Sodium Lignosulfonate-Based Emulsifiers for Asphalt Emulsion

Emulsified asphalt is a critical component of low-temperature pavement materials and plays a pivotal role in determining the durability of asphalt mixtures. Lignosulfonate, with advantages such as facile preparation, environmental friendliness, recyclability, and energy conservation, has been used in various fields, but the insufficient emulsifying capacity limits its application as an emulsifier for asphalt. To meet the needs of emulsified asphalt as pavement materials, the modification of sodium lignosulfonate (SL) was conducted by graft copolymerization and the Mannich reaction, resulting in two kinds of emulsifiers with high performance for asphalt emulsion. The optimal conditions for both modification processes were thoroughly examined by using ductility as the key indicator. The molecular composition and structure of the products were characterized by using Fourier transform infrared spectroscopy. Additionally, the emulsification performance and surface activity of the modified SL were evaluated, and the particle size of the emulsified asphalt was determined. The emulsification performance and the surface activity of the modified SL were significantly improved compared with those of the original SL. Notably, the emulsified asphalt by the modified SL exhibited superior performance and enhanced storage stability. The ductility of the emulsified asphalts at 15°C increases from 46.3 to ~70 mm, as well as the storage stability from 4.8% to ~2% before and after the addition of the modified SL. In contrast, the emulsifier with rich amide and amine groups by graft copolymerization is superior to that by the Mannich reaction for asphalt emulsification.