Relationship between Aggregate Packing Characteristics and Compactability of Hot-Mix Asphalt Mixes

Compaction of hot-mix asphalt (HMA) is an essential process in the construction of asphalt pavement as it is critical to the performance of the road infrastructure. The compaction process enables the asphalt mixtures to achieve stability, provide resistance to deformation (rutting) against traffic loading, reduce permeability of the layer, and improve its durability. One of the factors affecting compactability (or workability) of the HMA is its internal structure. The research work presented in this paper is aimed at investigating the influence of the internal structure of HMA based on aggregate gradation and packing characteristics on the compactability. Three coarse-graded HMA mixes were used to evaluate parameters that describe aggregate packing characteristics, including the gravel to sand ratio, gradation shape factor, as well as the traditional and revised rational Bailey ratios. HMA specimens were compacted using a Superpave gyratory compactor (SGC), and the data were analyzed to determine five parameters of HMA compactability. The HMA compactability parameters were then correlated to the aggregate packing parameters. Overall, the parameters of HMA compactability exhibited a strong correlation with the aggregate packing parameters. The outcomes of the study not only provide a better understanding of the influence of aggregate gradation and packing characteristics on HMA compactability, but also identify essential input parameters to be considered when developing models to simulate HMA compaction.