The rejuvenation effects of activated rubber pellets on reclaimed asphalt pavement during blending process

Activated rubber pellets (ARP), as an innovative semi-wet process rubberized asphalt technology, can be mixed into asphalt mixture using dry process and achieve performance comparable to the wet process. This merit makes it more convenient for application in the recycling of reclaimed asphalt pavement (RAP). However, an underlying issue is that whether the soft bitumen within the ARP can diffuse out during the blending process and affect the fusion between aged and new asphalt. The study aims to investigate the potential rejuvenation effects of ARP on RAP during the blending process. A special diffusion test was developed using cylindrical rubber specimens cut from actual tires, which were first activated by soft bitumen, then the activated rubber specimens were immersed into bitumen of different aging levels at different temperatures to measure the mass change and calculate the diffusion coefficients. To reveal the inside-out diffusion of the soft bitumen within the swollen rubber specimen and its impact on the composition of aged bitumen, the Fourier transform infrared spectroscopy (FTIR) analysis and gel permeation chromatography (GPC) tests were conducted. In addition, the blending efficiency and cracking resistance of RAP-included mixtures when rejuvenated by ARP were evaluated by the mobilization index and cracking index. The results indicate that the soft bitumen within ARP could diffuse out when being mixed with RAP, which temporarily decreased the large molecule proportions in the aged bitumen and improved the blending efficiency and cracking resistance of RAP.