Epoxy-Modified Asphalt Binder: Effects of Mixing Procedure, Curing Behavior, and Resin Type on Rheological and Temperature-Dependent Performance

Epoxies are increasingly recognized as reactive polymers for asphalt modifiers because of their crosslinking abilities, which can improve the asphalt binder’s elasticity, durability, and resistance to permanent deformation. This study investigates the modification of a conventional asphalt binder using epoxy resin. Three epoxy dosages, two resin curing techniques, and three mixing procedures were examined. It was found that improper addition sequences or prolonged mixing promoted phase separation and incomplete polymer dispersion in the asphalt binder, especially at higher epoxy dosages. Short, high-shear mixing with the addition of curing agent first yielded the most homogeneous modified asphalt binders up to 30% epoxy content. Epoxy modification improved the high-temperature performance grade (PG) from 64 °C for the control and 10% epoxy-modified binders to 70 °C for both the 20% and 30% epoxy-modified binders. Increasing epoxy content also enhanced high-temperature rutting resistance, as demonstrated by increased G*/sinδ values, reduced non-recoverable creep compliance (Jnr), and improved elastic recovery (R) in the Multiple-Stress Creep and Recovery (MSCR) test. In contrast, LAS fatigue life decreased with increasing epoxy content, while low-temperature performance decreased for the 10% and 20% epoxy-modified binders but remained similar to the control binder at 30% epoxy content. Overall, the findings show that careful optimization of epoxy dosage, mixing strategy, and curing schedule are essential for practical field implementation.