Abstract
Open Graded Friction Course (OGFC) is a type of hot mix asphalt which contains interconnecting voids that provide improved pavement surface drainage during rainfall. This thin layer of permeable asphalt pavement is placed on top of traditional dense graded asphalt. Across the United States the use and performance of OGFC has been highly variable. The estimated service life for such a pavement has been determined to be 8 to 12 years with good to very good durability and surface friction performance. Recycled Asphalt Pavement (RAP) has been employed in the production of new asphalt roadways for many years. RAP is a very useable and available resource in the asphalt pavement industry. While there are only a few reasons for not using RAP such as unpredictability and lack of research, the benefits of using it are numerous. Currently, the use of RAP in OGFC is forbidden by many US state transportation agencies. However, with fluctuating oil prices, diminishing natural resources, and environmental issues, the use of RAP is more important than ever. Currently, OGFC mixtures are created with many different types of binders, both modified and unmodified. However, little direction is given as to what might be the best choice. There is a strong possibility that the right combination of RAP and modified binder may produce an OGFC with the same, if not better, performance as what is presently being specified. The intent of this research was to determine the possibility of incorporating RAP into open graded friction course mixtures and whether the binder type employed in the mixture will affect the overall pavement performance. Utilizing current design specifications, multiple OGFC mixtures were designed with various RAP contents and asphalt binders. These mixtures were subject to a barrage of tests which included measuring their ability to resist abrasion loss, binder draindown, cracking, rutting, and moisture susceptibility. Other testing included the ability for the mixture to be easily compacted as well allowing the permeation of water through it. Rutting testing employed the use of the industry standard Asphalt Pavement Analyzer (APA). On the other hand, cracking and moisture susceptibility testing utilized the fairly new Semicircular Bending Test (SCB). Through this study it was determined that it is possible to design an open graded friction course which utilizes RAP. This possibility is only achieved when the proper materials are used. RAP must be properly fractionated and the asphalt binder must be modified whether it is with polymer or rubber. The test results combined with a life cycle cost analysis (LCCA) demonstrated that highly modified asphalt (HiMA) or an asphalt rubber binder (AR) combined with 15% or 25% RAP have the ability to perform the same if not better than a typical PG64-28 as specified in the state of Massachusetts.