Characterization of aggregate resistance to degradation in stone matrix asphalt mixtures

Stone matrix asphalt (SMA) mixtures rely on stone-on-stone contacts among particles to resist applied forces and permanent deformation. Aggregates in SMA should resist degradation (fracture and abrasion) under high stresses at the contact points. This study uses conventional as well as advanced imaging techniques to evaluate aggregate characteristics and the resistance-of aggregates to degradation. Aggregates from different sources and aggregate types with various shape characteristics were used in this study. The micro-Deval test was used to measure aggregate resistance to abrasion. The aggregate imaging system was used to examine the changes in aggregate characteristics caused by abrasion forces in the micro-Deval. The resistance of aggregates to degradation in the SMA was evaluated through the analysis of aggregate gradation before and after compaction with conventional mechanical sieve analysis and nondestructive X-ray computed tomography. The findings of this study led to the development of an approach for evaluating aggregate resistance to degradation in SMA. This approach measures aggregate degradation in regard to abrasion, breakage, and loss of texture.