Comparative analysis of cold-mixed epoxy asphalt models for molecular dynamics simulation: structural, curing and mechanical properties

Cold-mixed epoxy asphalt (CEA) is a superior pavement material that can be constructed and cured at room temperature, attracting increasing attention. However, the lack of research on CEA molecular model selection, structure, and energy evolution during curing has limited the accuracy of CEA performance research. To address this, three kinds of CEA molecular models were established: the Mixing model, the epoxy resin (ER)-asphalt interface (RA) model, and the ER-asphalt-ER interface (RAR) model. Their accuracy in describing the basic properties, structure, energy evolution, and mechanical properties of CEA was investigated and compared with experimental results. The RAR model was found to be the closest to the real structure. The curing process did not change the phase structure of CEA significantly, which maintained a "sea-island" structure with new hydrogen bonds forming between the ER and asphalt molecules. The crosslinking of ER consumed polar epoxy groups in CEA, resulting in a decrease of valence bond energy by up to 29.1% and an increase of van der Waals energy by up to 104.3% for the RAR model. The curing network also restricted the molecular chain movement and fixed the intermolecular distance and orientation. It was suggested that uniaxial tension simulation should be performed at 3 × 10^–5/fs under the NPT ensemble when not studying yield behavior. The main fracture mechanisms of CEA were crack deflection, pinning, debonding, and asphalt particle pull-out. Many short-range rigid segments in CEA also explained its high strength.