Effect of Phenyl Functional Groups on the Stability of Dodecyl Sulfonate Emulsified Asphalt

Emulsified asphalt is widely acknowledged as an environmentally friendly technology that contributes to the advancement of sustainable development in road engineering by conserving resources and reducing hazardous fumes during paving. However, the stability of emulsified asphalt is crucial to its performance, especially after long-term storage or transport, which is significantly affected by the structure of the emulsifier. In this study, three dodecyl sulfonate emulsifiers [i.e., sodium dodecyl sulfonate (SDSN), sodium dodecylbenzene sulfonate (SDBS), and sodium dodecyl diphenyl ether disulfonate (SLDED)] with zero, one, and two phenyl functional groups in their lipophilic group were utilized to explore the effects of phenyl functional groups and emulsifier concentrations on the stability of dodecyl sulfonate emulsified asphalt using a storage stability test and particle size distribution test. Moreover, molecular simulation was employed to explore the underlying mechanism of the phenyl functional groups on the stability of emulsified asphalt. The results demonstrated that the incorporation of the phenyl functional group performed a negative effect on the adsorption of emulsifiers at the water–asphalt interface at low dosages of 3% and 5% by weight. Due to the steric hindrance of the phenyl functional group and the overlap of SLDED's lipophilic and hydrophilic groups, SDBS and SLDED exhibited a stronger electrostatic potential than that of SDSN. SDBS emulsified asphalt displayed greater stability compared with SDSN emulsified asphalt, but SLDED emulsified asphalt conducted worse stability than both SDBS and SDSN emulsified asphalts because of its pronounced electrostatic potential distribution and intricate molecular structure. Therefore, it is recommended for suitable incorporation of phenyl functional groups in the emulsifiers to enhance the formation of a stable monolayer film at the water–asphalt interface.