Characterization of particle movement in Superpave gyratory compactor at meso-scale using SmartRock sensors

Compaction is one of the most critical steps in asphalt pavement construction that ultimately impacts pavement performance. In the laboratory, the Superpave gyratory compaction (SGC) method is widely accepted because it applies both shear and compression simultaneously to the mixture and can best simulate the field compaction. However, research has also found that the mechanical properties of asphalt mixtures between SGC compacted specimens and field cores were different, which can be, at least partially, attributed to the different internal structure and air void distribution of the resulting mixtures. Current knowledge about SGC has not given insight into particle interaction characteristics during the compaction process. Therefore, this study aims to employ a real-time particle motion sensor, SmartRock, to investigate the particle movement characteristics during the SGC compaction process, understand how such movement can be related to the air void distribution of SGC specimens, and provide preliminary explanation about the gyratory compaction mechanisms from the meso-scale. It was found that particle's relative rotation pattern was directly related to mixture density change during compaction. The compaction process can be divided into three stages and the onset of the third stage generally matched with the conventional locking point definition. By placing the SmartRock sensor at different locations within a SGC mold, it was found that the particle located at mid-depth layer received more effective compaction as compared to the particle located at the bottom.