Abstract:

In order to reveal the influence mechanism of coarse aggregate profile characteristics on the mesoscopic mechanical properties of asphalt mixtures, this study employed digital image processing technique to obtain the profile characteristics of coarse aggregates, constructed discrete element models of coarse aggregates with multiple morphological features, and studied the impact of aggregate geometric morphology on the mesoscopic mechanical response of asphalt mixtures in conjunction with a uniaxial penetration virtual testing system. The results indicate that a mixed tensile-compressive stress mode exists at aggregate contact points in the DEM-based uniaxial penetration model. Compressive stress accounts for 40%–50% of the total stress，tensile stress for 10%–20%，and combined tensile-compressive stress for 30%–40%. The effect of uniaxial penetration load leads to a rapid increase in the number of microcracks. In mixtures with a high content of needle-like aggregates, the microcracks at the aggregate-asphalt interface quickly connect to form through cracks. Microcracks are mainly induced by shear stress, accounting for about 90% of the total number of microcracks; the number of microcracks caused by tensile stress is relatively small, accounting for about 10% of the total. The longest microcrack can reach 10mm, while the shortest crack length is 0.2mm. The mixture with a higher amount of cubic aggregates can effectively resist load effects due to the skeleton interlocking effect, resulting in a smaller distribution area of micro-cracks and lower stress levels. The research findings provide a theoretical basis for the selection of coarse aggregates during asphalt pavement construction and for improving the processing quality of coarse aggregates.

Key words: asphalt mixture, coarse aggregate morphology, Discrete Element Method, compaction state, mechanical performance