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PAGE21-學校代碼:學號:學校代碼:學號:外文文獻及翻譯外文文獻及翻譯(題題目:AboutBuidingontheStructureDesign學生姓名:學院:土木工程學院系別:建筑工程系專業(yè):土木工程(建筑工程方向)班級:土木指導教師:二〇年六月英文原文:BuildingconstructionconcretecrackofpreventionandprocessingAbstractThecrackproblemofconcreteisawidespreadexistencebutagaindifficultinsolveofengineeringactualproblem,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.From《CANADIANJOURNALOFCIVILENGINEERING》中文原文:建筑施工混凝土裂縫的預防與處理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(yīng)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(yīng)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(yīng)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(yīng)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?;炷翝仓螅谟不^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,從而使混凝土內(nèi)部溫度升達70℃左右甚至更高)。由于混凝土的體積較大,大量的水化熱聚積在混凝土內(nèi)部而不易散發(fā),導致內(nèi)部溫度急劇上升,而混凝土表面散熱較快,這樣就形成內(nèi)外的較大溫差,較大的溫差造成內(nèi)部與外部熱脹冷縮的程度不同,使混凝土表面產(chǎn)生一定的拉應(yīng)力。當拉應(yīng)力超過混凝土的抗拉強度極限時,混凝土表面就會產(chǎn)生裂縫,這種裂縫多發(fā)生在混凝土施工中后期。在混凝土的施工中當溫差變化較大,或者是混凝土受到寒潮的襲擊等,會導致混凝土表面溫度急劇下降,而產(chǎn)生收縮,表面收縮的混凝土受內(nèi)部混凝土的約束,將產(chǎn)生很大的拉應(yīng)力而產(chǎn)生裂縫,這種裂縫通常只在混凝土表面較淺的范圍內(nèi)產(chǎn)生。溫度裂縫的走向通常無一定規(guī)律,大面積結(jié)構(gòu)裂縫??v橫交錯;梁板類長度尺寸較大的結(jié)構(gòu),裂縫多平行于短邊;深入和貫穿性的溫度裂縫一般與短邊方向平行或接近平行,裂縫沿著長邊分段出現(xiàn),中間較密。裂縫寬度大小不一,受溫度變化影響較為明顯,冬季較寬,夏季較窄。高溫膨脹引起的混凝土溫度裂縫是通常中間粗兩端細,而冷縮裂縫的粗細變化不太明顯。此種裂縫的出現(xiàn)會引起鋼筋的銹蝕,混凝土的碳化,降低混凝土的抗凍融、抗疲勞及抗?jié)B能力等。主要預防措施:一是盡量選用低熱或中熱水泥,如礦渣水泥、粉煤灰水泥等。二是減少水泥用量,將水泥用量盡量控制在450kg/m3以下。三是降低水灰比,一般混凝土的水灰比控制在0.6以下。四是改善骨料級配,摻加粉煤灰或高效減水劑等來減少水泥用量,降低水化熱。五是改善混凝土的攪拌加工工藝,降低混凝土的澆筑溫度。六是在混凝土中摻加一定量的具有減水、增塑、緩凝等作用的外加劑,改善混凝土拌合物的流動性、保水性,降低水化熱,推遲熱峰的出現(xiàn)時間。七是高溫季節(jié)澆筑時可以采用搭設(shè)遮陽板等輔助措施控制混凝土的溫升,降低澆筑混凝土的溫度。八是大體積混凝土的溫度應(yīng)力與結(jié)構(gòu)尺寸相關(guān),混凝土結(jié)構(gòu)尺寸越大,溫度應(yīng)力越大,因此要合理安排施工工序,分層、分塊澆筑,以利于散熱,減小約束。九是在大體積混凝土內(nèi)部設(shè)置冷卻管道,通冷水或者冷氣冷卻,減小混凝土的內(nèi)外溫差。十是加強混凝土溫度的監(jiān)控,及時采取冷卻、保護措施。十一是預留溫度收縮縫。十二是減小約束,澆筑混凝土前宜在基巖和老混凝土上鋪設(shè)5mm左右的砂墊層或使用瀝青等材料涂刷。十三是加強混凝土養(yǎng)護,混凝土澆筑后,及時用濕潤的草簾、麻片等覆蓋,并注意灑水養(yǎng)護,適當延長養(yǎng)護時間,保證混凝土表面緩慢冷卻。在寒冷季節(jié),混凝土表面應(yīng)設(shè)置保溫措施,以防止寒潮襲擊。