Performance and low-carbon assessment of polymer modification processes for emulsified asphalt based on grey rational analysis

The preparation of emulsified asphalt is often challenged by initial aging and high energy consumption, particularly during high-temperature modification and inefficient emulsification. This study evaluates the performance and environmental impacts of emulsified asphalt modified with innovative waterborne polymers, featuring self-crosslinking properties. Four modifiers-epoxy resin, acrylate, nitrile rubber, and polyurethane-were incorporated at 3%, 6%, and 9% dosages. Adhesion tests revealed that all self-crosslinking polymers significantly improved bonding strength, with polyurethane achieving the highest increase (over 30% compared to the control). Rheological analyses explored using Multiple Stress Creep and Recovery tests showed that acrylate, epoxy resin, and polyurethane enhanced rutting resistance by increasing zero Viscosity and ηM values, while nitrile rubber had a softening effect. Fatigue resistance, assessed through dissipated energy calculations, also improved with crosslinking polymers but declined with nitrile rubber. Conversely, Glover–Rowe parameters at 180 kPa and 450 kPa indicated a moderate increase in low-temperature cracking susceptibility for crosslinking polymers, whereas nitrile rubber reduced cracking potential. Life-cycle assessment demonstrated that the use of waterborne polymers reduced total energy consumption by 16.55%-17.94% and carbon emissions by 15.64%-16.88% compared to traditional hot-mix processes. Finally, Grey Relational Analysis ranked 9% polyurethane-modified asphalt as the optimal formulation considering the high-temperature environment, balancing mechanical performance and environmental benefits. Waterborne nitrile rubber showed deteriorated high-temperature rutting resistance but excellent fatigue resistance, which were suitable for anti-cracking at low temperature. These findings confirm that self-crossilinking waterborne polymers can enhance asphalt emulsion performance while reducing lifecycle energy use and emissions.