcompressivestrengthandmakesconcrete moreductile.
5. At10%ofsilicafumeand20%offlyashreplacement tocementthesplittensilestrengthisincreasedupto 60.85%whencomparedtoconventionalconcretefor 28days.
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2. In split tensile and flexural tests, it is noticed that crackwidthhasbeenreducedduetothepresenceof steelfiberswhencomparedtoconventionalspecimen.
4. At10%ofsilicafumeand20%offlyashreplacement tocementthecompressivestrengthisincreasedupto 20.34%whencomparedtoconventionalconcretefor 28days.
6. At10%ofsilicafumeand20%offlyashreplacement to cement the flexural strength is increased up to 38.74% whencomparedtoconventionalconcretefor 28days
7. Additionofsilicafumeandflyashasreplacementto cementinconcreteitsnormalconsistencyandinitial settingtimeincreaseswiththeincreaseinpercentage and final setting time decreases with increase in percentage.
8. Use of mineral admixtures in concrete causes significantreductioninthevolumeofvoidsandhence reducesthepermeabilityofconcretemixbecauseof itshighfinenessandformationofC S Hgel.
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 12 | Dec 2021 www.irjet.net p ISSN: 2395 0072 © 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page152 Flexural strength of concrete 14.06 15.6 19.5 15.6 19.46 15.52 15.3 0 5 10 15 20 25 CC S10F10 S10F20 S10F30 S15F10 S15F20 S15F30N/mm2instrengthflexuraldays28 Proportions of concrete 28 DAYS FLEXURAL STRENGTH 0.5% of steel fibers Chart-3: Flexuralstrengthat28daysforvarious percentagesofSilicaFumeandFlyAsh Comparison of tests on concrete TABLE 3: 28Daysstrengthcomparisoninpercentage TypeTestof F10S10 S10 F20 F30S10 F10S15 F20S15 F30S15 Compressivestrength 10.7% 20.34 % 12.51% 10% 9.8% 5.11% TensileSplitTest 37.61% 60.85 % 47.70% 29.66% 37% 18.04% FlexuralTest 10.99% 38.74 % 10.99% 38.42% 10.45% 8.85 Compressivestrengthoncylinder 9.21% 19.37 % 9.15% 6.18% 13.35% 5.86% Sis%ofsilicafume;Fis%offlyash From the above table it is observed that the percentagevariationofcompressivestrength, splittensile strengthandflexuralstrengthismaximumat10%ofsilica fume and 20% of fly ash replacement with 0.5% of steel hookfibersasadmixture. 4. CONCLUSIONS investigationBasedontheresultsobtainedfromtheexperimentalthefollowingconclusionsweremade
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