Long Term Performance Evaluation of Superpave Mixes

In 1994, the end product of the Strategic Highway Research Project (SHRP) was the asphalt concrete mix design methodology known as the SUperior PERforming Asphalt PAVEments (Superpave) system. As part of the SHRP Long Term Pavement Performance (LTPP) program, an experiment identified as Specific Pavement Study (SPS-9) was established to evaluate the long term performance of the Superpave mix design methodology. At each project location, three main test sections were constructed incorporating: the conventional agency mix design; the Superpave Level I mix design; and the Superpave Level I mix design with an alternative Performance Graded (PG) asphalt binder. Further supplementary test sections were also constucted at the majority of SPS-9 projects, evaluating the use of other PG asphalt binders and the use of Reclaimed Asphalt Pavement (RAP) with the Superpave mix design. This paper provides a field performance comparison and analysis of the Superpave Level I mix design methodology with conventional agency Marshall mix design methodology using the LTPP SPS-9 experiment. In addition, an assessment of the impact in variations of PG asphalt binder grades and RAP is established using statistical analysis of field distresses. Field distresses evaluated in the study include: rutting; fatigue cracking; and low temperature cracking.