The use of reclaimed asphalt pavement (RAP) in hot-mix asphalt (HMA) has grown as transportation agencies seek to reduce costs and limit landfill waste. Working with RAP allows for the reuse of the aggregate and its asphalt coating, reducing waste. The asphalt coating needed for HMA is largely found on the finer aggregates, resulting in a dominantly finer graded mixture, reducing its compressive strength and increasing its susceptibility to rutting. Recycled asphalt shingles (RAS) have around five times the asphalt content found on fine RAP aggregate, which can offset this issue by supplying an alternative asphalt binder, allowing for more coarse aggregate to be introduced, improving overall pavement performance and durability.

This study investigates the feasibility of incorporating RAS into high-RAP mixtures, reducing dependence on fine RAP binder. The control is a 100% RAP HMA with a baseline gradation of 60% fine aggregate and 40% coarse aggregate. A 5% RAS dosage by total mix weight was added based on manufacturer recommendations. Subsequent designs adjust the fine-to-coarse ratio while holding RAS constant to identify mixtures that meet or surpass the control’s performance. The performance was assessed through the IDEAL-CT test (ASTM D8225) for cracking tolerance and the HT-IDT test (ASTM D6931) for indirect tensile strength (ITS), benchmarked against NYSDOT thresholds of CT index ≥ 135 and ITS ≥ 35 psi.

Incorporating RAS improved the CT index by up to 6% and increased ITS as much as 15%. A mix containing 5% RAS, 35% RAP sand, and 60% RAP stone satisfied the ASTM D6931 strength requirement but didn’t consistently achieve the ASTM D8225 cracking criterion. The shortfall in the CT index values is believed to come from an underestimation of the RAS performance grade (PG), resulting in the mixture being stiffer than expected.