Study on the cracking behavior of asphalt mixture by discrete element modeling with real aggregate morphology

This research aimed to investigate the crack resistance of asphalt mixtures via laboratory tests and discrete element modelling. For the construction of virtual cracking model, the interactive 2D modeling method based on various software and the establishment method of 3D aggregate are proposed. The description method of crack path is also improved.When establishing the 2D model, considering the mesostructural characteristics of an AC-20 asphalt mixture, the aggregate-asphalt mortar-void three-phase structure was established based on PFC2D software and image processing. Taking into account the gradation and form of coarse aggregate, a 3D model incorporating real aggregate shapes was constructed by PFC3D. Based on the numerical model, semi-circular bending and tensile tests of specimens with pre-cut slits of different lengths were conducted to analyse their stress levels, cracking process and crack locations under low-temperature conditions. Taking the fracture performance parameters as an evaluation index, the feasibility of the numerical simulations was verified in comparison to laboratory test data. In the early phase of model loading, the stress distribution has the characteristics of a compression-tension zone. Crack formation undergoes a process of smooth expansion and rapid penetration, and cracks in the compression zone pass through the aggregate. The failure state presented by the particle flow program was in general agreement with the crack evolution results obtained from the tests. Additionally, the fracture parameters of the simulations had a favourable overlap with the experimental observations, indicating that the discrete element simulations can adequately represent the crack propagation process in asphalt mixes. This approach is effective for in-depth and efficient exploration of the cracking performance of asphalt mixtures.