A comparative approach: Using combined DEM-CFD model and CT-scanning data for porous asphalt pore structure analysis

In recent years, the Discrete Element Method (DEM) has been widely utilised for the virtual reconstruction of porous asphalt (PA) mixes. However, limited attention has been directed toward aggregate size selection in DEM modelling. To address this, a numerical approach integrating DEM and Computational Fluid Dynamics (CFD) was developed in this study to explore the relationship between aggregate size and pore characteristics, incorporating computed tomography (CT)-scanned and computational PA mixes. Various particle size distributions (PSDs) and realistic aggregate configurations captured from laboratory samples were used in DEM model preparations to compare pore characteristics with CT-scanned PA mixes. This study investigated variations in pore structures, including porosity, pore size, air void (AV) distribution, and tortuosity, under different aggregate gradations. Differences in pore structures between experimental and computational samples were examined across three gradation ranges: (i) 4.75–13.2 mm, (ii) 2.36–13.2 mm, and (iii) 1.18–13.2 mm. Results indicate that numerical PA samples exhibit high similarity to experimental data in terms of AV distribution and pore number distribution when the minimum aggregate size is smaller than 2.36 mm. The tortuosity of numerical PA mixes is approximately two times lower than that of experimental samples and remains largely unaffected by changes in aggregate gradation. While numerical samples contain significantly fewer pores smaller than 0.1 mm² or larger than 10 mm² compared to experimental samples, the cumulative distribution curves maintain high similarity, particularly as the minimum aggregate size decreases.