Improved Practical Model for Permeability and Implications for the Design of High-Performance Hot-Mix Asphalt

The purpose of this paper is to present an empirical model to estimate hot-mix asphalt (HMA) permeability with the use of common compositional factors. The model is an improvement of one originally developed as part of NCHRP Projects 9-25 and 9-31 but uses an expanded data set to provide a better model. The elimination of unrealistic mixture compositions from the data set and the consideration of additional potential predictors have resulted in a model with significantly improved accuracy and usefulness. The model predicts that permeability increases primarily with increases in air voids. However, aggregate properties also affect permeability: increases in nominal maximum aggregate size and decreases in mean aggregate particle size (D50) tend to decrease HMA permeability. The model suggests that, when durability is an important concern, fine aggregate gradations should be used for HMA mix designs.