17 Study of the Temperature Influence on Concrete Hydration Exothermic Rate

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1、StudyoftheTemperatureInfluenceonConcreteHydrationExothermicRateAbstract:RecentachievementsaboutconcretehydrationexothermicmodelsbasedonArrheniusequationhaveimprovedcomputationaccuracyformassconcretetemperaturefield.Butpropertyofactivationenergyandgasconstant(Ea/R)hasnotbeenwe

2、llstudiedyet.FromlatestexperimentsitisshownthatEa/Robviouslychangeswiththehydrationdegreewithoutfixedform.Inthispaper,therelationshipbetweenhydrationdegreeandEa/Risstudiedandanewhydrationexothermicmodelisproposedtouseitandtestifyit.Withthoseachievements,massconcretetemperatur

3、efieldwitharbitraryboundaryconditioncanbecalculatedmoreprecisely.Keywords:hydrationexothermicmodel,Arrheniusequation,activationenergy,hydrationdegree,temperaturerisemodel.1IntroductionThermalcrackisoneofthemostcommoncracksofconcrete[1,2].Hydrationexothermicbehavioroftheconcre

4、teshouldbetakenintoconsiderationwhencalculatingmassconcretetemperaturefield[3,4].Adiabatictemperaturerisecanbemeasuredbyconcreteadiabatictemperaturemeasuringdeviceorbackanalyzedbythedataoffieldexperiment[5,6].Adiabatictemperaturerisegotbyconcreteadiabatictemperaturemeasuringd

5、eviceismoreaccurateandlessexpensivethanbackanalysisfromfieldexperiment.However,hydrationexothermicrateoftheconcreteisinfluencedbyconcretetemperaturedurationwhichshouldbetakenintoconsideration[7-10].Therehavebeenseveralconcreteadiabatictemperaturerisemodelstosolvethisprobleman

6、dseveralofthemarebasedonArrheniusequation[11-14].Howevertherearesomecommonproblems:(1)Forthosemodels,theratiobetweentheactivationenergyandthegasconstantisreducedtoaconstantorsimplyconsideredasafixedfunctiontype.13Laboratorytestsinthispapershowedthatthosereductionsarenotproper

7、forallkindsofconcrete.(2)Forthosemodels,adiabatictemperaturerisegotbydevicecannotbedirectlyappliedincalculationbecausedifferentplacementtemperaturescanleadtodifferentadiabatictemperaturerise.Sotheyshouldbechangedintoadiabatictemperaturerisebasedonequivalenttime,orhydrationexo

8、thermicrateundernormalsituation.However,laboratorytestsinthispapersh