Accurately Tracking Migration of Particles Based on Discrete-Element Simulation during Compaction Process

Aggregate particles migrate and rearrange their spatial positions during the compaction process. To analyze the migration law, an accurate method to track migration of particles is proposed using discrete-element simulation and experimental verification. First, the coarse aggregates were generated based on realistic aggregate shapes using a three-dimensional (3D) Blu-Ray scanner. Subsequently, the fine aggregates, ranging from 0.075 to 2.36 mm, and asphalt mastic were replaced with balls with a radius of 0.7 mm. Then the three-dimensional dynamic compaction models of asphalt mixture were established using the Superpave gyratory compaction method and Marshall impact compaction method. Next, the migration tracking test of particles was developed adopting particle marking, step-by-step compaction, and CT scanning. Finally, the accuracy and efficiency of the virtual models were validated using the experimental data from the migration tracking test. The results indicate that the established compaction models can accurately track the aggregates particles and measure the migration indexes. The compaction methods have a great influence on the migration behavior. The displacement of the particles for the Superpave gyratory compaction method is greater than that for the Marshall method, and the displacement is multidirectional, whereas the displacement of particles for the Marshall impact compaction method mainly are vertical.