Maximizing the Utilization of the Treated RAP by a Two-Step Enhancement Method in Recycled Asphalt Mixtures

ABSTRACT In a circular economy toward zero waste, reclaimed asphalt pavement (RAP) as a secondary resource into new asphalt pavement is one of the important waste management strategies for circularity. In view of the issues of low RAP usage and performance variation of recycled asphalt mixtures (RAM), this paper developed a two-step treatment method to enhance the properties of the coarse RAP as aggregates by removing old mortar and to restore the properties of old mortar/fine RAP by using a rejuvenating agent. First, the aged asphalt was extracted from RAP to evaluate its aging degree. The recycled asphalt mortar was prepared with fine RAP. The changes in surface morphology of recycled asphalt mortars were characterized by a computerized tomography scan, and the influence of the rejuvenating agent on the performance of recycled asphalt mortars was evaluated by a dynamic shear rheological test and a Bending Beam Rheometer test. Finally, RAM were prepared with 60 % of the treated RAP, and their properties were evaluated, including the water stability, low-temperature, and fatigue performance. Experimental results demonstrated that the rheological behavior and low-temperature performance of the recycled asphalt mortar can be effectively recovered by incorporating an appropriate rejuvenating agent with related parameters even better than that of the new asphalt mortar. Regarding RAM that incorporated a high dosage of the treated RAP, its pavement performance can be improved, and this proves the feasibility of using a high percentage of RAP in recycled asphalt pavements.