Abstract
Though the first of 26 Specific Pavement Study 9 (SPS-9) experiments was built more than 9 years ago to assess the field performance of the Superpave® asphalt and mix design and analysis system, there has been no definitive report on the experiment's overall field performance. This analysis therefore evaluates the performance of the SPS-9 experiments through the use of the 2001 distress data available from the Long-Term Pavement Performance information management system database. Field distresses evaluated in this study included rutting, fatigue cracking, longitudinal wheelpath and nonwheelpath cracking, and transverse cracking. In addition to the field distress evaluation, a statistical analysis was conducted to determine whether a performance difference exists between the Superpave "correct" performance-graded (PG) binder section and the Superpave alternative PG binder section designed to exhibit early distress at each of the SPS-9 sites. The statistical analysis relates the distresses through means (t-test) and variances (F-test). The data analysis indicates that more than 78% of the Superpave sections have no cracking and more than 80% have only nominal rutting. When cracking occurred, fatigue and longitudinal nonwheelpath cracking were the predominant distresses. For the Superpave binder sections, distresses began to appear within 4 years of construction, with overlays outperforming new pavements and agency sections performing as well as or better than Superpave sections. Surprisingly, the results of the t-test and the F-test analysis showed no statistical difference (at the 95% confidence level) in the fatigue cracking, longitudinal wheelpath cracking, longitudinal nonwheelpath cracking, and rutting distresses between the Superpave binder sections and the Superpave alternative binder sections. However, a statistical difference (based on the F-test) existed for transverse cracking performance between the two PG binder sections.
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