材料概論雙語(yǔ)第五章水泥

CementandConcreteMaterialsCementandConcreteMaterials

5.1PortlandCementandItsMajorConstituentPhases5.1.1PortlandCementGeneral

Portlandcementismadebyheatingamixtureoflimestoneandclay,orothermaterialsofsimilarbulk,compositionandsufficientreactivityultimatelytoatemperatureofabout1450℃.partialfusionoccursandnodulesofclinkerareproduced.Theclinkertypicallyhasacompositionintheregionof67％CaO,22％SiO2,5％Al2O3,3％Fe2O3,3％othercomponents,andnormallycontainsfour

majorphases,called

alite,belite,Alite

(Ca3SiO5)ItisthemostimportantconstituentofallnormalPortlandcementclinkers,ofwhichitconstituent50％～

70％.aluminateandferrite.Itconstitutes15％～

30％ofnormalPortlandcementclinkers.

Belite(Ca2SiO4)

Aluminate(Ca3Al2O6)

Itconstitutes5％～

10％ofmostnormalPortlandcementclinkersFerrite(Ca2AlFeO5)Itmakesup5％～

15％ofnormalPortlandcementclinkers5.1.2TypesofPortlandCement

Standardspecificationsare,ingeneral,basedpartlyonchemicalcompositionorphysicalpropertiessuchasspecificsurfacearea,andpartlyonperformancetests,suchassettingtimeorcompressivestrengthdevelopedunderstandardconditions.Thestandardspecificationswithwhichsuchcementsmustcomplyaresimilar,butnotidentical,inallcountriesandnamesareusedtodefinethematerial.

Ithasbeenproducedinvariousways,suchasvaryingthecompositiontoincreasethealitecontent,finergrindingoftheclinker,andimprovementsinthemanufacturingprocess.WhitePortlandcement

TheyaremadebyincreasingtheradioofAl2O3toFe2O3andthusrepresenttheoppositeextremeincompositiontosulfate-resistingPortlandcement.5.1.3CementChemicalNomenclatureandOtherAbbreviationsRapid–hardeningPortlandcement

thustricalciumsilicate,Ca3SiO5,canbewrittenas3Ca·SiO2.Thisdoesnotimplythattheconstituentoxideshaveanyseparateexistencewithinthestructure.Itisusualtoabbreviatetheformulaeofthecommoneroxidestosingleletters,suchasCforCaOorSforSiO,Ca3SiO5thusbecomingC3S.TechniquesChemicalformulaeincementchemistryareoftenexpressedassumsofoxides;MaterialsC-S-H=poorlycrystallingoramorphouscalciumsilicatehydrateofunspecifiedcomposotionPropertiesorreactionsAR=aluminaratioASR=alkalisilicareactionDEF=delayedettringiteformationBEI=backscatteredelectronimagingBSE=backscatteredelectron5.2GettingAcquaintedwithConcreteConcretehasseveralunusualcharacteristicsthatmakeitthemostversatileandwidelyusedofallconstructionmaterialsGettingAcquaintedwithConcretePropertiesDesiredinFreshorPlasticConcretePropertiesDesiredinHardenedConcretePropertiesofConcreteVariablesThatInfluenceConcreteQualityConsumerProductSafetyPropertiesDesiredinFreshorPlasticConcreteAlthoughfreshlymixedconcreteisplasticforashorttimeonly,certainpropertiesaredesiredatthisstagebecausetheyaffectthequalityandcostofthehardenedconcrete.PropertiesDesiredinHardenedConcreteHardenedconcreteshouldbedurable,strong,watertightandresistanttoabrasion.AllofthesepropertiesareinfluencedbythequalityofthePortlandcementpaste.PropertiesofConcreteFreshlymixedconcretecanbeformedintopracticallyanyshape.Concretecanwithstandheatandfire.Whileitcanlosestrengthwhenthetemperaturehighenough.Concreteresistsvermin,termitesandrodent.VariablesThatInfluenceConcreteQualityWater-cementRatioAggregateGradationAirEntrainmentConsumerProductSafety

