外文翻译一二

DiscusstheconstructiontemperatureandcrackoftheconcretelightlyThesummary,throughobservationliveformanyyears,throughconsultingthemonographaboutstresswithintheconcrete,explaintoconcretetemperaturereason,on-the-spotconcretecontrolandmeasure,preventionofcrackoftemperaturethatcrackproduce.KeywordConcreteTemperaturestressCrackControlTheconcreteoccupiestheimportantpositioninmodernengineeringconstruction.Buttoday,thecrackoftheconcreteiscomparativelygeneral,thecracksarenearlyomnipresentinthescienceofbridgebuilding.Thoughwetakevariouskindsofmeasuresinconstructing,careful,butthecrackstilloccursnowandthen.Tracingittoitscause,itisoneofthemincompletelythatourchangetoconcretetemperaturestresspaysattentionto.Inthelargevolumeconcrete,temperaturestressandtemperaturecontrolaresignificant.Thisismainlybecauseofthereasonoftworespects.Firstofall,concreteoftenappearthetemperaturecrackinnotconstructing,influencetheglobalityanddurabilityofthestructure.Secondly,inthecourseofoperating,thetemperaturechangehasremarkableinfluencethatcan'tbeignoredonthestressstateofthestructure.Whomwemeettoconstructtemperaturecrackinmainly,soonlytoorigincauseofformationandtreatmentmeasure,concreteofcrackmakeadiscussioninconstructingthistext.ReasonofacrackHavemanykindsofreasonstoproducethecrackintheconcrete,itismainlythechangesoftemperatureandhumidity,fragilityanddisparityoftheconcrete,andthestructureisunreasonable,therawmaterialsnotuptostandard(ifthealkaliaggregatereact),thetemplateisoutofshape,thefoundationdoesnotsubsideetc.evenly.Thecementemitsalargeamountofheatofhydrationwhentheconcreteishardenned,insidetemperatureisrisingconstantly,causethestressofdrawingonthesurface.Inthecourseofloweringthetemperature,isitcongealfoundationpayrestraintomixalwayslaterstage,willpresentthestressofdrawingwithintheconcrete.Reducingoftemperaturecansurfacecauseheavystressofdrawingveryinconcretetoo.Whenthesedrawthestressandgobeyondresistingtheabilityofsplittingofconcrete,namelywillpresentthecrack.Alotofinsidehumidityofconcretechangeverylightorchangerelativelyslow,surfacehumiditymightchangeheavytheviolentchangetakesplacing.Suchasmaintainingthoroughly,when婚g秀e屋t用t规i惹n团g到守w仿e斯t定t汇e嘴r榨速w肿h核e娃n阵烦n践o锹t垂轿d柳o驶i彻n萍g突,脊c保o践n格t计r晃a嫩c率t知还s勒u城r盒f承a仿c鸭e顷腔t像h碌e离r蔑e窝横a标r筋e蒜n适'温t掀已d滋e暂f摘o哥r漂m子a茧t践i链o枯n厅鬼d享o吃i汉n秧g棋,幕姓o尘f挥t立e咬n枯把c珍a答u见s鼓e河净t堪h雾e饿愤c袄r构a寿c天k尤看t狂o糠o齿.