Discrete Element Simulation of Aggregate Sphericity and Orientation: An Approach to Improving the Understanding of Asphalt Concrete

Many studies have concluded that mineral aggregate properties such as sphericity and orientation play very important roles in determining asphalt concrete (AC) performance. Their observations of existing studies however, came from the combined effects of many factors such as air voids, aggregate gradations, asphalt binder properties, etc. The objective of this study is to investigate the isolated effects of aggregate sphericity and orientation angles on the creep stiffness of AC mixtures. Instead of using the traditional experiment-based methods, this study utilizes discrete element simulation of idealized AC mixtures. To build the AC microstructure, previously developed user-defined discrete element model was utilized; known as the rounded aggregate R model. The mechanical interactions in the digital specimens were simulated with the previously developed viscoelastic discrete element model. Through this study, it was observed that: 1) aggregate sphericity and orientation have significant impact on AC creep stiffness; 2) the effects of aggregate sphericity indices were correlated with that of aggregate orientation angles and vice versa.