Fracture Energy Evaluation of “Interstitial Asphalt Mixtures”

Having an adequate coarse aggregate structure in any asphalt mixture may not be enough to accurately distinguish the cracking performance of an asphalt mixture: indeed, it has been proved that the interstitial volume (IV) can affect asphalt mixtures cracking performance. The IV is defined as the volume with in the coarse aggregate structure filled with finer material, binder and air voids (interstitial components). Several surveying activities on pavement sections made with mixtures designed with Dominant Aggregate Size Range (DASR), which is the coarse aggregate that forms the structural interactive network of aggregate, have been developed in the past. This paper presents an experimental study, recently developed at the University of Florida, aimed at investigating how interstitial components are influenced by different variables, as types of aggregates, aggregate gradation and by binders. The DASR-IC model was used to identify a range of mixtures to be tested by first designing the coarse aggregate structure with adequate inter-locking and then varying the fine portion of the gradation. Laboratory test results from Superpave Indirect Tension Test (IDT) clearly showed that the IV characteristics have a significant effect on asphalt mixture fracture performance.