Enhancing the compatibility of cold-mixed epoxy asphalt binder via graphene oxide grafted plant oil-based materials

Cold-mixed epoxy asphalt (CEA) has attracted extensive attention in overloaded and steel bridge pavement and maintenance engineering because of its room temperature construction and low energy consumption. However, the compatibility of epoxy resin and asphalt in CEA is still a challenge, limiting its application to some extent. This study aims to enhance the compatibility of CEA with low amounts of plant oil-based compatibilizers and suggest appropriate methods for assessing the compatibility of CEA. GO-grafted epoxidized soybean oil (GOESO) and GO-grafted soybean oil (GOSO) were synthesized and used to modify CEA. The GO and ESO (or SO) solutions were prepared at concentrations of 0.5 mg/mL and 5 mg/mL, respectively. The pH of the solution was adjusted to 5∼6 before heating. The results showed that 0.2 wt% of GO-modified oil-based compatibilizers had similar effects as 30 wt% of oil-based compatibilizers and did not significantly alter the crystal and chemical structures of the CEAs. GOESO is the preferred recommended GO-modified compatibilizer because of the enhanced compatibilizing ability of the epoxy groups in ESO. The compatibilization mechanism involved the effects of the oils on the chemical structures, curing reaction rate, and microstructures of CEAs. The proportion of asphalt particles larger than 20 μm and the reaction rate had strong correlations with the mechanical properties of the cured CEAs. Molecular dynamics simulations revealed that GOSO reduced the solubility parameter (δ) and Flory-Huggins parameter (χ) difference between components A and B by 39.4% and 65.8%, respectively, while GOESO increased the δ and χ difference between components A and B by 10.4% and 15.8%, respectively.