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Microstructureevolutionofhydrationproductsoftricalcium silicateunderdissolution
LIWenwei,LIShuguang,LIXinyu,YANGHuamei
(ChinaThreeGorgesCorporation,HydraulicConcreteInstitute,Beijing 100038,China)
Abstract:Thedamconcreteintheunderwaterzoneissusceptibletodissolutiondamageduetotheleachingofcal
ciumions,whichresultsinthedecalcificationanddissolutionofcementhydrationproducts,andfurtherleadsto
thedeteriorationandfailureofthedamconcreteperformance.Todeeplyrevealthedeteriorationmechanismofdam
concrete ,itisnecessarytoclarifytheevolutionlawofthemorphologyandmicrostructureofcementhydrationprod
uctsunderdissolution.Asthemainmineralphaseofcement ,thehydrationproductcharacteristicsoftricalciumsil
icate(C 3 S)significantlyaffecttheperformanceofcementandconcrete.Therefore,high - purityC 3 Swasprepared
andthen soaked in ammonium chloride solution with differentconcentrationsafterhydration , to simulate
accelerateddissolutionprocedureofcementhydrationproducts.Thecomposition ,micro - nanostructureandmor
phologyofthedissolvedproductswereinvestigatedbycombiningthermogravimetricanalysis,nuclearmagneticres
onance ,scanningelectronmicroscopeandnitrogenadsorption.TheresultsshowedthatthehydrationproductofC 3 S
wasneutralizedwiththeammonium chloridesolution ,andthepH valueofthesolutionincreased.ThelowerpH
valueandmoreobviouslydecalcifiedofthehydrationproductsafterreactionwiththeincreaseoftheconcentrationof
ammoniumchloride ,demonstratedthatthedissolutiondegreeiscloselyrelatedtoenvironmentalconditions.The
dissolutionwouldreducethechemicalbindingwatercontentofthehydratedcalciumsilicate (C - S - H)gelamongce
menthydrationproducts ,causethepolymerizationofthesiliconchainstructure,coarsentheporestructureandin
tensifythehollownessofC - S - Hgel.Thedeteriorationdegreeofstructureandmorphologyincreasedcontinuously
withtheincrementofdissolutiondegree ,whichprovidestheoreticalbasisforexplanationofconcretedissolution
mechanismatmicro - nanoscale.
Keywords:dissolution;C 3 S;C - S - Hgel;chemicalboundwater;siliconnuclearmagnetic;micromorphology
(责任编辑:韩 昆)
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