Effect of Superpave Gyratory Compactor Type on Compacted Hot-Mix Asphalt Density

The SUperior PERforming Asphalt PAVEments (Superpave) gyratory compactor was developed as a tool in the Superpave mix design system to better simulate the field compaction of hot-mix asphalts. All Superpave gyratory compactors are designed to meet the specification criteria found in AASHTO TP4. At the present time, AASHTO TP4 does not contain a precision statement. Furthermore, many agencies have reported differences in the bulk specific gravity of compacted samples from different Superpave gyratory compactors, which have been properly calibrated. Data are presented and analyzed from three gyratory compactor proficiency sample testing programs, from field project Superpave gyratory compaction comparisons, and from mix design and quality control and assurance results from a state department of transportation. The data were then analyzed to determine the statistical (precision) and potential project implications that result from the observed differences. The results indicate that the precision of the Superpave gyratory compactor is better than the mechanical Marshall hammer. However, there were significant differences between the bulk specific gravity of mixes compacted in different gyratory compactors. These differences could potentially lead to discrepancies during the mix design verification and quality control and assurance testing of a given mix.