Modelling asphalt mastic stiffness using discrete element analysis and micromechanics-based models

This study uses the discrete element method (DEM) to simulate the dynamic mechanical behaviour of asphalt mastics. Asphalt mastics are defined as dispersions of aggregate fillers within a medium of asphalt binder. The fillers refer to the fraction of mineral aggregate passing the 200-mesh sieve, (i.e. smaller than 75 μm). Mastic measurements obtained using the dynamic shear rheometer were compared to DEM predictions and available micromechanics-based models. Three asphalt binders (ABD-1, AAM-1 and ABM-1) and four mineral fillers (glacial gravel, granite, limestone and greywacke) were used to prepare the mastics in this study. The stiffening effect of the mineral fillers was investigated at different filler volume fractions. The DEM results captured the stiffening behaviour of asphalt mastics as a function of the volumetric concentration of mineral fillers. The DEM results exhibited a high rate of stiffening that is typically observed in experimental measurements of mastics at relatively low volume concentrations of fillers. Compared to the DEM results, the micromechanics-based models were not sensitive to the dynamic shear modulus of the asphalt binder, and they underestimated the stiffening effect of the mineral fillers.