論混凝土的施工溫度與結(jié)構(gòu)裂縫

Ontheconstructionofconcretetemperatureandcracks1.thecausesofthecracksCracksinconcreteareavarietyofreasons,mainlytemperatureandhumiditychanges,brittleandunevenconcrete,aswellasthestructureisirrational,failureofrawmaterials(suchasalkali-aggregatereaction),templatedeformation,andsoonthebasisofdifferentialsettlement.Theconcretetohardenoffalargenumberofcementduringthehydrationheat,theinternaltemperaturerisingonthesurfacecausedbytensilestress.Lateinthecoolingprocess,duetocoagulationonthebasisoforbeboundbytheold,willemergeintheconcretetensilestress.Lowertemperaturesintheconcretesurfacewillbealotoftensilestress.Whenthetensilestressbeyondthecapacityofconcretecrack,thecrackswillappear.Anumberofconcretechangesintheinternalhumidityorchangesverylittleslow,butpossiblechangesinsurfacehumidityormoredramaticchanges.Suchasconservation,failedtokeepdrywhenwet,surfaceshrinkagedeformationofconcretesubjecttointernalconstraints,butalsooftenleadstocracks.Short-termloadingatthetimeofultimatetensiledeformationonly(0.6~1.0)×104,thelimitoflong-termloadingspaceswhentheonlystretchdeformation(1.2~2.0)×104.Unevenlyasaresultofrawmaterials,water-cementratioofinstability,andtransportationandpouringintheprocessofsegregationphenomena,inthesamepieceofconcreteinthetensilestrengthisuneven,therearemanylowtensilecapacity,easytofractureinaweakposition.Inreinforcedconcrete,thetensilestressismainlybornebythesteel,concreteissubjecttocompressivestress.Inplainconcreteorreinforcedcoagulationontheedgeofthesiteifthestructureofthetensilestressappearstoberelyingonitsownconcretecommitment.2.thermalstressanalysisAccordingtotheformationofthermalstresscanbedividedintothefollowingthreestages:(1)early:Sincethebeginningofpouringconcretetocementtheendofexothermicbasicgeneralabout30days.Twocharacteristicsofthisstage,first,toreleasealargenumberofcementhydrationheat,andtheotheristheelasticmodulusofcoagulationdramaticchanges.Modulusofelasticityasaresultofchangeswithinthisperiodintheformationofresidualstressintheconcrete.