Open-graded friction course (OGFC) is a surface course used in many states. OGFC improves highway safety by increasing wet weather surface traction and reducing spray from wet surfaces. It also provides a much quieter surface by reducing noise generated at the tire-pavement interface. However, in some cases, OGFC was not as durable as desired, resulting in shorter service life and inconvenience to the public.
To increase the OGFC mixtures’ service life, the Florida Department of Transportation (FDOT) contracted the Texas A&M Transportation Institute to evaluate asphalt binder formulations and mix. The research compared OGFC mixtures with a conventional polymer-modified binder and a heavily polymer-modified (HP) binder, using Kraton’s highly modified asphalt (HiMA) technology. Superpave performance grading, Fourier transform infrared spectroscopy (FTIR) and numerical modeling simulations were conducted. The researchers tested mixtures for resistance to rutting, and degradation and cracking after conditioning, which represents many years of service. The study included a comparison of life-cycle costs between the two binders’ mixtures, which accounted for initial construction and projected replacement costs and the time between replacement events.
Research results showed that the HiMA-based “HP binder mixtures were almost twice as resistant to raveling in the more realistic, long-term condition” (FDOT). Mixtures using HiMA technology were estimated to last over 50 percent longer than conventional binder mixtures before requiring replacement. The researchers summarized that using HiMA-based HP binders in OGFC “would reduce maintenance and replacement, yielding substantial savings.” Improving OGFC durability can help reduce the number of accidents and save lives, an example of the Positive Difference that Kraton strives to achieve.