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1、EffectofReplacingPartofOrdinaryPortlandCementbyGranitePowderonCompressiveandFlexuralStrengthofUHPCKeywords:granitepowder,ultrahighperformanceconcrete(UHPC),electricflux,porestructure,compressivestrengthPresenterofthepaperduringtheConference:Ling-weiHeTotalnumberofpagesofthepaper(thefirstpagesandthel
2、icencetopublishexcluded):7EffectofReplacingPartofOrdinaryPortlandCementbyGranitePowderonCompressiveandFlexuralStrengthofUHPC1.ing-weiHe,TaoJi,Yong-ningLiangandBao-chunChenCollegeofCivilEngineering,FuzhouUniversity,Fuzhou,Fujian350116,ChinaAbstract:TheeffectofreplacingpartofordinaryPortlandcementbygr
3、anitepowderontheelectricflux,porestructure,compressiveandflexuralstrengthofUHPCunderautoclavedcuringwasinvestigated.TheresultsshowthatwhenpartofordinaryPortlandcementisreplacedbygranitepowderfrom0%to15%,theelectricflux,averageporesizeandthetotalporevolumedecrease,andthecompressivestrengthandflexural
4、strengthof7daysand14daysimprove;whenpartofordinaryPortlandcementisreplacedbygranitepowderfrom15%to20%,theelectricflux,averageporesizeandthetotalporevolumeincrease,thecompressivestrengthandflexuralstrengthdecrease.When15%ofordinaryPortlandcementisreplacedbygranitepowder,theporestructureofUHPCisthebes
5、tanditscompressivestrengthandflexuralstrengtharethehighest.Keywords:granitepowder,ultrahighperformanceconcrete(UHPC),electricflux,porestructure,compressivestrength1. INTRODUCTIONSincethe20thcentury,thedevelopmentofbuildingmaterialsisrapid,andvarioustypesofnewmaterialsappearedandwereappliedtotheengin
6、eering.Ultrahighperformanceconcrete(UHPC)isakindofcement-basedcompositewithultrahighstrength,hightoughness,strongdurabilityandgoodvolumestability11_3LThecementitiousmaterialsofUHPCaremainlycomposedofcementandsilicafume.Inrecentyears,manyinvestigatorsusedslagandfly-ashtoreplacepartofcementandsilicafu
7、me.Thoughthecontentofcementandsilicafumedecreased,UHPCwithhighcontentofmineraladmixtureshowedexcellentmechanicalproperty141.ThecompressivestrengthofUHPCwithlimepowderattheageof28dayswashigherthanthatwithoutlimepowder151.ThereweresynergisticeffectbetweenricehuskashandsilicafumeinUHPC,andthecompressiv
8、estrengthofUHPCwithalittlericehuskashwashigherthanthatwithoutricehuskash.Soflyash,slag,limepowderandricehuskashcanbeusedtoprepareUHPC.Granitepowderisakindofwastematerialcomingfromgraniteprocessingprocess.Thegranitepowderoccupiesalargeamountoflandresourcesanddoesharmtohumanlivingenvironment.Theeffici
9、entuseofgranitepowderbecomesanurgentproblem171.TherewerefewreportaboutthepreparationofUHPCusinggranitepowder.Thispaperinvestigatedtheporestructure,permeability,compressivestrengthandflexuralstrengthofUHPCunderautoclavedcuring,inwhichapartofordinaryPortlandcement(OPC)wasreplacedbygranitepowder.2. RAW
10、MATERIALS,MIXPROPORTIONANDTESTMETHOD2.1 RawmaterialsGrade42.5R(Chinesecementgradingsystem)Portlandcementwithapparentdensityof3050kgm3,manufacturedbyFujianLianShicementCo.Ltd,PRChina,wasadopted.TheperformancesofthecementareshowninTable1.ThesilicafumeproducedbyXiningFerroalloyFactoryinQinghaiProvince,
