Preliminary study on the microscopic damage behaviors of surface aggregates during the skid resistance degradation of asphalt pavements

To elucidate the deterioration mechanism of asphalt pavement skid resistance under sustained wheel loading, a micromechanical study was conducted on the wear evolution of pavement surface aggregates. Wear tests were performed on individual surface aggregates, and computerized tomography (CT) nondestructive testing was employed to investigate the microcrack propagation behavior of aggregates under cumulative wheel loading. First, the aggregate morphology and internal structure were reconstructed and optimized in three dimensions through a workflow comprising histogram optimization, filtering, and registration. Subsequently, microcracks in the aggregates were segmented and extracted through the application of various algorithms. Based on a comparative evaluation of applied algorithms, a segmentation procedure specifically designed for small-scale crack identification was proposed. Finally, the cracks in aggregates before and after wear were quantitatively characterized. The results show that wheel-induced wear not only induces the propagation and coalescence of adjacent cracks but also generates new microcracks on the surfaces of aggregates. Moreover, crack propagation is neither unidirectional nor linear, but instead develops tortuously throughout the three-dimensional space. Subsequently, a comparative analysis of aggregate damage evolution in various directions was conducted. It was found that the damage extension of pavement aggregates primarily originated from the cumulative tire-pavement friction effect during vehicle driving. In addition, the vertical pressure exerted by wheel loads also contributes to the damage, resulting in a tendency to expand in depth. Overall, this study provides insights into the crack evolution mechanism of coarse aggregates under wheel loading, offering a reference for further exploration of the skid resistance degradation mechanism of asphalt pavements. • Investigated the microcrack evolution in aggregates during the wear process of asphalt pavement. • Employed X-CT to track and visualize the evolution of microcracks in aggregates before and after wear, and proposed a method for small-scale cracks segmentation and extraction. • Cumulative wheel loading promotes both crack coalescence and the formation of new microcracks in aggregates, with tortuous propagation in three dimensions. • Crack propagation predominantly occurs in wheel’s travel direction, with extension also observed along the wheel load direction. • Findings reveal fundamental damage pathways of aggregates and mechanisms of skid resistance degradation.