Nanoscale damage mechanisms at the interface between polyurethane-modified asphalt mixture and adhesive in bridge expansion joints

To address interfacial stripping in seamless expansion joints, this study combines molecular dynamics (MD) simulations and nanoscale experiments to investigate the adhesion performance of two adhesives—an epoxy (E200) and a PMA-based adhesive—at the polyurethane-modified asphalt (PMA)-concrete interface. MD models with COMPASS force field and NVT ensemble compute binding energy and adhesion work; pull-off and oblique shear tests assess macroscopic properties. Results show electrostatic forces dominate interactions for both adhesives. Two nanoscale damage mechanisms emerge: E200’s strong electrostatic anchoring to concrete causes cohesive failure within PMA; the PMA adhesive, with weaker anchoring and lower interfacial energy, leads to mixed interface failure. A cross-scale structure–failure correlation is established. A Kriging model (R2=0.823) serves only for trend analysis. These findings provide theoretical and experimental support for adhesive selection in seamless joint design.