(2)medium-term:fromthebasicroleofcementheatuntiltheendofthestabletemperatureoftheconcretecoolingtime,duringthisperiod,thetemperaturestresswasmainlyduetocoolingandtheoutsideconcretecausedbytemperaturechanges,stressandearlyformationoftheseresidualstresssuperpositionphase,duringwhichthecoagulationoftheelasticmoduluschangedlittle.(3)late:concretecompletelycoolingperiodaftertheoperation.Thermalstressismainlycausedbyexternaltemperaturechanges,thestressandthefirsttwo-phasesuperpositionofresidualstress.Underthethermalstresscausedbythereasonscanbedividedintotwocategories:(1)self-stress:thereisnoconstraintontheborderorcompletelystaticstructure,iftheinternaltemperaturedistributionisnonlinear,duetostructuralconstraintsarisingfromtheirco-temperaturestress.Forexample,theconversionlayerofitsrelativelylargersize,concretecoolingsurfacetemperaturelow,theinternaltemperaturesarehigh,thesurfacetensilestress,compressivestressappearsinthemiddle.(2)boundbystress:thestructureofallorpartoftheboundaryboundbytheoutsideworldcannotbefree-formdeformationcausedbystress.Roofbox,suchasconcreteandconcretebarrier.Boththetemperatureandtheconcretestressisoftencausedbyshrinkageofthecombinedeffectofstress.Knowntobeinaccordancewithanaccurateanalysisofthetemperatureofthethermalstressdistribution,sizeisamorecomplextask.Inmostcases,theneedtorelyonmodeltestornumericalcalculation.Creepofconcretesothatthetemperaturethereisconsiderablestressrelaxation,thermalstresscalculation,wemustconsidertheeffectsofcreep,isnolongercalculatedindetailhere.3.temperaturecontrolandmeasurestopreventthecracksInordertopreventcracking,reducethethermalstresscancontroltheconditionsoftemperatureandtoimprovethebindingoftwoaspects.Temperaturecontrolmeasuresareasfollows:(1)usedtoimprovetheaggregategradation,dryhardconcrete,mixedmixture,addair-entrainingagentorplasticizer,etc.measurestoreducetheamountofcementconcrete;內(nèi)(萄2)mix巨ingco謊ncrete牧byad鹿dingw桂atero猜rcool灘ingwa足terwi饑llbe怖gravel丈andp憶ouring聽(tīng)concr亡eteto燃reduc賞ethe樸temper唯ature;同(半3)pou場(chǎng)ringh怨otday咽stor裝educe安thepo茶uring勿ofcon翅crete句thickn階ess,t玉heuse斧ofpo儉uring揮heatl穗evels;營(yíng)(拋4)lai武dinc迷oncret扛ewate辨rpipe座s,acc稻essto模cold好water召tocoo錄l;犬(扣5)the選provi遭sions直ofrea坑sonabl留etime棟,the貢temper隸ature建dropw嘉henth箱esurf踏acein殃sulati年on,co傅ncrete遭surfa沸cein胳order你toavo慮idas嶼harpt利empera饅tureg趕radien列t;榨(予6)Con綠struct處ionof頭long-襲terme去xposur能etob寸lockt甚hesur乏faceo譯fthe很concre竟tepou啞ring,概orthi榴n-wall蘋(píng)edstr鹽ucture伯s,the鋸rmali摘nsulat塑ionin蛾thec稠oldse津asont低otake親measu筐res;議Measur草esto載improv區(qū)ethe款constr廣aints辰are:且(僅1)ar鹽easona系blesu遮b-bloc所kjoin嗎t(yī)s;善(罰2)bas伏isto烈avoid尾toomu們chups魂andd濤owns;哥(販3)rea性sonabl妻earra陸n(yōu)gemen鍋tsfor男thec瓶onstru耀ction渡proces邊s,to棕avoid駐excess統(tǒng)ivesi茫deele灰vation云andl陵ong-te拾rmexp候osure;躬Inadd期ition,咱toim絞prove燒thepe邁rforma啦nceof活concr訊eteto驟impro屢vethe劫anti-鋪cracki弓ngabi份lity,蔽tostr劣engthe犧nthe搶conser慶vation干,top累revent外surfa喘cedry撤ing,i貼npart擺icular豆,ist珠oensu遮rethe慧quali螺tyof詢(xún)concre移teis少veryi覺(jué)mporta刊ntto暑preven陵tcrac釘ks,sh睜ouldp漠a(chǎn)yspe暑ciala衣ttenti暴onto雁avoid反cross-炊cracks貫appea乏rsto章restor份ethe吃integr撤ityof根itss燙tructu青reit祖isver國(guó)ydiff拖icult,變soth瀉econs細(xì)tructi譽(yù)onsho傘uldbe跑topr門(mén)event編theoc視curren柴ceof稼cross-置cuttin裁gthe圖mainc掃rack.兇Incon前crete聯(lián)constr糧uction顧,ino錯(cuò)rdert此oincr蜻easet托hetur粗nover醋rateo突fthe察templa繞te,of恩tenre亭quire港newpo疏uring避concre削teas報(bào)soona坦sposs戶(hù)ible.產(chǎn)Whent拋hecon撈crete姜temper君ature烏ishig澡herth租anthe晌tempe榨rature揚(yáng)shoul陳dbea霧ppropr扎iatet回ocons鵲idert鮮ime,s差oast狼oavoi證dthe糕early咐cracks朽inth毛econc抹retes后urface咬.New魄pourin贏gearl啞y,al吧otof犧thesu叔rface店tensil蜓estre介ss,a繭"tempe毯rature扇shock院"phen宗omenon您.Conc紙retep剝ouring辨inth路eearl博yheat蠢ofhy婚dratio滑nasa柄resul銜toft游hedis談semina繭tiono燃fthe佛surfac習(xí)ecaus莖edby躺alarg唉etens底ilest苗ress,誓whent根hesur頭facet次empera脊turei專(zhuān)shigh碧ertha菜nthe膚temper圍ature殃atthi僻stime組tore或movet飾hetem心plate,濤asha樸rpfal叨lins拘urface押tempe膚rature惰isbo移undto剃lead屯totem腔peratu題regra塵dient,尋soan撇addit習(xí)ional往oneon回thes澇urface書(shū)tensi內(nèi)lestr迷ess,t煤hermal叫stres電ssupe朱rposit窗ionan結(jié)dhydr屋ation,奸coupl哈edwit黑hthe扮shrink傷ageof逆concr愚ete,伯Tensil谷estre挽ssto框reach瘦thesu禾rface將ofgre吃atval傅ue,th摟ereis戀thed覽anger超oflea庸dtoc叼racks,簡(jiǎn)buti覽fina記timel奪ymann斷eraft角erthe剃remov法alof垃thete器mplate拳onth乒esurf過(guò)aceco蓬verage愚ofa燭light側(cè)insula州tingm漁ateria返l,suc胞hasf押oamsp丸ongea撞ndso文on,ha河veac默oncret鍛esurf交aceto璃preve削ntexc敞essive零tensi駛lestr播ess,w的ithsi盟gnific杯antre峽sults.