Laboratory Study on Gradation Design and Pavement Performance of Fine and Porous Asphalt Concrete PAC-5

Porous asphalt concrete (PAC) is recognized for its outstanding noise reduction capability, which tends to improve as the aggregate particle size decreases, suggesting that PAC-5 may offer superior noise reduction performance. However, the gradation design principles and pavement performance of PAC-5 remain unclear. In this study, 13 different gradations of PAC-5 were developed by varying key particle size parameters, including sieve passing rate and aggregate content. The volumetric indices of the specimens were tested, with percent air void selected as the primary research variable to quantify its correlation with these key particle size parameters. Additionally, the pavement durability, sound absorption performance, and overall noise reduction performance of PAC-5 were evaluated. The results indicate that the sieve passing rate of 2.36 mm and aggregate contents of 2.36–4.75 and 4.75–9.5 mm significantly influence the percent air void of PAC-5. The sound absorption coefficient (SAC) spectrum of PAC-5 peaks around 800–1,250 Hz. As the percent air void of PAC-5 increases, the SAC peak shifts toward higher frequencies, and the sound absorption performance improves. The overall noise reduction performance of PAC-5 is exceptional, surpassing that of PAC-10 due to its denser texture distribution. Moreover, as the percent air void increases, the surface texture level rises, leading to richer surface air channels and a reduction in high-frequency noise. These findings provide a theoretical basis for more precise gradation design of PAC-5 and the pavement performance when used as a noise-reducing surface.