Performance of asphalt mixtures with high recycled materials content and recycling agents

Abstract

ABSTRACTRecycled asphalt mixtures with high amounts of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) can be excessively stiff, brittle, and prone to cracking. The use of recycling agents, or rejuvenators, can significantly reduce mixture stiffness and improve performance, specifically cracking resistance. In this study, the performance of recycled and rejuvenated asphalt mixtures from several field projects, located in different environmental zones across the United States, was evaluated considering various recycling agent dosages determined by the contractors. Field core test results and the visual distress surveys of the field projects demonstrated that using the field recycling agent dosages yielded poor mixture performance. Laboratory test results demonstrated that adding the recycling agent at the dosage to match the continuous high-temperature performance grade (PGH) of the rejuvenated binder blend (virgin/base binder, recycled binder, and recycling agent) to that of the target binder PGH specified based on climate and traffic requirements yielded improved mixture performance. The rejuvenated mixtures at this recycling agent dosage showed significant reduction in stiffness and improved cracking resistance, and facilitated the use of higher quantities of recycled materials, regardless of aging level, while maintaining rutting resistance after short-term aging.