Effect of Coarse Aggregate Morphology on Permanent Deformation Behavior of Hot Mix Asphalt

Abstract

This paper defined a complete set of imaging based indices for different levels of coarse aggregate morphologies, i.e., the flat and elongated (FE) ratio, angularity index (AI), and surface texture (ST) index, and investigated their effects on permanent deformation behavior of hot mix asphalt (HMA). Image analyzed coarse aggregates were used to prepare eighteen Superpave HMA specimens using job mix formulas from ten State highway agencies and tested for permanent deformation at a specified high temperature. The permanent deformation data when linked to the morphological indices of the coarse aggregate, showed the best correlations with the ST index. The FE ratio demonstrated no measurable effects on the permanent deformation due to low percentage of flat and elongated particles used in the mixes. The influences of the AI and ST indices on the permanent deformation were especially significant when differences in the asphalt mix aggregate gradations were properly considered. A possible mechanism of coarse aggregate morphology affecting the stability and permanent deformation behavior of HMA was proposed in terms of particle geometrical interference in HMA.