Influence Mechanism of Coarse Aggregate Morphology on Meso-Mechanical Behavior of Asphalt Mixtures

To reveal the influence mechanism of coarse aggregate profile characteristics on the meso-mechanical properties of asphalt mixtures, this study employed digital image processing technology to obtain the profile characteristics of coarse aggregates and constructed discrete element models of coarse aggregates with multiple morphological features. Combined with a virtual uniaxial penetration test system, the impact of aggregate geometry on the meso-mechanical response of asphalt mixtures was investigated. The results indicate that a mixed tensilecompressive stress mode exists at aggregate contact points, with compressive stress accounting for 40%~50%, tensile stress for 10%~20%, and mixed stresses for 30%~40% of the total. The application of uniaxial penetration load leads to rapid growth in microcrack numbers. In mixtures with higher elongated and flat aggregate content, microcracks at the aggregate-asphalt interface connect more readily to form through cracks, whereas mixtures with higher cubical aggregate content exhibit smaller microcrack distribution areas and lower stress levels. Microcracks are mainly induced by shear stress, accounting for about 90% of total microcracks; the number of microcracks caused by tensile stress is relatively small, accounting for about 10%. The maximum microcrack length reaches 10 mm, while the minimum is approximately 0.2 mm. For mixtures rich in cubical coarse aggregates, skeleton interlocking effectively resists loading. These findings provide theoretical support for coarse aggregate selection in asphalt pavement construction and quality improvement in aggregate processing.