Milling process simulation of old asphalt mixture by discrete element

Great amount of milling materials are produced every year because of the rapid increase of pavement maintenance. However, the utilization of the milling materials is still low because many broken aggregates and large-piece of asphalt mixture are produced in the milling process. Improving the quality of milling materials to increase its recyclability is an important research direction. In this study, a discrete element model of asphalt mixture was established, AC-16 asphalt mixture specimens were created, which used Styrene-butadiene-styrene (SBS) modified asphalt after aging, and the parameters of the PFC model were determined by uniaxial compression test and simulation of the test by PFC. The force of the cutter tool was analyzed, the optimal conditions for reducing the damage of asphalt mixture aggregate and avoiding the cutting down of asphalt mixture into larger pieces in the milling process were investigated through the simulation of milling process under different milling conditions. Results show that for AC-16 asphalt mixture, using a cutting speed of 0.5 m/s and cutting angle of 45° can reduce the amount of broken aggregates, and the cutting angle of 40° when the cutting depth is 25 mm at a cutting speed of 1 m/s should not be adopted to avoid the milling down of large pieces of old asphalt mixture.