Study on fracture evolution characteristics of concrete containing aggregate and its statistical damage constitutive model based on acoustic emission characteristics
In order to understand the evolution characteristics of damaging cracks in aggregate concrete, a finite element model of concrete containing aggregate was established using numerical simulation method of statistical damage theory, through which the crack propagation process, acoustic emission law and peak intensity under different working conditions were obtained and the concept of damage degree was defined based on the numerical results of acoustic emission. The results show that the crack evolution under different working conditions presents X-shaped expansion, which is composed of “wing crack” and “reverse wing crack”. The main failure mode of “wing crack” initiation and propagation is tensile failure; the initiation of “reverse wing crack” is caused by shear failure, followed by tension-shear composite failure in the propagation phase. The larger the inclination angle of the prefabricated crack is, the greater the percentage of the aggregate content is and the greater the peak strength of the specimen is, but the increase of compressive strength of the specimens caused by the former is smaller than that by the latter. The damage propagation of the specimens during loading process went through four stages, namely, linear elastic deformation stage, crack initiation stage, crack accelerated propagation stage and damage stable development stage. It is found that the larger the percentage of the aggregate content is, the smaller the inclination angle of the prefabricated crack is and the greater the maximum damage degree is. The range of damage degree under different working conditions is 0.85- 0.94. The failure modes of aggregate can be divided into four types, which are deflected winding crack, crack arrest, crack adsorbed by aggregate, and crack through aggregate. In this paper, deflected winding crack is the main failure mode in the numerical simulation.