【正文】 結(jié)合經(jīng)。但由于蒸發(fā)等原因常引起水分損失，從而推遲或妨礙水泥的水化，表面混凝土最容易而且直接受到這種不利影響?；炷系谋卮胧┏３Ｒ灿斜竦男ЧＲ环矫媸顾嗨饔庙樌M行，以期達到設(shè)計的強度和抗裂能力。3）防止老混凝土過冷，以減少新老混凝土間的約束。從溫度應(yīng)力觀點出發(fā)，保溫應(yīng)達到下述要求：1）防止混凝土內(nèi)外溫度差及混凝土表面梯度，防止表面裂縫?；炷恋脑缙陴B(yǎng)護實踐證明，混凝土常見的裂縫，大多數(shù)是不同深度的表面裂縫，其主要原因是溫度梯度造成寒冷地區(qū)的溫度驟降也容易形成裂縫。（9）摻外加劑混凝土和易性好，表面易抹平，形成微膜，減少水分蒸發(fā)，減少干燥收縮。（7）摻加外加劑可使混凝土密實性好，可有效地提高混凝土的抗碳化性，減少碳化收縮。（6）混凝土在收縮時受到約束產(chǎn)生拉應(yīng)力，當(dāng)拉應(yīng)力大于混凝土抗拉強度時裂縫就會產(chǎn)生。（4）減水防裂劑可以改善水泥漿的稠度，減少混凝土泌水，減少沉縮變形。（2）水灰比是影響混凝土收縮的重要因素，使用減水防裂劑可使混凝土用水量減少25%。增大毛細孔徑可降低毛細管表面張力，但會使混凝土強度降低。為保證混凝土工程質(zhì)量、防止開裂、提高混凝土的耐久性，正確使用外加劑也是減少開裂的措施之一?；炷梁弯摻罨炷两Y(jié)構(gòu)的表面常常會發(fā)生細而淺的裂縫，其中大多數(shù)屬于干縮裂縫。但加筋后結(jié)構(gòu)內(nèi)的裂縫一般就變得數(shù)目多、間距小、寬度與深度較小了。鋼的線脹系數(shù)與混凝土線脹系數(shù)相差很小，在溫度變化時兩者間只發(fā)生很小的內(nèi)應(yīng)力。只是對一般鋼筋混凝土有影響。在混凝土澆筑初期，由于水化熱的散發(fā)，表面引起相當(dāng)大的拉應(yīng)力，此時表面溫度亦較氣溫為高，此時拆除模板，表面溫度驟降，必然引起溫度梯度，從而在表面附加一拉應(yīng)力，與水化熱應(yīng)力迭加，再加上混凝土干縮，表面的拉應(yīng)力達到很大的數(shù)值，就有導(dǎo)致裂縫的危險，但如果在拆除模板后及時在表面覆蓋一輕型保溫材料，如泡沫海棉等，對于防止混凝土表面產(chǎn)生過大的拉應(yīng)力，具有顯著的效果。當(dāng)混凝土溫度高于氣溫時應(yīng)適當(dāng)考慮拆模時間，以免引起混凝土表面的早期裂縫。控制溫度的措施如下：（1）采用改善骨料級配，用干硬性混凝土，摻混合料，加引氣劑或塑化劑等措施以減少混凝土中的水泥用量；（2）拌合混凝土?xí)r加水或用水將碎石冷卻以降低混凝土的澆筑溫度；（3）熱天澆筑混凝土?xí)r減少澆筑厚度，利用澆筑層面散熱；（4）在混凝土中埋設(shè)水管，通入冷水降溫；（5）規(guī)定合理的拆模時間，氣溫驟降時進行表面保溫，以免混凝土表面發(fā)生急劇的溫度梯度；（6）施工中長期暴露的混凝土澆筑塊表面或薄壁結(jié)構(gòu)，在寒冷季節(jié)采取保溫措施；改善約束條件的措施有：（1）合理地分縫分塊；（2）避免基礎(chǔ)過大起伏；（3）合理的安排施工工序，避免過大的高差和側(cè)面長期暴露；此外，改善混凝土的性能，提高抗裂能力，加強養(yǎng)護，防止表面干縮，特別是保證混凝土的質(zhì)量對防止裂縫是十分重要，應(yīng)特別注意避免產(chǎn)生貫穿裂縫，出現(xiàn)后要恢復(fù)其結(jié)構(gòu)的整體性是十分困難的，因此施工中應(yīng)以預(yù)防貫穿性裂縫的發(fā)生為主?；炷恋男熳兪箿囟葢?yīng)力有相當(dāng)大的松馳，計算溫度應(yīng)力時，必須考慮徐變的影響，具體計算這里就不再細述。要想根據(jù)已知的溫度準確分析出溫度應(yīng)力的分布、大小是一項比較復(fù)雜的工作。（2）約束應(yīng)力：結(jié)構(gòu)的全部或部分邊界受到外界的約束，不能自由變形而引起的應(yīng)力，如箱梁頂板混凝土和護欄混凝土。根據(jù)溫度應(yīng)力引起的原因可分為兩類：（1）自生應(yīng)力：邊界上沒有任何約束或完全靜止的結(jié)構(gòu)，如果內(nèi)部溫度是非線性分布的，由于結(jié)構(gòu)本身互相約束而出現(xiàn)的溫度應(yīng)力。（3）晚期：混凝土完全冷卻以后的運轉(zhuǎn)時期。由于彈性模量的變化，這一時期在混凝土內(nèi)形成殘余應(yīng)力。2）溫度應(yīng)力的分析根據(jù)溫度應(yīng)力的形成過程可分為以下三個階段：（1）早期：自澆筑混凝土開始至水泥放熱基本結(jié)束，一般約30天。但是在施工中混凝土由最高溫度冷卻到運轉(zhuǎn)時期的穩(wěn)定溫度，往往在混凝土內(nèi)部引起相當(dāng)大的拉應(yīng)力。在素混凝土內(nèi)或鋼筋混凝上的邊緣部位如果結(jié)構(gòu)內(nèi)出現(xiàn)了拉應(yīng)力，則須依靠混凝土自身承擔(dān)?；炷潦且环N脆性材料，抗拉強度是抗壓強度的1/10左右，短期加荷時的極限拉伸變形只有（～）104，長期加荷時的極限位伸變形也只有（～）104。許多混凝土的內(nèi)部濕度變化很小或變化較慢，但表面濕度可能變化較大或發(fā)生劇烈變化。氣溫的降低也會在混凝土表面引起很大的拉應(yīng)力?；炷劣不陂g水泥放出大量水化熱，內(nèi)部溫度不斷上升，在表面引起拉應(yīng)力。我們遇到的主要是施工中的溫度裂縫，因此本文僅對施工中裂縫的成因和處理措施做一探討。首先，在施工中混凝土常常出現(xiàn)溫度裂縫，影響到結(jié)構(gòu)的整體性和耐久性。在大體積混凝土中，溫度應(yīng)力及溫度控制具有重要意義。盡管我們在施工中采取各種措施，但裂縫仍然時有出現(xiàn)。關(guān)鍵詞：　混凝土　　溫度應(yīng)力 　裂縫　　控制。 Secondly, backfill varia and ponding should clear up the pit bottom in the front, respond to densification with layers when backfill. Waterproof structure vicinity layer pounds true backfill, self is a reliable and economical as well water proofing drapery under the ground. In project basement engineering construction Shanghai, since organizing water proofing down to earth strictly with all above seven passes, the concrete is under construction, effect is paratively ideal. The percolating water phenomenon does not appear.ConclusionsConstruction temperature and relation of crack in concrete the above carry on preliminary discussion of theory and practice, though the academia has different theories to origin cause of formation and puting technology of the concrete crack, but to concrete prevention and improving the measure suggestion to relatively unify, application in practice result fine too at the same time, concrete to is it observe, pare more by us to want in constructing, analyse more, summarize more after going wrong, bine many kinds of prevention and deal with the measure, the crack of the concrete can be avoided.