SUPERPAVE GYRATORY COMPACTION GUIDELINES

This digest summarizes key results of NCHRP Project 9-9, Refinement of the Superpave Gyratory Compaction Procedure. Of particular interest, it presents a recommended reduction in the Ndesign table in AASHTO PP28, Practice for Designing Superpave HMA, from the original 28 traffic and climate combinations to 4, provides specific Ndesign levels for base mixes, and recommends setting the Superpave short-term aging mix temperature equal to the equiviscous compaction temperature. The Superpave gyratory compaction procedure, developed under the Strategic Highway Research Program (SHRP), is the method required for all Superpave mix designs and mixture process control. The gyratory compactor must provide a density in the compacted laboratory specimen that closely approximates the ultimate density of the hot mix asphalt (HMA) mixture obtained in the pavement when subjected to traffic loads and climate conditions so that an appropriate optimum asphalt content can be selected during the laboratory mix design process.