Volume 3, Issue 6 (June 2006)
A Comprehensive Examination of the Internal Angle of Gyration for the Superpave Gyratory Compactor
The Superpave gyratory compactor (SGC) is the “centerpiece” of the Superpave system. Hot-mix asphalt (HMA) specimens are compacted in the laboratory using the SGC through the application of pressure and an applied angle of gyration. The original compaction specification for the SGC requires the angle of gyration to be 22°±0.35 mrad (1.25±0.02 deg), measured externally to the compaction mold. Due to concerns regarding the inability of different compactors to produce HMA specimens with similar density, the Dynamic Angle Validation (DAV) kit was developed to measure the angle of gyration internally, or inside the mold. The DAV requires the use of HMA for the internal angle determination; logistical concerns and other issues led to the introduction of devices—the Rapid Angle Measurement (RAM) and the Hot-Mix Simulator (HMS)—which mechanically simulate the load placed on the SGC by the mix being compacted. This paper presents a summary of the state-of-the-practice concerning the internal angle of gyration and addresses potential strategies for implementing an internal angle specification into routine Superpave mixture design and quality control practices.