Analysis of Mesoscopic Parameters of Porous Asphalt Concrete and Its Impact on Permeability Performance

Porous asphalt concrete (PAC) is widely recognized for its excellent performance in drainage, noise reduction, and environmental protection due to its high interconnected porosity. However, challenges remain in relationships between mesoscopic void parameters and permeability performance. To reveal the influence mechanism of meso-structural parameters on the permeability performance of PAC, the X-ray CT scanning and computational fluid dynamics (CFD) simulation techniques were combined in this study. A PAC-13 mixture was selected and prepared with target porosities of 18%, 20%, and 25%. The three-dimensional meso-structure of the specimens was measured using a CT scanner with a resolution of 0.08 mm, and the void parameters were extracted using Image J v1.8.0 software. The mesoscopic parameters of PAC and its impact on permeability performance were analyzed. Moreover, a three-dimensional void model was reconstructed using Avizo 9.0 software. The seepage performance was analyzed using CFD simulation. The results show that the roundness, the ratio of long to short axes, and the equivalent diameter of the voids increase linearly with porosity from 18% to 25%. The void number distribution shows a Gaussian characteristic. The permeability coefficient of PAC mixtures gradually increases linearly with the increase in porosity from 18% to 25%. Good relationships can be found between mesoscopic distribution characteristics and the permeability coefficient, where the coefficients of determination are larger than 0.97. The surface seepage pressure is nearly ten times more than the bottom pressure. The influence depth of seepage pressure is deeper with the increase in porosity, while the seepage velocity increases with the increase in porosity. This study offers valuable insights into the functional design and performance optimization of PAC materials.