Influence of Nanosilica Sol on the Performance and Anti-Aging Behavior of SBR-Emulsified Asphalt

Styrene–butadiene rubber (SBR)-modified emulsified asphalt is widely used in microsurfacing and other preventive maintenance treatments due to its good low-temperature performance and cost-effectiveness; however, the limited high-temperature performance of the SBR-modified system, together with the inherently thin microsurfacing overlay structure, which is more sensitive to aging, results in more pronounced performance deterioration under aging conditions. This study introduces nano-silica sol as a modifier. Nano-silica sol was incorporated at dosages of 0%, 2%, 4%, 6%, and 8% by mass of binder. The high-temperature rheological behavior of the binders before and after modification was characterized by temperature sweep tests, multiple stress creep and recovery, and zero-shear viscosity measurements. On this basis, all binders were subjected to ultraviolet (UV) accelerated aging, and the effect of nano-silica sol on the antiaging resistance of SBR-emulsified asphalt was evaluated using linear amplitude sweep, Fourier transform infrared (FT-IR) spectroscopy, and fluorescence microscopy (FM). The results indicate that the incorporation of nano-silica sol increases the complex shear modulus of SBR-emulsified asphalt and reduces its temperature susceptibility and significantly improves the elastic recovery performance of the asphalt binder. In addition, nano-silica sol markedly enhances the complex viscosity of the binder, leading to improved resistance to flow deformation at high temperatures. FT-IR and FM results indicate that, compared with the UV-aged unmodified binder, the binder modified with 4% nano-silica sol shows a 17.4% decrease in the carbonyl index and a 36.7% increase in the fluorescence area fraction of the SBR phase, suggesting that nano-silica sol effectively retards the aging-induced degradation of the SBR polymer.