Effects of filling degree on skid resistance in fluid mastic asphalt mixtures

Macrotexture is critical for pavement skid resistance in wet conditions, yet conventional mixtures face a trade-off between durability and texture depth. This study proposes Fluid Mastic Asphalt (FMA), a skeleton-superdense mixture in which flowable asphalt mastic fills the aggregate skeleton. By adjusting the filling degree, macrotexture can be controlled while maintaining high durability. FMA mixtures with varying filling degrees and asphalt–aggregate ratios were evaluated through abrasion and rutting tests. Results recommend an optimal filling degree of 94%–96%. Compared with AC and SMA, FMA exhibits superior skid durability, with BPN degradation rates reduced by 34.5% and 19.5%, respectively. For MTD, FMA retains values above 1.4 mm after abrasion, reaching 4 and 1.65 times those of AC and SMA. An XGBoost model was developed to analyze FMA skid resistance degradation, with SHAP values quantifying the contributions of input factors.