Impacts of air-void structures on the rutting tests of asphalt concrete based on discretized emulation

To investigate the impacts of inner air-void structures on the high temperature performance of dense-graded asphalt concrete, the digital models of rutting plate composed of asphalt mastics, coarse aggregates and porosity were constructed by the discretized emulating software PFC 3D. Then, curves of rutting depth during virtual rutting tests were recorded, which matched with the laboratory-measured results. The similarity between these test curves verified that the virtual rutting test can be a feasible way to predict the rutting behavior of asphalt concrete. After that, the inner structure characteristics of air voids including porosity, size, horizontal and vertical distribution were put into the emulation software to investigate their effects on rutting behavior. Results show that larger porosity in asphalt concrete leads to worse rutting resistance, and this is especially true when air voids are concentrated in the middle section of the testing sample. In fact, the middle section contributes most to the rutting formation compared with other sections. In terms of vertical distribution, air voids concentrated in the mid-upper region of rutting plate have adverse effects on the rutting resistance. Moreover, sizes of air voids also influence the rutting behavior and the impact depends on aggregate gradations.