Polyurethane-Modified Epoxy Crack Sealant for Climate-Specific Asphalt Pavement Repair

Polyurethane-modified epoxy crack sealants can combine the cohesive strength of epoxy networks with the flexibility required for asphalt pavement crack repair. However, their selection under different winter pavement-temperature conditions requires an integrated evaluation of workability, low-temperature transition, dimensional stability, aging resistance, and interfacial adhesion. In this study, six ambient-curing polyurethane-modified epoxy crack sealants (EUPC) were prepared and assessed under representative winter pavement-temperature conditions, with SBS-modified asphalt used as a reference. All EUPC formulations satisfied the 30 min construction-window requirement, showed Tg values below 0 °C, T5% values above 300 °C, and curing volume shrinkage no higher than 3.0%. After moisture–oxygen–ultraviolet coupled aging, the formulations retained a substantial proportion of both tensile strength and elongation, with EUPC-3/EUPC-4 showing a relatively balanced strength–ductility response. Compared with SBS-modified asphalt, the climate-matched EUPC formulations provided higher direct tensile adhesion, oblique shear adhesion, and flexural–tensile repair recovery. Overall, EUPC-1/EUPC-2, EUPC-3/EUPC-4, and EUPC-5/EUPC-6 are more suitable for mild, cold, and severe low-temperature winter conditions, respectively.