The Transport Properties译文.docx
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The Transport Properties译文.docx
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TheTransportProperties译文
外文参考资料
TheTransportPropertiesofConcreteundertheSimultaneousCouplingofFatigueLoadandEnvironmentFactors
WANGCaihui1,2,SUNWei1,2*,JINGJinyang1,2,HANJiande1,2,RONGHui1,2
(1.SchoolofMaterialsScienceandEngineering,SoutheastUniversity,Nanjing211189,China;2.JiangsuKeyLaboratoryofConstructionMaterials,Nanjing211189,China)
Abstract:
Asetofcouplingexperimentalinstrumentwasdesignedtostudythetransportpropertiesofchlorideioninconcreteundersimultaneouscouplingactionoffatigueloadandenvironmentalfactors.Firstlythewater-saturatedperformanceofmodernconcretewasinvestigated,thendiffusionperformanceofchlorideionunderdifferentstresslevelsanddifferenttemperaturewerestudiedrespectively;meanwhile,thetimedependentbehaviorofthechlorideiondiffusioninconcretewasalsoresearched.Theresultsshowedthatthesaturationdegreeofconcretecanreachashighas99%.Besides,diffusioncoefficientofchlorideionincreasedwithincreasingofthestresslevelandtemperature,andwhenthestresslevelandtemperatureareat0.6and60℃respectively,thediffusioncoefficientis6.3×10-14m2/s,moreoverthediffusioncoefficientofchlorideioninconcretedecreasedwithtimeunderthesimultaneouscouplingactionoffatigueloadandenvironmentfactors.
Keywords:
chloridediffusion;fatigueload;concrete;stresslevel;temperature;timedependent.
1Introduction
Excellentscholarshavedonemanystudiesonthechlorideiondiffusioninconcreteundertheactionofloads.Inthefield,literatures[1-10],studiedtheeffectofstaticandfatigueloadonthechlorideiondiffusion,theresultsshowedthattheeffectofstaticloadonthediffusionrateofchlorideionwaslesscomparedwiththefatigueload,buttheprocessesofloadandchlorideiondiffusionareindependent;WAlexGontar,JosephPMartin,andJohnS[11]usedtwokindsoffatiguecontrolmode(loadanddisplacement)tostudytherelationsofdiffusionandfatigueloadinginconcreteunderuniaxialcompression,andtheirresultshowedthatthediffusionperformanceofchloridewasalmostnotaffectedastheloadvaluebelow70%ofitsultimatestrength,whiletheirresearch[11]didnotachievethesimultaneouscouplingofloadandchlorideiondiffusion.NobuakiOtsuki[12],andPage[13],studiedthechlorideionsdiffusionatdifferenttemperaturesincementmortarandconcrete,butnotsimultaneouslyconsideringtheeffectoffatigueloadonthechlorideiondiffusion.Asforthetimedependentofchlorideiondiffusion,relatedliteratures[14,15]showedthatthediffusioncoefficientofchlorideiondecreasedwithtime,duetothechemicalandphysicalbondbetweenchlorideionandhydratedproductofconcretechangingthemicro-structure.Where,thechemicalbondwasfromthetricalciumaluminate(C3A)andtetracalciumaluminoferrite(C4AF)phasesofthecementareresponsibleforthebindingofchlorideionstoform“Fridel'ssalt,”3CaO.Al2O3CaCl210H2O,anditsferriteanalogue,3CaOFe2O3CaCl210H2Orespectively[16,17].WhenthepH>12.5,theFridel'ssaltwillincreasewithincreasingpH,whichreducedtheporosityofconcrete.However,theresearchoftimedependentofchlorideionsdiffusionalsodidnotsimultaneouslyconsidertheactionoffatigueload,especiallywithinashortertime.Finally,ShuanfaChen,Wei-DongLiao,Mu-lianZheng[18]achievedthecouplingofchlorideiondiffusionandfatigueloadbytakingsomemeasures,theresearchideaisbetterexceptfortheloadingsystemwithloweraccuracy,andotherscholars[19,20]havedonerelatedresearchinthisarea,butdidnotconsiderenvironmentalfactorssuchastemperature,saturateddegree,etal.
Inviewofaboveanalysis,asetofexperimentalinstrumentwasdesignedtoachievethesimultaneouscouplingoffatigueloadandenvironmentfactors.Byadoptingthecouplinginstrument,theeffectofstresslevelandtemperatureonthediffusionperformanceofchlorideioninconcrete,andtimedependentofdiffusionofchlorideionwereresearchedunderthesimultaneouscouplingactionoffatigueload,respectively.Additionally,itismoresignificantthatanewkindofacceleratedtestmethodforthechlorideiondiffusionisprovidedforresearchworker;andthepaper,insomeextent,canprovidebasicdataforthedurabilityresearchofconcrete,especiallythelifepredictionofthemajorengineering.
2Experimental
2.1Rawmaterials
TheusedcementisP•IanditschemicalandmineralcompositionwereshowninTable1andTable2.
2.2Specimenpreparation
Thecementitiousmaterials(Portlandcement),limestonegravelandriversandarefirstdry-mixedfor1min.Thenthewaterisputintothepre-mixedpowdersandmixedforanother3min.Afterthat,thefreshconcreteiscastedintosteelmouldsandcompactedusingavibratingtable.Thespecimensarestoredintheconditions(25℃,100%RH)for24h,thenremovedfromthemoulds,andcontinuetobecuredforthreemonthsinthesamecondition.Thesizeforconcretespecimenis70mm×70mm×280mm.
