Perspectives on the Stability of Emulsified Asphalt Based on Interfacial Rheological Characteristics

The oil–water interfacial film formed by emulsifier molecules adsorbed around asphalt droplets affects the stability of emulsified asphalt. This study investigated the stability of emulsified asphalt by characterizing interfacial rheological characteristics using the Langmuir trough method. Initially, optimal test parameters for the interfacial dilational rheometer, suitable for emulsified asphalt systems, were established, including barrier motion parameters, asphalt solvent type, and concentration. Subsequently, interfacial film rheological characteristics were analyzed for various emulsifier types and concentrations. Finally, the correlation and mechanisms linking interfacial rheological characteristics of the oil–water interface with dynamic shear rheometer (DSR) complex viscosity and zeta potential of emulsified asphalt were examined. Results indicated optimal motion parameters of 30 cycles, an interfacial film area of 65%, and a compressed film area of 55%. Furthermore, 2.5% by weight asphalt-trichloroethylene solutions exhibited greater differences in viscoelasticity indices at varying angular frequencies. The maximum interfacial film strength was observed at emulsifier concentrations of 0.5%–1% by weight. For cetyltrimethylammonium bromide emulsifier, the correlation coefficient R2 between interfacial dilatational viscosity and complex viscosity exceeded 0.9, and that between the interfacial dilatational modulus and zeta potential was above 0.89. For the same type of cationic emulsified asphalt, a higher interfacial dilational modulus indicates reduced sensitivity of asphalt droplets to disturbances, leading to better emulsion stability. In conclusion, the oil–water interface generated by the Langmuir trough effectively simulates the film formed by emulsifier molecules around asphalt droplets within the asphalt emulsion, thereby facilitating the evaluation of emulsified asphalt stability through interfacial rheological characteristics.