一、 翻譯淺談混凝土的施工過程中溫度與裂縫控制摘要 為了防止業(yè)主對混凝土工程的索要賠償,我們就必須做好過程中的溫度與裂縫控制。s best to adopt to solder connection, stop using and being needless to bind connection to the full3)When binding a reinforced bar, the iron wire head responds to inner bending.4)Strict control reinforced bars protective layer thickness. Minimal thickness of waterproof concrete reinforced bar protective layer is not smaller than 25mms, the protective layer weling water surface especially inadmissibility to disappoint error. The iron wire and reinforced bar that application buries in advance within mortar piece while using mortar heel block as protective layer, are bound solid. When the cavalry puts up the fixed reinforced bar if adopt a reinforced bar, also need to increase solders water iron plate or fixation just goes ahead, to strengthen waterproof effect in the heel block. This project uses new materials nylon to have fixed there is an effect39。 In addition, improve the performance of the concrete and improve and resist the ability of splitting, strengthen maintenance, prevent the surface from being done and contracted, especially guarantee the quality of the concrete is very important to preventing the crack, should pay special attention to avoiding producing and running through the crack, the globality resumed its structure after appearing is very difficult, so should rely mainly on preventing the emergence of the running through crack while constructing. In construction of concrete, for raise turnover rate of template, demand concrete form removal as soon as possible that build newly often. Should consider form removal time properly when concrete temperature is higher than the temperature, so as not to cause the superficial early crack of concrete. Building the early form removal newly, cause very large stress of drawing on the surface, the phenomenon that temperature is assaulted appears. Build initial stage in concrete, because heat of hydration is sent out, the surface causes sizable to draw the stress, surface temperature is also higher than temperature at this moment, remove the template at this moment, surface temperature is lowered suddenly, must cause temperature gradient, thus add and draw the stress on the surface, change and add with the heat of hydration stress, in addition, the concrete dries and contracts, the superficial stress of drawing reaches very great number value, have danger of causing the crack, but cover a lightduty heat insulator with on the surface in time after removing the template, for instance foam sponge, etc. , for prevent concrete surface from produce the too big stress of drawing, have remarkable results. Add muscle influence to large volume temperature stress of concrete very light, because large volume concrete include muscle to be rate very much low. Just