Simulation of mechanical behavior of asphalt concrete: Two-dimensional and three-dimensional micromechanics-based discrete element models

The mechanical properties and performance of asphalt concrete is governed by the properties of the aggregate gradation, shape, surface texture, modulus (or stiffness) and properties of the asphalt binder grade, binder modulus, asphalt--aggregate interactions, asphalt content, and air void distribution. The multiphase asphalt concrete is divided into aggregate, sand mastic and air void phases on the modeling. The sand mastic (mastic) phase includes fine aggregate and asphalt binder. The Nominal Maximum Aggregate Size (NMAS) of the mastic is within a certain range according to capacity of modeling. The maximum aggregate size in mastic is defined by the smallest units possible when the modeling and computing capacity is available.;The discrete element modeling approach was applied as a more realistic tool for predicting HMA mechanical properties. In the long run, micromechanical based discrete element modeling of asphalt concrete mixtures will provide several important benefits to the asphalt paving industry and research community. The discrete element method was applied to predict the mechanical properties of asphalt mixture. The microstructure of an asphalt mixture will be studied using the scanned image and X-ray computed tomography image. The gradation, shape and orientation effect of the aggregate will be applied in the asphalt mixture modeling. The DEM presented herein utilize the real three dimensional microstructure of the aggregates-mastic-air system captured with the help of image technology. The testing configuration of the asphalt concrete in the DEM is rectangular prism using uniaxial and biaxial compression test, cylindrical specimen using uniaxial tensile and compression test, hollow cylindrical specimen using tensile test, and cylindrical specimen using indirect tensile test. The asphalt binder and aggregate properties was used to predict the mechanical properties of an asphalt mixture within the low to high temperature and loading frequency range.;The stiffness behaviors of an idealized and a real microstructure of the asphalt mixture with different air void levels were also investigated. The asphalt mixture was modeled with the Discrete Element Modeling (DEM) approach for both two-dimensional (2D) and three-dimensional (3D) models. The models were also developed by the real 3D microstructure of the aggregates-mastic-air system captured by the X-ray computed tomography (CT) method, a non-destructive 3D image acquisition technique. In order to examine the stiffness behavior of an asphalt mixture, 2D and 3D discrete element models were used to predict mixture moduli of asphalt mixture at different air voids. The moduli of the 3D DEM and 2D DEM models were then compared with both the experimental measurements results. It was found that the 3D discrete element models successfully predicted the mixture modulus across a range of temperatures and loading frequencies. The 3D models of the heterogonous asphalt mixture will assist better understanding of load carrying mechanisms of asphalt mixtures to improve design and construction of asphalt pavements.