混凝土工藝中英文對照外文翻譯文獻(xiàn)

中英文對照外文翻譯文獻(xiàn)混凝土工藝中英文對照外文翻譯文獻(xiàn)混凝土工藝中英文對照外文翻譯文獻(xiàn)(文檔含英文原文和中文翻譯)ConcretetechnologyanddevelopmentPortlandcementconcretehasclearlyemergedasthematerialofchoicefortheconstructionofalargenumberandvarietyofstructuresintheworldtoday.Thisisattributedmainlytolowcostofmaterialsandconstructionforconcretestructuresaswellaslowcostofmaintenance.Therefore,itisnotsurprisingthatmanyadvancementsinconcretetechnologyhaveoccurredasaresultoftwodrivingforces,namelythespeedofconstructionandthedurabilityofconcrete.Duringtheperiod1940-1970,theavailabilityofhighearlystrengthportlandcementsenabledtheuseofhighwatercontentinconcretemixturesthatwereeasytohandle.Thisapproach,however,ledtoseriousproblemswithdurabilityofstructures,especiallythosesubjectedtosevereenvironmentalexposures.Withuslightweightconcreteisadevelopmentmainlyofthelasttwentyyears.Concretetechnologyisthemakingofplentifulgoodconcretecheaply.Itincludesthecorrectchoiceofthecementandthewater,andtherighttreatmentoftheaggregates.Thosewhicharedugnearbyandthereforecheap,mustbesized,washedfreeofclayorsilt,andrecombinedinthecorrectproportionssoastomakeacheapconcretewhichisworkableatalowwater/cementratio,thuseasilycomoactedtoahighdensityandthereforestrong.Ithardenswithageandtheprocessofhardeningcontinuesforalongtimeaftertheconcretehasattainedsufficientstrength.Abrams’law,perhapstheoldestlawofconcretetechnology,statesthatthestrengthofaconcretevariesinverselywithitswatercementratio.Thismeansthatthesandcontent(particularlythefinesandwhichneedsmuchwater)mustbereducedsofaraspossible.Thefactthatthesand“drinks”largequantitiesofwatercaneasilybeestablishedbymixingseveralbatchesofxkgofcementwithykgofstoneandthesameamountofwaterbutincreasingamountsofsand.Howeverifthereisnosandtheconcretewillbesostiffthatitwillbeunworkablethereforwporousandweak.Thesamewillbetrueifthesandistoocoarse.Thereforeforeachsetofaggregates,thecorrectmixmustnotbechangedwithoutgoodreason.Thisappliedparticularlytothewatercontent.Anydrinkableandmanyundrinkablewaterscanbeusedformakingconcrete,includingmostclearwatersfromtheseaorrivers.Itisimportantthatclayshouldbekeptoutoftheconcrete.Thecementiffreshcanusuallybechosenonthebasisofthemaker’scertificatesoftensileorcrushingtests,butthesearealwaysmadewithfreshcement.Wherestrengthisimportant,andthecementatthesiteisold,itshouldbetested.Thisstress,causingbreakage,willbeatensionsinceconcretesarefrom9to11timesasstrongincompressionasintension,Thisstress,themodulusofrupture,willberoughlydoublethedirecttensilebreakingstressobtainedinatensiletestingmachine,soaveryroughguessattheconpressivestrengthcanbemadebymultiplyingthemodulusofruptureby4.5.Themethodcanbeusedincombinationwiththestrengthresultsofmachine-crushedcubesorcylindersortensiletestpiecesbutcannototherwiseberegardedasreliable.Withthesecomparisons,however,itissuitableforcomparingconcretesonthesamesitemadefromthesameaggregatesandcement,withbeamscastandtestedinthesameway.Extremecareisnecessaryforpreparation,transport,platingandfinishofconcreteinconstructionworks.Itisimportanttonotethatonlyabitofcareandsupervisionmakeagreatdifferencebetweengoodandbadconcrete.Thefollowingfactorsmaybekeptinmindinconcretingworks.MixingThemixingofingredientsshallbedoneinamixerasspecifiedinthecontract.HandlingandConveyingThehandling&conveyingofconcretefromthemixertotheplaceoffinaldepositshallbedoneasrapidlyaspracticableandwithoutanyobjectionableseparationorlossofingredients.Wheneverthelengthofhaulfromthemixingplanttotheplaceofdepositissuchthattheconcreteundulycompactsorsegregates,suitableagitatorsshallbeinstalledintheconveyingsystem.Whereconcreteisbeingconveyedonchutesoronbelts,thefreefallordropshallbelimitedto5ft.(or150cm.)unlessotherwisepermitted.Theconcreteshallbeplacedinpositionwithin30minutesofitsremovalfromthemixer.PlacingConcreteNoconcreteshallbeplaceduntiltheplaceofdeposithasbeenthoroughlyinspectedandapproved,allreinforcement,insertsandembeddedmetalproperlysecurityinpositionandchecked,andformsthoroughlywetted(expectinfreezingweather)oroiled.Placingshallbecontinuedwithoutavoidableinterruptionwhilethesectioniscompletedorsatisfactoryconstructionjointmade.WithinFormsConcreteshallbesystematicallydepositedinshallowlayersandatsuchrateastomaintain,untilthecompletionoftheunit,aplasticsurfaceapproximatelyhorizontalthroughout.Eachlayershallbethoroughlycompactedbeforeplacingthesucceedinglayer.CompactingMethod.Concreteshallbethoroughlycompactedbymeansofsuitabletoolsduringandimmediatelyafterdepositing.Theconcreteshallbeworkedaroundallreinforcement,embeddedfixtures,andintothecomersoftheforms.Everyprecautionshallbetakentokeepthereinforcementandembeddedmetalinproperpositionandtopreventdistortion.Vibrating.Whereverpracticable,concreteshallbeinternallyvibratedwithintheforms,orinthemass,inordertoincreasetheplasticityastocompacteffectivelytoimprovethesurfacetextureandappearance,andtofacilitateplacingoftheconcrete.Vibrationshallbecontinuedtheentirebatchmeltstoauniformappearanceandthesurfacejuststartstoglisten.Aminutefilmofcementpasteshallbediscerniblebetweentheconcreteandtheformandaroundthereinforcement.Overvibrationcausingsegregation,unnecessarybleedingorformationoflaitanceshallbeavoided.Theeffectspentoncarefulgrading,mixingandcompactionofconcretewillbelargelywastediftheconcreteisbadlycured.Curingmeanskeepingtheconcretethoroughlydampforsometime,usuallyaweek,untilithasreachedthedesiredstrength.Solongasconcreteiskeptwetitwillcontinuetogainstrength,thoughmoreslowlyasitgrowsolder.Admixturesoradditivestoconcretearematerialsarematerialswhichareaddedtoitortothecementsoastoimproveoneormoreofthepropertiesoftheconcrete.Themaintypesare:1.Acceleratorsofsetorhardening,2.Retardersofsetorhardening,3.Air-entrainingagents,includingfrothingorfoamingagents,4.Gassingagents,5.Pozzolanas,blast-furnaceslagcement,pulverizedcoalash,6.Inhibitorsofthechemicalreactionbetweencementandaggregate,whichmightcausetheaggregatetoexpand7.Agentsfordamp-proofingaconcreteorreducingitspermeabilitytowater,8.Workabilityagents,oftencalledplasticizers,9.Groutingagentsandexpandingcements.Whereverpossible,admixturesshouldbeavouded,particularlythosethatareaddedonsite.Smallvariationsinthequantityaddedmaygreatlyaffecttheconcretepropertiesinanundesiraaleway.Anacceleratorcanoftenbeavoidedbyusingarapid-hardeningcementorarichermixwithordinarycement,orforveryrapidgainofstrength,high-aluminacement,thoughthisisverymuchmoreexpensive,inBritainaboutthreetimesascostlyasordinaryPortlandcement.Butintwenty-fourhoursitsstrengthisequaltothatreachedwithordinaryPortlandcementinthirtydays.Aretardermayhavetobeusedinwarmweatherwhenalargequantityofconcretehastobecastinonepieceofformwork,anditisimportantthattheconcretecastearlyinthedaydoesnotsetbeforethelastconcrete.Thisoccurswithbridgeswhentheyarecastinplace,andtheformworknecessarilybendsundertheheavyloadofthewetconcrete.Someretarderspermanentlyweakentheconcreteandshouldnotbeusedwithoutgoodtechnicaladvice.Asomewhatsimilareffect,milderthanthatofretarders,isobtainedwithlow-heatcement.Thesemaybesoldbythecementmakerormixedbythecivilengineeringcontractor.Theygiveoutlessheatonsettingandhardening,partlybecausetheyhardenmoreslowly,andtheyareusedinlargecastssuchasgravitydams,wheretheconcretemaytakeyearstocooldowntothetemperatureofthesurroundingair.IncountrieslikeBritainorFrance,wherepulverizedcoalisburntinthepowerstations,theash,whichisveryfine,hasbeenmixedwithcementtoreduceitsproductionofheatanditscostwithoutreducingitslong-termstrength.Uptoabout20percentashbyweightofthecementhasbeensuccessfullyused,withconsiderablesavingsincementcosts.Incountrieswhereair-entrainingcementcementcanbeboughtfromthecementmaker,noair-entrainingagentneedstobemixedin.Whenair-entrainingagentsdrawintothewetcementandconcretesome3-8percentofairintheformofverysmallbubbles,theyplasticizetheconcrete,makingitmoreeasilyworkableandthereforeenablethewater|cementratiotobereduced.TheyreducethestrengthoftheconcreteslightlybutsolittlethatintheUnitedStatestheiruseisnowstandardpracticeinroad-buildingwhereheavyfrostoccur.Theygreatlyimprovethefrostresistanceoftheconcrete.PozzolaneisavolcanicashfoundneartheItaliantownofPuzzuoli,whichisanaturalcement.Thenamehasbeengiventoallnaturalmineralcements,aswellastotheashfromcoalortheslagfromblastfurnaces,bothofwhichmaybecomecementswhengroundandmixedwithwater.PozzolanasofeithertheindustrialorthemineraltypeareimportanttocivilengineersbecausetheyhavebeenaddedtooridinaryPortlandcementinproportionsuptoabout20percentwithoutlossofstrengthinthecementandwithgreatsavingsincementcost.Theirmaininterestisinlargedams,wheretheymayreducetheheatgivenoutbythecementduringhardening.Somepozzolanashavebeenknowntopreventtheactionbetweencementandcertainaggregateswhichcausestheaggregatetoexpand,andweakenorbursttheconcrete.Thebestwayofwaterproofaconcreteistoreduceitspermeabilitybycarefulmixdesignandmanufactureoftheconcrete,withcorrectplacingandtighrcompactioninstrongformworkaralowwater|cementratio.Evenanair-entrainingagentcanbeusedbecausetheminuteporesarediscontinuous.Slow,carefulcuringoftheconcreteimprovesthehydrationofthecement,whichhelpstoblockthecapillarypassagesthroughtheconcretemass.Anasphaltorotherwaterproofingmeansthewaterproofingofconcretebyanymethodconcernedwiththequalityoftheconcretebutnotbyawaterproofskin.Workabilityagents,water-reducingagentsandplasticizersarethreenamesforthesamething,mentionedunderair-entrainingagents.Theirusecansometimesbeavoidedbyaddingmorecementorfinesand,orevenwater,butofcourseonlywithgreatcare.Therapidgrowthfrom1945onwardsintheprestressingofconcreteshowsthattherewasarealneedforthishigh-qualitystructuralmaterial.Thequalitymustbehighbecausetheworstconditionsofloadingnormallyoccuratthebeginningofthelifeofthemember,atthetransferofstressfromthesteeltotheconcrete.Failureisthereforemorelikelythenthanlater,whentheconcretehasbecomestrongerandthestressinthesteelhasdecreasedbecauseofcreepinthesteelandconcrete,andshrinkageoftheconcrete.Faultymembersarethereforeobservedandthrownoutearly,beforetheyenterthestructure,oratleastbeforeitThemainadvantagesofprestressedconcreteincomparisonwithreinforcedconcreteare:Thewholeconcretecross-sectionresistsload.Inreinforcedconcreteabouthalfthesection,thecrackedareabelowtheneutralaxis,doesnousefulwork.Workingdeflectionsaresmaller.Highworkingstressesarepossible.Inreinforcedconcretetheyarenotusuallypossiblebecausetheyresultinseverecrackingwhichisalwaysuglyandmaybedangerousifitcausesrustingofthesteel.Crackingisalmostcompletelyavoidedinprestressedconcrete.Themaindisadvantageofprestressedconcreteisthatmuchmorecareisneededtomakeitthanreinforcedconcreteanditisthereforemoreexpensive,butbecauseitisofhigherqualitylessofitneedstobeneedstobeused.Itcanthereforehappenthatasolutionofastructuralproblemmaybecheaperinprestressedconcretethaninreinforcedconcrete,anditdoesoftenhappenthatasolutionispossiblewithprestressingbutimpossiblewithoutit.Prestressingoftheconcretemeansthatitisplacedundercompressionbeforeitcarriesanyworkingload.Thismeansthatthesectioncanbedesignedsothatittakesnotensionorverylittleunderthefulldesignload.Itthereforehastheoreticallynocracksandinpracticeveryfew.Theprestressisusuallyappliedbytensioningthesteelbeforetheconcreteinwhichitisembeddedhashardened.Aftertheconcretehashardenedenoughtotakethestressfromthesteeltotheconcrete.Inabridgewithabutmentsabletoresistthrust,theprestresscanbeappliedwithoutsteelintheconcrete.Itisappliedbyjacksforcingthebridgeinwardsfromtheabutments.Thismethodshastheadvantagethatthejackingforce,orprestress,canbevariedduringthelifeofthestructureasrequired.Inthetenyearsfrom1950to1960prestressedconcreteceasedtobeanexperinmentalmaterialandengineerswonconfidenceinitsuse.Withthisconfidencecameanincreaseintheuseofprecastprestressedconcreteparticularlyforlong-spanfloorsorthedecksofmotorways.Whereeverthequantitytobemadewaslargeenough,forexampleinamotorwaybridge500mkong,providedthatmostofthespanscouldbemadethesameandnotmuchlongerthan18m,itbecameeconomicaltousefactory-precastprestressedbeams,atleastinindustrialareasnearaprecastingfactoryprestressedbeams,atleastinindustrialareasnearaprecastingfactory.Mostofthesebeamsareheat-curedsoastofreetheformsquicklyforre-use.Inthisperiodalso,intheUnitedStates,precastprestressedroofbeamsandfloorbeamswereusedinmanyschoolbuildings,occasionally32mlongormore.Suchlongbeamsoverasinglespancouldnotpossiblybesuccessfulinreinforcedconcreteunlesstheywerecastonsitebecausetheywouldhavetobemuchdeeperandmuchheavierthanprestressedconcretebeams.Theywouldcertainllybelesspleasingtotheeyeandoftenmoreexpensivethantheprestressedconcretebeams.Theseschoolbuildingshaveastrong,simplearchitecturalappealandwillbeapleasuretolookatformanyyears.Themostimportantpartsofaprecastprestressedconcretebeamarethetendonsandtheconcrete.Thetendons,asthenameimplies,arethecables,rodsorwiresofsteelwhichareundertensionintheconcrete.Beforetheconcretehashardened(beforetransferofstress),thetendonsareeitherunstressed(post-tensionedprestressing)orarestressedandheldbyabutmentsoutsidetheconcrete(pre-tensionedprestressing).Whiletheconcreteishardeningitgripseachtendonmoreandmoretightlybybondalongitsfulllength.Endanchoragesconsistingofplatesorblocksareplacedontheendsofthetendonsofpost-tensionedprestressedunits,andsuchtendonsarestressedupatthetimeoftransfer,whentheconcretehashardenedsufficiently.Intheothertypeofpretressing,withpre-tensionedtendons,thetendonsarereleasedfromexternalabutmentsatthemomentoftransfer,andactontheconcretethroughbondorarchorageorboth,shorteningitbycompression,andthemselvesalsoshorteningandlosingsometension.Furthershorteningoftheconcrete(andthereforeofthesteel)takesplacewithtime.Theconcreteissaidtocreep.Thismeansthatitshortenspermanentlyunderloadandspreadsthestressesmoreuniformlyandthusmoresafelyacrossitssection.Steelalsocreeps,butratherless.Theresultofthesetwoeffects(andoftheconcreteshrinkingwhenitdries)isthatprestressedconcretebeamsarenevermorehighlystressedthanatthemomentoftransfer.Thefactoryprecastingoflongprestressedconcretebeamsislikelytobecomemoreandmorepopularinthefuture,butonedifficultywillberoadtransport.Asthelengthofthebeamincreases,thelorrybecomeslessandlessmanoeuvrableuntileventuallytheonlysuitabletimeforittotravelisinthemiddleofthenightwhentrafficinthedistrictandtheroute,whethertheroadsarestraightorcurved.Precastingatthesiteavoidsthesedifficulties;itmaybeexpensive,butithasoftenbeenusedforlargebridgebeams.混凝土工藝及發(fā)展 波特蘭水泥混凝土在當(dāng)今世界已成為建造數(shù)量繁多、種類復(fù)雜結(jié)構(gòu)的首選材料。這主要?dú)w功于混凝土結(jié)構(gòu)的材料和施工成本以及維修費(fèi)用低。因此,隨著技術(shù)的不斷提高在施工速度和混凝土耐久性兩個方面取得突破已不足為奇。1940至1970年期間,提高高強(qiáng)硅酸鹽水泥混凝土混合物中的含水量從而使混凝土易于搬運(yùn)和處理的方法被廣為使用。然而，這種做法卻對結(jié)構(gòu)的耐久性產(chǎn)生很大的影響，特別是那些處于惡劣環(huán)境中的結(jié)構(gòu)。對于我們來說，輕質(zhì)混凝土主要是最近二十年來發(fā)展起來的。混凝土工藝就是便宜地制備大量優(yōu)質(zhì)混凝土的過程，包括正確選用水泥和水以及正確加工處理骨料。就進(jìn)開采價廉的骨料同時進(jìn)行篩分，洗去粘土或泥沙，并且以正確的比例重新組合，以便在低水灰比的情況下配置成和易性良好而且成本低廉的混凝土，這種混凝土因容易搗實到很高的密實度而具有很高的強(qiáng)度。混凝土隨著齡期而逐漸硬化，當(dāng)混泥土已經(jīng)達(dá)到足夠的強(qiáng)度后，水化的過程還會持續(xù)很長的一段時間。阿布拉姆斯定律，可能是混凝土工藝學(xué)最古老的定律，它指出混凝土強(qiáng)度的變化與其水灰比成反比。這意味著砂的含量（特別是需水量大的細(xì)沙）必須盡可能地減少。砂子能“喝”大量水的事實不難由下述實驗證明，在用水量相同但用砂量遞減的情況下，用Y公斤石子同X公斤水泥攪拌幾批混凝土。如果沒有砂子，混凝土就非常干硬而且和易性很差，因而孔多強(qiáng)度低。如果經(jīng)過細(xì)心的實驗，選擇正確的配合比。配合比一經(jīng)確定之后，沒有充分的理由是不能變動的。特別是針對于用水量。任何可飲用水和一些非飲用水都可用以配制混凝土，包括大部分取自?；蚝恿鞯那鍧嵥?。在混凝土中清除粘土是很重要的。水泥如果是新制成的，通常可根據(jù)制造廠的拉伸或壓碎實驗證明書來選用，但是這種實驗經(jīng)常是用新制成的水泥來做的。在強(qiáng)度極為重要的情況下，水泥在工地上存放過久時，水泥必須經(jīng)過試驗。由于混凝土的抗壓強(qiáng)度為其抗拉強(qiáng)度的9到11倍，引起斷折的應(yīng)力是拉應(yīng)力。此應(yīng)力即斷裂模量，大約為拉伸試驗機(jī)所得直接拉伸斷裂應(yīng)力值的兩倍。因此將彎折強(qiáng)度乘以4.5，可粗略地估計出抗壓強(qiáng)度。