Abstract:

In order to reveal the fracture mechanism of asphalt concrete ( AC) from the viewpoint of microstructure,first,the irregular three-dimension ( 3D) shape of coarse aggregate particles was described with overlapping spheres,and a 3D discrete element model of a small AC beam specimen was established by using the Fish language provided in the finite element software PFC3D,the random aggregate packing algorithm and the generation method of air voids. Next,the micro-parameters for the discrete element simulation were obtained according to the test results of uniaxial compression and splitting,with the relationship between the macro and the micro mechanical parameters being also considered. Then,the midpoint-bending fracture test of a user-defined 3D AC beam at －10 and 15℃ was simulated with PFC3D and the corresponding fracture curves were obtained. Finally,AC beams with their asphalt dosage,porosity and gradation similar to those of the AC model were frabricated,and some practical
fracture curves were obtained in laboratory. The results indicate that the established discrete element model fully considers the irregular shape,the gradation and the porosity of aggregate,so that it is capable of simulating the initiation and propagation of cracks during the bending fracture with high accuracy,and that the 3D discrete elementbased simulation can be used as a supplemental tool to evaluate the fracture properties of asphalt mixture.

Key words: road engineering, asphalt mixture, fracture behavior, three-dimension discrete element method, microstructure