土木工程外文翻译--混凝土施工裂缝原因及防治-建筑结构(编辑修改稿)

土木工程外文翻译--混凝土施工裂缝原因及防治-建筑结构(编辑修改稿)内容摘要：

ots of water surface layer. This phenomenon is not only affect lactation water, also influence the construction speed and quality of construction. Because the water gathered in separation between the two casting concrete surface layer, change, and watercement ratio in the water and took out some of the mortar, thus forming a layer of interlining content, destroyed the cohesive force of concrete and holistic. The size of the water concrete lactation with water water, water, lactation。 And with the temperature, water separation of time with temperature pletely and shortening, In addition, also with the position and fineness of cement. Therefore, in selecting slag cement should be chosen when the varieties, and lactation shall be adding waterreducing agent in concrete, to reduce the consumption. During construction, should be in water or mixing some tomography uniform rolling cement casting in water, with 3degrees vibration paction, continue again after a concrete casting. reasonable construction method (1) The concrete mixing and transportation. (a) white, accurate grasp of concrete proportion, especially the strict control of water consumption, the determination of sand. Records of every block water cement, sand and gravel, specific quantity, the application must be accurate to scale, by mixing. Good control of concrete slump and general shoulds not be too big, in 120 177。 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. Usi。