Compatibility of Recycled Binder Blends with Recycling Agents: Rheological and Physicochemical Evaluation of Rejuvenation and Aging Processes

Public and private sectors promote increased use of recycled materials in asphalt pavement construction. However, concerns exist about possible premature pavement embrittlement and cracking because of these aged materials. Recycling agents, or rejuvenators, are used to offset these concerns. Rejuvenation mechanisms can be inferred depending on the type of recycling agent, yet there is a lack of supporting experimental evidence, especially related to the recycling agent–asphaltene interaction. This study provides insight on the effects and mechanisms of rejuvenation through extensive rheological and physicochemical characterization by considering experimental variables such as type of recycling agent, type/proportion of recycled materials, and binder type. Rejuvenation was effective based on restoration to PG 70-22, reduction in the Glover–Rowe parameter, and reduction in the glass transition temperature midpoint and end. Chemical characterization was not conclusive, yet the results were interpreted as strong recycling agent–asphaltene polar interaction. Rheological benefits from rejuvenation were gradually lost with long-term aging.