Comparative Analysis of Volumetric Properties for Superpave Gyratory Compactors

The experience with the original Superpave gyratory compactors (SGCs) introduced into the paving industry in 1994 was very positive. Consequently, since 1995 several additional manufacturers have developed SGCs to meet the growing demand for such devices. Although these units generally meet the broad requirements of the original SGC specification developed by FHWA, their basic designs are somewhat different. To ensure a systematic means for evaluation of the compactors, FHWA developed a standard protocol, designated AASHTO PP35. This procedure was used to evaluate various gyratory compactors. By using the discriminating value of 0.010 for difference in bulk specific gravity (G_mb), the compactors were evaluated in terms of G_mb. The five gyratory compactors evaluated were the Rainhart, Test Quip, Troxler Electronic Laboratories, Inc. (Troxler), Model 4141, Pine Instrument Company (Pine) Model AFG1A, and Interlaken compactors. These compactors were compared with either Pine Model AFGC125X (Pine 1) or Troxler Model 4140 (Troxler 1) SGCs, which were used as reference compactors. In addition, the project included a comparison of two Pine compactors (Pine 1 and Pine 2) of the same model (AFGC125XS) with each other. A total of 336 specimens (48 specimens for each compactor) were prepared for all the compactors to fulfill the comparison. Eleven comparisons of each candidate compactor and the reference compactor were made during a 12-month period. All of the candidate compactors compared favorably with an existing SGC. It was found that all seven compactors would provide the same results within the given tolerance range under the rigid conditions of the AASHTO PP35 protocol.