Effects of clogging on void characteristics and sound absorption properties of porous asphalt pavements

Porous asphalt (PA) features a high void content with abundant connected voids that enable effective drainage and noise reduction. However, the internal voids may become clogged by external substances over time, resulting in a decline in noise reduction capability. This study systematically investigated the effects of target void content, clogging material, and clogging cycles on void characteristics and sound absorption performance. The methodology included material design, clogging simulation, CT scanning, and acoustic testing. Results show that void content was the primary factor affecting the initial sound absorption performance of PA-13. Specimens with a target void content of 25 % achieved an average sound absorption coefficient of 0.487 within the 500–1250 Hz frequency range. However, higher void content also increased susceptibility to clogging. Differences in gradation and density among clogging materials caused heterogeneous changed in void structure. Rubber powder predominantly accumulated in the top section of specimens, causing the highest sound absorption attenuation. In contrast, sand particles mainly clogged mid-sized voids while preserving partial connectivity. This led to a more gradual decline in sound absorption coefficient. The 630–2000 Hz frequency band consistently showed the highest absorption level, demonstrating it as the most significant range for PA-13 pavement acoustic performance. Grey correlation analysis identified clogging cycles and target void content as the dominant factors affecting sound absorption attenuation. Frequency response analysis further revealed that sound absorption efficiency in the 630–2000 Hz range was highly sensitive to void connectivity. Future research should explore the long-term relationship between void structure evolution and acoustic performance under sustained clogging conditions.