走Reinfo辦rcedc宗oncret硬eont垂helar另gevol格umeof碼therm蒼alstr宿essha傍slitt深leeff蜘ectbe永cause策thela嘗rgevo煉lumeo遍fconc額reter坑einfor馳cedwi劍thav研erylo光wrate參.Only拿onth犁egene詞ralim羅pacto址frein零forced污concr舍ete.N句ottoo隸high跡intem濃peratu踢reand鵲stres粉s覺(jué)below災(zāi)theyi鐵eldli賢mitun值derth煤econd款ition余ofthe高prope蛾rties菊ofste淹elis暢stable胞,and效witht座hestr挨ess,t震imean添dtemp聲eratur減ehas地nothin座gtod游o.Lin寧earex貫pansio旅ncoef掘ficien依tofs揮teela輪ndcon投crete橋linear拉expan獵sionc強(qiáng)oeffic師ientd升iffere印ncebe朵tween瑞thesm墊allch隸anges蠢intem勿peratu餐rebet倦weent元hetwo棍with跌onlya摩very簡(jiǎn)small爭(zhēng)stress政.Sinc薪ethe岔modulu成sofe悼lastic備ityof銀steel去toco筆ncrete銅elast認(rèn)icmod路uluso剪f7~符15-fol膨d,whe澆nthe屆stress經(jīng)reach穿edthe愧tensi遭lestr袖ength常ofcon京crete揉andcr桃acking順,the同steel圈stress張will生notex很ceed1聲00~箱200kg層/cm2.忌.So武,Want例tous眠einr故einfor殿cedco留ncrete瑞topr歪event驕theem弄ergenc耀eofs晌mallc啟racks服isdif兇ficult往.Howe冶ver,a靜ftert均herei按nforce斑dstru禁cture告ofthe云numbe昌rofc昏racks逮ingen勞eralh記asbec依omemo風(fēng)retha罩nasm卻alldi承stance筐,asm缸aller淡width饞andde罩pth.A算ndif航thedi段ameter牲ofst頸eelth幅inand秋close稈spaci慎ng,th昆ecrac非kresi鳴stance齒ofco泡ncrete役toen禿hance場(chǎng)theef楚fecto奇fbett庫(kù)er.Co棚ncrete怠andr昨einfor蹤cedco勻ncrete毅struc跑tureo乎fthe請(qǐng)surfac宋eofte單noccu夠rcrac部ksin但thina翁ndsha銀llow,叉mosto螺fthem對(duì)belon乖gingt衰oshri各nkage驢cracks懸.Whil巧ethis妹isge已nerall繡yshal押lowcr生acks,閃butit腿sstre啞ngtha皆nddur軌abilit院yoft杰hestr彎ucture虹isst跨illa傘certai芝nimpa竊ct.獵Inord饅erto常ensure孝theq砌uality青ofco盯ncrete嗽topr夾event譯cracki鐵ngand萌impro淚vethe遮durab誤ility鋸ofcon陜crete,譽(yù)thep罰roper鞏useof徑admix燒tures牌isals謠oone辭ofthe航measu再resto刷reduc挺ecrac垂king.客Sucha顛sthe晚useof劉anti-毫cracki膠ngage須ntand葡water列,inp糖ractic吊e,its場(chǎng)major堅(jiān)role藏incon局cludin爛gasf仁ollows港:抓(爭(zhēng)1)the祝exist權(quán)enceo嶼fala僅rgenu鐮mbero桿fpore浪sint震hecon那crete翻that,孩after陽(yáng)evapor蛇ation愿ofwat鼠ergen至erated扇byca華pillar牌ycapi妄llary帝tensio蘆n,def圍ormati敗onof已theco援ncrete喝shrin史kage.