【正文】 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。s shrinkage. This article mainly discussed type materials. One specific reasons are as follows: The temperature stress caused by fracture (temperature crack) temperature cracks in the main reason is caused by temperature difference. Temperature can be divided into three types: early concrete pouring, produce large amounts of the hydration heat, due to the concrete is a poor conductor of heat accumulation in concrete, the hydration heat to send out, often make internal temperatures rise, concrete and reinforced concrete surface temperature for outdoor environment temperature, it is formed, the temperature and temperature inside of condensate in early concrete tensile stress when more than concrete pressive strength, will cause cracking in concrete, In addition, in the dismantling formwork, surface temperature and reduce the temperature caused by fast, and will cause cracking. When the concrete temperature, maximum heat radiates to the minimum temperature, temperature, or use them with the highest temperature difference is the internal temperature, These three temperature will produce temperature crack. In these three temperature, is mainly caused by hydration heat and the temperature. Shrinkage crack contraction there are many causes, including drying shrinkage, plastic shrinkage, shrinkage, carbonation contraction, etc. Here mainly introduces drying shrinkage and plastic shrinkage. After drying shrinkage of concrete sclerosis, in dry environment, the water concrete to the loss caused by inside extroversion, concrete the shrinkage deformation cracks. The plastic shrinkage of cement and concrete in the activity of higher temperature, or in low watercement condition exacerbate cause craze. When the concrete surface water obviously decreased, lactation evaporation of water cannot get the timely supplements, then concrete is still in a state of plastic, by a concrete surface tension, uneven distribution will appear the cracks of concrete cracks, and further intensify the moisture inside body, and further expansion crack Second, the measures to prevent cracks From the above analysis, the crack is mainly caused by temperature difference and contraction, so in order to prevent the cracks of, will maximize reduce temperature and reduce the shrinkage of concrete, specific measures as follows. 1. Optimizing raw materials (1)Cement. The cement should be chosen according to the engineering properties, construction condition, climate and other technical requirements, prehensive consideration, to meet the strength and durability of concrete design requirements. When the choice should be labeled with cement concrete design match the label. For full strength of cement, cement, cement save from the label for concrete label to 2 times as appropriate. (2) aggregate. (a) coarse aggregate. The coarse aggregate concrete rubble is closegrained, must have the enough strength, hard to expand the coarse aggregate size. To ensure the concrete pouring dao closegrained, coarse aggregate maximum diameter less than the minimum size of the structural sections 1/4, also not greater than the minimum distance between steel for thickness 3/4, in 10 centimeters and concrete, allowing adopts maximum diameter 1 1/2 of the aggregate number, but it shall not exceed 25%. (b) fine aggr