Rheological and chemical characterisation of repeatedly recycled reclaimed asphalt binders using bio-based rejuvenating agents

Recycling first-generation reclaimed asphalt pavement materials (RAPM) has emerged as a sustainable solution to address the environmental and economic challenges of maintaining and reconstructing aged asphalt pavements. To support a circular economy and promote sustainable pavement construction, the feasibility of multiple recycling cycles must be explored. This study investigates the potential for repeated recycling of RAPM at a 100% recycling rate using bio-based rejuvenating agents (RAs). Physical, rheological, and performance properties, including softening point, frequency sweep (FS), Glover-Rowe (G-R) parameter, Multiple Stress Creep and Recovery (MSCR), and Linear Amplitude Sweep (LAS), together with Fourier Transform Infrared Spectroscopy (FTIR) analysis, were used to evaluate performance and oxidative aging of binders. Results show that while RAs mitigate aging effects, complete restoration, particularly in high-temperature performance and viscoelastic behaviour, remains challenging in the second recycling cycle. The rejuvenated binders showed reduced sensitivity to re-aging and re-rejuvenation. Fatigue resistance improved across multiple cycles. The G-R analysis revealed that rejuvenated asphalt blends were less prone to block cracking. However, FTIR analysis may not reliably quantify aging in repeated recycling scenarios. Overall, the findings demonstrate that RAPM can be successfully recycled once at a 100% recycling rate, whereas additional recycling cycles significantly compromise binder performance.