息Pores虜increa求sedca竿pillar專(zhuān)ydiam淡eterc逐anred兆u(yù)ceth柳esurf益acete寶nsion,虛butw觸ouldr饅educe杜thest嘉rength竭ofco管ncrete屑.嘴(落2)the載impac始tofw懇ater-c伍ement時(shí)ratio縮isan痛import牛antfa陪ctorf忘orcon攏crete壁shrink財(cái)age,t毀heuse唯ofan泡ti-cra工cking扇agent載canre嘉ducew溜aterc鮮onsump隙tionr目educed碰by25嚴(yán)%conc循rete.芒(糊3)the暮amoun篇tofc舉ement克concre授teis助alsoa禿nimpo并rtant抽factor遙insh淘rinkag幻e,wat坦eradd退ition果andsu漫btract扣ionmi鳴xedco衫ncrete瀉crack蛇ingag穗entin跟maint狐aining成the暖streng絮thof渣c(diǎn)oncre勸teund粘erthe歐condi趟tiono冠f15p論ercent撥canr壁educe泛theam短ounto臂fceme長(zhǎng)nt,ag予gregat遺esize辣,byi耀ncreas膛ingth壟eamou掀ntto臺(tái)supple抄ment.熱(嗓4)ant詢(xún)i-crac棟kinga她genta嘩ndwat暖ercan朝impro頌vethe叔consi探stency胳ofce臭ments消lurry仙tored撞uceth扛eblee哲dingo戒fconc稀rete,肝reduce受shrin誓kaged仁eforma扭tionS咬hen.喜(肌5)to搬improv胖eand庫(kù)cement融bonde五daggr叮egate,達(dá)ande精nhance閑thea清nti-cr厲acking蔑perfo肆rmance纏ofco守ncrete罷.旗(更6)混侮concre泰tebou某ndin姨theco鼠ntract秩ionpr向oduced翻byte威nsile季stress海,when癥thet煩ensile漫stres獲sisg窄reater敗than頁(yè)thete繳nsile融streng棕thof兇concre掘tewil友lbep愛(ài)roduce販dwhen皇thec浸racks.垃Water圓-reduc種ingag據(jù)entca和nbea軟neffe照ctive紀(jì)anti-c斜rackin遲goft射hecon袍crete鋒tensil止estre倍ngtht趨oincr忘ease,料asubs乎tantia匠lincr林easei宅nanti冠-crack為ingpe健rforma罷nceof瓜concr版ete.像(牲7)mix范ing-co早mpacti鞏ngcon少crete癢admixt虛uresc漫an,an般dcan勸effect漆ively鑰improv推ethe游carbon串a(chǎn)tion都resist目anceo財(cái)fconc習(xí)retet獵oredu衰cethe理carbo礙nation漏shrin駱kage.進(jìn)(五8)-dop蝶edwat屑er-red撐ucing吧agent梁after興theco洗ncrete量crack持ingre溜tardat追ionti僅medue駱,int寨heeff脹ective倚preve放ntion饅ofthe苦rapid漸hydra像tionh快eatof育cemen倒tbase磁donc陸ement粱toavo喊idlon降g-term捐resul月tofn旋on-con什densab墾leinc鞏rease真plasti右cshri蟻nkage.犁(伴9)-dop狼edwor而kabili吸tyof束concre嚷teadm穗ixture并s,and迅easy柄tofin旦dflat蝴surfa傷cesto栗form私amicr溫o-memb衰ranet孕oredu椅ceeva衰porati盒onand徹reduc狡edryi蔑ngshr衰inkage外.潛Manyh石avea到retard斃ingad窄mixtur膀etoi文ncreas夜ethe俗workab嫁ility括andim發(fā)prove歸thefu個(gè)nction士ofpl罩astici葵ty,we骨inen榆gineer壇ingpr升actice握inth貴isare矩ashou雜ldbe暫morec不ontras撒tand恒resear賄chexp返erimen朋tstha伶nsimp魄lyrel攻yingo考nexte寫(xiě)rnalc峽onditi社onsto材impro洋vemay想beev莖enmor猜esimp弱leand調(diào)econo賀mic.擔(dān)4.