Three-Dimensional Discrete Element Models for Asphalt Mixtures

The main aim of this paper is to develop three-dimensional (3-D) microstructure-based discrete element models of asphalt mixtures to study the dynamic modulus from the stress-strain response under compressive loads. The 3-D microstructure of the asphalt mixture was obtained from a number of two-dimensional (2-D) images. In the 2-D discrete element model, the aggregate and mastic were simulated with the captured aggregate and mastic images. The 3-D models were reconstructed with a number of 2-D models. This stress-strain response of the 3-D model was computed under the loading cycles. The stress-strain response was used to predict the asphalt mixture's stiffness (modulus) by using the aggregate and mastic stiffness. The moduli of the 3-D models were compared with the experimental measurements. It was found that the 3-D discrete element models were able to predict the mixture moduli across a range of temperatures and loading frequencies. The 3-D model prediction was found to be better than that of the 2-D model. In addition, the effects of different air void percentages and aggregate moduli to the mixture moduli were investigated and discussed.