| The dry-sprayed concrete is widely used in building foundation pit engineering,but the dry-sprayed concrete exists high rebound ratio and dust concentration that is harm for environment and people, and it is difficult to guarantee the quality of the concrete. This paper based on current construction equipment in building foundation pit engineering, aims to researching technique of reducing dust pollution and rebound ratio of sprayed concrete.This paper holds that the main reason of the dust pollution is that the cement particles is not fully mixing and wetting by water. The dust pollution in material mixing comes from that the cement particles is not wetting by water and run out of equipment system. The dust pollution in the working area comes from that the cement is not fully mixing and wetting by water.The main reason of the dust pollution is that the stone cannot stick of the wall quickly.This paper finds out the relationships between slump and sand rate of concrete and thickness, rebound ratio and strength by indoor simulation experimental.And it helps people improve the strength and reduce the slump by changing mix ratio of concrete.This paper develops a mixing-puddling spray gun which can make cement particles is fully mixing and wetting by water and reduce the dust pollution, and gains a patent on utility model. Comparing the old and the new gun, the experimental results show that the mixing-puddling spray gun can reduce dust pollution and rebound ratio effectively.According to the reason for the dust pollution,we design the dry-sprayed concrete with cement paste which can make cement particles is fully mixing and wetting by water. Comparing the old and the new method, we find out that the new one can decrease the dust pollution in material mixing by 93%, in the working area dust pollution decreased by 87%, improve sprayed concrete strength by 1.08 times.And we can make sure that best water-cement ratio of C20 sprayed concrete is 0.55. |
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