fsn_ 922-lianzhen xiao-2. hydration of portland cement-fp

1、EarlyagehydrationbehaviofcementpastesfromshrinkageelectricalresistivityresponsesWenchongSHILianzhenXIAO1DiZOUSchoolofMaterialsScienceEngineeringWuhanInstituteofTechnologyWuhan430073ChinaAbstractThepasteswithwatercementra

2、tiosof0.30.350.40.45werepreparedfmeasuringthechemicalshrinkage(CS)theautogenousshrinkage(AS)theelectricalresistivity(ERρ)duringhydrationperiodof168hrs(10080mins).TheCSvalueincreaseswiththeincreaseofwchowevertheASvaluethe

3、ERvaluedecreaseswiththeincreaseofwc.wchasagreaterinfluenceontheASresultsofcementpastesin1dthecementpastewithahigherwcshowsaexpansiontrendinearlyperiod.Thedifferentialcurveoftheresistivitycanrevealcementhydrationprocessme

4、intuitively.TheASCSvs.timeshowsalineartrendbytwodersofmagnitude.AnexponentialrelationshipbetweentheelectricalresistivitytheautogenousshrinkagefromeachpastegivesacluetoobtaintheASdevelopmenttendencyofapasteaccdingtoitsele

5、ctricalresistivity.iginalityTheassociatedhydrationphysicalparameterssuchasthechemicalshrinkagetheautogenousshrinkagetheelectricalresistivityweremeasuredthecrelationswerequantitativelyestablishedanalyzed.Keywds:Cementpast

6、echemicalshrinkageautogenousshrinkageelectricalresistivity1.IntroductionWhencementhydratesfwhichtheabsolutevolumeofhydrationproductsislessthanthesumofabsolutevolumeofreactantsthevolumeshrinksduringhydrationnamelychemical

7、shrinkage.Itrepresentsthechangeofabsolutevolumeofacementpaste.Befesettingthepastecannotfmasufficientstrengthtoresistshrinkagethevolumechangeofthepasteisthentheoutwardmanifestationofchemicalshrinkage.Afterhardeningthepast

8、efmaskeletonstructure(SuA.2008)volumecontractioncausedbychemicalshrinkagepartlyreflectedinthefmationofthepesinsidethepaste.Meanwhilewaterconsumptioncausedbyhydrationleadstoalowerrelativehuityaheavierselfdesiccation(PLura

9、.etal.2001)withincreasedcapillarypressureautogenousshrinkagehappens.Autogenousshrinkageisanexterivolumedefmationofconcreteundertheenclosedconditionhomothermalnoexternalfce(JensenOM.etal.2001).Watercementratioofcementpast

10、eisthedecisivefactinwhethertheincidenceofautogenousshrinkage.Thestudieshaveshownthat0.42isthecriticalwatercementratiofcompletehydrationofthecementitmeansASoccursonlywhenwcislowerthan0.42(T.CPowers.etal.1948)affectedbythe

11、typeofcementthecriticalwatercementratiousuallybetween0.360.48(BertilP.etal.2002).Fthecementbasedmaterialscementhydrationleadstowaterconsumptiontheelectricalresistivitychangeswiththedecreaseofliquidphaseincreaseofsolidpha

12、sethus1Crespondingauth:lz.xiao@Tel18995549041Figure.1settingtimesofdifferentwatercementratiosamples3.2ChemicalshrinkageThechemicalshrinkageresultsduring7dwereshowninFigure.2.ItcanbeseenthattheCScurveofeachpastedevelopswi

13、thtimeatafasterratein1d(1440min)thenbecomesslowerwithhydrationtimeafterwards.1dageisthedemarcationpointofshrinkagegrowthtrend.TheCSvaluesincreasewithwctheCScurvesgapamongthewcratiosbecomewiderwithhydrationtime.Figure.2th

14、echemicalshrinkagecurvesofcementpastesChemicalshrinkageiscausedbyhydrationreaction.Therefethevaluesofchemicalshrinkagereflectthehydrationreactionratequantitatively.Hydrationreactioniscontrolledbycrystalnucleationcrystalg

15、rowthinearlyagethehydraterateisfast.Withhydrationtimethehydrationproductwrapscementparticlesthushinderinghydrationprocesshydrationreactionisconvertedtobecontrolledbyphaseboundaryreactionhydraterategetsslower(YanP.etal.20

16、06).From2dto7dthechemicalshrinkageincreaseslinearlyitdemonstratesthatchemicalshrinkageisproptionaltothetimefenoughwaterisavailablenoothershrinkageoccurs.Fahigherwcmewaterissuppliedaroundthecementparticlesthehydrationreac