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

Abstract

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.