Interfacial synergistic effects of lignin-titanium dioxide composites in emulsified asphalt and their anti-aging performance.

Conventional surfactant-stabilized emulsified asphalt can achieve rapid emulsification by reducing oil-water interfacial tension. However, the interfacial film formed by surfactants has limited mechanical strength, making the emulsion prone to coalescence and demulsification during storage and transportation. In addition, surfactants mainly function during the emulsification stage and provide limited protection against thermo-oxidative and ultraviolet(UV) aging of the evaporative residue after emulsion breaking. In this study, lignin-TiO2 composite particles (LTiO2) were prepared by a hydrothermal method and combined with cetyltrimethylammonium bromide (CTAB) to construct a cationic emulsified asphalt system based on surfactant-particle synergy. LTiO2 significantly improved the storage stability of emulsified asphalt, reduced the average droplet size, and maintained a high zeta potential. Cryo-scanning electron microscopy(Cryo-SEM) results showed that LTiO2 promoted close droplet packing and a honeycomb-like network structure, thereby enhancing resistance to coalescence and demulsification. After short-term aging and UV aging, LTiO2 weakened the rheological hardening of the evaporative residue and reduced the growth of carbonyl and sulfoxide indices. Atomic force microscopy(AFM) further showed that LTiO2 inhibited aging-induced bee-like structure evolution and polar component aggregation. These results indicate that CTAB enables rapid interfacial tension reduction and droplet formation, while LTiO2 strengthens the oil-water interfacial film and improves the thermo-oxidative and UV aging resistance of the evaporative residue after demulsification. This study provides a new strategy for stable and green multifunctional emulsified asphalt.