Research on Mesostructured Characteristics of Asphalt Mixture Based on Particle Packing Theory

In order to investigate the influence of particle grading on the mesostructure of asphalt mixtures, particle packing theory was utilized to propose interference parameter for particle grading evaluation. Based on the X-ray CT, the asphalt mixture with different grading, compaction times and compaction modes (i.e. Marshell and Gyratory methods) was scanned and three-dimensionally reconstructed. Combined with digital image processing technique, void distribution of the asphalt mixture and contact relations of particles were extracted. Fractal theory was applied to calculate the fractal dimension of void volume and position. Finally, relations between interference parameter and 3D void fractal dimension, interference parameter and particle contact were analyzed. The results show that with the increase of compaction times, the number of large voids and middle voids increases first and then decreases in two specific compaction modes. The average volume of large void decreases with the increase of average volume of middle void. For small voids and micro voids, the number of voids increases continuously with the increase of compaction times but the average void volume does not change obviously. The continuity of void volume distribution decreases with the increase of interference parameters, while the homogeneity of spatial location distribution increases with the increase of interference parameters. The continuity of asphalt mixture with gyratory compaction is poorer than that of mixture with Marshall compaction, however, the homogeneity of asphalt mixture with gyratory compaction is better. The number of contact points of dominant aggregate increases with the increase of compaction times, with the descending order being OGFC, SMA and AC. The number of contact points declines with the increase of interference parameters.