Aggregate stress contribution in asphalt mixtures with the splitting tests based on the three-dimensional (3D) discrete element method (DEM)

Abstract In this study, the discrete element method (DEM) simulations were employed to assess the asphalt mixture’s splitting strength to investigate the mechanical aspects of asphalt mixtures under various loading conditions, including the stress transmission characteristics of individual aggregate and the contribution or response to the load-bearing capacity. The study involved an analysis of splitting tests on fine-graded AC-13 and medium-graded AC-20 asphalt mixtures at different temperatures. The mechanical responses of aggregates at different sizes were examined, and the relationships between aggregate loading contribution and mechanical interactions were explored by combining laboratory experiments with DEM simulations. The research shows that the load-displacement patterns in DEM simulations and lab experiments are very similar. This demonstrates that DEM simulations are applicable for conducting splitting tests on asphalt mixtures and the results are valid. The splitting strength decreases with increasing temperature under identical gradation conditions. At the constant temperature level, splitting strength is enhanced with large-sized aggregates/gradations in asphalt mixtures. As temperature rises, smaller-sized aggregates in both gradations bear a greater loading proportion, while the load-bearing ratio of intermediate-sized aggregates decreases. Comparing the two gradations of asphalt mixtures, it is evident that, at the same temperature, an increase in the gradation leads to a gradual increase in the load-bearing ratio of aggregates in the intermediate size range. In the case of the AC-20 gradation asphalt mixture, the largest-sized aggregates also exhibit an increasing load-bearing ratio compared to the AC-13 gradation, indicating that larger gradations result in a greater proportion of coarse aggregates carrying the loading. These research findings provide valuable insights and references for the cracking resistance performance of the asphalt pavement.