叢炸early鋸concre緞tecon商servat隊(duì)ion疼Practi栗cehas限prove醋dthat居thec閥ommon福concre夏tecra壇cks,t騎hemaj暴ority老ofsur腿f(wàn)acec填racks驕atdif夠ferent捆depth寨s,mai浪nlybe低cause俱ofthe驢tempe拘rature授gradi惑entca別usedb罷ythe尸coldt映empera糖turer鋤egion炎isals至ovuln壺erable朽toa外sharp醬falli塵nthe討format呼ionof慧crack曲s.Ins緩ulatio壽nsot動(dòng)hatth芹econc瞇retes剩urface稈topr拉event臘early繪cracki吼ngis妄partic便ularly趁impor探tant.懸Therma堆lstre首ssfro渾mthe稠point珍ofvie趙w,the荒insul馳ation果should魂meet謠thefo禍llowin登grequ片iremen愿ts:貓(燈1)to銳preven坑tthe雪concre娘teins鹿idean每douts滑ideth尊econc叮retes民urface愁tempe博rature介diffe巷rence刃andgr接adient言,top恰revent自surfa起cecra全cks.窩(壁2)to煌preven研tthe童concre槐tesup嗎er-col齊d,it鈴should躬bepo掃ssible縣toma遵kecon平crete唯theco凈nstruc夫tionp李eriod巖ofnot風(fēng)less你thant斧hemin利imumt儲(chǔ)empera抖tureo玉fconc通reteu蜂sedfo跡rthe域stabil項(xiàng)ityof益thet馳empera蛾ture.防(殃3)to驢preven掠tcold爆-oldc茫oncret逝eino伴rdert遙oredu艇cethe叢concr會(huì)etebe遮tween杰theol足dand膠newco茄nstrai泛nts.徐Early妻concre黨tecon國(guó)servat趁ion,t駐hemai順nobje照ctive住isto徹mainta遷inthe遭appro博priate宴tempe鈴rature款andh娛umidit辣ycond縮itions餅inor螞derto晉achie潛vethe豐effec截toft改woasp賣(mài)ects,權(quán)onthe格oneh冶and,t持hecon烈crete徹froma線(xiàn)dverse議tempe佳rature迫andh汗umidit盆ydefo鉤rmatio伴ninva岸siont費(fèi)oprev砍entth并eharm喬fulan倉(cāng)ddryi楚ngshr具inkage團(tuán).Ont澡heone突hand,殃toen掏ablet穗hesmo毫othpr袋ogress鏡ofce宮menth條ydrati顆on,wi緒thav兩iewto筑meet獵thede喪signc右apacit集yoft施hestr僵ength摧andcr潤(rùn)ackre畏sistan瀉ce.窄Approp挪riate琴condit秧ionso狠ftemp都eratur襖eand慚humidi鋸tyare燕inter貸relate伙d.Coa曠gulati梁onon瘋thein報(bào)sulati駱onoft襲enhas汁thee盟ffect誕ofmoi勇sture.吧Theore戴tical稍analys測(cè)isof暫fresh虎concre社tecon溪tained漿inth云ewate不rfull森ymeet牛sthe玻requir銅ements雨ofce開(kāi)menth愁ydrati悠onand臉more淺than.掙Howeve難r,due唐toev努aporat舍ionan泳dothe濃rfact漸orsof星tenca浴usewa黎terlo么ss,th跳ereby剪delay黃orpre擾ventt氧hehyd殊ration攝ofce堵ment,饅concre幫tesur可facea煎ndmos色tlike株lyto瞧bedir屬ectly設(shè)affect微edby惜sucha翻negat災(zāi)iveim博pact.鐮Concre陵tepou開(kāi)ring,貞theref采oreth歡efirs鏡tfew尊daysa節(jié)ftert甩hecri蠅tical蝴period健ofco居nserva架tioni濟(jì)nthe撇constr留uction崖shoul叉dpay負(fù)attent型ionto斬.怕5.用切conclu這dingr新emarks湊Above文thete俊mperat駛ureof德concr毅etean任dcrac喜ksin憤theco岸nstruc登tiono籮fthe歐relati焦onbet殼weent碼heory述andpr溝actice貝ofth抱eprel格iminar郊ystud柄y,alt困hough掘the腥academ羨iccom獨(dú)munity窩about濾thec臨auses陣ofcra干cksin傷concr擔(dān)etean才dcalc拾ulatio都nmeth衡odsar辯ediff弊erent甚theori食es,bu門(mén)tspec遇ificm晨easure降stop甩revent積andi跡mprove巧theo賊pinion捐itis牽quite饑unifo勿rmAt訂thesa撞metim與e,the察appli趣cation甲inpr搶actice礦isal僑soar閱elativ脂elygo援odeff摔ect,c渡oncret獻(xiàn)econs沫tructi廉onand鉛more雄depend掠sono挖urobs狠ervati那on,an菠dmore尊,when揉compa礎(chǔ)redto丑multi盯-issue謙analy窩sis,a臟ndmor腐esum桿up,co愉mbined附with磨awide齡range速ofpr患eventi百onmea霉sures,叛thec驟racks廟inthe利concr輸eteis買(mǎi)compl熱etely勁avoide革d.的論混凝土的施面工溫度與結(jié)構(gòu)寨裂縫余1立.驗(yàn)裂縫的原會(huì)因達(dá)泉混凝土中產(chǎn)生棒裂縫有多種原主因，主要是溫束度和濕度的變黃化，混凝土的慧脆性和不均勻柴性，以及結(jié)構(gòu)賴(lài)不合理，原材記料不合格（如柔堿骨料反應(yīng)）退，模板變形，己基礎(chǔ)不均勻沉渾降等。鍋混凝土硬化期賠間水泥放出大宏量水化熱，內(nèi)依部溫度不斷上灌升，在表面引宜起拉應(yīng)力。后浴期在降溫過(guò)程役中，由于受到票基礎(chǔ)或老混凝千上的約束，又開(kāi)會(huì)在混凝土內(nèi)咸部出現(xiàn)拉應(yīng)力輔。氣溫的降低囑也會(huì)在混凝土耗表面引起很大糊的拉應(yīng)力。當(dāng)政這些拉應(yīng)力超喜出混凝土的抗彩裂能力時(shí)，即凝會(huì)出現(xiàn)裂縫。塊許多混凝土的絲內(nèi)部濕度變化這很小或變化較租慢，但表面濕糊度可能變化較壓大或發(fā)生劇烈章變化。如養(yǎng)護(hù)望不周、時(shí)干時(shí)善濕，表面干縮據(jù)形變受到內(nèi)部悶混凝土的約束浙，也往往導(dǎo)致便裂縫?；炷粱厥且环N脆性材如料，抗拉強(qiáng)度吊是抗壓強(qiáng)度刮的孔1巧／托1狼0嘗左右，短期加帝荷時(shí)的極限拉幫伸變形只有厭（碼0.隊(duì)6浩～窩1.惑0似）析×10陳4勿，長(zhǎng)期加荷時(shí)似的極限位伸變上形也只有槽（家1.春2未～恰2.燦0商）孝×104拴.先由于原材料不鑄均勻，水灰比績(jī)不穩(wěn)定，及運(yùn)犧輸和澆筑過(guò)程炎中的離析現(xiàn)象寄，在同一塊混鉗凝土中其抗拉寧強(qiáng)度又是不均尤勻的，存在著犬許多抗拉能力周很低，易于出擴(kuò)現(xiàn)裂縫的薄弱蘇部位。在鋼筋狂混凝土中，拉單應(yīng)力主要是由孫鋼筋承擔(dān)，混島凝土只是承受天壓應(yīng)力。在素泰混凝土內(nèi)或鋼障筋混凝上的邊臉緣部位如果結(jié)鑄構(gòu)內(nèi)出現(xiàn)了拉層應(yīng)力，則須依嘉靠混凝土自身剩承擔(dān)。一般設(shè)眉計(jì)中均要求不吉出現(xiàn)拉應(yīng)力或袍者只出現(xiàn)很小創(chuàng)的拉應(yīng)力。但剛是在施工中混害凝土由最高溫蒙度冷卻到運(yùn)轉(zhuǎn)拳時(shí)期的穩(wěn)定溫袍度，往往在混炎凝土內(nèi)部引起淘相當(dāng)大的拉應(yīng)禿力。有時(shí)溫度僚應(yīng)力可超過(guò)其榆它外荷載所引叔起的應(yīng)力，因術(shù)此掌握溫度應(yīng)書(shū)力的變化規(guī)律訓(xùn)對(duì)于進(jìn)行合理軟的結(jié)構(gòu)設(shè)計(jì)和軋施工極為重要傲。文2浴.姨溫度應(yīng)力的分尸析歌根據(jù)溫度應(yīng)力半的形成過(guò)程可蝴分為以下三個(gè)思階段：央（統(tǒng)1燥）早期：自澆飲筑混凝土開(kāi)始脂至水泥放熱基岡本結(jié)束，一般帶約時(shí)3橋0炒天。這個(gè)階段倒的兩個(gè)特征，訴一是水泥放出郊大量的水化熱海，二是混凝上郵彈性模量的急炕劇變化。由于喬彈性模量的變姿化，這一時(shí)期的在混凝土內(nèi)形膜成殘余應(yīng)力。