11、PRChina.TheSiO2contentofsilicafumeisover90%,particlesizeis0.1-0.2microns,meanparticlesizeis0.162micronsandapparentdensityis2293kgm3.Themeanparticlesizeofquartzpowderis50micronsandthecontentofSiO2isover99.5%,whichwasproducedbyJingYouSandandGravelsalesCo.LtdinAnhuiProvince,PRChina.Thequartzsandwasprod
12、ucedbyJingYouSandandGravelsalesCo.LtdinAnhuiProvince,PRChina.ThechemicalcompositionsandphysicalpropertiesofthequartzsandarelistedinTable2.Thelengthofsteelfibersis13mmandthediameteris0.15-0.2mm,whichwasdesignedandmanufacturedbyGanzhouDayeMetallicFibresCo.LtdinJiangXiProvince,PRChina.ThetypeofCX-8supe
13、rplasticizerwiththewaterreducingratioof25%producedbyChuangXianEngineeringmaterialsCo.LtdinFuzhou,PRChina,wasadopted.ThewaterwasthetapwaterinFuzhoumunicipalarea.ThegranitestonepowerwasmanufacturedinLianjiangcountyofFujianprovince,PRChina.Thespecificsurfaceareaofgranitestonepoweris588m2kg,andthedensit
14、yis2293kgm3.ThechemicalcompositionsarelistedinTable3.Table1:PerformanceofcementSpecificsurfacearea(m2kg)Lossonignition(%)Settingtime(min)Flexuralstrength(MPa)Compressivestrength(MPa)InitialsettingFinalsetting3d28d3d28d3611.071251855.78.527.545Table2:PhysicalandchemicalindicatorsofthequartzsandSizeCh
15、emicalconstituents(%)MeshnumberParticlesize(m)SiO2Fe2O328-90600-16099.50.02Table3:Chemicalcompositionsofthegranitestonepower(%)LossonignitionSiO2AI2O3Fe2O3CaOMgOK2ONa2O0.7283.212.021.762.310.543.394.722.2 MixproportionThesameamountcementwasreplacedbygranitepowder.ThemixproportionisshowninTable4.Wate
16、rtobinderratiowas0.18.ThedosageofSuperplaslicizerwas2.5%ofcement(byweight).Thedosageofsteelfiberinvolumewas2%(byweight).Replacementratios()ofgranitepowderinTO,T5,T10,T15,T20were0%,5%,10%,15%,20%(byweight)respectively.Table4:MixproportionofUHPCmixedwithgranitepowder(kgm3)No.CementSilicafumeGranitepow
17、derFinesandSuperplasticizerWaterSteelfiberQuartzpowderTO701.5210.50.0820.817.5164.2156.0259.6T5666.4210.535.1820.817.5164.2156.0259.6TlO631.3210.570.2820.817.5164.2156.0259.6T15596.2210.5105.3820.817.5164.2156.0259.6T20561.1210.5140.4820.817.5164.2156.0259.62.3 Experimentandmethodology2.3.1 Mixingpr
18、ocessSuperplasticizerwasdissolvedinwaterevenly,andasuperplasticizersolutionwasobtained.Cement,silicafume,quartzpowder,granitepowderandquartzsandwereputintoamixingpot,andthemixturewaspre-stirredfor3minites.Then90%ofsuperplasticizersolutionwasadded,andthemixturewasstirredfor3minites;theremainedsuperpl
19、asticizersolutionwaspouredintothemixture,andthemixturewasstirredforanother3minites.Finallythesteelfiberwasaddedandthemixturewasstirredfor3-5minites.2.3.2 MoldingandcuringThemixturewaspouredinto40mm40mm160mmmoldsafterthemixingprocess.Andthenthemoldswiththefilledfreshmixturewerevibratedonavibrationtab
20、lefor120times.Themoldswereremovedafter24hoursstandardcuring.Thenthespecimenswereunderautoclavecuring(Namely,vacuumizedforhalfanhour,andincreasedtemperatureandpressurein1hour,andmaintainedthetemperatureof190-200andpressureof1.2MPafor6hours,andreducedpressureto0MPain2hour).Afterautoclavecuring,thespec
