Influence of recycling agent on binders of varying ages and effects on subsequent aging

Understanding the influence of recycling agents (RA) on different aged binders and their impact on subsequent aging mechanisms is vital for the effective recycling of aged binders and identifying threshold RA dosages. The present study aims to investigate the interaction effects of RA through an integrated framework by analysing chemical characteristics using Saturates, Aromatics, and Resins with Asphaltene determinator (SAR-AD) method and Fourier Transform Infrared (FTIR) spectroscopy, while corroborating these findings through microstructural changes captured using Atomic Force Microscopy (AFM). Recycled blends prepared with binders aged to three extents and varying RA dosages were tested in unaged and long-term aged conditions. Results indicate that RA increases lighter hydrocarbons, balances asphaltene-maltene polarity, and promotes non-covalent interactions, with the quantum of influences reducing as RA dosage and RAP binder age increase. These mechanisms contribute to softening and dispersion effects, with the dispersion persisting with subsequent aging, indicating that RA alters the aromatisation process. The findings reveal that beyond a threshold RA dosage, its primary effect is softening the binder, while its impact on functional groups and dispersion becomes marginal.