Upcycled waste for sustainable roads: Exploring the synergistic effects of off-spec fly ashes and rejuvenators on asphalt binder aging

This study examines the effects of four distinct off-specification fly ashes (OFA) and three rejuvenators on the properties of unmodified asphalt (UMA) and polymer-modified asphalt (PMA). One of the rejuvenators is a novel formulation derived from upcycled food waste (FWBO). It was hypothesized that incorporating OFA into the binders could act as a potential aging-retardant additive for asphalt binders rather than merely as part of the aggregate fines. The binders and blends were subjected to two aging cycles in a Pressure Aging Vessel (PAV). Following the first aging cycle, rejuvenation treatments were applied using two commercially available rejuvenators and the novel FWBO rejuvenator. Considering the benefits previously reported for using certain classes of fly ash with asphalt and promoting high-quality utilization of post-service reclaimed asphalt binders, this study aimed to 1) evaluate the synergetic influence of the fly ash and rejuvenator combination on asphalt binder aging, and 2) introduce the new FWBO as a promising rejuvenator for asphalt binders. The aging-related chemical changes were assessed using Fourier transform infrared spectroscopy (FTIR). The loss of ductility in the binders was measured using ΔT_c as an indicator of the effect of aging on binder durability. The Glover-Rowe (G-R) Parameter and the Cross-over Modulus and Frequency (G_c*, ω_c) were employed to evaluate the aging state of rejuvenated binders. The results showed that some fly ash additives were associated with either a reduction or maintenance of the oxidation level as that of the neat binder, indicating a slower aging rate for these fly ash blends compared to the binder alone for both cycles of PAV aging. The use of rejuvenators further improved the aging resistance of the UMA with fly ash blends, suggesting high potential synergy for some sources of fly ash. Furthermore, our research demonstrated that FWBO merits utilization as an environmentally sustainable rejuvenator for asphalt pavements, with effectiveness comparable to the two commercially accessible rejuvenators evaluated. Combining OFA and FWBO presents an opportunity to establish circularity within the paving industry. Our research is a clear example of circulating waste within this industry through upcycling.