Comprehensive evaluation of sound absorption property in dual-layer porous concrete pavement

Porous concrete pavement is recognized as an environmentally friendly surface capable of mitigating urban traffic noise and is increasingly applied in urban roads with strict acoustic requirements. While numerous studies have examined its sound absorption performance, most have focused on single-layer structures, which differ from the more common dual-layer applications. This study investigates the sound absorption performance of various dual-layer porous concrete pavement configurations using the mean sound absorption coefficient across the 200-2000 Hz frequency range. The tested parameters included aggregate size, cement-to-aggregate ratios, and layer thicknesses in the upper and lower layers. Results show that aggregate size and cement-to-aggregate ratio in both layers influence absorption effectiveness and shift the dominant absorption frequencies, but do not affect the number of dominant frequencies. By contrast, layer thickness influences absorption effectiveness, shifts dominant frequencies, and changes the number of dominant frequencies. For a total thickness of 10 cm, the optimal configuration consists of a surface layer with smaller aggregates and a low cement to aggregate ratio over a lower layer with larger aggregates and a low cement-to-aggregate ratio. For a total thickness of 15 cm, using smaller aggregates with low cement-to-aggregate ratios in both layers provides better absorption.