A DEM generalized Kelvin contact model for predicting damage in asphalt mixtures

Over the years, thermal cracking, moisture damage and fatigue cracking might occur in the top layers of flexible pavements. Taking this fact into consideration, this study presents a three-dimensional (3D) particle model based on the discrete element method
(DEM) following the Laguerre-Voronoi diagrams of the grain structure of asphalt mixtures to investigate their fracture behaviour. An incremental generalized Kelvin (GK) contact model is adopted to represent the viscoelasticity and viscoplasticity present in asphalt materials. Moreover, the cracking behaviour is modelled with a bilinear model and compared with the response obtained with a simple brittle model implemented within the framework of the adopted GK model. A parametric study is conducted in order to evaluate
the influence of the fracture input parameters on the general stress-strain behaviour. A virtual asphalt mastic sample was generated and submitted to a tensile test and the results compared with laboratory data. After previous calibration of the contact parameters, the results obtained for the viscoelastic behaviour, cumulative strain, peak stress and the crack path in the sample showed a good agreement with experimental data. The bilinear model in association with the GK model predicted a numerical response closer to the observed experimentally than the response predicted with a simple brittle model.