Mix-mode fracture behavior in asphalt concrete: Asymmetric semi-circular bending testing and random aggregate generation-based modelling

The thermal or reflective fracture in asphalt pavement often occurs due to both shear or tension stress, simultaneously, which can be referred to the mix -mode fracture. However, most of the research in the literature focused on the pure tension or shear fracture behavior but not the hybrid effects. Therefore, this study aims to investigate the mix -mode fracture behavior and fracture resistance performance of asphalt concrete through both indoor experiments and virtual modeling methods. The Asymmetric Semi -Circular Bending (ASCB) test was employed to assess the mix -mode fracture behavior of specimens. A meso-scale virtual finite element model of the asphalt concrete was also established to simulate the mix -mode fracture process and microcrack damage evolution based on polygonal random aggregate generation method. By comparing the simulation results with indoor test results, the reliability of the finite element simulation was verified. The results indicate that virtual experiments can effectively simulate the fracture process of asphalt concrete, and the fracture process always proceeds in the direction of lower energy consumption. Meso-scale simulation experiments revealed the crack evolution mechanism of mix -mode fracture in asphalt concrete. Microcracks in the pure tension fracture mode tend to connect and form a continuous fracture surface, exhibiting lower strength and apparent brittleness. With the increase in shear proportion, the connectivity of microcracks within the specimen decreases, demonstrating higher strength. The distribution pattern of microcracks in asphalt concrete at the meso-scale was analyzed based on the failure ratio of cohesive elements and the fracture modes, and the evolution degree of mix -mode fracture and the proportion of tensile failure mode in different fracture modes were quantitatively studied, thereby revealing the meso-scale cracking mechanism of asphalt concrete.