Lignin-based aqueous epoxy emulsified asphalt: Preparation, performance characterization, and sustainable applications

Under the macro-background of the global carbon neutrality strategy driving the transition of transportation infrastructure construction materials toward “bio-based green production,” the frequent occurrence of distresses such as potholes during pavement maintenance poses extreme challenges to the overall performance of repair materials. In this context, the use of aqueous epoxy emulsified asphalt is regarded as an effective maintenance solution. However, its large-scale application still faces practical challenges, particularly regarding the carbon footprint associated with petroleum dependence and the fluctuating economic costs of synthetic raw materials. As a renewable resource with abundant reserves and excellent affinity with asphalt, lignin provides a strategic opportunity to break this deadlock. This study developed a “green preparation method for lignin-based aqueous epoxy emulsified asphalt.” Lignin-based aqueous epoxy resin was synthesized through simple chemical grafting of lignin with glycerol triglycidyl ether (GTE). Furthermore, the thermodynamic spontaneity and chemical bonding process of the grafting reaction were demonstrated at the molecular level using electrostatic potential (ESP) calculations and FTIR spectroscopy. Performance evaluations indicate that the construction of a three-dimensional cross-linking network within the system, when the lignin-based aqueous epoxy content reaches 12 wt%, is the physical essence behind the enhancement of macro-performance. Moreover, rheological and interfacial thermodynamic analyses confirmed that this network significantly reinforces the high-temperature rheological properties and adhesion performance of the system. At the mixture level, performance tests including high-temperature rutting, low-temperature bending, and moisture stability confirmed that the proposed material maintains robust high-temperature stability while balancing low-temperature crack resistance and resistance to hydrothermal damage. Furthermore, a simplified life cycle assessment (LCA) indicates that the incorporation of lignin-based aqueous epoxy provides a potential reduction of approximately 10% in global warming potential compared to conventional bisphenol A-based systems. This research not only achieves the transformation of industrial byproducts into green pavement toughening agents but also provides a scientific basis and technical pathway for the development of high-performance, cost-effective, and eco-friendly road maintenance materials.