1、 Ready Mixed Concrete early Crack and prevention measures 商品混凝土早期裂缝的成因 及防治措施 学 生 姓 名 ： 王 昀 学 生 班 级： 土木 0648 班 所 在 学 院： 土 木 学 院 所 学 专 业： 土 木 工 程 专 业 方 向： 建 筑 工 程 指 导 教 师： 袁志仁老师 教 师 职 称： 讲 师 土 木 学 院 2010 年 4 月 15 日 1 Ready Mixed Concrete Crack and early prevention measures Abstract: This paper on the
2、engineering practice prone to early fracture analysis and description, but also introduced a number of targeted prevention and control measures With the continuous expansion of the scale of construction and quality of construction works to raise awareness of the importance of commodities for its con
3、crete technical and economic advantages, in particular, is stable, reliable, good quality favored by construction units. However, the use of commercial concrete construction quality of works is also a lot of accidents, the most common problem when the number of cracks, in particular the coefficient
4、of the surface plate, mass concrete walls, as well as undesirable, such as construction technology of concrete cracks caused by the problem resulting in a lot of unnecessary disputes, some cracks in the early morning, if dealt with early detection, then the structure will not affect the appearance a
5、nd use. Concrete is a solid, liquid, gas, a combination of non-homogeneous composite material, after forming as the temperature, humidity and other environmental conditions will be formed under the influence of the naked eye can not see the micro-cracks in the concrete composition of materials and m
6、icro - different structures as well as the environmental impact of different causes of the cracks in the concrete have a very complicated and only works in this article the author encountered in the actual situation on the early cracks in the prevention of the causes and a little note. 1, aggregate
7、concrete cracks caused by plastic setting When in the pouring of concrete, due to vibration and gravity the role of rods, sinking aggregate, cement increased, until this fall when the side to stop the concrete to harden, when such a fall by the plastic template, steel and embedded parts of inhibitio
8、n ( subsidence or a template, move) the cracks will appear, which cracks appear in most of half an hour after pouring concrete to 3 hours, still in the plastic state of concrete, 2 concrete surface when the immediate disappearance of Shuiguang along the beams and plates reinforced the direction of t
9、he above occur, mainly Slump Concrete, and subsidence caused by too much. Also during the construction process of banding, if the bad template, templates, subsidence, movement of such cracks will appear. Prevention measures to meet the pumping and construction under the premise of minimizing the col
10、lapse of concrete, the construction process should be kept under observation in the displacement of the template and trace the dense poured concrete, the vibration can not leak, over-vibration, and in the first Vibration 20 30mm after the interval after the resumption of the second vibration. If suc
11、h cracks in the concrete before the final setting of concrete trowel surface to re-use of wood rubbed smooth hair, can heal the cracks. 2, plastic shrinkage cracks After pouring the concrete is still in plastic state, as a result of surface evaporation caused by excessive cracks, this kind of crack
12、on the surface appear more seamless, shape irregular, varying the length of width, was cracked like a depth less than 50mm, but sheet if the concrete in the structure of clay mixed with large quantities of silt are likely to be penetrated. The main causes of concrete after pouring about 3 4 hours is
13、 not covered by the surface, especially the flat structure in the hot or windy weather evaporation concrete surface too quickly, or be the basis for the excessive water templates, as well as the hydration of the concrete itself Higher heat causes rapid contraction of the concrete to the concrete str
14、ength at this time near zero, can not resist the deformation caused by stress cracking, and evaporation from the concrete to absorb water faster, plastic shrinkage cracks more easily, and the goods Because concrete can be pumped in order to satisfy, the mobility of the machine when the collapse of c
15、oncrete and sand ratio much larger than that of ordinary concrete, coupled with the summer construction and mass concrete in the mixing retarder, so its low early strength particularly vulnerable to water loss, the formation of cracks in the surface easily. Prevention approach is the construction units in a timely manner after the pouring of
