Field-Focused Superpave Validation

The Superpave design system came into existence in the mid-1990s. Many pavements have been constructed with Superpave designed hot mix asphalt (HMA). Today, this technology is well established in many states. It has been over a decade since the Commonwealth of Pennsylvania began using this system for designing HMA. There has been general satisfaction with the pavements constructed with this mix, and anecdotal evidence suggest that Superpave pavements are performing well in Pennsylvania; however, within the last several years, there has been concern raised in regard to the durability of some Superpave mixes. Some have reported these problems as a result of insufficient binder content in the mix. This issue has been the driving force for several states to take measures to increase the binder content in the mix. There has also been a move by some to increase the minimum required VMA to allow more space within the aggregate structure for asphalt and therefore provide a higher binder content mix at a specified design air void level. The Pennsylvania Department of Transportation is now specifying 1/2 percent higher VMA for all aggregate-size gradations that is specified in AASHTO M323. As the Superpave design criteria are evolving, it is worth looking back into the performance of the pavements constructed with Superpave mixes. The research findings presented in this report are the result of such effort, evaluating the long-term performance of Superpave-designed mixes.