句至T况h堪e秒谅c身o腰n眠c院r烛e陷t柜e吧暑i黎s父谱a本喷k锈i执n竞d弱摘o虑f闲今f惧r区a检g册i期l奥i啄t叉y郊蓄m磨a锹t羽e驰r躲i狱a努l惕尖,倍帐t裁e心n汗s秆i堪l伞e赌延s通t途r尝e顾n残g句t钥h未踢i弦s蚁睡a乏b麻o兰u朽t挎给1衡/箩1幅0转恼o甘f跟狠t疏h奖e绩火c妇o译m莲p扑r再e篇s让s败i绿o并n筋环s浮t快r坏e保n替g倘t捐h趟,届膛i战s受花i销t配耻c墨a劳r冷r阿y爬造o犁n萌委o税n虏e能'平s槐前s拼h纲o友u丢l朴d兼e滋r兽芒o惩r迈诸b慕a辫c蔬k嗓哈l疼i充m苍i宋t脏扬w厕h短e视n墓枝d食r淘a饲w叨失o错u相t茄它o沉f苍颈s池h姿a撇p驾e盘询t百o屋悬h坦a处v古e伤槽*油1誉0旁4匠括o昌n泪l专y位牛,听想i央s月恢i润t阶晋c略a雨r交r爽y活堤o蚁n岗期o返n典e揭'椒s部鞋s杂h膜o爆u赢l陈d督e歉r兰制o投r指阴b羽a屑c静k傲示l付i锤m铲i尼t巩松l源o逢c持a玩t灾i勉o鱼n哈响w挥h击e屠n踪果s偷t泛r厚e建t茫c际h内驼o券u遭t素甘o联f情帐s役h们a尸p貌e舅叔t蛇o础茎t易h怒e谅r利e蜂晓i寺s还膨*套1等0枣4因赌t扬o勾扭a吩d刺d巨烤f涛o击r办望a呢公l州o瓣n精g播浊t胸i乘m把e耻果t但o掀淋a聪d址d偷窗a短翼s爱h轨o好r赚t释译t盯i抗m撕e框.存扎B饼e绞c矿a世u茫s副e经倦r茄a期w嫩拦m镜a今t说e桂r吼i逐a极l奸s央针e赚v狐e我n挥,饿命w丢a篇t肿e全r誉苹d妙u杜s拌t好锈t醉h仆a解n园眉u炮n药s供t枯a捧b夜l并e苗,悼手t国r御a最n谅s肝p作o浙r昨t饺耻a招n盼d葵斩b侵u芬i雕l奏d锻壁p医h挎e龙n偿o以m美e略n灶o蒜n调宣o甜f效掏e捧m锋a栏n阻a席t减i歉n况g茄坦o肠f辱辩c叶o粒u浓r示s悉e从,周船i内t翁s告餐t殿e镰n索s密i絮l慈e虑书s骑t始r助e款n币g件t劈h例稻i畏s堂餐n日o线t辅睡e乘v奖e封n纸虚i拼n议匀t把h轰e晶常s纳a还m智e开呆c徐o沸n棒c秧r吸e荷t伙e畅,白爷a吐理l蚂o拍t虚检o煎f镰烫r酸e遍s接i旬s扶t塘摔t射h势e披砍a再b俯i斧l荣i味t在y底堤o啊f旨昂d朱r服a俱w坦i叠n轨g慰扛v巨e搂r秆y艰炎l副o辨w客,亦斧i寇t窑帝i狭s虽裂a砌p索t倾宋t番o脚谊p岩r四e拘s举e袍n符t服歼t袖h依e强惰w缩e需a兄k额丙p料o暴s圾i项t摩i伯o捷n菠忆o析f距同t铸h垄e熟雷c袋r快a饺c侦k揭.途促A张m舒o悠n义g红红a染r耳m肌o廊r届e症d硬顿c肥o消n蚊c副r纲e灾t坝e萌允,贫兔d勿r化a蚂w分秃s晨t复r判e淋s偿s痛倘t想o彼寸u转n眉d净e麦r宅t竟a弓k墙e阶松b插y帅佛r撇e呈i井n烛f构o跪r档c麦i矮n绢g载蜜b租a凭r赌剑m样a糠i例n联l哲y红查,圈患c衔o坐n留c员r罗e盒t然e拳礼b悔e祝a报r怜缺s束t乔r挨e孩s亿s司榨o誓f大烤k伐e给e劝p柴i盒n使g载雁j吨u刊s播t奶.着棕O奏r控堵r墓e姜i往n茧f袜o吃r乌c额i俘n撑g搅吨b蝴a搂r谊彼m供i中x跌沸i剑f很逢e手d籍g腥e络宵p约o浪s姜i拌t利i甘o萌n框贪g乡o那n咐e眨半t严o与铁t厨o列舱c铁o拢n夜g纵e续a嫩l惜既p礼r绸e尝s蓬e盆n养t厉猜t橡h命e止印s净t况r救e趁s态s绕尚o乱f斗粘d喂r览a惕w世i灯n亩g肤贵i距n沉血t付h蒙e叮厦s恨t愿r馋u昂c闷t混u注r私e傻械i赏n顿辜p厦l点a杜i聚n疼遵c属o何n刻c姑r叔e练t广e桶,辈完m缴u斥s可t穷诵r有e友l格y企菠o略n粉够t回h俩e济略c净o各n侮c莫r吸e妄t敲e侧柜o陵n鞋e波s首e邀l荡f订霜t气o军抬b阿e齐a箱r潜稀.书循R滥e均q轿u右i迫r绳e蝴糠t岁o隔冻a无v闷o闸i柴d脖用t嚷h底e杜饺s铅t酬r拘e志s暖s词被o肥f抱欧d塘r肌a耍w英i燕n玉g超播o锋r婚选o双n弊l纲y你未v途e燕r盏y沙环s谁m李a沙l村l字悟s窜t抱r赶e做s哗s扰趋o样f灿轮d厅r匪a评w金i纹n击g牵蜓a窝p忆p燃e末a阴r碗s贫输o浑f召括t柄h筛e固恢t易h屿e但愚g把e究n慎e镜r宏a幸l伴科d国e型s禽i姐g辽n萌.饥破B够u己t糠桐t括h翠e握对c淹o遣n敌c秤r亲e蜘t减e纤粘i冰s伟溜c驻o棵o嚼l为e植d纷拨f阅r消o蒜m拍去m降a罩x研i仙m贤u霸m风金t寻e松m颈p沉e舍r从a链t掀u号r昨e弟终t隐o迷是t讲h讨e矿档s秋t势e潜a茫d盾y舟镰t悟e幸m铁p答e捧r木a特t慕u姓r群e器汇o郊f购铺o涉p积e它r咏a钥t予i央n寿g本群p瓦e扎r家i社o射d时康i饰n葡波c牺o析n梅s恶t粉r裳u街c乘t继i佣n夕g依,钻丢o候f夏t梅e否n结搜c世a熄u缩s狮e佣剧s洒i廊z仁a株b两l圣e握醒t墨o犹纤d喂r眠a仓w港先t劣h尸e宗评s梳t论r车e容s装s燕胜w险i贫t振h铅i源n采呀t额h涉e款番c系o姑n展c陈r垄e涛t财e帝.违功T抱h胡e逃院t泳e阅m歌p皇e肿r铺a泄t狠u窃r垫e亩妙s蜡t相r抵e短s对s乒铁c烟a匪n馋漏e称x菠c房e鸦e村d哈乌o魔t容h暗e洒r畅啦o斗u叫t智s侄i是d谢e钉s造酷a长n功d停谎l萄o刑a抵d纠金t兄h趁e齿颠s样t异r刘e蛾s昆s喊e认s异奇c臂a刘u帅s皇e更d虽悉s牙o涉m烈e宋t根i应m积e粉s尼,愉登k订n蓝o抛w施济c棍h架a拐n怀g处e俊便l隙a滨w须坦,描知t感e洪m遵p征e默r晌a钳t际u夺r总e嫌罚o状f金摄s阅t嘱r辆e朗s展s祖凳f互o欢r蓝辅c逢a伸r煎r限y孕池o处n蝇适r萝e种a之s骄o辞n寻a叮b象l速e阁因s蛙t夸r逮u淹c抬t俯u逃r敬a完l易抖d威e饱s洲i罚g喝n念楼a矛n练d皱占c亭o铁n肥s沟t顶r伞u带c溉t局钉e诸x吼t辰r母e允m序e宋l杜y倚凑i于m亿p灵o锤r忌t锦a斗n羞t遭.友

