Characterizing air void effect on fracture of asphalt concrete at low-temperature using discrete element method

Abstract

Air void plays an important role in the crack resistance of asphalt concrete. Although the impact of porosity on the fracture resistance of asphalt concrete has been studied in the literature, there is a lack of fundamental analysis of void characteristics (e.g., void size and void distribution) under different loading and temperature conditions. Hence, a series of edge cracked semi circular bend (SCB) tests are performed in mode I fracturing, mode II fracturing and mixed mode I & II fracturing at −6°C and 10°C. A heterogeneous fracture modeling approach using different porosity, void sizes and void distributions based on discrete element method (DEM) is utilized to simulate the fracture process of SCB tests. Experiments and heterogeneous simulations are combined to investigate the impact of void characteristics (porosity, void size and void distribution) on the fracture performance and crack propagation of asphalt concrete. Porosity, void size and void distribution have considerable effects on the fracture performance and crack propagation of asphalt concrete. The fracture toughness and the time at which peak load occurs reduced with the increasing porosity and void size. The impact of void size is more significant than that of porosity. At −6°C, the impact of void characteristics on crack propagation is not significant, except in mode II fracturing. The crack in mode II fracturing no longer passes through aggregates, and tends to bypass aggregate with the increasing porosity. At 10°C, cracks tend to move away aggregate/mastic interface and pass through mastic with the increasing porosity and void size. The distribution of void in cracking initiation zone is a key factor for the fracture performance and crack propagation of asphalt concrete.