Strategic Highway Research Program gyratory compaction for predicting air voids of Saskatchewan SPS-9A asphalt mixes after 10 years of performance in the field
Many Saskatchewan provincial highways exhibit permanent deformation that is mostly attributed to reduction in air voids in hot mix asphalt concrete surfacing. The Saskatchewan Ministry of Highways and Infrastructure (MHI) currently use the Marshall compaction method for hot mix asphalt concrete (HMAC) design and placement quality control and quality assurance. It has been found that the Marshall compaction method does not accurately predict field air voids. Therefore, MHI identified the need to evaluate the SuperpaveTM gyratory compaction method to predict field air voids of typical Saskatchewan asphalt mixes. This paper presents a summary of laboratory and field volumetric as well as rapid triaxial mechanistic material properties of typical Saskatchewan asphalt mixes. This research considered seven asphalt mixes from the Radisson Specific Pavement Study (SPS)-9A test site comprising two conventional Saskatchewan Marshall Type 71 mixes, five SuperpaveTM mixes, and a SuperpaveTM recycled mix. This research determined that Marshall compaction and the gyratory compaction at 1.25° gyration angle underestimate the collapse of field air voids. This research also showed that the gyratory compaction method at 2.00° angle of gyration more accurately predicted field air voids of the asphalt mixes constructed as part of test site.