Prolongedcontactbetweenwetcementandconcretemixturesshouldbeavoided.Contactwithfreshlymixedcement,mortar,grout,orconcretemaycauseskinirritationorburns.Keepallcementandconcretemixturesandproductsoutofsmallchildren.5.3Concrete：StrengthandBehaviorCencretematerialsarewidelyusedinourdailylifesuchasbuildings,bridges,sidewalks.Strengthisanimportantindicatortoassessthecommontypesofconcretehardeningproperties1.impression，tension，shearandsoonaretheinfluenceontheload-carryingcapacityofbothplainandreinforcedstructures2.Itismosteasilytodeterminetheconcerningstrength3.TheresultofstrengthtestscanbeusedasqualitativeindicationsofotherpropertiesofhardenedconcreteUniaxialBehaviorCompressionStrengthAndTensionStrengthThetypicalstress-strain（應(yīng)力-應(yīng)變）relationshipforconcretesubjectedtouniaxialcompressionisshowninpicture5.3Ifunloadingconcreteinthelinearzone，theunloadingcurvedemonstratesonlyminornonlinearity。Whenreloading，asmallhysteresisloop（磁滯回線)isformed，asshowninpicture5.4SignificanceofresultsThestrengthofconcreteinuseisimportant.Thestrengthofconcretecompressive,tensile,shear,bending,andbondstrength.Whichthemaximumcompressivestrength,tensilestrengthminimum.TheconcreteengineeringmajorpressureTherefore,theexperimentsdoconcretecompressivestrengthtestingconcretestrengthgradetodeterminetheschoolofthemixingratio,andprovidethebasisforthecontrolofthequalityofconstructionThedestructionofthestateoftheconcretespecimens1.Formingmold2.Scale3.Materialtestingmachine5.4UsesofConcretePlainconcreteisdefinedasconcretecontainingnoreinforcementConcreteintodayhasbeenusedverywidely5.4.1ReinforcedConcreteThroughaddingreinforcementinconcreteandworktogethertoimprovethemechanicalpropertiesofconcreteacombinationofmaterials.Reinforcedconcretecanbeunderalotofpressurearewidelyusedinconstruction

PrestressedconcretePrestressedconcreteisthroughthetensionbar(rope),reinforcedconcretestructuressubjectedtoexternalloadinbeforetheconcretetensioninadvancebyacertainpressurestressofconcretePrestressedconcreteisalargebuildingnecessarymaterials.Theintensitymustbehigh,withhighstrengthreinforcedadapt,ensurereinforcementtoplayitsfullrole,andcaneffectivelyreducecomponentsectionsizeandreduceweight.

Rapidhardening,earlystrength,maketheearlyprestress,speeduptheconstructionprogressandimproveequipmentutilization.Processisrelativelycomplicated,thehighqualityrequirements.Needtohavesomespecialequipment,suchastensionmachine

PrecastConcreteInrecentyears,precastconcretewithitslowcost,excellentperformance,becomeconstructiontobebestowedfavoronnewly.Variousstyle,weightandexcellentflexuralstrengthandperformanceofthebarricade,tank,exteriorwall,buildinganddecoratetheareastobewidelyapplied5.4.4

LightweightconcreteLightweightconcretecanbemadewiththeuseofeithergasgeneratingchemicals,orlightweightaggregatessuchasexpandedshale,clay,andslagInsulatinglightweightconcreteUnitweightofabout20to70poundspercubicfoot;compressivestrengthsseldomexceed1000psi.StructurallightweightconcreteUnitweightofabout115poundspercubicfoot;28-daycompressivestrengthsseldominexceedof2000psi.Semi-lightweightconcreteUnitweightof115to130poundspercubicfoot.Lightweightconcrete5.4.5

ThinshellThinshellofconcretewerefirstusedinEuropeintheearil1920s.theuseofconcreteshellshasincreasedgreatlyintheUSinrecentyears.Thinshellstructurewithconcreterigidmaterialstovarioussurfaceformsasheetstructure.Aspatialstressstatus,mainbearingsurfaceinsidetheaxialforceandbendingmomentandtorque,isverysmall,sotheconcretestrengthcanbefullyutilized.Itisaspatialstructure,strengthandstiffnessisverygood.Advantage:lightweight,materialsaving,largespan;優(yōu)勢(shì)：重量輕，節(jié)省材料，大跨度；Defect:Complexshape,useofcast-in-placeconstruction,structurecalculationiscomplex,time-consuming.缺陷：復(fù)雜的形狀，用現(xiàn)澆施工，結(jié)構(gòu)計(jì)算是復(fù)雜的，耗時(shí)的。Shotcrete

Pressuresprayingpouringfinestoneconcreteconstructionmethod.Commonlyusedintunnelliningconcreting,walls,ceilingandotherthin-walledstructureorotherstructureoftheliningandsteelstructureprotectionlayer.67Construction5.4.whenproperlymadeandapplied,shotcreteisanextremelystronganddenseconcreteandhashighresistance