【正文】 tion, reinforced bar fabrication and bind, concrete stirring and mixing system and transport, concrete concrete covibration beat with a stick, construction joint practice, concrete curing and dismantle model and beingready for backfill and so on are very critical to quality method to ensure that waterproof concrete self waterproof, and the way of practice has wan out. Method being under construction Fabrication and Installation According to the concrett of closely knit , demand of reason why to form board since the waterproof also concrete have made and have assembled corresponding rise is special , be to require that not leaving out thick fluid , firm closely knit block of wood deformation , water absorption Character should be small and ought to give priority to select and using bamboo slab rubber form board or the steel form.. Strict control form board room gap size, necessary exceeding 2 mms uses foam rubber or plastic to squeeze a crack in , porous form board nonutility 19 without exception to board face Be ready for wall post at the same time rotting the prevention and cure job Adopt the cement mortar pouring same ,indicia in before the root segment sticking the foam rubber or plastic strip , the bottom puts on a cement mortar , concrete a concrete, first 5 cm ~ 10 cm. Since waterproof, concrete structure wall thickness is mostly more infertile .Be to ensure that ponent geometry dimension , Chang adopt the inside and outside bolt to pull the measure meeting attention to, responds to on play receive bolt centre interpose stop water iron plate, to prevent water from forming pilotage passage along bolt leakage. Assembing reinforoement Waterproof concrete structure has demanding as follows to the reinforced bar 1) reinforced bar should adopt twisted steel as far as possible , increases by hold wrap a force posing in reply a water ability 2) reinforced bars connect should try one39。 (3)Rational arrangement construction process, prevent the too big discrepancy in elevation and side from exposing for a long time。t out of shape and stress not cause not free. Such as case roof beam roof concrete and guardrail concrete. This two kinds of temperature stresses draw back stresses caused to act on with the doing of concrete together frequently. It is a more plicated job to want to analyse the distribution , size of the temperature stress accurately according to known temperature. In case of great majority , need to rely on the model test or the number value to calculate. To is it make temperature stress have sizable limp to creep concrete, at the stress accounting temperature, must consider the influence that creep , calculate concretly that no longer states thinly here. Control and preventing the measure of the crack of 3 temperature For prevent crack , lighten temperature stress can from control temperature and is it is it set about to restrain terms from two to improve. The measure of controlling temperature is as follows: (1)Is it improve aggregate grade mix , is it do rigid concrete to spend , mix mixture to adopt, is it guide angry pharmaceutical or plastification pharmaceutical ,etc. measure in order to reduce cement consumption of concrete to add。 