What will happen to the concrete pouring in the mixing plant in the hot summer?
Source: mixing machinery, release time: September 11, 2017 11:10:39, click:
There are some problems in pouring concrete in concrete mixing plant in hot weather, which is due to the high temperature of concrete. And in many cases, the evaporation rate of fresh concrete increases. These problems are related to the mixing, pouring and curing of concrete. It is necessary to formulate reasonable construction technology and procedures for each project (there are one or more of the above conditions) and strictly abide by them; it is very important to maintain consistency, and it will cause trouble to break away from easily established specifications.
The high ambient temperature in the concrete mixing plant increases the water consumption of concrete and the temperature of fresh concrete, which leads to the acceleration of slump loss and hydration reaction. The latter leads to the accelerated setting of concrete, but the long-term strength decreases. In addition, rapid evaporation may cause plastic shrinkage and cracking, and subsequent cooling of hardened concrete will produce tensile stresses. It is generally believed that plastic shrinkage cracks will occur when the evaporation rate of water is greater than the rate of bleeding rising to the surface. However, cracks have also been observed under a layer of water and become obvious under dry conditions. When the evaporation rate per hour is greater than 1.0kg/m2, plastic cracks are easy to appear.
The plastic shrinkage cracks in concrete mixing plant may be deep, ranging in width from 0.1 to 3 mm, sometimes short, sometimes as long as 1 m. Once produced, it closes. The decline of environmental relative humidity will promote the formation of such cracks. Therefore, the causes of cracks appear to be complex. In the following temperature and hot weather, concrete mixing plant will have some complex conditions: if air entrainment will be difficult, this can be made up by using more air entraining agent. A related problem is that if the cold concrete is poured and expanded at a high temperature, the air in the concrete will also expand, thus reducing the strength. For example, this will happen when the concrete mixing plant is pouring horizontal plates, but the pouring of vertical plates will not. Because steel formwork can prevent expansion. If the wind speed exceeds 4.5mls, it will worsen the situation; both wind shields and sun visors are beneficial.