Project Details

The recycling of asphalt pavements has become a very routine procedure throughout the country. Research has shown that the Recycled Asphalt Pavement (RAP) recovered from construction sites still contains usable materials, both in the recycled aggregates and recycled binder. However, since the RAP binder has been aged during its service life, the use of RAP in new pavement construction may cause the stiffness of the blended binder to increase. Due to this increased stiffness, it is sometimes necessary for a “grade shift” in the virgin binder in order to result in the specifications for the desired performance grade. As this complicates the procedure most contractors limit the use of RAP to 20% in order to avoid the need for a grade shift. This has resulted in large amounts of RAP going unused. The use of higher percentages of RAP in construction would provide initial cost savings. However, a life cycle cost analysis is needed in order to determine whether use of higher percentages of RAP provides an economical advantage for the life cycle, not just initially. In order to predict life cycle costs, the fatigue life and rut resistance of mixtures containing various amounts of RAP will be compared to a 100% virgin material mixture. The fatigue life and rut resistance of the mixtures were calculated from laboratory testing using Frequency Sweep Testing and Repeated Simple Shear Tests using Superpave Simple Shear Tester (SST). The SHRP A-003A surrogate models and the Asphalt Institute models were both used in order to predict pavement performance using the results from the Frequency Sweep Testing and the Repeated Simple Shear Test. Based on these results, the life cycle economic analysis were completed and the optimum percentages of RAP were determined for use in the construction of new pavements.