9 Discuss the construction temperature and crack of the concrete lightly By G. K. Kululanga, W. Kuotcha, R. McCaffer, Member, ASCE, and F. EdumFotwe ,The American Society of Civil Engineers The summary Through observation live for many years, through consulting the monograph about stress within the concrete, explain to concrete temperature reason , onthespot concrete control and measure , prevention of crack of temperature that crack produce. Keyword: Concrete。試驗(yàn)證明，防水混凝土早期脫水或養(yǎng)護(hù)過程缺水 ，將大幅度降低其抗?jié)B性能。在澆筑豎壁時(shí)應(yīng)在接縫處先澆一層 5cm～ 10 cm厚的同標(biāo)號(hào)水 泥砂漿銜接層，以保證接縫處振搗密實(shí)。防水混凝土澆筑應(yīng)嚴(yán)格分層進(jìn)行 ，并一次連續(xù)施工完成前后及上下層之間接頭應(yīng)嚴(yán)格控制在 水泥的初凝時(shí)間內(nèi)為此 ，可將操作工人分成幾個(gè)作業(yè)組同時(shí)相 向或相背而行。 防水混凝土鋼筋保護(hù)層最小厚度不小于 25 mm，特別是迎水面的保護(hù)層不允許有負(fù)誤差，用砂漿墊塊作保護(hù)層時(shí)，應(yīng)用預(yù)埋在砂漿塊內(nèi)的鐵絲與鋼筋綁扎 牢固。 結(jié)合 經(jīng)驗(yàn) ，對(duì)模板的設(shè)計(jì)、制作安裝、鋼筋綁扎、混凝土澆筑及養(yǎng)護(hù)等關(guān)鍵工序的操作要點(diǎn)進(jìn)行了闡述，并介紹了成型后混凝土的質(zhì)量控制標(biāo)準(zhǔn)，以降低工程造價(jià)，具有很好的經(jīng)濟(jì)和社會(huì)效益。 3）防止老混凝土過冷，以減少新老混凝土間的約束。減水防裂劑可有效的提高的混凝土抗拉強(qiáng)度，大幅提高混凝土的抗裂性能。例如使用減水防裂劑，筆者在實(shí)踐中總結(jié)出其主要作用為： （ 1）混凝土中存在大量毛細(xì)孔道，水蒸發(fā)后毛細(xì)管中產(chǎn)生毛細(xì)管張力，使混凝土干縮變形。在溫度不太高及應(yīng)力低于屈服極限的條件下，鋼的各項(xiàng)性能是穩(wěn) 4 定的，而與應(yīng)力狀態(tài)、時(shí)間及溫度無關(guān)。 溫度的控制和防止裂縫的措施 為了防止裂縫，減輕溫度應(yīng)力可以從控制溫度和改善約束條件兩個(gè)方面著手。 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。但是在施工中混凝土由最高溫度冷卻到運(yùn)轉(zhuǎn)時(shí)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。氣溫的降低也會(huì)在混凝土表面引起很大的拉應(yīng)力。 在大體積混凝土中，溫度應(yīng)力及溫度控制具有重要意義。 摘 要本文通過多年的現(xiàn)場(chǎng)觀察，通過查閱有關(guān)混凝土內(nèi)部應(yīng)力方面的專著，對(duì)混凝土溫度裂縫產(chǎn)生的原因、現(xiàn)場(chǎng)混凝土溫度的控制和預(yù)防裂縫的措施進(jìn)行等進(jìn)行闡述。其次，在運(yùn)轉(zhuǎn)過程中，溫度變化對(duì)結(jié)構(gòu)的應(yīng)力狀態(tài)具有顯著的不容忽視的影響。如養(yǎng)護(hù)不周、時(shí)干時(shí)濕，表面干縮形變受到內(nèi)部混凝土的約束，也往往導(dǎo)致裂縫。這個(gè)階段的兩個(gè)特征，一是水泥放出大量的水化熱，二是混凝上彈性模量的急劇變化。如箱梁頂板混凝土和護(hù)欄混凝土。當(dāng)混凝土溫度高于氣溫時(shí)應(yīng)適當(dāng)考慮拆模時(shí)間，以免引起混凝土表面的早期裂縫。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。 （ 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％。 （ 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 . 5 許多外加劑都有緩凝、增加和易性、改善塑性的功能，我們?cè)诠こ虒?shí)踐中應(yīng)多進(jìn)行這方面的實(shí)驗(yàn)對(duì)比和研究，比單純的靠改善外部條件，可能會(huì)更加簡(jiǎn)捷、經(jīng)濟(jì)。 適宜的溫濕度條件是相互關(guān)聯(lián)的。 施工方法 6 模板制作與安裝 由于防水混凝土特別強(qiáng)調(diào)密實(shí)性，所以對(duì)模板的制作和安裝也相應(yīng)提高 了要求 ，即要求密實(shí)不漏漿，堅(jiān)固不變形 ，吸水性要小 ，宜優(yōu)先選用竹膠板模板或鋼模板。 2)當(dāng)使用外加劑，應(yīng)將外加劑制成一定濃度的溶液后加入攪 拌機(jī)內(nèi)，不得將外加劑的干粉或高濃度溶液直接加入攪拌機(jī)內(nèi)， 防止攪拌不均勻而局部集中，既失去外加劑作用 ，又影響混凝土質(zhì)量。 3)堅(jiān)持開門子下料或用串桶 (溜槽 )下料。 應(yīng)盡量少留或不留，當(dāng)混凝土澆筑受到設(shè)備或支模條件的限制時(shí)，則可在征得設(shè)計(jì)單 位的同意后，在規(guī)定部位留置水平施工縫，一般留在底板以上 200 mm 處的豎壁上工程中采用新工藝 —— 膨脹性橡膠止水帶處理施工 縫的方法，取代常用方法，諸如企 口式施工縫、高低式施工縫、平 口施工縫等。當(dāng)構(gòu)筑物防水工作結(jié)束后應(yīng)立即進(jìn)行回填土施工。Control 1. The concrete occupies the important position in modern engineering construction. But today, the crack of the concrete is paratively general, the cracks are nearly omnipresent in the science of bridge building. Though we take various kinds of measures in constructing, careful, but the crack still occurs now and then. Tracing it to its cause, it is one of them inpletely that our change to concrete temperature stress pays attention to