【正文】 of mass concrete construction is a vital work. Maintain proper maintenance is mainly to control temperature and humidity, temperature, promote concrete outside the normal development of the strength of concrete and prevent the cracks of concrete and development. According to the specific circumstances of should as far as possible much maintenance period of time, after dismantling formwork should immediately, covering protection to prevent recent climate, sudden cold temperature, prevent and control in early concrete cracks and medium. The massive concrete curing, not only to satisfy the need that still should increase by artificial temperature control, due to temperature caused by deformation of the concrete cracking. After the pletion of the concrete curing time to keep the concrete surface spraying maintenance, such as reducing often humid heat outside pour cans, and prevent dry crack and promote the stable growth of concrete strength. In general 18h 12 ~ after pouring in immediately start maintenance, maintenance time not less than 28d or design age. 4 Cooled If in the hightemperature seasonal construction, should be in early general refrigeration adopted to reduce the water temperature, but the peak of concrete, water cannot too long, for a long time can cause excessive temperature range of temperature stress caused by large. In order to cut inside and outside, still should temperature in summer jiamoqiuchu undertake metaphase is cooled by water, river, general middle water lasted about two months. Later, water is made concrete cylindrical blocks the necessary measures to juncture grouting, generally USES water and cooling water through the bination scheme. Third, the conclusion Concrete crack, especially large volume concrete crack is currently scholars and engineering is an important problem of attention, through the above analysis, the material of mass concrete crack is mainly posed of temperature stress and concrete39。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。其中具體原因如下 ： 溫度應力引起裂縫（溫度裂縫） 目前溫度裂縫產(chǎn)生主要原因是由溫差造成的。 (1)水泥。(b)細骨料。緩凝劑的作用一是延緩混凝土放熱峰值出現(xiàn)的時間，二是改善和易性，減少運輸過程中的塌落度損失。 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。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，準確后才能拌制。拆模時間應根據(jù)氣溫和強度情況而定。采用這種方案，適用于結(jié)構(gòu)的平面尺寸一般不宜太大，施工時從短邊開始，沿長邊推進比較合適。 養(yǎng)護是大體積混凝土施工中一項十分關(guān)鍵的工作。后期通水是使混凝土柱狀塊達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 混凝土澆注完畢后，應及時灑水養(yǎng)護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，促進混凝土強度的穩(wěn)定增長。這種方案適用于單位時間內(nèi)要求供應的混凝土較少，不象第一種方案那樣集中。但是如果此時受到冷空氣的襲擊，或者過分通風散熱，使表面溫度降溫過大就很容易導致裂縫的產(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。 (b)混凝土拌好后在出倉運輸過程中，要防止產(chǎn)生分離、泌水、砂漿流失等現(xiàn)象，應縮短運輸時間，混凝土裝卸不可過滿。所以，在選用礦渣水泥時應盡量選擇泌水性的品種，并應在混凝土中摻入減水劑，以降低用水量。 (4)大體積混凝土所選用的原材料應注意以下幾點： ① 粗骨料宜采用連續(xù)級配，細骨料宜采用中砂。 (a)減水劑。 (2)骨料。這里主 要介紹干燥收縮和塑性收縮。而對于非荷載產(chǎn)生的裂縫，由于原因復雜，則很難處理和防止。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度和厚度，及時做好養(yǎng)護工作，這樣就可盡量避免混凝土裂縫了。Construction cracks in concrete, causes and prevention Construction cracks of concrete reason for the external and internal. The initial mainly refers to the internal defects of concrete in early concrete, its internal hardening process will exist numerous micropores, airpocket and micro cracks, External refers to the load reason: temperature crack, dry shrinkage effect etc. In these, can produce various forms of concrete cracks. To grasp the construction process of raw materials, in pouring process configuration of progress and thickness, grasp timely maintenance work well, which can avoid concrete cracks. A, The cause of the tear initial defects of concrete Concrete is posed of cement, sand aggregate, mixed with water and other materials and formation of heterogeneity brittle materials. In the beginning, because hardened concrete construction and deformation, a series of problems, such as constraint in the concrete shape sclerosis will exist numerous micropores, airpocket and micro cracks of concrete that us