土木工程材料第四章1课件

Ch4ConcreteandMortar4.1Propertiesoffreshconcrete（新拌砼）4.2Mixing拌合,Placing浇筑andCuring4.3PropertiesofHardenedConcrete4.4MixproportioninganddesignADefinitionofPortlandCementConcrete（PCC）Amixtureof:PortlandCementFineAggregateCoarseAggregateWaterAirCementandwatercombine,changingfromamoist,plasticconsistencytoastrong,durablerock-likeconstructionmaterialbymeansofachemicalreactioncalled“hydration”.VolumetricproportionsofconstituentsofPCC2-8%air25-40%cementpaste60-75%aggregate4.1Propertiesoffreshconcrete4.1.1Propertiesoffreshconcrete4.1.2FactorsaffectingConsistency(稠度)andWorkability(和易性)4.1.3Segregation(离析)andBleeding(泌水)4.1.1PropertiesoffreshconcreteWorkability（和易性）Consistency（稠度）Slump（坍落度）Workability（和易性）Workabilitycanbedefinedastheeasewithwhichafresh-concretemixcanbehandledfromthemixertothefinalstructure.ExpressedbythreecharacteristicsConsistency稠度Mobility流动性Compatibility相容性;

保水性和易性是指新拌混凝土易于各工序施工操作（搅拌、运输、浇灌、捣实等）并能获得质量均匀、成型密实的性能。影响和易性的主要因素：1、水泥浆的数量。与流动性以及粘聚性相关2、水泥浆的稠度。3、砂率此外水泥品种、骨料种类、粒形和级配、外加剂、时间、温度等，都对混凝土拌和物的和易性有一定影响SlumptestSlumptestMold:slumpcone坍落度筒Bottomdiameterof200mmtopdiameterof100mmheightof300mmProcedureofSlumptesta.Filltheconeusingstandardprocedureb.Strikeoffexcessc.RaisethemoldandmeasurethedisplacementoftheoriginalcenterofthespecimenTypesofslumpNear-zeroslumpVerydrymixNormalslumpProperlyproportionedconcreteShearslumpConcretelacksplasticityandcohesionCollapseslumpLean,harshorextremelywetconcreteRecommendedslumpsforvarioustypeofconstructionTypeofconstructionSlump(mm)MaxMinFootings,caissons,foundationwallsandsubstructurewalls7525Beams,columnsandwalls10025Pavementandslabs7525Massconcrete50254.1.2FactorsaffectingConsistencyandWorkabilityInternalFactorsCementpropertiesProportionofcement,Typesofcement,FinenessAggregatepropertiesSurfaceareaofaggregate,shape,gradation,maximumsizeofaggregateWatercontentWater-to-Cementratio

水灰比AdmixturesWater-reducingadmixture,air-entrainingadmixture减水剂、引气剂TherelationshipofslumpandtemperatureslumpTemperatureTherelationshipofslumpandtimeTimeSlump4.1.3SegregationandBleedingSegregation离析andBleeding泌水resultsinNonhomogeneity不均匀性Excessivebleeding----WeaktoplayerSegregationReasonsofsegregationVerywetmixtures,lackoffinepart