21、imensweretransferredtothestandardcuringroomtocureuntiltest.2.3.3 TestmethodsCompressivestrengthandcompactnessareimportantmechanicalpropertiesofconcrete,whichwerecarriedoutaccordingtotheChinesecodeGB/T17671-1999andGB/T50082-2009,respectively.AporosimetryanalyzerofV-Sorb2800Swasusedtotesttheporestruct
22、ureofthespecimens.3. RESULTSANDANALYSIS3.1 CompressivestrengthandflexuralstrengthofUHPCTheexperimentalresultsofcompressivestrengthaU)andflexuralstrength(fi)ofUHPCwithpartoftheordinaryPortlandcementreplacedbygranitepowderareshowninFigs.1-2.Fig. 1 Compressive strengthFig.2 Flexural strengthAsshowninFi
23、g.l,astheamountofordinaryPortlandcementreplacedbygranitepowderincreasesfrom0%to15%,thecompressivestrengthsofUHPCat7daysand14daysincreasefrom147.7MPato190.3MPaandfrom164.IMPato192.4MPa,respectively.Namely,thecompressivestrengthat7daysand14daysareimprovedat28.84%and17.2%,respectively.Whenthecontentofg
24、ranitepowderinsteadofordinaryPortlandcementexceeds15%,thecompressivestrengthsofUHPCat7daysand14daysdecreasefrom190.3MPato160.1MPaandfrom33.9MPato29.1MPa,namely15.87%and14.2%,respectively.Whenthesubstitutionamountofgranitepowderis15%,theincreaseofcompressivestrengthismostlyobvious.AsshowninFig.2,asth
25、eamountofordinaryPortlandcementreplacedbygranitepowderincreasesfrom0%to15%,theflexuralstrengthsofUHPCat7daysand14daysincreasefrom27.3MPato33.9MPaandfrom28.2MPato34.6MPa,respectively.Namelytheflexuralstrengthsat7dand14dareimprovedat24.2%and22.7%,respectively.Whenthecontentofgranitepowderinsteadofordi
26、naryPortlandcementexceeds15%,theflexuralstrengthsofUHPCat7daysand14daysdecreasefrom33.9MPato29.1MPaandfrom34.6MPato29.8MPa,namely14.2%and13.9%respectively.Whenthesubstitutionamountofgranitepowderis15%,theincreaseofflexuralstrengthismostlyobvious.3.2 PorestructureofUHPCTheinfluenceofgranitepowdercont
27、ent,whichisusedtoinsteadpartofordinaryPortlandcement,ontheporestructureofUHPCisshowninTable5.Table5:PorestructureofUHPCNo.Accumulativetotalporousvolume(mLg)Averageporediameter(nm)Percentageofporevolumeindifferentpore-sizerange(%)Harmlesspore(200nm)TO0.0018479.8161.4317.4714.576.63T50.0017669.3862.66
28、17.1214.355.87TlO0.0016128.5562.0417.5113.896.56T150.0015648.4761.3718.3613.976.30T200.0016218.6260.5818.7514.636.04AsshowninTable5,theaverageporediameterofUHPCissmall.Theproportionofharmlessporeandlittleharmfulporeishigh,andexceeds70%.Asthecontentofgranitepowder,whichreplacedordinaryPortlandcement,
29、changesfrom0to15%,averageporediameterandthetotalporevolumeofUHPCdecrease.Theaverageporediameterdecreasesby13.66%andtheporestructurebecomesdenser.Whenthecontentofgranitepowderexceeds15%,averageporediameterandthetotalporevolumeofUHPCincrease.3.3 Anti-permeabilityofUHPCTheanti-permeabilitytestresultsof
30、UHPCwithpartofordinaryPortlandcementreplacedbygranitepowderareshowninTable6.Table6showsthattheelectricfluxofUHPCishigherthan100OCbecauseoftheexistingofsteelfiber.Withtheincreasingofreplacementratioofgranitepowderintherangeof0%to15%,theporestructureofUHPCbecomesmorecompact,andtheelectricfluxreduces,a
