Using thermodynamic parameters to study self-healing and interface properties of crumb rubber modified asphalt based on molecular dynamics simulation

The thermodynamic property of asphalt binder is changed by the addition of crumb rubber, which in turn influences the self-healing property as well as the cohesion and adhesion within the asphalt-aggregate system. This study investigated the self-healing and interface properties of crumb rubber modified asphalt (CRMA) using thermodynamic parameters based on the molecular simulation approach. The molecular models of CRMA were built with representative structures of the virgin asphalt and the crumb rubber. The aggregate was represented by SiO2 and Al2O3 crystals. The self-healing capability was evaluated with the thermodynamic parameter wetting time, work of cohesion and diffusivity. The interface properties were evaluated by characterizing the adhesion capability, the debonding potential and the moisture susceptibility of the asphalt-aggregate interface. The self-healing capability of CRMA is found to decrease as the rubber content increases. The asphalt-Al2O3 interface with higher rubber content has stronger adhesion and moisture stability. But the influence of crumb rubber on the interfacial properties of asphalt-SiO2 interface has no statistical significance. Comparing with the interfacial properties of the asphalt-SiO2 interface, the asphalt-Al2O3 interface is found to have a stronger adhesion but a worse moisture susceptibility for its enormous thermodynamic potential for water to displace the asphalt binder.