Five-Year Performance of Improved Open-Graded Friction Course on the NCAT Pavement Test Track

Abstract

Open Graded Friction Course (OGFC) mixtures are used as the final riding surface on roadways as they offer many benefits, such as reducing hydroplaning, reducing splash and spray behind vehicles for improved driver visibility, improving wet-pavement friction, and reducing surface reflectivity during wet-weather conditions. Despite these benefits, the use of OGFC has diminished over the years due to durability and service-life issues. The typical OGFC pavements in Alabama have exhibited premature distresses (e.g., raveling) after approximately six or seven years in service. Therefore, there is a need to change the current OGFC mix design procedure to improve the mix durability. In this study, three modified OGFC mixtures were designed based on a 12.5-mm OGFC mix design previously approved by the Alabama Department of Transportation (ALDOT) and paved in three test sections (E9A, E9B, and E10) on the National Center for Asphalt Technology pavement test track to evaluate possible changes to ALDOT’s OGFC mix design procedure. The ALDOT-approved mix design lasted less than 20 million equivalent single-axle loads (ESALs) on I-85, a few miles from the test track, whereas the three modified OGFC mixtures lasted more than 20 million ESALs and remained in place for another research cycle (10 millions ESALs) on the test track. The three modified OGFC mixtures also showed improved laboratory performance characteristics compared with those of the ALDOT-approved OGFC mixture. Based on the field and laboratory test results, adjustments made in the three modified OGFC mixtures can potentially improve the long-term field performance of OGFC mixtures in Alabama.