Microanalysis of silane coupling agent graft-activated waste crumb rubber and its interfacial interaction with asphalt-aggregate in the dry process

• The microstructure of graft activated waste crumb rubber was characterized. • The interface model of aggregate-waste crumb rubber-asphalt in dry process of molecular simulation was established. • The interaction between graft activated waste crumb rubber and asphalt in dry process was evaluated. The weak interaction capability between waste crumb rubber and asphalt binder in rubber asphalt mixtures produced by the dry process poses challenges in practical applications. To enhance the interaction between waste crumb rubber and asphalt binder in the dry process and fill the research gap in revealing their interaction mechanisms at the molecular simulation scale, waste crumb rubber was pretreated with silane coupling agent graft activation in the laboratory, and its activation effect and mechanism were investigated. Subsequently, the interfacial interaction between graft activated waste crumb rubber and asphalt binder in the dry process was explored from the perspective of molecular simulation. The research findings are as follows: After graft activation treatment with silane coupling agent, the water contact angle of waste crumb rubber increased, and its surface morphology became fluffy and uneven. There were significant changes in the functional group contents of C–H bonds and O–H bonds, indicating that the silane coupling agent was successfully grafted onto the surface of waste crumb rubber, thereby enhancing its interfacial interaction with the asphalt binder. Molecular simulation results revealed that the graft activated waste crumb rubber exhibited the highest diffusion coefficient and mean square displacement in the asphalt-aggregate system, with a lower peak relative concentration compared to non-activated waste crumb rubber. The dehydration condensation reaction occurs between the hydroxyl group at one end of the silane coupling agent hydrolysate product molecule and the hydroxyl group on the surface of the crumb rubber, while the 3-aminopropyl group at the other end produces a strong physical adsorption effect with the asphalt, thereby effectively enhancing their mutual interaction. This study aims to provide scientific guidance on the interfacial interaction characteristics between graft activated waste crumb rubber and asphalt binder in the dry process.