Impact of aggregate packing on dynamic modulus of hot mix asphalt mixtures using three-dimensional discrete element method

Aggregates are the major component of hot mix asphalt (HMA) mixtures. The properties of aggregates and the way of aggregate packing have important influence on the performance of HMA mixtures. Because the dynamic modulus is considered as the most important HMA property influencing the field fatigue and rutting performance of a flexible pavement and are used in the mechanistic-empirical pavement design guide for determining the stress–strain responses of the pavements, a study of the impact of aggregate packing on dynamic modulus will provide insight on the HMA mix design and the material performance evaluation. This paper studies the effect of aggregate size distribution and angularity distribution on dynamic modulus using a 3D discrete element method (DEM). Angular particles are generated using an image-based ball-clumping approach which requires significantly reduced number of balls and is capable of capturing the particle shape and angularity effect. These particles are assigned to the DEM dynamic modulus specimen based on the angularity distributions of the actual experimental specimen. A 3D DEM dynamic modulus model is thus established and calibrated using experimental data. This calibrated model is further used to evaluate how the different aggregate packing due to the change of the proportions of aggregate particles and the change of aggregate angularities can result in the change of dynamic modulus.