Durability of bio-modified recycled asphalt shingles exposed to oxidation aging and extended sub-zero conditioning

The use of recycled asphalt shingles (RAS) in pavement construction has received significant attention due to its economic and environmental advantages. However, asphalt binder in RAS is significantly aged and requires modification before application to ensure it does not compromise pavement performance. The paper introduces a novel approach to modify RAS to facilitate its application in new construction while examining the feasibility of rejuvenating RAS via bio-modification. In addition, this study investigates the durability of the modified RAS, referred to as bio-modified shingles (BMS), by exposing BMS to both severe oxidation aging and sub-zero extended conditioning followed by a comprehensive thermo-mechanical characterization. Study results showed the performance of RAS was significantly improved after bio-modification. The performance improvement was reflected in BMS having lower viscosities, stiffnesses, shear susceptibilities, crossover temperatures, while having higher m-values and failure strains compared to RAS asphalt. It was further observed that the enhancement lasted even after BMS was exposed to severe oxidation aging and 72 hr conditioning at −18 °C indicating an enhanced durability of BMS. The latter can be attributed to molecular interactions between the bio-modifier and aged asphalt disturbing the molecular packing of asphaltene and wax molecules. Such molecular packing is known as a dominant mechanism for hardening at sub-zero temperatures. This paper contributes to the body of knowledge and practice by providing insights on the merits of revitalizing recycled asphalt shingles to enhance its durability and facilitate its application in construction to promote sustainable construction practices.