Densification behavior of asphalt mixture and its relation with particle dynamic responses during gyratory compaction

Compaction of asphalt mixture is a critical step of the pavement construction, which determines the performance and durability for asphalt pavement. The densification behavior of asphalt mixture is complicated and its workability is prone to be affected by the material composition and construction conditions. Knowing the compaction process is of great significance for improving the pavement construction quality. This study aims to investigate the densification behavior of asphalt mixture in the compaction process and its correlation with dynamic responses of the built-in Smart Aggregate. Through Los Angeles abrasion tests and aggregate imaging measurement system, 40 kinds of coarse aggregates with different morphologies were prepared and employed to carry out gyratory compaction tests for asphalt mixtures. The height decline and density growth of the mixtures were concerned in different compaction stages. Meanwhile, the Smart Aggregate was embedded in the mixture to capture the particle dynamic responses, which were further correlated to the densification behavior of the mixture. The results show that material factors have the significant influence on the compaction process after the mixture has been compacted to the P-1 at which the height change is less than 1 mm. The gyratory compaction process can be divided into different stages of 0 similar to P-1, P1 similar to P-0.1, P-0.1 similar to P-0 according to the change in mixture height, and every gyration would enable the percentage of maximum theoretical specific gravity (G(mm)) increase with 1.46 %, 0.3 %, 0.11 % in the corresponding stage. After the threshold point P-0, the increment of compaction degree after per gyration is less than 0.05 %. AC and SMA-13 mixtures would achieve the 95.5 %similar to 97.4 % of G(mm) when they are compacted to locking point of P-0. Asphalt mixture height is highly related to the relative rotation of the embedded Smart Aggregate. Change in the mixture height can be characterized by the variation of particle relative rotation, which could be further adopted to determine the locking state of asphalt mixture compaction in real-time.