土木工程专业英语 教学课件 作者 陈瑛 2.1 Materials for Concrete and Mix Proportions .ppt

《土木工程专业英语 教学课件 作者 陈瑛 2.1 Materials for Concrete and Mix Proportions .ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、2.1MaterialsforConcreteandMixProportionsConstituentsofconcreteMixtureofaggregateandpastePaste(30to40%)Portlandcement(7%to15%byVol.)Water(14%to21%byVol.)Aggregates60%to70%CoarseaggregatesFineaggregatesAdmixturesThe10-20-30-40Rule?Theessentialingredientsofconcrete.?Atypicalconcrete

2、batch,byvolume,contains?10%cement?20%waterandair?30%sand?40%gravelCement,Water,FineandCoarseAggregatesAdmixture(Chemicals)CementGelStone-likeMaterialMixtureReaction(Water+Cement)Hydration(ExothermicReaction)ProducingSignificantHeatBondingfineandcoarseaggregatesPortlandCementDrypo

3、wderofveryfineparticlesFormsapastewhenmixedwithwaterChemicalreaction-HydrationGelPastecoatsalltheaggregatestogetherHardensandformsasolidmassWaterNeededfortwopurposes:chemicalreactionwithcementworkabilityOnly1/3ofthewaterisneededforchemicalreactionMorewater(twicethanasneededforrea

4、ctionwithcement)areaddedforworkabilityExtrawaterremainsinporesandholesresultsinporosityGoodforpreventingplasticshrinkagecrackingandworkabilityBadforpermeability,strength,durability.AggregatesCheapfillersHardmaterialProvideforvolumestabilityPreventvolumechangesProvideabrasionresis

5、tanceAdmixturesSetretardingadmixtures缓凝剂Setacceleratingadmixtures速凝剂Waterreducingadmixtures减水剂Superplasticizers高效减水剂Airentrainingadmixtures加气剂Mineralflyash（粉煤灰）silicafume（硅灰）slags(矿渣）DesirablepropertyofplasticconcreteWorkability:workintoallpartsofcontainingformseaseofplacementres

6、istancetosegregationhomogeneousmassSlumptestConsistencyAbilitytoflowDesirablepropertyofhardenedconcreteStrengthStronginCompressionweakintensiontensilestrength~1/10ofcompressionstrengthsteelisusedtoreinforceconcreteDurability:abrasionresistancetoughnessWater-tightnessStrengthofCon

7、creteaffectedby:Water/Cementratio(seeFigurenext)Curingconditions(moistorair,Figurenext)Durability:weather,suchascycleoffreezingandthawing(high-strength,airentrainedconcrete)seawaterordeicingsalt(sulfatesdeteriorateconcrete;solution:TypesIIorV)VariationofCompressivestrengthwithwat

8、er/cementratioTheEffectofCuringonCompres