Laboratory Investigation of the Effects of Asphalt Mixture Volumetric Properties on the Permeability and Durability of Open-Graded Friction Course

This study investigates the volumetric properties and performance relationships of open-graded friction course (OGFC) mixtures by examining the effects of interconnected air voids (IAVs), asphalt film thickness (FT), and the D 10 (particle size index) on permeability and durability. A central composite design combined with response surface methodology was employed to evaluate two aggregate gradations. The results indicated that IAV was the key factor influencing permeability. Increasing FT improved durability by reducing Cantabro loss, particularly in coarse mixtures dependent on binder bridging, while simultaneously decreasing permeability. The reduction in permeability was more pronounced in 12.5-mm nominal maximum aggregate size (NMAS) mixtures, as a result of binder accumulation in major drainage pathways. Among the gradation parameters, D 10 was more influential than NMAS. At equivalent IAV levels, mixtures with larger D 10 values exhibited higher permeability. IAV is recommended as an effective adjustment factor for balancing permeability and durability, given its strong correlation with both performance criteria. For the mixtures evaluated, a 5% to 7% improvement in durability required a reduction of 4 to 6 mm/s in permeability, along with decreases of approximately 1.0% to 1.5% in air voids and 0.8% to 1.2% in IAVs. Incorporating IAVs, FT, D 10 , and NMAS, an empirical model ( R 2 = 0.829) for OGFC permeability was developed, providing a reliable, predictive tool to support OGFC mix design. These findings highlight the potential of volumetric-informed design practices to achieve a better balance between drainage performance and durability, advancing performance-oriented OGFC optimization.