Interfacial modulation behaviour of bio-rejuvenator in aged asphalt based on surface wetting characteristics and diffusion spatiotemporal variation

This study aims to systematically investigate the interfacial rejuvenation mechanism between rejuvenators and aged asphalt through two refined processes of surface wetting and diffusion spatiotemporal variation. The dynamic contact angles and surface tension of the rejuvenators on the aged asphalt surface were quantitatively measured to characterise the wetting behaviour. The spatiotemporal evolution of rejuvenator diffusion into aged asphalt was thoroughly elaborated based on the established diffusion equation. These results indicate that the molecular structure can be a primary factor to be considered in affecting the surface tension of the rejuvenator, and that the wetting process of the rejuvenator derived from liquefaction products can spontaneously occur. Inter-diffusion occurs at the interface, which is attributed to density differences between aged asphalt and the rejuvenator. The addition of ester components can cause a significant increase in the diffusion coefficient. The effect of temperature on the diffusion coefficient is directly related to the state transformation of aged asphalt, whereas the diffusion time has a limited effect. The wetting speed and diffusion indices show a strong correlation. The established spatiotemporal evolution equation can describe the diffusion behaviour of rejuvenators into aged asphalt.