31、ndtheanti-permeabilityofUHPCincreases.Whenthereplacementratioexceeds15%,Withtheincreasingofreplacementratioofgranitepowder,theelectricfluxofUHPCincreasesandanti-permeabilityofUHPCdecreases.Table6:ExperimentresultofUHPCchlorideionpermeabilityNo.Electricflux(C)PermeabilitygradeTO1743.05lowT51556.38low
32、TlO1417.69lowT151387.90lowT201509.98low4. ANALYSISANDDISCUSSIONThecompactnessofconcrete,thetypeandquantityofhydrationproductsaretwoimportantfactorstodeterminethestrengthofconcrete.(1)Granitepowderhascertainactivityunderautoclavedcondition,andtheactiveSiO2ofgranitepowderreactswiththeCa(OH)2attheinter
33、facialtransitionzoneofUHPCtoproducehydratedcalciumsilicate,whichincreasethecompactnessofUHPC.Inaddition,thenucleationeffectofgranitepowderalsomakescementhydrationreactionmoresufficiently(namelychemicaleffect).(2)Theaverageparticlesizeofgranitepowderparticles(specificsurfaceareaof588m2kg)issmallertha
34、nthatofordinaryPortlandcement(specificsurfaceareaof361m2kg).Granitepowderparticlesfilltheinternalmicroscopicpores,whichmakesporestructureofUHPCmorecompact(physicaleffect).Therefore,whenpartofordinaryPortlandcementisreplacedbygranitepowderfrom0%to15%,althoughtheamountsofcementandhydrationproductsared
35、ecreased,thechemicaleffectandphysicaleffectofgranitepowderplayadominantrole.Accordingly,theaverageporesizeandthetotalporevolumedecrease(Table5),andtheelectricfluxdecreases(Table6);theinterfacialtransitionzoneofUHPCbecomesmorecompact,andthecompressivestrengthandflexuralstrengthofUHPCimprove(Figs1-2).
36、WhenthereplacementratioofordinaryPortlandcementbygranitepowderexceeds15%,itisdifficultforthechemicaleffectandphysicaleffecttooffsetthenegativeeffectsofthereducedhydrationproducts,andtheaverageporesizeandtotalporevolumeincrease(Table5);theelectricfluxincreases(Table6),andthecompressivestrengthandflex
37、uralstrengthofUHPCdecline(Figs1-2).5. Conclution-WhentheordinaryPortlandcementispartiallyreplacedbygranitepowderintherangeof0%-15%,theamountofhydrationproductsdecrease.Howeverthenucleationeffectandthepozzolaniceffectunderautoclavecuringofgranitepowder(chemicaleffect),andthemicro-aggregatefillingeffe
38、ct(physicaleffect)ofgranitepowderplayadominaterole.Thereforetheaverageporediameterandtotalporevolumereduce;theelectricfluxreducesandthecompressivestrengthandflexuralstrengthofUHPCincrease.-Whenthegranitepowderreplacementratioisgreaterthan15%,thechemicaleffectandphysicaleffectofgranitepowderarediffic
39、ulttooffsetthenegativeeffectcausedbythereductionofhydrationproducts.Thereforetheaverageporediameterandtotalporevolumeincrease;theelectricfluxreducesandthecompressivestrengthandflexuralstrengthofUHPCdecrease.-Whenthegranitepowderreplacementratiois15%,theporestructureofUHPCisthedensest,andthecompressi
40、vestrengthandflexuralstrengthofUHPCisthehighest.ACKNOWLEDGEMENTSTheworkswassupportedbytheStateKeyProgramofNationalNaturalScienceofChina(GrantNo.U1305245).REFERENCES1 Chan,Y.W.andChu,S.H.,Effectofsilicafumeonsteelfiberbondcharacteristicsinreactivepowderconcrete,CementandConcreteResearch,34(7)(2004)11
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