混凝土工艺中英文对照外文翻译文献

中英文对照外文翻译文献混凝土工艺中英文对照外文翻译文献混凝土工艺中英文对照外文翻译文献(文档含英文原文和中文翻译)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.混凝土工艺及发展 波特兰水泥混凝土在当今世界已成为建造数量繁多、种类复杂结构的首选材料。这主要归功于混凝土结构的材料和施工成本以及维修费用低。因此,随着技术的不断提高在施工速度和混凝土耐久性两个方面取得突破已不足为奇。1940至1970年期间,提高高强硅酸盐水泥混凝土混合物中的含水量从而使混凝土易于搬运和处理的方法被广为使用。然而，这种做法却对结构的耐久性产生很大的影响，特别是那些处于恶劣环境中的结构。对于我们来说，轻质混凝土主要是最近二十年来发展起来的。混凝土工艺就是便宜地制备大量优质混凝土的过程，包括正确选用水泥和水以及正确加工处理骨料。就进开采价廉的骨料同时进行筛分，洗去粘土或泥沙，并且以正确的比例重新组合，以便在低水灰比的情况下配置成和易性良好而且成本低廉的混凝土，这种混凝土因容易捣实到很高的密实度而具有很高的强度。混凝土随着龄期而逐渐硬化，当混泥土已经达到足够的强度后，水化的过程还会持续很长的一段时间。阿布拉姆斯定律，可能是混凝土工艺学最古老的定律，它指出混凝土强度的变化与其水灰比成反比。这意味着砂的含量（特别是需水量大的细沙）必须尽可能地减少。砂子能“喝”大量水的事实不难由下述实验证明，在用水量相同但用砂量递减的情况下，用Y公斤石子同X公斤水泥搅拌几批混凝土。如果没有砂子，混凝土就非常干硬而且和易性很差，因而孔多强度低。如果经过细心的实验，选择正确的配合比。配合比一经确定之后，没有充分的理由是不能变动的。特别是针对于用水量。任何可饮用水和一些非饮用水都可用以配制混凝土，包括大部分取自海或河流的清洁水。在混凝土中清除粘土是很重要的。水泥如果是新制成的，通常可根据制造厂的拉伸或压碎实验证明书来选用，但是这种实验经常是用新制成的水泥来做的。在强度极为重要的情况下，水泥在工地上存放过久时，水泥必须经过试验。由于混凝土的抗压强度为其抗拉强度的9到11倍，引起断折的应力是拉应力。此应力即断裂模量，大约为拉伸试验机所得直接拉伸断裂应力值的两倍。因此将弯折强度乘以4.5，可粗略地估计出抗压强度。此方法可同机械压碎立方体或圆柱体或拉伸试件等的强度试验结果配合使用，否则，这种方法就适宜于用梁对各种混凝土进行比较，梁是以同样同样方式浇制和试验的，而混凝土是在同一工地上由同样的骨料和水泥配制的。施工过程中必须要特别注意混凝土的准备、运输、浇筑及浇筑完成等工作。稍许的留意和监督就会使混凝土质量的好坏产生很大的差异，注意到这一点很重要。混凝土施工中，以下因素应当谨记。搅拌各组成材料应当按合同中的规定在搅拌机中搅拌。装卸输送混凝土混凝土从搅拌机到最终浇筑位置间的装卸运输应当既快又好的完成，不发生离析或成分损失。无论什么时候，从搅拌设备到浇筑地点之间的距离，不应使混凝土变稠或离析，运输系统中要安装合适的搅拌器。混凝土应通过斜槽或输送带进行传送，除非允许，否则自由下落高度应当控制在5ft（或150cm）。混泥土应当在30min内从搅拌机运送到浇筑地点。浇筑混凝土浇筑混凝土之前，浇筑地点必须经过完全的检查并经允许，所有钢筋、预埋件及内置金属恰当可靠地安装到位并经检查合格，模范完全侵湿（冰雪天气除外）或上油。