Mechanical properties and normal-incidence sound absorption performance of crumb-rubber-modified porous asphalt mixtures

Abstract

Porous asphalt mixtures provide effective drainage and acoustic-energy absorption, but their mechanical durability under thermal and moisture exposure remains an important engineering concern. This study evaluated the effects of wet-process crumb rubber (CR) dosage on the mechanical, volumetric, moisture-related, and normal-incidence sound absorption performance of OGFC-13 mixtures. CR dosages of 0%, 10%, 15%, 20%, and 25% by mass of the base asphalt were investigated, and the corresponding mixtures were designated R-0, R-10, R-15, R-20, and R-25. Paired specimens were evaluated before and after accelerated laboratory aging at 85 °C for 120 h to compare their relative aging susceptibility. A comprehensive performance index (CPI) and weight-sensitivity analysis were further used to evaluate the overall performance of the mixtures under different engineering priorities. R-15 exhibited the highest unaged dynamic stability of 5450 cycles/mm and the lowest Cantabro loss, whereas R-20 provided the highest low-temperature deformation capacity and normal-incidence sound absorption, with a peak absorption coefficient of 0.79 and an average coefficient of 0.50. Under the baseline engineering weighting scenario, the CPI values of R-15 and R-20 were 76.42 and 76.22, respectively. Weight-sensitivity analysis showed that the preferred dosage varied between 15% and 20% as the engineering priorities changed. The results indicate that a CR dosage of 15–20% provides a stable high-performance range for OGFC-13 mixtures. Approximately 15% CR is recommended for heavy-traffic applications in which rutting resistance and aging durability are prioritized, whereas approximately 20% CR may be preferred where low-temperature, moisture, or acoustic performance is given greater importance.