此方法可同機(jī)械壓碎立方體或圓柱體或拉伸試件等的強(qiáng)度試驗結(jié)果配合使用，否則，這種方法就適宜于用梁對各種混凝土進(jìn)行比較，梁是以同樣同樣方式澆制和試驗的，而混凝土是在同一工地上由同樣的骨料和水泥配制的。施工過程中必須要特別注意混凝土的準(zhǔn)備、運(yùn)輸、澆筑及澆筑完成等工作。稍許的留意和監(jiān)督就會使混凝土質(zhì)量的好壞產(chǎn)生很大的差異，注意到這一點很重要?；炷潦┕ぶ?，以下因素應(yīng)當(dāng)謹(jǐn)記。攪拌各組成材料應(yīng)當(dāng)按合同中的規(guī)定在攪拌機(jī)中攪拌。裝卸輸送混凝土混凝土從攪拌機(jī)到最終澆筑位置間的裝卸運(yùn)輸應(yīng)當(dāng)既快又好的完成，不發(fā)生離析或成分損失。無論什么時候，從攪拌設(shè)備到澆筑地點之間的距離，不應(yīng)使混凝土變稠或離析，運(yùn)輸系統(tǒng)中要安裝合適的攪拌器?；炷翍?yīng)通過斜槽或輸送帶進(jìn)行傳送，除非允許，否則自由下落高度應(yīng)當(dāng)控制在5ft（或150cm）?；炷嗤翍?yīng)當(dāng)在30min內(nèi)從攪拌機(jī)運(yùn)送到澆筑地點。澆筑混凝土澆筑混凝土之前，澆筑地點必須經(jīng)過完全的檢查并經(jīng)允許，所有鋼筋、預(yù)埋件及內(nèi)置金屬恰當(dāng)可靠地安裝到位并經(jīng)檢查合格，模范完全侵濕（冰雪天氣除外）或上油。澆筑混凝土應(yīng)當(dāng)無間斷地連續(xù)進(jìn)行，澆筑部分完整，或接縫可靠。入?；炷翍?yīng)當(dāng)有條理地按薄層澆注，并保持這種的速度，直到澆筑完整個單元，整個單元的塑形表面大致水平。每一層混凝土應(yīng)當(dāng)在后一層澆筑前進(jìn)行壓實。密實方法:混凝土在澆筑期間或澆筑后立即使用合適的工具進(jìn)行密實?；炷翍?yīng)包裹鋼筋及內(nèi)置夾具，填滿模板空間。要采取措施保證鋼筋和預(yù)埋金屬的準(zhǔn)確位置，防止變形。振搗:澆筑過程中，混凝土應(yīng)當(dāng)在模板內(nèi)進(jìn)行內(nèi)部振搗，以此來增加可塑性，使其充分密實從而改善表面組織及觀感，還便于混凝土的澆筑。振搗應(yīng)持續(xù)到整批混凝土完全混合，外觀均勻且表面開始泛光。在混凝土與模板間以及鋼筋周圍，可以看出一薄層水泥漿膜。過度的振搗會引起離析、不必要的泌水，或生成浮漿，應(yīng)當(dāng)避免。如果混凝土養(yǎng)護(hù)得很差，那么在精心選定的混凝土的級配、拌合和密實成型上所耗費(fèi)的精力將是徒勞無益的。養(yǎng)護(hù)是指在一定的時間內(nèi)，通常是一個星期內(nèi)，充分保持混凝土的濕度，直到它達(dá)到所要求的強(qiáng)度。只要保持混凝土潮濕不干，它就能繼續(xù)獲得強(qiáng)度，雖然齡期越長，混凝土強(qiáng)度的增長越來越慢?；炷恋膿胶蟿┗蛲饧觿?，是摻合劑混凝土或水泥中的各種材料，以便改善混凝土的某個或幾方面的特性。其主要類型是：1.凝結(jié)或硬化方面的速凝劑，2.凝結(jié)或硬化方面的緩凝劑，3.加氣劑，包括起泡劑或泡沫劑，4.發(fā)氣劑5.火山灰，高爐礦渣水泥，粉煤灰6.水泥和骨料間化學(xué)反應(yīng)的抑制劑，抑制劑可能引起骨料膨脹7.混凝土防水用或降低混凝土滲透性的外加劑8.改善和易性的外加劑，通常叫塑化劑9.灌漿劑及膨脹水泥在可能的情況下，應(yīng)當(dāng)盡量避免使用摻合劑，特別是避免使用須在施工現(xiàn)場摻合的摻合劑，所摻和的數(shù)量有微小的變化就可能對混凝土的性質(zhì)有很大的影響，而且甚至數(shù)量準(zhǔn)確時，也可能使混凝土性質(zhì)變劣，達(dá)不到要求。采用以下方法往往能夠避免使用速凝劑，采用速凝水泥或者采用普通水泥而配比較富，或者使用能很快獲得強(qiáng)度的水泥，即高礬土水泥，盡管這種水泥成本很高，在英國，其成本約為普通勃蘭特水泥的三倍。但是在23小時內(nèi)，它的強(qiáng)度就等于普通水泥30天所能達(dá)到的強(qiáng)度。天氣溫暖而又要將大量的混凝土澆注到一套模板內(nèi)時，可能需要使用緩凝劑，而且重要的是使當(dāng)天早些時候澆注的混凝土在澆注后來的混凝土以前不凝結(jié)。這種情況往往發(fā)生在現(xiàn)場澆注的橋梁中，即當(dāng)模板在濕混凝土重載作用下勢必發(fā)生彎曲變形。某些緩凝劑對混凝土起長期的消弱作用，沒有良好的技術(shù)指導(dǎo)不得使用。采用低熱水泥能得到類似于緩凝劑的作用，但卻能起到比之更為緩和的效果。低熱水泥可由水泥制造廠商發(fā)售，或者由土木工程承包廠商配制。低熱水泥在凝結(jié)和硬化時放出的熱量較少，部分煙癮是因其硬化較慢，因而用于像重力壩那樣的小型混凝土工程中。重力壩的混凝土可能需要數(shù)年才能冷卻到周圍大氣的溫度。在英國或法國這樣一些國家中，電站里燃燒的是煤粉，其煤灰很細(xì)，已經(jīng)摻到水泥中以降低水泥產(chǎn)生的熱量，并降低水泥成本，但不降低其后期強(qiáng)度。已經(jīng)成功地應(yīng)用了高達(dá)水泥重量的20％的粉煤灰摻加量，顯著地降低了水泥的成本。在一些國家中，可從水泥制造廠處買到加氣水泥，故不需要在摻入加氣劑。當(dāng)加氣劑將3-8％的呈十分細(xì)小的氣泡狀得空氣吸進(jìn)濕的水泥和混凝土中時，這些氣泡使混凝土塑化，易于澆注成型，但是降低數(shù)值很小，所以在美國對有很嚴(yán)重凍害出現(xiàn)的筑路工程中，現(xiàn)在的標(biāo)準(zhǔn)做法是使用加氣劑。加氣劑大大地改善了混凝土的抗凍性。白塯火山灰是一種產(chǎn)于意大利波佐理鎮(zhèn)附近的火山灰，這時一種天然水泥。所有天然礦物質(zhì)膠凝材料都曾命