Establishment of Precision of Dynamic Angle Validation Kit with Hot-Mix Simulator for Superpave Gyratory Compactors

Superpave^® hot-mix asphalt (HMA) specimens are compacted in the laboratory with the Superpave gyratory compactor (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 degrees), measured externally to the compaction mold. Questions concerning the ability of different compactors to produce HMA specimens of the same mix with the same density led to the development of the dynamic angle validation (DAV) kit, which measures the angle of gyration internally (on the inside of the mold). The DAV procedure requires the use of HMA to measure the internal angle of gyration. Because of practical limitations of performing measurements with HMA and questions concerning the proper HMA mix to use in the measurements, a companion device—the hot-mix simulator (HMS)—was introduced, which effectively simulates the load placed on the SGC by an HMA specimen when used in conjunction with the DAV. An interlaboratory study was conducted in accordance with ASTM E691–99 to establish the precision of the internal angle measurement provided by the DAV-HMS combination. A total of 10 DAV-HMS units and five SGC models were included in the study. Estimates were developed of both repeatability (within laboratory) and reproducibility (between laboratories) for the DAV-HMS device for all five SGC models.