Air-Void Distribution Analysis of Asphalt Mixture Using Discrete Element Method

Heterogeneous air void distribution is a common phenomenon in asphalt mixtures and is intimately related to the behavior of the asphalt mixture. Air void distribution within an asphalt mixture specimen is related to several factors, such as compaction effort, method of compaction (equipment), and aggregate gradation. In this study, virtual digital specimens generated by an open source discrete element method (DEM) program were utilized to investigate the effect of compaction factors on air void distribution. The compaction processes of a Superpave gyratory compactor (SGC) and a vibratory compactor were simulated by DEM. Effects of aggregate gradation, specimen height, mold size, mold shape, and compaction method on the inhomogeneous distributions of air voids were studied through statistical analyses. The results from DEM simulation were in good agreements with laboratory test results as well as those found in the literature. This research demonstrated that DEM simulation could be a potentially helpful tool for analyzing asphalt mix compaction and selecting appropriate aggregates for asphalt mix design.