Research On Early Age Anti-cracking Performance Of Ready-mixed Concrete

With the rapid development of the economy, the applicant of the pre-mixed concrete is more and more wide. And the followed problem of concrete crack effecting the durability and applicability is normal, which is now regarded by the experts and researchers. The difference between the pre-mixed concrete and normal concrete is that the former is produced together and sell to consumers in the form of goods. The composition and the fluidity are also different.For the pre-mixed concrete develops late, the related study at home and abroad is not too much. So it mainly consults to the crack control technology of normal concrete. On the basis of lots of references, by summing up the reasons and rules of the concrete cracking and the character of pre-mixed concrete, together with the theoretical analysis and flat experiment, this paper makes the conclusion that the best reinforcement ratio of the pre-mixed concrete is 1.5%. By analyzing the anti-cracking mechanism of expansion agent, polypropylene fiber and shrinkage agent on the pre-mixed concrete, together with flat experiment research, the conclusion is that pre-mixed concrete with shrinkage agent only results to the best anti-cracking performance. By analyzing the mechanism of reinforcing bar and concrete, the mechanism of expansion agent to pre-mixed concrete, the interaction between reinforcing bar and expansion agent and their joint mechanism to pre-mixed concrete, together with experiment research, better anti-cracking measurement is obtained to guide the practice of engineering design and construction. By studying the reason and development of temperature crack, the hydration heat of the huge-volume pre-mixed and normal concrete are calculated. Combined with the practice projects, the temperature develop and the peak value are predicted. The better temperature control program is obtained by analyzing the predicted and fact value.The paper studied the crack control technology of the pre-mixed concrete, and the results may be used in the later theory research and construction design.