Property improvement of epoxy emulsified asphalt modified by waterborne polyurethane in consideration of environmental benefits

Waterborne epoxy modified emulsified asphalt (EMEA) has the shortcomings of insufficient toughness and poor aging resistance, which limits its application of low-carbon cold-paving technology in plateau zones. To obtain a cold-mix asphalt binder with excellent performance, waterborne polyurethane (WPU) was utilized to modify EMEA in this work. Properties, modification mechanism, action process, environmental benefits, and cost-benefit of composite-modified emulsified asphalt (CMEA) were analyzed. Results show that CMEA had good rutting resistance, low-temperature rheological, tensile toughness, adhesion with aggregate and moisture damage resistance, and aging resistance properties. These were closely related in that WPU was cross-linked with the waterborne epoxy resin (WER) to form an interpenetrating polymer network (IPN) structure, when the space network structure of WER and the soft and hard segments of WPU worked together. Based on the above results, it was recommended that EA containing 4.0 wt% WER was modified by 7.5 wt% WPU to achieve the best pavement properties. Furthermore, it was discovered that a physical process by which WER and WPU modified EA, served as a skeleton connection and toughening agent. CMEA has excellent performance and is especially suitable for use in low-temperature and strong aging areas, while can bring good environmental benefits.