Evaluation of Asphalt Mix Stability Using Compaction Properties and Aggregate Structure Analysis

This paper presents a methodology to evaluate the aggregate structure stability in hot mix asphalt (HMA). The HMA response in the Superpave Gyratory Compactor (SGC) is used to derive an index, referred to as the Contact Energy Index (CEI), that reflects the energy utilized in establishing contacts among aggregate particles. Then, a three-dimensional (3-D) finite element model of the SGC is presented, and the CEI calculated from the finite element model is compared with experimental measurements. The 3-D finite element model is shown to give CEI results similar to measurements. Image analysis techniques are used to measure the evolution of the aggregate structure in terms of orientation and contacts during compaction. The image analysis results are compared with experimental measurements of CEI. The comparison shows strong correlation between the number of contacts, the resistance of the aggregate structure to re-orientation and the CEI value.