Influence of cyclodextrin structure on the thermo-oxidative aging resistance of asphalt binder

Thermo-oxidative aging of asphalt is a key challenge facing modern road surfacing technology. The aim of this study is to evaluate zeolite–cyclodextrin hybrid fillers as functional asphalt modifiers, with a focus on their ability to mitigate short- and long-term oxidative aging. Fly ash–derived NaP1 zeolite was functionalized with α-, β-, or γ-cyclodextrin and subsequently loaded with water–waste engine oil (WEO) mixtures at water-to-oil ratios ranging from 1:1 to 1:4. The hybrids were characterized using BET surface area analysis, XRF, FTIR, and CHN. Asphalt binders were modified with 5 wt% of the hybrids and subjected to TFOT and TFOT + PAV aging. Mechanical and physicochemical changes were assessed using penetration, softening point, viscosity measurements, FTIR, 1 H NMR, TLC–FID, and AFM. The hybrid fillers reduced aging indices (SPI and VAI) by up to 28% compared to the reference binder. FTIR and 1 H NMR confirmed suppressed formation of oxidation-related functional groups (C=O, S=O), while AFM revealed refined surface morphology and reduced roughness. The NaP1–αCD systems exhibited the most pronounced anti-aging performance; while the 1:4 water-to-oil ratio achieved the lowest SPI value after long-term aging, the 1:1 and 1:2 formulations provided the most balanced stabilization of the binder’s physicochemical and nanomechanical properties.