Analysis of strength composition of asphalt mixture based on skeleton contact characteristics

Under the compaction effort, asphalt-coated aggregate particles migrate as the aggregate-asphalt particle system undergoes structural rearrangement, thereby forming a stable spatial structure. To analyze the strength composition of asphalt mixtures on mesoscopic level, the self-developed experimental devices and discrete element compaction model were employed. A skeleton contact model for asphalt mixtures was established adopting three-dimensional dynamic virtual compaction test. The mechanism of asphalt mixture strength was investigated from the perspectives of skeleton structure and asphalt mortar. The research indicates that the skeleton contact index exhibits a good linear relationship with the composite angularity index, maximum migration force, skeleton bonding index, and skeleton lubrication index. Aggregate of variously-sized mutually interlocking and friction, driving the skeleton structure to adjust with the synergistic effect of particle migration and contact behaviors to achieve the stable state. Except for AC-13 L aggregate-asphalt system, the skeleton contact index evinced a robust correlation with the strength indices. A skeleton-dense model for asphalt mixtures was developed, incorporating the stability of the aggregate skeleton stability and the bonding-filling effects of the asphalt mortar. The skeleton-dense index has a good linear correlation with the maximum migration shear stress, and can good discriminates the strength of different mixtures.