土木工程外文翻譯

第第頁BuildingconstructionconcretecrackofpreventionandprocessingDimosiM《CANADIANJOURNALOFCIVILENGINEERING》Abstract：Thecrackproblemofconcreteisawidespreadexistencebutagaindifficultinsolveofengineeringactualproblem,thistextcarriedonastudyanalysistoalittlebitfamiliarcrackproblemintheconcreteengineering,andaimatconcretethecircumstanceputforwardsomeprevention,processingmeasure.Keyword:ConcretecrackpreventionprocessingForewordConcrete'sising1kindisanticipatebythefreestonebone,cement,waterandothermixturebutformationoftheinadditionmaterialofqualitybrittlenessnotandallmaterial.Becausetheconcreteconstructiontransformwithoneself,controletc.aseriesproblem,hardenmodelofintheconcreteexistencenumeroustinyhole,spiritcaveandtinycrack,isexactlybecausethesebeginningstartblemishofexistencejustmaketheconcretepresentonesomenotandallthecharacteristicofquality.Thetinycrackisakindofharmlesscrackandacceptconcreteheavy,defendShenandalittlebitotherusefunctionnotacreationtoendanger.Butaftertheconcretebesubjectedtolotuscarry,differenceintemperatureetc.function,tinycrackwouldcontinuouslyofexpandwithconnect,endformationwecanseewithouttheaidofinstrumentsofmacroviewthecrackbealsothecrackthattheconcreteoftensayintheengineering.ConcretebuildingandGoupieceusuallyalltakesewertomakeof,becauseofcrackofexistenceanddevelopmentusuallymakeinnerpartofreinforcingbaretc.materialcreationdecay,lowerreinforcedconcretematerialofloadingability,durableandanti-Shenability,influencebuildingofexternalappearance,servicelife,severitywillthreatarrivepeople'slifeandpropertysafety.Alotofallofcrashofengineeringsisbecauseoftheunsteadydevelopmentofthecrackwiththeresultthat.Modernagescienceresearchwithagreatdealofoftheconcreteengineeringpracticecertificate,intheconcreteengineeringcrackproblemisineluctable,alsoacceptableincertainlyofthescopejustneedtoadoptvalidofmeasurewillitendangerdegreecontrolatcertainofscopeinside.Thereinforcedconcretenormisalsoexplicitprovision:Somestructureatplaceofdissimilarityundertheconditionallowexistencecertainthecrackofwidth.Butatunderconstructionshouldasfaraspossibleadoptavalidmeasurecontrolcrackcreation,makethestructuredon'tappearcrackpossiblyorasfaraspossibledecreasecrackofamountandwidth,particularlywanttoasfaraspossibleavoidharmfulcrackofemergence,insureengineeringqualitythus.Concretecrackcreationofthereasonbealotofandhavealreadytransformedtocauseofcrack:Suchastemperaturevariety,constringency,inflation,theasymmetrysinktosinketc.reasoncauseofcrack;Haveoutsidecarrythecrackthatthefunctioncause;Protectedenvironmentnotappropriatethecracketc.causedwithchemicaleffect.Wantdifferentiationtotreatintheactualengineering,work°outaproblemaccordingtotheactualcircumstance.Intheconcreteengineeringthefamiliarcrackandtheprevention1.StemSuocrackandpreventionStemtheSuocrackmuchappearaftertheconcreteprotectbeoverofaperiodoftimeorconcretesprinkletobuildtocompletebehindofaroundaweek.InthecementsyruphumidityofevaporatewouldcreationstemSuo,andthiskindofconstringencyiscan'tnegative.StemSuocrackofthecreationbemainisbecauseofconcreteinsideoutsidehumidityevaporatedegreedissimilaritybutcausetotransformdissimilarityofresult:Theconcreteissubjectedtoexteriorconditionofinfluence,surfacehumiditylossleadquick,transformbigger,innerpartdegreeofhumidityvarietysmallertransformsmaller,biggersurfacestemtheSuotransformtobesubjectedtoconcreteinnerpartcontrol,creationmorebigpullshoulddintbutcreationcrack.Therelativehumidityismorelow,cementsyrupbodystemSuomorebig,stemtheSuocrackbemoreeasycreation.StemtheSuocrackismuchsurfaceparallellinesformorthenetshallowthincrack,widthmanybetween0.05-0.2mm,theflatsurfacepartmuchseeinthebigphysicalvolumeconcreteandfollowitmoreinthinnerbeamplankshorttodistribute.StemSuocrackusuallytheanti-Shenofinfluenceconcrete,causethedurableoftherusteclipseinfluenceconcreteofreinforcingbar,underthefunctionofthewaterpressuredintwouldcreationthewaterpowersplitcrackinfluenceconcreteofloadingdintetc..ConcretestemtheSuobemainwithwaterashoftheconcreteratio,thedosageofthecomposition,cementofcement,gathertoanticipateofthedosageofthepropertyanddosage,inadditionetc.relevant.Mainpreventionmeasure:Whilebeingtochoosetousetheconstringencyquantitysmallercement,generallowhotwatermireandpowderashfromstovecementintheadoption,lowerthedosageofcement.TwoisaconcreteofstemtheSuobesubjectedtowaterashratioofinfluencemorebig,waterashratiomorebig,stemSuomorebig,sointheconcretematchtheratiothedesignshouldasfaraspossiblecontrolgoodwaterashratioofchoosetouse,theChanaddinthemeantimeaccommodationofreducewater.Threeisstrictcontrolconcretemixblendwithunderconstructionofmatchratio,useofconcretewaterquantityabsolutecan'tbiginmatchratiodesigngivesettleofusewaterquantity.Fouristheearlierperiodwhichstrengthenconcretetoprotect,andappropriateextensionprotectofconcretetime.Winterconstructionwanttobeappropriateextensionconcreteheatpreservationtooverlaytime,andTu2Shuaprotecttoprotect.Fiveisaconstitutiontheaccommodationisintheconcretestructureoftheconstringencysew.2.TheSuconstringencycrackandpreventionSuconstringencyistheconcreteisbeforecondense,surfacebecauseoflosewaterquickerbutcreationofconstringency.TheSuconstringencycrackisgeneralatdryheatorstrongwindtheweatherappear,crack'smuchpresentinginthecenterbreadth,bothendsbeinthecenterthinandthelengthbedifferent,witheachothernotcoherentappearance.Shortercrackgenerallong20-30cm,thelongercrackcanreachtoa2-3m,breadth1-5mm.Itcreationofmainreasonis:TheconcreteiseventuallyalmosthavingnostrengthorstrengthbeforetheNingverysmall,perhapsconcretejusteventuallyNingbutstrengthveryhour,besubjectedtoheatorcomparestrongwinddintofinfluence,theconcretesurfacelosewatertoleadquick,resultininthecapillarycreationbiggernegativepressbutmakeaconcretephysicalvolumesharplyconstringency,butatthistimethestrengthofconcreteagaincan'tresistitsconstringency,thereforecreationcracked.TheinfluenceconcreteSuconstringencyopenthemainfactorofcracktohavewaterashratio,concreteofcondensetime,environmenttemperature,windvelocity,relativehumidity...etc..Mainpreventionmeasure:OneischoosetousestemtheSuovaluesmallerhigherHuosoursaltoftheearlierperiodstrengthorcommontheHuosourbrinemire.Twoisstrictthecontrolwaterashratio,theChanaddtoefficientlyreducewatertoincrementthecollapseofconcretefalladegreeandwitheasy,decreasecementandwaterofdosage.Threeistosprinklebeforebuildingconcrete,waterbasiclevelandtemplateeventosoakthrough.Fourisintimetooverlaytheperhapsdampgrassmatoftheplasticsthinfilm,hempsliceetc.,keepconcreteeventuallybeforetheNingsurfaceismoist,perhapsspraytoprotectetc.tocarryonprotectintheconcretesurface.Fiveisintheheatandstrongwindtheweathertowanttoestablishtohidesunandblockbreezefacilities,protectintime.3.SinktosinkcrackandpreventionThecreationwhichsinktosinkcrackisbecauseofthestructurefoundationsoilqualitynotandevenly,loosesoftorreturntofillsoildishonestorsoakinwaterbutresultintheasymmetrysinktodeclinewiththeresultthat;Perhapsbecauseoftemplatejustdegreeshortage,thetemplateproppeduptooncebeapartfrombigorpropupbottomloosemoveetc.tocause,especiallyatwinter,thetemplatepropupatjellysoilup,jellythesoilturnjellyempresscreationasymmetrytosinktodeclineandcauseconcretestructurecreationcrack.Thiskindcrackmanyisdeepenterorpiercethroughsexcrack,italignmenthavesomethingtodowithsinkingtosinkacircumstance,generalfollowwithgroundperpendicularorpresent30°s-45°Capedirectiondevelopment,biggersinktosinkcrack,usuallyhavecertainofwrong,crackwidthusuallywithsinktodeclinequantitydirectproportionrelation.Crackwidthundertheinfluenceoftemperaturevarietysmaller.Thefoundationaftertransformstabilitysinktosinkcrackalsobasictendinstability.Mainpreventionmeasure:Oneisrightnessloosesoftsoil,returntofillsoilfoundationaconstructionattheupperpartstructurefrontshouldcarryonnecessityofHangsolidwithreinforce.Twoisthestrengththatassurancetemplateisenoughandjustdegree,andpropupfirm,andmakethefoundationbesubjectedtodinteven.Threeiskeepconcretefromsprinkleinfusingthefoundationintheprocessissoakbywater.Fouristimethattemplatetoredowntocan'tbetooearly,andwanttonoticetodismantleamoldorderofsequence.Fiveisatjellysoiltoptaketoestablishtemplatetonoticetoadoptcertainofpreventionmeasure.4.TemperaturecrackandpreventionTemperaturecrackmuchtheoccurrenceisinbigsurfaceordifferenceintemperaturevarietyofthephysicalvolumeconcretecomparetheearthareaoftheconcretestructure.Concreteaftersprinklingtobuild,inthehardeningtheprocess,cementwaterturnacreationagreatdealofofwaterturnhot,.(bethecementdosageisinthe350-550kg/m3,eachsignsquarethericeconcretewillreleaseacaloriesof17500-27500kJandmakeconcreteinternalthusthetemperaturerisetoreachto70℃orsoevenhigher)Becausethephysicalvolumeofconcretebemorebig,agreatdealofofwaterturnhotaccumulateattheconcreteinnerpartbutnoteasysendforth,causeinnerpartthetemperaturehoick,buttheconcretesurfacespreadhotmorequick,soformationinsideoutsideofbiggerdifferenceintemperature,thebiggerdifferenceintemperatureresultininnerpartandexteriorhotthedegreeofthebulgecoldSuodissimilarity,makeconcretesurfacecreationcertainofpullshoulddint.Whenpullshoulddintexceedtheanti-ofconcretepullstrengthextremelimit,concretesurfacemeetingcreationcrack,thiskindofcrackmuchoccurrenceaftertheconcreteunderconstructionperiod.Intheconcreteofunderconstructionbedifferenceintemperaturevarietymorebig,perhapsisaconcretetobesubjectedtoassaultofcoldwaveetc.,willcauseconcretesurfacethetemperaturesharplydescend,butcreationconstringency,surfaceconstringencyoftheconcretebesubjectedtoinnerpartconcreteofcontrol,creationverybigofpullshoulddintbutcreationcrack,thiskindofcrackusuallyjustinmoreshallowscopeoftheconcretesurfacecreation.Thealignmentofthetemperaturecrackusuallynonesettleregulation,bigareastructurethecrackoftenmaneuverinterleave;Thesizebiggerstructureofthebeamplanklength,thecrackrunparallelwithshortsidemore;Thoroughwithpiercethroughsexoftemperaturecrackgeneralandshortsidedirectionparallelismorcloseparallelism,crackalonglongsidecentthesegmentappear,inthecentermoreairtight.Crackwidththesizebedifferent,besubjectedtotemperaturevarietyinfluencemoreobvious,wintercomparebreadth,summermorenarrow.Theconcretetemperaturecrackthattheheatinflationcauseisusuallyinthecenterthethickbothendsbethin,butcoldSuocrackofthickthinvarietynottooobvious.Theemergenceofthethiskindcrackwillcausetherusteclipseofreinforcingbar,thecarbonizationofconcrete,theanti-jellywhichlowerconcretemelt,anti-tiredandanti-Shenabilityetc..Mainpreventionmeasure:Oneisasfaraspossiblechoosetouselowhotormediumhotwatermire,likemineralresiduecement,powderashfromstovecement...etc..Twoisadecreasecementdosage,cementdosageasfaraspossiblethecontrolisinthe450kg/m3following.Threeistolowerwaterashratio,waterashofthegeneralconcreteratiocontrolbelow0.6.Fourisimprovementtheboneanticipateclasstogotogetherwith,theChanaddpowderashfromstoveorefficientlyreducewateretc.tocometoreducecementdosageandlowerwatertoturnhot.Fiveisanimprovementconcreteofmixblendtoprocessacraft,lowersprinkleofconcretetobuildtemperature.SixistheinadditionthattheChanaddahaveoffixedamounttoreducewaterandincreaseSu,slowNingetc.functionintheconcrete,improvementtheconcretemixtomatchathingofmobility,protectwater,lowerwatertoturnhot,postponehotFengofemergencetime.Sevenistheheatseasonsprinkletobuildcantheadoptiontaketoestablishtohidesunplanketc.assistancemeasurecontrolconcreteofWenSheng,lowertosprinkletemperatureofbuildtheconcrete.Eightisthetemperatureofbigphysicalvolumeconcreteshouldthedintrelatetostructuresize,concretestructuresizemorebig,temperatureshoulddintmorebig,sowantreasonablearrangementconstructionworkpreface,layering,centthepiecesprinkletobuild,fortheconvenienceofinspreadhot,letupcontrol.Nineisatgreatinnerpartconstitutionofthephysicalvolumeconcretecooloffpiping,coldwaterperhapscoldaircooloff,letupconcreteofinsideoutsidedifferenceintemperature.Tenisthesupervisionwhichstrengthenconcretetemperature,adopttocooloffintime,protectionmeasure.11istoreservetemperatureconstringencytosew.12istoletuptocontrol,sprinkleproperbeforebuildingconcreteintheJirockandoldconcretetopbuilda5mmorsosandmatalayerorusageasphaltetc.materialTu2Shua.13istostrengthenconcretetoprotect,theconcreteaftersprinklebuildusemoistgrassLianintime,hempslice'setc.overlay,andattentionsprinklewatertoprotect,appropriateextensionprotecttime,assurancetheconcretesurfacebeslow-movingcooloff.Atthecoldseason,concretesurfaceshouldconstitutionheatpreservationmeasure,inordertopreventcoldwaveassault.14istheallocationbealittleamountintheconcreteofreinforcingbarperhapsaddfibermaterialconcreteoftemperaturecrackcontrolatcertainofscopeinside.5.CrackandpreventionthatthechemicalreactioncauseAlkalibone'santicipatingthecrackthatreactioncrackandreinforcingbarrusteclipsecauseisthemostfamiliarinthereinforcedconcretestructureofbecauseofchemicalreactionbutcauseofcrack.Theconcreteblendafuturereunioncreationsomealkalescenceion,theseionwithsomeactivitytheboneanticipatecreationchemicalreactionandabsorbsurroundingsenvironmentinofwaterbutthephysicalvolumeenlarge,makeconcretecrisploose,inflationopencrack.Inthiskindofcrackgeneralemergenceconcretestructureusageperiod,onceappearverydifficultremediable,soshouldatunderconstructionadoptvalidthemeasurecarryonprevention.Mainofpreventionmeasure:Whilebeingtochoosetoanticipatewiththealkaliactivitysmallfreestonebone.Twoistheinadditionwhichchoosetouselowlyemirewithlowalkaliorhavenoalkali.ThreeistheChanwhichchoosetouseaccommodationwithanticipatetorepressanalkalibonetoanticipatereaction.Becausetheconcretesprinkletobuild,flapDaobadperhapsisareinforcingbarprotectionlayerthinner,theharmfulmaterialgetintoconcretetomakereinforcingbarcreationrusteclipse,thereinforcingbarphysicalvolumeoftherusteclipseinflation,causeconcretebulgecrack,thecrackofthiskindtypemuchisacracklengthways,followthepositionofreinforcingbarappear.Usuallyofpreventmeasurefromhave:Oneisassurancereinforcingbarprotectionthethicknessofthelayer.Twoisaconcreteclasstogotogetherwithtowantgood.ThreeisaconcretetosprinkletonoteandflapDaoairtightsolid.FourisareinforcingbarsurfacelayerTu2Shuaantisepsiscoating.CrackprocessingTheemergenceofthecracknotonlywouldinfluencestructureofwholewithjustdegree,returnwillcausetherusteclipseofreinforcingbar,accelerationconcreteofcarbonization,lowerdurableandanti-ofconcretetired,anti-Shenability.Thereforeaccordingtothepropertyofcrackandconcretecircumstancewewantdifferentiationtotreat,intimeprocessing,withassurancebuildingofsafetyusage.Therepairmeasureoftheconcretecrackismaintohavethefollowingsomemethod:Surfacerepairmethod,infusesyrup,theQiansewmethod,thestructurereinforceamethod,concretedisplacementmethod,electricitychemistryprotectionmethodandimitatetolivingfromhealmethod.Surfacerepairthemethodbeakindofsimple,familiarofrepairmethod,itmainbeapplicabletostabilityandtostructureloadingtheabilitydon'thavethesurfacecrackofinfluenceanddeepentercrackofprocessing.Theprocessingmeasurethatisusuallyisasurfaceincrackdauberycementsyrup,thewreathoxygengummireoratconcretesurfaceTu2Shuapaint,asphaltetc.antisepsismaterial,atprotectionofinthemeantimeforkeepingconcretefromcontinueundertheinfluenceofvariousfunctiontoopencrack,usuallycanadoptionthesurfaceincrackgluetostickglassfiberclothetc.measure.1,infusesyrup,theQiansewmethodInfuseasyrupmethodmaintheconcretecrackbeenapplicabletohaveinfluenceorhavealreadydefendShenrequesttothestructurewholeofrepair,itismakeuseofpressureequipmentsgumknotthematerialpressintothecrackofconcrete,gumknotthematerialhardenbehindandconcreteformationonebewhole,thusreinforceofpurpose.Theincommonusegumknotmaterialhasthecementthesyrup,epoxy,AJiCXisouresterandgatherammoniaestertoequalizetolearnmaterial.TheQiansewamethodisthatthecrackbeakindofmostincommonusemethodin,itusuallyisfollowthecrackdigslot,theQianfillSuintheslotorrigidwatermaterialwithattainclosingcrackofpurpose.TheincommonuseSumaterialhasPVCgummire,plasticsointment,theDJirubberetc.;Incommonuserigidwatermaterialisthepolymercementsandsyrup.2,thestructurereinforceamethodWhenthecrackinfluencearriveconcretestructureoffunction,willconsiderationadopttoreinforceamethodtocarryonprocessingtotheconcretestructure.Thestructurereinforcemediumincommonusemainhavethefollowingafewmethod:Thepieceofenlargementconcretestructureineveryaspectaccumulate,outsidetheCapedepartmentoftheGoupiecepacktypesteel,adoptionprepareshouldthedintmethodreinforce,gluetosticksteelplatetoreinforce,increasetoestablishfulcrumtoreinforceandjettheconcretecompensationreinforce.3,concretedisplacementmethodConcretedisplacementmethodisprocessingseveritydamageconcreteofakindofvalidmethod,thismethodbefirstwilldamageoftheconcretepickandgetridof,thenagaindisplacementgointonewofconcreteorothermaterial.Theincommonusedisplacementmaterialhave:Commonconcreteorthecementsandsyrup,polymerorchangesexpolymerconcreteorsandsyrup.4,theelectricitychemistryprotectionmethodTheelectricitychemistryantisepsisistomakeuseofinflictionelectricfieldinliethequalityofelectricitychemicaleffect,changeconcreteorreinforcedconcretetheenvironmentappearanceoftheplace,thebluntnessturnreinforcingbartoattainthepurposeofantisepsis.Cathodeprotectionmethod,chlorinesalt'swithdrawingamethod,alkalescencetorecoveramethodisachemistryprotectionmethodinthreekindsofincommonusebutvalidmethod.Theadvantageofthiskindofmethodisaprotectionmethodundertheinfluenceofenvironmentfactorsmaller,applyreinforcingbar,concreteoflong-termantisepsis,sincecanusedforcrackstructurealreadycanalsousedfornewsetupstructure.5,imitatetolivingfromlegalmoreImitatetolivingfromhealthemethodbeakindofnewcracktreatment,itsmimicrylivingcreatureorganizationsecreteacertainmaterialtowardssufferingwoundpartauto,butmakethewoundparthealoffunction,joinsomeandspecialcomposition(suchascontaintoglueknotoftheliquidXinfiberorcapsule)intheconcreteofthetraditionthecomposition,atconcreteinnerpartformationtheintelligencetypeimitatetolivingfromhealnervenetworksystem,betheconcreteappearcracksecreteapartsofliquidXinfibercanmakethecrackre-heal.ConclusionThecrackiswidespreadintheconcretestructureexistenceofakindofphenomenon,itofemergencenotonlywilllowertheanti-Shenofbuildingability,influencebuildingofusagefunction,andwillcausetherusteclipseofreinforcingbar,thecarbonizationofconcrete,lowerthedurableofmaterial,influencebuildingofloadingability,sowanttocarryontotheconcretecrackearnestresearch,differentiationtreat,adoptionreasonableofthemethodcarryonprocessing,andatunderconstructionadoptvariousvalidofpreventionmeasuretopreventioncrackofemergenceanddevelopment,assurancebuildingandGoupiecesafety,stabilitywork.