Analysis of Hot-Mix Asphalt Lab Compactability Using Lab Compaction Parameters and Mix Characteristics

The compactability of hot-mix asphalt (HMA) mixtures is often used to describe how easy or difficult it is to compact a mixture on a roadway. Several asphalt researchers have proposed the use of laboratory-measured parameters for mixtures and their components as indicators of HMA compactability and resistance to permanent deformation. In this study, laboratory parameters used to represent field compactability of HMA mixtures, such as the compaction energy index and Bailey method ratios, were compared with the compaction slope, the locking point, and the number of gyrations required to reach 92% of the theoretical maximum specific gravity. Once the relationships among these parameters were established, basic mix parameters such as gradation, aggregate shapes, binder grade, and mix volumetric properties were used to explain why some mixtures are more compactable than others in the gyratory compactor. The results suggested that any of the parameters mentioned above can be used to describe compactability in the laboratory. Gradation type, aggregate type, and aggregate size were the most significant variables that can be used to explain the compactability of specimens compacted with the Superpave^® gyratory compactor.