裕A忙n刻a牛l财y傅s扎i候s摄扩o独f宏制2亲矿t梅e视m恨p挣e际r痰a墨t倘u瓦r边e喜承s怖t缝r名e评s箱s朽e课s期Canbedividedintofollowingthreestagesaccordingtotheformingprocessofthetemperaturestress:(1)Itisearly:Buildconcreteisitisitoverbasicallytosendoutheattocementtobegin,generallyoneonedaybyoneself.Twocharacteristicsatthisstage,first,thecementemitsalargeamountofheatofhydration,second,mixandcongealthechangingsharplyofelasticmodelquantity.Becauseofthechangeofelasticmodelquantity,formtheremainingstressintheconcreteinthisperiod.(2)Middleperiod:Uptilltheconcreteiscooleduntilstabilitytemperaturefromcementsendoutheatfunctionbasicallywhenexpiring,inthisperiod,thetemperaturestressismainlybecausethecoolingoftheconcreteandexternaltemperaturechangecause,thesestressesandremnantsstressesthatisformedinearlydaysaresuperposed,mixandcongealtheelasticmouldamountthatgoestoanddoesnotchangemuchduringthisperiod.(3)Laterperiod:Operationperiodafterthecompletecoolingofconcrete.Temperaturestresswhetherexternaltemperaturechangecausemainly,thesestressesandfirsttwokindsofremnantsstressesesarechangedandadded.Canbedividedintotwokindsaccordingtothereasonwhythetemperaturestresscauses:(1)Spontaneousstress:Therearenotanyrestraintortotallystaticstructureattheborder,ifinsidetemperatureisnon-lineardistribution,temperaturestressappearingbecausestructurerestrainsfromeachother.Forexample,thebodyofmoundofthebridge,thephysicaldimensionisrelativelylarge,surfacetemperatureislowwhentheconcreteiscooled,insidetemperatureishigh,presentthestressofdrawingonthesurface,presentthestressofpressinginthemiddle.(2)Restrainthestress:Allofthestructureonesoritrestrainexternalonesomeborder,can'toutofshapeandstressnotcausenotfree.Suchascaseroofbeamroofconcreteandguardrailconcrete.Thistwokindsoftemperaturestressesdrawbackstressescausedtoactonwiththedoingofconcretetogetherfrequently.Itisamorecomplicatedjobtowanttoanalysethedistribution,sizeofthetemperaturestressaccuratelyaccordingtoknowntemperature.Incaseofgreatmajority,needtorelyonthemodeltestorthenumbervaluetocalculate.Toisitmaketemperaturestresshavesizablelimptocreepconcrete,atthestressaccountingtemperature,mustconsidertheinfluencethatcreep,calculateconcretlythatnolongerstatesthinlyhere.Controlandpreventingthemeasureofthecrackof3temperatureForpreventcrack,lightentemperaturestresscanfromcontroltemperatureandisitisitsetabouttorestraintermsfromtwotoimprove.Themeasureofcontrollingtemperatureisasfollows:(1)Isitimproveaggregategrademix,isitdorigidconcretetospend,mixmixturetoadopt,isitguideangrypharmaceuticalorplastificationpharmaceutical,etc.measureinordertoreducecementconsumptionofconcretetoadd;(2)Addwaterorthewatertocoolthebrokenstoneinordertoreducethetemperatureofbuildingoftheconcretewhilemixingandshuttingtheconcrete;(3)Reducethethicknessofbuildingwhilebuildingtheconcreteonhotday,utilizeandbuildtheaspecttodispeltheheat;(4)Burythewaterpipeundergroundintheconcrete,enterthecoldwatertolowerthetemperatureopenly;(5)Stipulaterationalformremovaltime,thetemperaturekeepswarmthesurfacewhileloweringsuddenly,incasethattherapidtemperaturegradienttakesplaceintheconcretesurface;(6)Theconcretewithmediumandlong-termandexposedconstructionbuildsapieceofsurfaceorthinwallstructure,takethemeasureofkeepingwarmincoldseason;Themeasureofimprovingconditionofrestrainingis:(1)Divideandsewanddivideonerationally;(2)Preventthefoundationfromrisingandfallingtoobig;(3)Rationalarrangementconstructionprocess,preventthetoobigdiscrepancyinelevationandsidefromexposingforalongtime;Inaddition,improvetheperformanceoftheconcreteandimproveandresisttheabilityofsplitting,strengthenmaintenance,preventthesurfacefrombeingdoneandcontracted,especiallyguaranteethequalityoftheconcreteisveryimportanttopreventingthecrack,shouldpayspecialattentiontoavoidingproducingandrunningthroughthecrack,theglobalityresumeditsstructureafterappearingisverydifficult,soshouldrelymainlyonpreventingtheemergenceoftherunningthroughcrackwhileconstructing.Inconstructionofconcrete,forraiseturnoverrateoftemplate,demandconcreteformremovalassoonaspossiblethatbuildnewlyoften.Shouldconsiderformremovaltimeproperlywhenconcretetemperatureishigherthanthetemperature,soasnottocausethesuperficialearlycrackofconcrete.Buildingtheearlyformremovalnewly,causeverylargestressofdrawingonthesurface,thephenomenonthat"temperatureisassaulted"appears.Buildinitialstageinconcrete,becauseheatofhydrationissentout,thesurfacecausessizabletodrawthestress,surfacetemperatureisalsohigherthantemperatureatthismoment,removethetemplateatthismoment,surfacetemperatureisloweredsuddenly,mustcausetemperaturegradient,thusaddanddrawthestressonthesurface,changeandaddwiththeheatofhydrationstress,inaddition,theconcretedriesandcontracts,thesuperficialstressofdrawingreachesverygreatnumbervalue,havedangerofcausingthecrack,butcoveralight-dutyheatinsulatorwithonthesurfaceintimeafterremovingthetemplate,forinstancefoamsponge,etc.,forpreventconcretesurfacefromproducethetoobigstressofdrawing,haveremarkableresults.Addmuscleinfluencetolargevolumetemperaturestressofconcreteverylight,becauselargevolumeconcreteincludemuscletoberateverymuchlow.Justhaveinfluenceonthegeneralarmoredconcrete.Ontermsthattemperatureisnotveryhighandthestressislessthanlimitofsurrendering,everyperformanceofthesteelissteady,andhavenothingtodowithstressstate,timeandtemperature.Linebloatedcoefficientofsteelandconcretelinebloatedcoefficientdifferenceverylight,takeplacelittleinternalstressveryonlybetweenthetwowhilechangingintemperature.Becauseelasticmouldamountofsteelconcreteelasticmould7~15ofquantity,reachasinteriorconcretestresstensilestrengthandwhenfracturing,thestressofthereinforcingbarwillnotexceed10000kg/cm2..Soisitisitpreventtinyappearancedifficultyverymuchofcrackfromtomakeuseofreinforcingbartowantamongconcrete.Butthecrackinthestructuregenerallybecomesnumerous,theintervalislittle,thewidthanddeptharesmallerafteraddingthemuscle.Andifdiameterofreinforcingbardetailedandwhenintervaldense,toimproveconcreteresistresultofpersonwhosplitbetter.Concreteandsurface,armoredconcreteofstructurecantakeplacedetailedandshallowcrackoften,amongthemthegreatmajoritybelongtoanddoanddrawbackthecrack.Thoughthiskindofcrackisgenerallyallrelativelylight,itstillshavecertaininfluenceontheintensityanddurabilityofthestructure.Inordertoguaranteeconcreteprojectquality,preventfracturing,improvethedurabilityoftheconcrete,usetheadmixturetoreduceoneofthemeasuresthatfracturescorrectly.Whetherisitreducewaterisitsplitpharmaceuticaltodefend,Isummarizehismainfunctioninpracticetouse.(1)ThereisporeDaoofalargenumberofmaointheconcrete,producecapillarytensioninthecapillaryafterwaterisevaporated,makeconcreteisitcontractoutofshapetodo.Increasingthethinapertureofhaircanreducethecapillarysurfacetension,butwillmaketheintensityofconcretereduce.Thissurfacetensiontheoryhasalreadybeenconfirmedintheworldasfarbackasthesixties.(2)Waterdustthaninfluenceimportantfactorthatconcreteshrink,isitreducewaterisitsplitpharmaceuticalcanmakeconcretewaterconsumptionreduceby25%todefendtouse.(3)Cementconsumptionimportantfactor,concreteofpersonwhoshrinktoo,isitaddandsubtractwaterisitsplitconcretereducible15%ofthecementconsumptionontermsthatkeeptheintensityofconcreteofpharmaceuticaltodefendtomix,itsvolumeissupplementedbyincreasingaggregateconsumption.(4)Reducewaterisitsplitpharmaceuticalcanimproveconsistencyofgrout,reduceconcretesecreteinktodefend,reduceandsinkanddrawbackdeforming.(5)Improveglueingthestrengthofformingofthegroutandaggregate,theconcreteimprovedresiststheperformanceofsplitting.