lecture3混凝土结构设计原理-英文课件.ppt

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1、Lecture3-FundamentalsJune6,2003CVEN444LectureGoalsConcretePropertiesSteelPropertiesConcreteMixingandProportioningQualityWorkabilityEconomicalInthedesignofconcretemixes,threeprincipalrequirementsforconcreteareofimportance:ConcreteMixingandProportioningQualityofconcreteismeasuredbyitsstrengthanddu

2、rability.Theprincipalfactorsaffectingthestrengthofconcrete,assumingasoundaggregates,W/Cratio,andtheextenttowhichhydrationhasprogressed.Durabilityofconcreteistheabilityoftheconcretetoresistdisintegrationduetofreezingandthawingandchemicalattack.ConcreteMixingandProportioningWorkabilityofconcretema

3、ybedefinedasacompositecharacteristicindicativeoftheeasewithwhichthemassofplasticmaterialmaydepositedinitsfinalplacewithoutsegregationduringplacement,anditsabilitytoconformtofineformingdetail.ConcreteMixingandProportioningEconomicaltakesintoaccounteffectiveuseofmaterials,effectiveoperation,andeas

4、eofhandling.Thecostofproducinggoodqualityconcreteisanimportantconsiderationintheoverallcostoftheconstructionproject.ConcreteMixingandProportioningTheinfluenceofingredientsonpropertiesofconcrete.ConcreteMixingandProportioning3.WorkabilityWorkabilitymeasuredbyslumptestLayer1:Fill1/3full.25stokesLa

5、yer2:Fill2/3full.25stokesLayer3:Fillfull.25stokesLiftconeandmeasureslump(typically2-6in.)123412”slumpConcreteMixingandProportioningSlumptest-Themeasurementoftheconsistencyofthemixisdonewiththeslump-conetest.Therecommendconsistencyforvariousclassesofconcretestructures.ConcreteMixingandProportioni

6、ng4.AdmixturesApplications:ImproveworkabilityAccelerateorretardsettingandhardeningAidincuringImprovedurabilityConcreteMixingandProportioning4.AdmixturesAir-Entrainment:AddairvoidswithbubblesHelpwithfreeze/thawcycles,workability,etc.Decreasesdensity:reducesstrength,butalsodecreasesW/CSuperplastic

7、izers:increaseworkabilitybychemicallyreleasingwaterfromfineaggregates.ConcreteMixingandProportioning5.TypesofCementTypeI:GeneralPurposeTypeII:LowerheatofhydrationthanTypeITypeIII:HighEarlyStrengthHigherheatofhydrationquicker