Preparation and rheological properties of bio-based toughened epoxy asphalt

To address the high brittleness, poor compatibility, and high cost of epoxy asphalt for bridge deck paving, this study developed a bio-based toughened epoxy asphalt using epoxidised soybean oil (ESO). The optimal formulation was determined through Brookfield viscosity and tensile tests, while compatibility, rheological behavior, and mechanical performance were evaluated using fluorescence microscopy, dynamic shear rheometer (DSR), bending beam rheometer (BBR), and multiple stress creep recovery (MSCR) tests. The optimal epoxy-to-asphalt mass ratio was 40:60, with E-51 epoxy resin, H-113 curing agent, ESO, diluent (501), and BDMA catalyst at a ratio of 20:10:1:2:1. ESO markedly improved low-temperature cracking resistance: at −18 °C, the stiffness modulus decreased by 51.08% and the creep rate increased by 32.8% compared with conventional epoxy asphalt. Despite a slight reduction in high-temperature stiffness, the ESO-modified epoxy asphalt maintained a higher complex shear modulus than commercial 812 epoxy asphalt and exhibited the highest creep recovery rate and lowest non-recoverable creep compliance. These results demonstrate an improved balance between low- and high-temperature performance and provide a systematic formulation strategy for bio-based epoxy asphalt.