Evaluating Recycling Efficiency of Plant-Asphalt Mixtures Containing RAP/RAS

With the continuing increase in the use of recycled asphalt pavement (RAP) and recycled asphalt shingle (RAS) for highway construction, there is a concern over how much of the aged asphalt binder inside RAP/RAS can be blended into virgin asphalt binder. In this study, the RAP/RAS binder mobilization rates of 13 different mixtures produced by three different types of asphalt plants in Tennessee were determined using fluorescence microscopy and gel permeation chromatography (GPC). A multiple regression model was developed to explore the factors critical to enhancing the mobilization rate of the RAP/RAS binder. Results showed that the RAP/RAS binder mobilization rate was significantly lower than 100% for most mixtures, indicating that only part of the RAP/RAS binder was mobilized during the production process. The mixing and delivery temperatures had significant influence on the mobilization rate of RAP/RAS binder. In addition, the aging degree of RAP/RAS binder also significantly affected the mobilization rate.