(6)Concreteisitproducestressofdrawingtorestrainfromwhileshrinking,crackwhendrawingthestressandisgreaterthanconcretetensilestrengthcanproduce.Reducewaterisitsplitpharmaceuticaleffectiveconcretetensilestrengthofimprovementverytodefend,improveresistingtheperformanceofsplittingofconcretebyawidemargin.(7)Itcanmaketheconcretedensitygoodtoaddtheadmixturetomix,canimproveresistingcarbonizationofconcreteeffectively,reducecarbonizationtoshrink.(8)Isitreducewaterisitsplitslowcoagulationtimeproperconcreteunderpharmaceuticaltodefend,onthebasisofpreventingthefastwaterofcementfromsendingoutheateffectivelytomix,preventtheplasticityshrinkthatbringsbecausethecementisnotcongealedforalongtimefromincreasing.(9)Mixadmixtureconcreteandgettingeasyandkind,surfaceeasytofeelflat,formlittlemembrane,reducethemoisturetoevaporate,reducedrilyandshrink.Alotofadmixtureallhavethefunctionsofslowcoagulation,increasingandapt,improvementplasticity,theexperimentthatweshouldcarryoninthisrespectmoreintheprojectpracticeiscomparedwithandstudied,thanleanagainstnotimprovingtermsmoresimple,maygettingsimpleandmoredirect,economy.Earlymaintenanceof4concretePracticehasproved,thecommoncrackofconcrete,mostisthesurfacecrackofdifferentdepth,mainreasonitswhethertemperaturegradientcausecoldtemperatureofarealowertooeasytoformcracksuddenly.Sosaythewarm-keepingoftheconcreteisespeciallyimportanttopreventingtheearlycrackofsurface.Fromtheviewpointoftemperaturestress,shouldreachandrequiretokeepwarmfollowingly:1)Preventconcreteinternalandexternaltemperaturepoorandconcretesurfacegradientfrom,preventthesurfacecrack.2)Preventconcretefromtobeultraandcold,shouldisitisitmaketheminimumtemperatureisnotlowerthanthesteadytemperatureofconcreteservicetimeconstructiontimeinconcretetotrytotryone'sbest.3)Preventtheoldconcretesubcooling,inordertoreducetherestraintamongtheoldandnewconcrete.Theearlymaintenanceoftheconcrete,themainpurposeliesinkeepingthesuitablewarmandhumidcondition,inordertogettheresultoftworespects,ontheotherhandmaketheconcreteavoidtheinvasionandattackoftheunfavorableandwarm,humidityoutofshape,theonesthatpreventfromharmfullyarecoldtocontractanddotocontract.Ononehandmakecementwaterfunctiongoonsmoothly,isinthehopeofreachingtheintensitydesignedandresistingtheabilityofsplitting.Thesuitablewarmdampconditionisinterrelated.Mixwarm-keepingmeasurepaidtocongealoftenprotectwetresultstoo.Analyse,waterconcreteincludemoisturecanmeetdemand,cementofwaterhaveenoughandtosparenewlytheoretically.Butbecausethereasonofevaporatingetc.oftencauseslossesofthemoisture,thuspostponeorhinderwaterofthecementfrom,thesurfaceconcretereceivesthiskindofadverseeffecteasiestlyanddirectly.Keyperiodwhenmaintainedininitialafewdaysaftersotheconcreteisbuilt,shouldpayattentiontoconscientiouslyinconstructing.5、ConclusionsConstructiontemperatureandrelationofcrackinconcretetheabovecarryonpreliminarydiscussionoftheoryandpractice,thoughtheacademiahasdifferenttheoriestoorigincauseofformationandcomputingtechnologyoftheconcretecrack,buttoconcretepreventionandimprovingthemeasuresuggestiontorelativelyunify,applicationinpracticeresultfinetooatthesametime,concretetoisitobserve,comparemoremorebyustowantinconstructing,analysemore,summarizemoreaftergoingwrong,combinemanykindsofpreventionanddealwiththemeasure,thecrackoftheconcretecanbeavoided.浅谈混凝土的施工温度与裂缝摘要通过多年的现场观察，通过查阅有关混凝土内部应力方面的专著，对混凝土温度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施进行等进行阐述。关键词混凝土温度应力裂缝控制混凝土在现代工程建设中占有重要地位。而在今天，混凝土的裂缝较为普遍，在桥梁工程中裂缝几乎无所不在。尽管我们在施工中采取各种措施，小心谨慎，但裂缝仍然时有出现。究其原因，我们对混凝土温度应力的变化注意不够是其中之一。在大体积混凝土中，温度应力及温度控制具有重要意义。这主要是由于两方面的原因。首先，在施工中混凝土常常出现温度裂缝，影响到结构的整体性和耐久性。其次，在运转过程中，温度变化对结构的应力状态具有显著的不容忽视的影响。我们遇到的主要是施工中的温度裂缝，因此本文仅对施工中混凝土裂缝的成因和处理措施做一探讨。1、裂缝的原因混凝土中产生裂缝有多种原因，主要是温度和湿度的变化，混凝土的脆性和不均匀性，以及结构不合理，原材料不合格（如碱骨料反应），模板变形，基础不均匀沉降等。混凝土硬化期间水泥放出大量水化热，内部温度不断上升，在表面引起拉应力。后期在降温过程中，由于受到基础或老混凝上的约束，又会在混凝土内部出现拉应力。气温的降低也会在混凝土表面引起很大的拉应力。当这些拉应力超出混凝土的抗裂能力时，即会出现裂缝。许多混凝土的内部湿度变化很小或变化较慢，但表面湿度可能变化较大或发生剧烈变化。如养护不周、时干时湿，表面干缩形变受到内部混凝土的约束，也往往导致裂缝。混凝土是一种脆性材料，抗拉强度是抗压强度的1／10左右，短期加荷时的极限拉伸变形只有（0.6～1.0）×104，长期加荷时的极限位伸变形也只有（1.2～2.0）×104.由于原材料不均匀，水灰比不稳定，及运输和浇筑过程中的离析现象，在同一块混凝土中其抗拉强度又是不均匀的，存在着许多抗拉能力很低，易于出现裂缝的薄弱部位。在钢筋混凝土中，拉应力主要是由钢筋承担，混凝土只是承受压应力。在素混凝土内或钢筋混凝上的边缘部位如果结构内出现了拉应力，则须依靠混凝土自身承担。一般设计中均要求不出现拉应力或者只出现很小的拉应力。但是在施工中混凝土由最高温度冷却到运转时期的稳定温度，往往在混凝土内部引起相当大的拉应力。有时温度应力可超过其它外荷载所引起的应力，因此掌握温度应力的变化规律对于进行合理的结构设计和施工极为重要。2、温度应力的分析根据温度应力的形成过程可分为以下三个阶段：（1）早期：自浇筑混凝土开始至水泥放热基本结束，一般约30天。这个阶段的两个特征，一是水泥放出大量的水化热，二是混凝上弹性模量的急剧变化。由于弹性模量的变化，这一时期在混凝土内形成残余应力。（2）中期：自水泥放热作用基本结束时起至混凝土冷却到稳定温度时止，这个时期中，温度应力主要是由于混凝土的冷却及外界气温变化所引起，这些应力与早期形成的残余应力相叠加，在此期间混凝上的弹性模量变化不大。（3）晚期：混凝土完全冷却以后的运转时期。温度应力主要是外界气温变化所引起，这些应力与前两种的残余应力相迭加。根据温度应力引起的原因可分为两类：（1）自生应力：边界上没有任何约束或完全静止的结构，如果内部温度是非线性分布的，由于结构本身互相约束而出现的温度应力。例如，桥梁墩身，结构尺寸相对较大，混凝土冷却时表面温度低，内部温度高，在表面出现拉应力，在中间出现压应力。（2）约束应力：结构的全部或部分边界受到外界的约束，不能自由变形而引起的应力。如箱梁顶板混凝土和护栏混凝土。这两种温度应力往往和混凝土的干缩所引起的应力共同作用。要想根据已知的温度准确分析出温度应力的分布、大小是一项比较复杂的工作。在大多数情况下，需要依靠模型试验或数值计算。混凝土的徐变使温度应力有相当大的松驰，计算温度应力时，必须考虑徐变的影响，具体计算这里就不再细述。3、温度的控制和防止裂缝的措施为了防止裂缝，减轻温度应力可以从控制温度和改善约束条件两个方面着手。控制温度的措施如下：（1）采用改善骨料级配，用干硬性混凝土，掺混合料，加引气剂或