建筑施工混凝土裂縫的預防與處理迪默斯M《加拿大土木工程學報》摘要：混凝土的裂縫問題是一個普遍存在而又難于解決的工程實際問題，本文對混凝土工程中常見的一些裂縫問題進行了探討分析，并針對具體情況提出了一些預防、處理措施。關(guān)鍵詞：混凝土裂縫預防處理前言混凝土是一種由砂石骨料、水泥、水及其他外加材料混合而形成的非均質(zhì)脆性材料。由于混凝土施工和本身變形、約束等一系列問題，硬化成型的混凝土中存在著眾多的微孔隙、氣穴和微裂縫，正是由于這些初始缺陷的存在才使混凝土呈現(xiàn)出一些非均質(zhì)的特性。微裂縫通常是一種無害裂縫，對混凝土的承重、防滲及其他一些使用功能不產(chǎn)生危害。但是在混凝土受到荷載、溫差等作用之后，微裂縫就會不斷的擴展和連通，最終形成我們?nèi)庋劭梢姷暮暧^裂縫，也就是混凝土工程中常說的裂縫?；炷两ㄖ蜆?gòu)件通常都是帶縫工作的，由于裂縫的存在和發(fā)展通常會使內(nèi)部的鋼筋等材料產(chǎn)生腐蝕，降低鋼筋混凝土材料的承載能力、耐久性及抗?jié)B能力，影響建筑物的外觀、使用壽命，嚴重者將會威脅到人們的生命和財產(chǎn)安全。很多工程的失事都是由于裂縫的不穩(wěn)定發(fā)展所致。近代科學研究和大量的混凝土工程實踐證明，在混凝土工程中裂縫問題是不可避免的，在一定的范圍內(nèi)也是可以接受的，只是要采取有效的措施將其危害程度控制在一定的范圍之內(nèi)。鋼筋混凝土規(guī)范也明確規(guī)定：有些結(jié)構(gòu)在所處的不同條件下，允許存在一定寬度的裂縫。但在施工中應盡量采取有效措施控制裂縫產(chǎn)生，使結(jié)構(gòu)盡可能不出現(xiàn)裂縫或盡量減少裂縫的數(shù)量和寬度，尤其要盡量避免有害裂縫的出現(xiàn)，從而確保工程質(zhì)量?；炷亮芽p產(chǎn)生的原因很多，有變形引起的裂縫：如溫度變化、收縮、膨脹、不均勻沉陷等原因引起的裂縫；有外載作用引起的裂縫；有養(yǎng)護環(huán)境不當和化學作用引起的裂縫等等。在實際工程中要區(qū)別對待，根據(jù)實際情況解決問題?；炷凉こ讨谐Ｒ娏芽p及預防:1.干縮裂縫及預防干縮裂縫多出現(xiàn)在混凝土養(yǎng)護結(jié)束后的一段時間或是混凝土澆筑完畢后的一周左右。水泥漿中水分的蒸發(fā)會產(chǎn)生干縮，且這種收縮是不可逆的。干縮裂縫的產(chǎn)生主要是由于混凝土內(nèi)外水分蒸發(fā)程度不同而導致變形不同的結(jié)果：混凝土受外部條件的影響，表面水分損失過快，變形較大，內(nèi)部濕度變化較小變形較小，較大的表面干縮變形受到混凝土內(nèi)部約束，產(chǎn)生較大拉應力而產(chǎn)生裂縫。相對濕度越低，水泥漿體干縮越大，干縮裂縫越易產(chǎn)生。干縮裂縫多為表面性的平行線狀或網(wǎng)狀淺細裂縫，寬度多在0.05-0.2mm之間，大體積混凝土中平面部位多見，較薄的梁板中多沿其短向分布。干縮裂縫通常會影響混凝土的抗?jié)B性，引起鋼筋的銹蝕影響混凝土的耐久性，在水壓力的作用下會產(chǎn)生水力劈裂影響混凝土的承載力等等?；炷粮煽s主要和混凝土的水灰比、水泥的成分、水泥的用量、集料的性質(zhì)和用量、外加劑的用量等有關(guān)。主要預防措施：一是選用收縮量較小的水泥，一般采用中低熱水泥和粉煤灰水泥，降低水泥的用量。二是混凝土的干縮受水灰比的影響較大，水灰比越大，干縮越大，因此在混凝土配合比設(shè)計中應盡量控制好水灰比的選用，同時摻加合適的減水劑。三是嚴格控制混凝土攪拌和施工中的配合比，混凝土的用水量絕對不能大于配合比設(shè)計所給定的用水量。四是加強混凝土的早期養(yǎng)護，并適當延長混凝土的養(yǎng)護時間。冬季施工時要適當延長混凝土保溫覆蓋時間，并涂刷養(yǎng)護劑養(yǎng)護。五是在混凝土結(jié)構(gòu)中設(shè)置合適的收縮縫。2.塑性收縮裂縫及預防塑性收縮是指混凝土在凝結(jié)之前，表面因失水較快而產(chǎn)生的收縮。塑性收縮裂縫一般在干熱或大風天氣出現(xiàn)，裂縫多呈中間寬、兩端細且長短不一，互不連貫狀態(tài)。較短的裂縫一般長20-30cm，較長的裂縫可達2-3m，寬1-5mm.其產(chǎn)生的主要原因為：混凝土在終凝前幾乎沒有強度或強度很小，或者混凝土剛剛終凝而強度很小時，受高溫或較大風力的影響，混凝土表面失水過快，造成毛細管中產(chǎn)生較大的負壓而使混凝土體積急劇收縮，而此時混凝土的強度又無法抵抗其本身收縮，因此產(chǎn)生龜裂。影響混凝土塑性收縮開裂的主要因素有水灰比、混凝土的凝結(jié)時間、環(huán)境溫度、風速、相對濕度等等。主要預防措施：一是選用干縮值較小早期強度較高的硅酸鹽或普通硅酸鹽水泥。二是嚴格控制水灰比，摻加高效減水劑來增加混凝土的坍落度和和易性，減少水泥及水的用量。三是澆筑混凝土之前，將基層和模板澆水均勻濕透。四是及時覆蓋塑料薄膜或者潮濕的草墊、麻片等，保持混凝土終凝前表面濕潤，或者在混凝土表面噴灑養(yǎng)護劑等進行養(yǎng)護。五是在高溫和大風天氣要設(shè)置遮陽和擋風設(shè)施，及時養(yǎng)護。3.沉陷裂縫及預防沉陷裂縫的產(chǎn)生是由于結(jié)構(gòu)地基土質(zhì)不勻、松軟或回填土不實或浸水而造成不均勻沉降所致；或者因為模板剛度不足，模板支撐間距過大或支撐底部松動等導致，特別是在冬季，模板支撐在凍土上，凍土化凍后產(chǎn)生不均勻沉降，致使混凝土結(jié)構(gòu)產(chǎn)生裂縫。此類裂縫多為深進或貫穿性裂縫，其走向與沉陷情況有關(guān)，一般沿與地面垂直或呈30°-45°角方向發(fā)展，較大的沉陷裂縫，往往有一定的錯位，裂縫寬度往往與沉降量成正比關(guān)系。裂縫寬度受溫度變化的影響較小。地基變形穩(wěn)定之后，沉陷裂縫也基本趨于穩(wěn)定。主要預防措施：一是對松軟土、回填土地基在上部結(jié)構(gòu)施工前應進行必要的夯實和加固。二是保證模板有足夠的強度和剛度，且支撐牢固，并使地基受力均勻。三是防止混凝土澆灌過程中地基被水浸泡。四是模板拆除的時間不能太早，且要注意拆模的先后次序。五是在凍土上搭設(shè)模板時要注意采取一定的預防措施。4.溫度裂縫及預防溫度裂縫多發(fā)生在大體積混凝土表面或溫差變化較大地區(qū)的混凝土結(jié)構(gòu)中?；炷翝仓?，在硬化過程中，水泥水化產(chǎn)生大量的水化熱，（當水泥用量在350-550kg/m3，每立方米混凝土將釋放出17500-27500kJ的熱量，從而使混