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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. [ABSTRACT FROM AUTHOR]

The incorporation of high percentage (>30%) recycled asphalt pavement (RAP) into asphalt mixtures has become more popular. Various methods have been proposed to determine how much of RAP binder can be effectively blended into virgin binder. However, few methods can be used to test the blending efficiency of plant-produced asphalt mixtures. This study proposed a method of measuring the blending efficiency of plant-produced mixtures using Fourier Transform Infrared Spectroscopy (FTIR). Three types of asphalt mixtures, including one warm mix, two hot mixes with or without rejuvenator, were used to validate the proposed method. Results indicate that RAP particles varied in oxidation, but mixing RAP binder with virgin binder could reduce this heterogeneity. Among the three mixtures, warm mix showed the highest blending efficiency, while adding rejuvenator had a limited effect on the blending efficiency. The proposed method was further verified using Gel Permeation Chromatography (GPC). [ABSTRACT FROM AUTHOR]