新拌混凝土的性能-外文翻译.doc

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1、PropertiesofFreshConcreteEditedbyH.-J.WierigFreshconcreteisamixtureofwater,cement,aggregateandadmixture(ifany).Aftermixing,operationssuchastransporting,placing,compactingandfinishingoffreshconcretecanallconsiderablyaffectthepropertiesofhardenedconcrete.Itisimportantthattheconstituentmaterialsremai

2、nuniformlydistributedwithintheconcretemassduringthevariousstagesofitshandlingandthatfullcompactionisachieved.Wheneitheroftheseconditionsisnotsatisfiedthepropertiesoftheresultinghardenedconcrete,forexample,strengthanddurability,areadverselyaffected.Thecharacteristicsoffreshconcretewhichaffectfullco

3、mpactionareitsconsistency,mobilityandcompactability.Inconcretepracticetheseareoftencollectivelyknownasworkability.Theabilityofconcretetomaintainitsuniformityisgovernedbyitsstability,whichdependsonitsconsistencyanditscohesiveness.Sincethemethodsemployedforconveying,placingandconsolidatingdaconcrete

4、mix,aswellasthenatureofthesectiontobecast,mayvaryfromjobtojobitfollowsthatthecorrespondingworkabilityandstabilityrequirementswillalsovary.Theassessmentofthesuitabilityofafreshconcreteforaparticularjobwillalwaystosomeextentremainamatterofpersonaljudgment.Inspiteofitsimportance,thebehaviourofplastic

5、concreteoftentendstobeoverlooked.Itisrecommendedthatstudentsshouldlearntoappreciatethesignificanceofthevariouscharacteristicsofconcreteinitsplasticstateandknowhowthesemayalterduringoperationsinvolvedincastingaconcretestructure.13.1WorkabilityWorkabilityofconcretehasneverbeenpreciselydefined.Forpra

6、cticalpurposesitgenerallyimpliestheeasewithwhichaconcretemixcanbehandledfromthemixertoitsfinallycompactedshape.Thethreemaincharacteristicsofthepropertyareconsistency,mobilityandcompactability.Consistencyisameasureofwetnessorfluidity.Mobilitydefinestheeasewithwhichamixcanflowintoandcompletelyfillth

7、eformworkormould.Compactabilityistheeasewithwhichagivenmixcanbefullycompacted,allthetrappedairbeingremoved.Inthiscontexttherequiredworkabilityofamixdependsnotonlyonthecharacteristicsandrelativeproportionsofthecon