Effect of RAP gradation subdivision and addition of a rejuvenator on recycled asphalt mixture engineering performance

The utilization of reclaimed asphalt pavement (RAP) is an important way for pavement construction to move toward a low impact and sustainable practice, but there are still many problems in the preparation of recycled asphalt mixtures with a high percentage of RAP. In this study, an RAP gradation subdivision method was proposed and used to divide RAP gradation into four types. Based on two kinds of RAP gradations after pretreatment and four kinds of RAP gradations after subdivision, a pretreated recycled asphalt mixture (RAM-PR) and a subdivided recycled asphalt mixture (RAM-SR) with different RAP contents were prepared. By testing Marshall design indices and high-temperature performance, it was found that the coefficients of variation in stability, flow, dynamic stability and rutting depth of RAM-SR containing 60 % RAP were 11.9 %, 68.1 %, 88.3 % and 20.7 % lower than those of RAM-PR, respectively. Combined with the research results of the long-term engineering performance of RAM-SR, the maximum tensile strain of RAM-SR containing 40 % RAP and rejuvenator after long-term aging was 9.6 % higher than that containing 35 % RAP without rejuvenator, and the rejuvenator can also improve the long-term water stability of RAM-SR. In areas with low requirements for low temperature performance, the maximum RAP content of RAM-SR in the group with the rejuvenator can reach 60 %.