Evaluation of the compaction characteristics of unbound material using the superpave gyratory compactor

During previous full scale tests at the National Airport Pavement Facility (NAPTF) at Atlantic City, - USA, significant consolidation of the subbase layer occurred during aircraft trafficking accompanied by shear flow failure in the underlying low strength subgrade material. In order to understand the compaction and shear flow characteristics of the subbase layer during construction and trafficking, the material was compacted in the Superpave Gyratory Compactor (SGC) at various stress levels and at different moisture contents. Since the SGC is primarily used for compaction of asphalt concrete, the compaction characteristics in the Superpave Gyratory Test were calibrated to field compaction of the subbase material during construction at similar moisture contents. The field data collected included the change in density of the subbase layer during compaction with number of passes of the roller. The calibration was done by comparing the shape of the curve. The calibration provided the benchmark values for laboratory evaluation of unbound material in SGC, such as stress level and the gyratory angle of testing. The shape of the compaction curve and the density at various gyrations levels provided an insight into the understanding of the compaction characteristics of the subbase material under roller compaction. This paper provides the airport pavement designers the efficacy of using the SGC as a means of evaluating the performance of unbound material during compaction.