Evaluation of the diffusion and distribution of the rejuvenator for hot asphalt recycling

• Different rejuvenators have much different properties and recycling effects.
• Rejuvenator with lower viscosity has better diffusivity but worse thermal stability.
• It is difficult for rejuvenator to fully diffuse into RAP asphalt.
• Nonuniform distribution of rejuvenator negatively affect recycling performances.

This study focused on the diffusion and distribution of the rejuvenator in the aged asphalt of reclaimed asphalt pavement (RAP) materials during hot recycling. Diffusion tests were designed based on the penetration test and the dynamic shearing rheometer (DSR) test to evaluate the diffusivity of the rejuvenator in aged asphalt. The phased extraction and recovery test and the asphalt mortar transfer test were designed to determine the distribution of the rejuvenator during the recycling of asphalt and the distribution of the recycled asphalt within the asphalt mixture during recycling, respectively. Performance tests, including the wheel tracking test, low-temperature bending beam test and freeze-thaw splitting test, were conducted to evaluate the influences of the rejuvenator distribution on the performances of the asphalt mixture during recycling. The viscosity, components and rejuvenator thermal stability are found to have important influences on the diffusivity and distribution of the rejuvenator in aged asphalt. During the short blending process of recycling the asphalt mixture, it is difficult for the rejuvenator to fully diffuse into the aged asphalt. Therefore, the property and distribution of the recycled asphalt tends to be nonuniform in the asphalt mixture during recycling. This nonuniformity can lead to poor high-temperature anti-rutting performance, poor low-temperature cracking resistance and poor moisture stability of the recycled asphalt mixture.