Matrix-specific anti-aging response of functionalized graphene-modified asphalt binders under thermal-oxidative and ultraviolet aging: Multiscale structural and chemical evidence

Functionalized graphene has shown potential for improving asphalt aging resistance, but whether its effective dosage can be transferred between neat and polymer-modified binders remains unclear. This study compared the same polyvinylpyrrolidone-functionalized graphene (PGR) in neat asphalt and 4.0 wt% SBS modified asphalt subjected to rolling thin-film oven aging followed by ultraviolet exposure for up to 288 h. Conventional properties were used for dosage screening, while atomic force microscopy (AFM), saturates-aromatics-resins-asphaltenes (SARA) fractionation, gel permeation chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR) were applied to representative binders to examine the accompanying structural and chemical changes. The effective PGR dosage differed markedly between the two formulations. For neat asphalt, 1.0 wt% PGR reduced the viscosity aging index after the most severe sequential aging from 149.0% to 60.5% and substantially improved ductility retention. In the SBS modified asphalt system, 0.3–0.5 wt% PGR produced the most favorable response, with 0.3 wt% providing the better overall balance between aging resistance and dosage efficiency. At this dosage, the viscosity aging index decreased from 108.1% to 47.7%, while the carbonyl-index increase and SBS-related CC loss were reduced from 123% to 69% and from 60.6% to 26.5%, respectively. The multiscale results indicate that PGR was associated mainly with moderated colloidal and molecular size redistribution in neat asphalt, whereas its effect in the SBS-containing binder additionally involved better retention of local adhesion and SBS-related unsaturation. The findings provide measurement-based evidence for matrix-specific anti-aging response.