How does warm mix asphalt (WMA) perform compared to hot mix asphalt (HMA) in the long term? How is foam different than chemical additives? What happens to an asphalt mix when WMA is used in conjunction with RAP? These and many other questions are on the minds of USDOT, FHWA and State Highway Agency leadership. In order to find answers, the FHWA’s LTPP launched a new Specific Pavement Study (SPS) that will monitor the long-term performance of WMA. The purpose of the SPS-10 experiment, as explained on LTPP’s website, is to “narrow the knowledge gap that currently exists between the performance of WMA and HMA pavements...SPS-10...is designed to explore how a set of primary factors influence pavement performance. These factors include the WMA technology used, environmental elements (temperature and moisture), and traffic loadings.”
Projects are planned across the U.S. The first projects were constructed in 2015, with plans to construct more in 2016. Currently, the SHA tracks the project’s performance for five to six years post construction, with performance data being posted to the FHWA’s LTPP Database.
Each project has three core test sections: a HMA control, WMA with foam, and WMA with a chemical additive. Highway agencies have the opportunity to include supplemental test sections in order to perform additional research that meets their specific needs. The Oklahoma Department of Transportation (ODOT) is a great example of an Agency that is strategically partnering with the FHWA, LTPP and other key players in order to monitor road performance. As part of ODOT’s trial, contractor TJ Campbell chose to use Evotherm® and Evoflex® CA. Ingevity, under the leadership of Richard Steger, P.E., is also assisting ODOT with asphalt binder and mix testing. These results are expected in approximately two months, while LTPP is expected to publish their data by 2017.
We applaud ODOT on their SPS-10 efforts and look forward to the results. Keep up the great work while we wait.