部分约束条件下中低水灰比混凝土开裂的预测

Cracking Prediction of Medium and Low Water-Cement Ratio Concrete under Partially Restrained Condition

通过自制的混凝土环形约束收缩试验装置,对部分约束条件下中低水灰比(0.30,0.35和0.40)混凝土内部(环向)拉应力及拉应力水平的发展规律进行了研究,建立了通过拉应力水平预测混凝土早期开裂的预测模型.研究结果表明,部分约束条件下混凝土早期拉应力水平的安全控制值为50%;当早期拉应力水平超过55%时,混凝土发生开裂的危险性较大.对于拟用于工程中的混凝土,可在试验室条件下对其进行部分约束收缩试验,然后依据开裂预测模型预测其工程应用后的开裂情况.

A ring-shaped testing system was developed to measure the tensile stress（circumferential direction） of concrete prisms samples which were under partially restrained conditon. The water-cement ratios of tested concretes were 0.30,0.35 and 0.40 respectively. A cracking prediction model based on tensile stress level was set up to predict the probability of cracking in concrete materials. It is concluded that if tensile stress level of early age is within 50%, the concrete is less prone to cracking; if it is higher than 55% ,concrete is more susceptible to early age cracking. On the basis of this cracking prediction model, the probability of concrete structure cracking could be predicted primarily by experiment in the lab.