2.3Experimentalparameters
StresslevelS:
theratioofstressfromcyclicloadingandstaticloadstrength;Diffusioncoefficient,D,unitsm2persecond;TemperatureTort,where,TastheKelvindegreeorabsolutetemperaturewithunitsk,ttheFahrenheittemperaturewithunits℃.
2.4Experimentalinstruments
TheexperimentalinstrumentsincludeU.S.810MaterialTestingSystem(MTS),providingthefatigueloadwithsinewave,andenvironmentalcontainer,simulatingthevariationoftemperature;
Asetofcouplinginstrumentisusedtoachievethesimultaneouscouplingoffatigueloadandchlorideiondiffusion.
Loadingsystemiscontrolledbyforcewiththewayoffour-pointbending.
2.5Testmethod
2.5.1Testforsaturationdegreeofconcrete
Firstlyconcretespecimenisdriedat105℃inadryingoventoconstantweightrecordedasM0.Secondly,theconcretespecimenareplacedinalaboratoryenvironmentandnaturallycooledtoroomtemperature;Thirdly,concretespecimenareplacedintoasaturatedvacuumapparatustoconstantweight;Moreover,concretespecimenissealedwithSiliconegreaseofhighaltitudewiththicknessofabout1mm,andatransparenttapeisattachedtosiliconeresinlayerlightly,atlast,notetheweightofspecimenasM∞,thedefinitionofsaturationdegreeofconcretespecimenislistasEq.
(1):
(1)
Where,
isthesaturationdegreeofconcrete,wheresissaturation,i=1,2,3…..,drepresentsday.
2.5.2Couplingmethodoffatigueloadandenvironmentalfactors
Themostimportantsectionofcouplingmethodistheself-designedcouplinginstrument,composedoftwocontainerswithglassfiberreinforcedplastics,waterpipeandsmall-sizedpump.FirstlythetwocontainersareusedtoholdtheNaClsolutionandpipeisthechannelforthecycleofNaClsolution.Besides,thesmall-sizedpumpprovidesthepowerforthecycleofNaClsolution.Thisinstrumenthastwoadvantagesthatoneisthatachievingthesimultaneouslycouplingoftheprocessofchlorideiondiffusionandfatigueload;anotheristhatkeepconstantfortheconcentrationofNaClsolutionduringexperiment.
Toachievethesimultaneouscouplingoffatigueloadandprocessofchlorideiondiffusion,thefollowingstepswereadopted:
tosetuptheparameterofMTSincludingstresslevel,loadingfrequency,waveofloadandcontrolmodel(displacementorforce)etc;toadjustdistancefourpivots:
fortheovertwopivots,thedistancebetweenthemis210mm,whereastheothertwopivotsis70mm;TheconcretespecimenwastakenoutfromthesaturatedsolutionofCa(OH)2,thecontainerwasfixedonthebendingplaneofspecimen,whichwassealedas1.6.1;
Moreover,thespecimenwasplacedontheMTS,thenthetwocontainerswereconnectedwithpipes;StartingtheMTSandsmall-sizedpump,theexperimentwasfinishedindifferenttimefordifferentrequirement.Anenvironmentalcabinetwasusedtosimulatetemperaturechangeofenvironmentforachievingthecouplingoffatigueload,temperatureandchlorideiondiffusion.
Inthisstudy,loadingfrequencywas10Hz,stresslevelof0.25,0.35,0.4,0.45,0.5,0.55,0.6andthetemperatureof20℃,30℃,45℃,60℃weresetfordifferentexperiments.
2.5.3Feasibilityrequirementofexperiment
Inordertosuccessfullycarryoutthestudyoftransportperformanceofchlorideioninconcreteundercouplingactionoffatigueloadandtemperature,theresultsmustmeet100%orapproximate100%concretesaturationdegreeduringtesting,nofractureinconcretespecimen,andnolessthan30-mmdiffusiondepthofchlorideioninconcrete.
2.5.4Thetestofchlorideiondiffusion
Thespecimenwereplacedinalabenvironmentfor24haftertheendofcouplingaction,thenweredrilledfromthebendingofspecimentoobtainpowderwithintervalof5mmfor6times.Putthepowderintotheovenwiththetemperatureof105℃,maintainingfor2h,followingthe"WaterTransportEngineeringConcreteTestCode"JTJ270-98[21].
3Resultsanddiscussion
Innaturalconditions,chloridetransportinconcretegenerallycompliancewiththefollowingmechanismsorways[22]:
diffusion,permeationandcapillaryabsorptionincludingphysicalandchemicaladsorption.Diffusionisduetosaturatedconcreteorwhenmoistureconcentrationoftheconcreteisashighas99%;penetrationisdefinedthatthechlorideionandwatertransportinconcretewiththewaterpressuregradient;capillaryadsorptionisthatthechlorideionisadsorbedontheconcretewithlowhumidityduetocapillarysuctioncausedbyadsorptionofthetransmissionbehavior.GenerallyusetheFick's2ndlawtoconsidertheone-dimensionaldiffusionofchlorideion,suchasEq.2,
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