【正文】 后期通水是使混凝土柱狀塊達(dá)到接縫灌漿的必要措施，一般采用通河水和通制冷水相結(jié)合的方案。 養(yǎng)護(hù) 混凝土澆注完畢后，應(yīng)及時(shí)灑水養(yǎng)護(hù)以保持混凝土表面經(jīng)常濕潤，這樣既減少外界高溫倒罐，又防止干縮裂縫的發(fā)生，促進(jìn)混凝土強(qiáng)度的穩(wěn)定增長。 養(yǎng)護(hù)是大體積混凝土施工中一項(xiàng)十分關(guān)鍵的工作。這種方案適用于單位時(shí)間內(nèi)要求供應(yīng)的混凝土較少，不象第一種方案那樣集中。采用這種方案，適用于結(jié)構(gòu)的平面尺寸一般不宜太大，施工時(shí)從短邊開始，沿長邊推進(jìn)比較合適。但是如果此時(shí)受到冷空氣的襲擊，或者過分通風(fēng)散熱，使表面溫度降溫過大就很容易導(dǎo)致裂縫的產(chǎn)生，所以在混凝土在拆模后，特別是低溫季節(jié)，在拆模后立即采取表面保護(hù)。拆模時(shí)間應(yīng)根據(jù)氣溫和強(qiáng)度情況而定。 (b)混凝土拌好后在出倉運(yùn)輸過程中，要防止產(chǎn)生分離、泌水、砂漿流失等現(xiàn)象，應(yīng)縮短運(yùn)輸時(shí)間，混凝土裝卸不可過滿。記錄每一次攔制用水、水泥、砂、碎石的具體數(shù)量，各擋砂石料都必須通過磅秤，準(zhǔn)確后才能拌制。所以，在選用礦渣水泥時(shí)應(yīng)盡量選擇泌水性的品種，并應(yīng)在混凝土中摻入減水劑，以降低用水量。 但是，水化熱低的礦渣水泥的析水性比其它水泥大，在澆筑層表面有大量水析出。 (4)大體積混凝土所選用的原材料應(yīng)注意以下幾點(diǎn)： ① 粗骨料宜采用連續(xù)級配，細(xì)骨料宜采用中砂。緩凝劑的作用一是延緩混凝土放熱峰值出現(xiàn)的時(shí)間，二是改善和易性，減少運(yùn)輸過程中的塌落度損失。 (a)減水劑。(b)細(xì)骨料。 (2)骨料。 (1)水泥。這里主 要介紹干燥收縮和塑性收縮。其中具體原因如下 ： 溫度應(yīng)力引起裂縫（溫度裂縫） 目前溫度裂縫產(chǎn)生主要原因是由溫差造成的。而對于非荷載產(chǎn)生的裂縫，由于原因復(fù)雜，則很難處理和防止。但是混凝土在受到荷載、溫度、收縮等作用下，微裂縫就會不斷擴(kuò)展和連通，最終形成肉眼可見的宏觀裂縫，也就是混凝土工程中常說的裂縫，這會對混凝土結(jié)構(gòu)的使用性能和耐久性產(chǎn)生不利的影響。施工過程中要掌握好原材料的配置，在澆筑過程中把握好進(jìn)度和厚度，及時(shí)做好養(yǎng)護(hù)工作，這樣就可盡量避免混凝土裂縫了。 20 mm. To minimize the mouth 3 concrete temperature. (b) concrete mixing in a storehouse after good transport process, to prevent to produce separation, lactation water, mortar loss should shorten transportation time, concrete loading not too full. (2)Concrete pouring and open mode. Pouring process may be closegrained, vibration to vibration time should be uniform in surface functional plasma advisable, uniform spacing, vibrating force scope affected overlap 1/2 advisable, after casting, paction, surface must, in order to prevent the surface crack. Try to avoid in the solar radiation, high time due to the needs of the project if pouring in summer construction, avoid noon pouring temperature period, try to arrange at night. Time should be removed, according to air temperature and strength. In the actual temperature curing of the concrete conditions of strength, strength design of concrete center and 75%, the lowest temperature control surface in 25 degrees Celsius, expected the concrete surface temperature drop more than 9 degrees Celsius above does not allow removed. (3) Do surface insulation protection of mass concrete temperature crack, is mainly caused by excessive temperature. Concrete pouring, due to internal heat faster, more surface temperature will form the internal and external surface by internal restraint, contraction, but the tensile stress, not more than usually have small tensile strength and the concrete cracks. But if the air raid, or by excessive ventilation cooling, make the surface temperature will easily lead to excessive temperature crack in the concrete, and so on, especially after dismantling formwork, low season in the immediate surface protection. To prevent excessive temperature crack, cause surface. In addition, the average day temperature in 2 ~ 3d consecutive decline not less than 6 ~ 8 degrees Celsius, 28d age concrete surface must surface within the protection. (4) Of the mass concrete casting: Construction scheme, besides should satisfy each place of concrete in early before a new concrete are covered and rammed finished outside, still should consider structure size, steel pipe, buries the bolts and leave, concrete and hydration heat supply, the influence of factors such as the monly used method has the following kinds: Comprehensive stratified: In the first layer after pouring all prehensive casting, casting back second, should make the first layer of concrete yet, so early, continuous casting until pletion by far. Using this scheme, applicable to the general structure of planar size shoulds not be too big, when construction from the short side began to push along the long side, is more appropriate. When necessary, can be divided into two sections from middle to both ends to or from the middle and construction. Section 2 layer: Concrete casting, starting from scratch, casting a certain distance to the second floor, so after pouring in other layers on casting. Due to the total number of layers, therefore, af