評(píng)（填2鬼）中期：自水央泥放熱作用基擱本結(jié)束時(shí)起至片混凝土冷卻到威穩(wěn)定溫度時(shí)止億，這個(gè)時(shí)期中躺，溫度應(yīng)力主做要是由于混凝丙土的冷卻及外孟界氣溫變化所遠(yuǎn)引起，這些應(yīng)紡力與早期形成界的殘余應(yīng)力相拍疊加，在此期礎(chǔ)間混凝上的彈有性模量變化不抽大。藝（瘡3珠）晚期：混凝艷土完全冷卻以?huà)伜蟮倪\(yùn)轉(zhuǎn)時(shí)期愈。溫度應(yīng)力主隱要是外界氣溫常變化所引起，叉這些應(yīng)力與前于兩種的殘余應(yīng)刃力相迭加。店根據(jù)溫度應(yīng)力拜引起的原因可葛分為兩類(lèi)：扁（檢1屈）自生應(yīng)力：芒邊界上沒(méi)有任飄何約束或完全繼靜止的結(jié)構(gòu)，媽如果內(nèi)部溫度執(zhí)是非線(xiàn)性分布變的，由于結(jié)構(gòu)浸本身互相約束荷而出現(xiàn)的溫度攔應(yīng)力。例如，芳轉(zhuǎn)換層其結(jié)構(gòu)毛尺寸相對(duì)較大儀，混凝土冷卻球時(shí)表面溫度低如，內(nèi)部溫度高惑，在表面出現(xiàn)噴拉應(yīng)力，在中慮間出現(xiàn)壓應(yīng)力習(xí)。賽（分2嫌）約束應(yīng)力：羞結(jié)構(gòu)的全部或情部分邊界受到估外界的約束，終不能自由變形濕而引起的應(yīng)力組。如箱梁頂板遲混凝土和護(hù)欄史混凝土。膨這兩種溫度應(yīng)挑力往往和混凝趙土的干縮所引透起的應(yīng)力共同啞作用。魂要想根據(jù)已知最的溫度準(zhǔn)確分旺析出溫度應(yīng)力漠的分布、大小撈是一項(xiàng)比較復(fù)催雜的工作。在幟大多數(shù)情況下句，需要依靠模竿型試驗(yàn)或數(shù)值蘭計(jì)算?；炷晾系男熳兪箿囟葔?mèng)應(yīng)力有相當(dāng)大摟的松馳，計(jì)算糕溫度應(yīng)力時(shí)，買(mǎi)必須考慮徐變各的影響，具體忌計(jì)算這里就不靈再細(xì)述。趨3瞞.敗溫度的控制和識(shí)防止裂縫的措歉施唐為了防止裂縫庫(kù)，減輕溫度應(yīng)拆力可以從控制享溫度和改善約廁束條件兩個(gè)方建面著手。落控制溫度的措閉施如下：鉗（紛1泰）采用改善骨秒料級(jí)配，用干聽(tīng)硬性混凝土，然摻混合料，加浩引氣劑或塑化輛劑等措施以減蛋少混凝土中的捷水泥用量；述（隆2膚）拌合混凝土價(jià)時(shí)加水或用水漫將碎石冷卻以餡降低混凝土的純澆筑溫度；秩（因3盆）熱天澆筑混替凝土?xí)r減少澆捧筑厚度，利用根澆筑層面散熱嗎；樣（蒙4謀）在混凝土中濟(jì)埋設(shè)水管，通歐入冷水降溫；榴（汗5賄）規(guī)定合理的宗拆模時(shí)間，氣符溫驟降時(shí)進(jìn)行裳表面保溫，以咬免混凝土表面宗發(fā)生急劇的溫帶度梯度；殼（計(jì)6黃）施工中長(zhǎng)期般暴露的混凝土汽澆筑塊表面或忌薄壁結(jié)構(gòu)，在頭寒冷季節(jié)采取石保溫措施；但改善約束條件尊的措施是：過(guò)（鞠1脊）合理地分縫鎮(zhèn)分塊；名（弓2盾）避免基礎(chǔ)過(guò)方大起伏；凝（留3便）合理的安排憂(yōu)施工工序，避勁免過(guò)大的高差失和側(cè)面長(zhǎng)期暴氧露；濱此外，改善混復(fù)凝土的性能，啦提高抗裂能力執(zhí)，加強(qiáng)養(yǎng)護(hù)，怠防止表面干縮柱，特別是保證鍵混凝土的質(zhì)量蝦對(duì)防止裂縫是質(zhì)十分重要，應(yīng)響特別注意避免東產(chǎn)生貫穿裂縫刷，出現(xiàn)后要恢捉復(fù)其結(jié)構(gòu)的整落體性是十分困淡難的，因此施坊工中應(yīng)以預(yù)防稍貫穿性裂縫的裝發(fā)生為主許。蒸犯在混凝土的施崖工中，為了提坡高模板的周轉(zhuǎn)稿率，往往要求母新澆筑的混凝傘土盡早拆模。躍當(dāng)混凝土溫度歇高于氣溫時(shí)應(yīng)究適當(dāng)考慮拆模箏時(shí)間，以免引映起混凝土表面椒的早期裂縫。敘新澆筑早期拆音模，在表面引飽起很大的拉應(yīng)劑力，出障現(xiàn)京“友溫度沖湊擊虧”桃現(xiàn)象。在混凝關(guān)土澆筑初期，洪由于水化熱的豈散發(fā)，表面引災(zāi)起相當(dāng)大的拉恒應(yīng)力，此時(shí)表耳面溫度亦較氣捏溫為高，此時(shí)為拆除模板，表絡(luò)面溫度驟降，未必然引起溫度交梯度，從而在饒表面附加一拉鉛應(yīng)力，與水化怖熱應(yīng)力迭加，蘇再加上混凝土促干縮，表面的款拉應(yīng)力達(dá)到很驅(qū)大的數(shù)值，就剝有導(dǎo)致裂縫的缺危險(xiǎn)，但如果棍在拆除模板后缺及時(shí)在表面覆犯蓋一輕型保溫躁材料，如泡沫旱海棉等，對(duì)于輛