Ruggedness Evaluation of the Dynamic Angle Validation Kit for Superpave Gyratory Compactors

Superpaver hot-mix asphalt (HMA) specimens are compacted in the laboratory with the Superpave gyratory compactor (SGC). The SGC compacts specimens through 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°), measured externally against the compaction mold. Questions about the ability of different compactors to produce HMA specimens of the same mix having the same density led to development of the dynamic angle validation (DAV) kit, which measured the angle of gyration internally (on the inside of the mold). Two task groups were formed independently to develop a standard specification for DAV usage; the groups combined efforts and produced AASHTO PP48, with a companion ASTM specification slated for consideration in the fall of 2003. The specifications did not include a statement of precision and bias. The task groups conducted a ruggedness study using the guidelines contained in ASTM C-1067 and E-1169. Factors considered in the ruggedness study included height of mix used in the mold with the DAV, number of gyrations used to determine the angle of gyration, operating temperature of the DAV, and the nominal maximum aggregate size of the mix used with the DAV. Six SGC models were included in the study. The ruggedness study showed no factor significantly affected the DAV-measured angle. The findings clear the way for a planned interlaboratory study to establish the precision of the angle of gyration measured with the DAV.