十四是混凝土中配置少量的鋼筋或者摻入纖維材料將混凝土的溫度裂縫控制在一定的范圍之內(nèi)。5.化學反應(yīng)引起的裂縫及預防堿骨料反應(yīng)裂縫和鋼筋銹蝕引起的裂縫是鋼筋混凝土結(jié)構(gòu)中最常見的由于化學反應(yīng)而引起的裂縫。混凝土拌和后會產(chǎn)生一些堿性離子,這些離子與某些活性骨料產(chǎn)生化學反應(yīng)并吸收周圍環(huán)境中的水而體積增大,造成混凝土酥松、膨脹開裂。這種裂縫一般出現(xiàn)中混凝土結(jié)構(gòu)使用期間,一旦出現(xiàn)很難補救,因此應(yīng)在施工中采取有效措施進行預防。主要的預防措施:一是選用堿活性小的砂石骨料。二是選用低堿水泥和低堿或無堿的外加劑。三是選用合適的摻和料抑制堿骨料反應(yīng)。由于混凝土澆筑、振搗不良或者是鋼筋保護層較薄,有害物質(zhì)進入混凝土使鋼筋產(chǎn)生銹蝕,銹蝕的鋼筋體積膨脹,導致混凝土脹裂,此種類型的裂縫多為縱向裂縫,沿鋼筋的位置出現(xiàn)。通常的預防措施有:一是保證鋼筋保護層的厚度。二是混凝土級配要良好。三是混凝土澆注要振搗密實。四是鋼筋表層涂刷防腐涂料。裂縫處理裂縫的出現(xiàn)不但會影響結(jié)構(gòu)的整體性和剛度,還會引起鋼筋的銹蝕、加速混凝土的碳化、降低混凝土的耐久性和抗疲勞、抗?jié)B能力。因此根據(jù)裂縫的性質(zhì)和具體情況我們要區(qū)別對待、及時處理,以保證建筑物的安全使用。混凝土裂縫的修補措施主要有以下一些方法:表面修補法,灌漿、嵌縫封堵法,結(jié)構(gòu)加固法,混凝土置換法,電化學防護法以及仿生自愈合法。表面修補法是一種簡單、常見的修補方法,它主要適用于穩(wěn)定和對結(jié)構(gòu)承載能力沒有影響的表面裂縫以及深進裂縫的處理。通常的處理措施是在裂縫的表面涂抹水泥漿、環(huán)氧膠泥或在混凝土表面涂刷油漆、瀝青等防腐材料,在防護的同時為了防止混凝土受各種作用的影響繼續(xù)開裂,通??梢圆捎迷诹芽p的表面粘貼玻璃纖維布等措施。1、灌漿、嵌縫封堵法灌漿法主要適用于對結(jié)構(gòu)整體性有影響或有防滲要求的混凝土裂縫的修補,它是利用壓力設(shè)備將膠結(jié)材料壓入混凝土的裂縫中,膠結(jié)材料硬化后與混凝土形成一個整體,從而起到封堵加固的目的。常用的膠結(jié)材料有水泥漿、環(huán)氧樹脂、甲基丙烯酸酯、聚氨酯等化學材料。嵌縫法是裂縫封堵中最常用的一種方法,它通常是沿裂縫鑿槽,在槽中嵌填塑性或剛性止水材料,以達到封閉裂縫的目的。常用的塑性材料有聚氯乙烯膠泥、塑料油膏、丁基橡膠等等;常用的剛性止水材料為聚合物水泥砂漿。2、結(jié)構(gòu)加固法當裂縫影響到混凝土結(jié)構(gòu)的性能時,就要考慮采取加固法對混凝土結(jié)構(gòu)進行處理。結(jié)構(gòu)加固中常用的主要有以下幾種方法:加大混凝土結(jié)構(gòu)的截面面積,在構(gòu)件的角部外包型鋼、采用預應(yīng)力法加固、粘貼鋼板加固、增設(shè)支點加固以及噴射混凝土補強加固。3、混凝土置換法混凝土置換法是處理嚴重損壞混凝土的一種有效方法,此方法是先將損壞的混凝土剔除,然后再置換入新的混凝土或其他材料。常用的置換材料有:普通混凝土或水泥砂漿、聚合物或改性聚合物混凝土或砂漿。4、電化學防護法電化學防腐是利用施加電場在介質(zhì)中的電化學作用,改變混凝土或鋼筋混凝土所處的環(huán)境狀態(tài),鈍化鋼筋,以達到防腐的目的。陰極防護法、氯鹽提取法、堿性復原法是化學防護法中常用而有效的三種方法。這種方法的優(yōu)點是防護方法受環(huán)境因素的影響較小,適用鋼筋、混凝土的長期防腐,既可用于已裂結(jié)構(gòu)也可用于新建結(jié)構(gòu)。5、仿生自愈合法仿生自愈合法是一種新的裂縫處理方法,它模仿生物組織對受創(chuàng)傷部位自動分泌某種物質(zhì),而使創(chuàng)傷部位得到愈合的機能,在混凝土的傳統(tǒng)成分中加入某些特殊成分(如含粘結(jié)劑的液芯纖維或膠囊),在混凝土內(nèi)部形成智能型仿生自愈合神經(jīng)網(wǎng)絡(luò)系統(tǒng),當混凝土出現(xiàn)裂縫時分泌出部分液芯纖維可使裂縫重新愈合。結(jié)論裂縫是混凝土結(jié)構(gòu)中普遍存在的一種現(xiàn)象,它的出現(xiàn)不僅會降低建筑物的抗?jié)B能力,影響建筑物的使用功能,而且會引起鋼筋的銹蝕,混凝土的碳化,降低材料的耐久性,影響建筑物的承載能力,因此要對混凝土裂縫進行認真研究、區(qū)別對待,采用合理的方法進行處理,并在施工中采取各種有效的預防措施來預防裂縫的出現(xiàn)和發(fā)展,保證建筑物和構(gòu)件安全、穩(wěn)定地工作。
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