浇筑混凝土应当无间断地连续进行，浇筑部分完整，或接缝可靠。入模混凝土应当有条理地按薄层浇注，并保持这种的速度，直到浇筑完整个单元，整个单元的塑形表面大致水平。每一层混凝土应当在后一层浇筑前进行压实。密实方法:混凝土在浇筑期间或浇筑后立即使用合适的工具进行密实。混凝土应包裹钢筋及内置夹具，填满模板空间。要采取措施保证钢筋和预埋金属的准确位置，防止变形。振捣:浇筑过程中，混凝土应当在模板内进行内部振捣，以此来增加可塑性，使其充分密实从而改善表面组织及观感，还便于混凝土的浇筑。振捣应持续到整批混凝土完全混合，外观均匀且表面开始泛光。在混凝土与模板间以及钢筋周围，可以看出一薄层水泥浆膜。过度的振捣会引起离析、不必要的泌水，或生成浮浆，应当避免。如果混凝土养护得很差，那么在精心选定的混凝土的级配、拌合和密实成型上所耗费的精力将是徒劳无益的。养护是指在一定的时间内，通常是一个星期内，充分保持混凝土的湿度，直到它达到所要求的强度。只要保持混凝土潮湿不干，它就能继续获得强度，虽然龄期越长，混凝土强度的增长越来越慢。混凝土的掺合剂或外加剂，是掺合剂混凝土或水泥中的各种材料，以便改善混凝土的某个或几方面的特性。其主要类型是：1.凝结或硬化方面的速凝剂，2.凝结或硬化方面的缓凝剂，3.加气剂，包括起泡剂或泡沫剂，4.发气剂5.火山灰，高炉矿渣水泥，粉煤灰6.水泥和骨料间化学反应的抑制剂，抑制剂可能引起骨料膨胀7.混凝土防水用或降低混凝土渗透性的外加剂8.改善和易性的外加剂，通常叫塑化剂9.灌浆剂及膨胀水泥在可能的情况下，应当尽量避免使用掺合剂，特别是避免使用须在施工现场掺合的掺合剂，所掺和的数量有微小的变化就可能对混凝土的性质有很大的影响，而且甚至数量准确时，也可能使混凝土性质变劣，达不到要求。采用以下方法往往能够避免使用速凝剂，采用速凝水泥或者采用普通水泥而配比较富，或者使用能很快获得强度的水泥，即高矾土水泥，尽管这种水泥成本很高，在英国，其成本约为普通勃兰特水泥的三倍。但是在23小时内，它的强度就等于普通水泥30天所能达到的强度。天气温暖而又要将大量的混凝土浇注到一套模板内时，可能需要使用缓凝剂，而且重要的是使当天早些时候浇注的混凝土在浇注后来的混凝土以前不凝结。这种情况往往发生在现场浇注的桥梁中，即当模板在湿混凝土重载作用下势必发生弯曲变形。某些缓凝剂对混凝土起长期的消弱作用，没有良好的技术指导不得使用。采用低热水泥能得到类似于缓凝剂的作用，但却能起到比之更为缓和的效果。低热水泥可由水泥制造厂商发售，或者由土木工程承包厂商配制。低热水泥在凝结和硬化时放出的热量较少，部分烟瘾是因其硬化较慢，因而用于像重力坝那样的小型混凝土工程中。重力坝的混凝土可能需要数年才能冷却到周围大气的温度。在英国或法国这样一些国家中，电站里燃烧的是煤粉，其煤灰很细，已经掺到水泥中以降低水泥产生的热量，并降低水泥成本，但不降低其后期强度。已经成功地应用了高达水泥重量的20％的粉煤灰掺加量，显著地降低了水泥的成本。在一些国家中，可从水泥制造厂处买到加气水泥，故不需要在掺入加气剂。当加气剂将3-8％的呈十分细小的气泡状得空气吸进湿的水泥和混凝土中时，这些气泡使混凝土塑化，易于浇注成型，但是降低数值很小，所以在美国对有很严重冻害出现的筑路工程中，现在的标准做法是使用加气剂。加气剂大大地改善了混凝土的抗冻性。白塯火山灰是一种产于意大利波佐理镇附近的火山灰，这时一种天然水泥。所有天然矿物质胶凝材料都曾命