Effect of Pore Characteristics on Sound Absorption Ability of Permeable Pavement Materials

Permeable pavement materials are attracting great attention due to the superior benefits in fast drainage, driving safety, and noise reduction effectiveness. This study investigated the sound absorption behaviors of permeable pavement materials, including permeable cement concrete (PCC) and open-graded friction course asphalt mixture (OGFC). The sound absorption coefficients (SACs) of dense-graded cement concrete and dense-graded asphalt mixture were also measured for comparison. The sound absorption test was conducted by the impedance tube method according to ASTM E1050-19. Computed tomography (CT) scanning tests were conducted to obtain the pore characteristics of PCC and OGFC, including porosity distribution, pore size, and coordination number (CN). The porosity distribution, pore size distribution, and CN distribution presented a symmetrical trend of decreasing, then increasing, and then decreasing with the increase of specimen height. When OGFC and PCC showed similar porosities, the pore number of PCC was significantly larger than that of OGFC. Comparisons of the peak SAC and the average SAC were made between PCC and OGFC. Correlations were made between the SAC and the pore characteristics. Results indicated that with increasing porosity, the peak SAC and the average SAC both increased significantly for PCC and OGFC. The characteristic pore size, pore number, and CN distribution together affected the SAC. At the same porosity, OGFC mixtures presented larger average SAC compared to PCC, which was ascribed to the fact that more pores with larger size and a better pore connectivity existed in OGFC mixtures.