Rate-dependent fracture modeling of asphalt concrete using the discrete element method

The discrete element method (DEM) represents a convenient and powerful tool for studying effects of material microstructure on fracture mechanisms in asphalt concrete. In this paper, the rate-dependency of asphalt concrete is investigated using a cohesive zone model with bulk viscoelastic properties combined with bilinear post-peak softening. Details of the constitutive models implemented in the DEM, with particular emphasis on the verification of viscoelastic models, are presented. Experimental test results based on a disk-shaped compact tension test are obtained under different loading rates and those are compared to numerical simulations with the help of the rate-dependent model. Homogeneous and heterogeneous model results are compared, where heterogeneous models are constructed to consider aggregate morphology for particles larger than 1.18 mm. The relative importance of time-dependence and the consideration of material heterogeneity in the simulation of monotonic Mode I fracture tests are demonstrated.