The significant accumulation of reclaimed asphalt pavement (RAP) represents critical resource waste. Preparing recycled permeable asphalt concrete (RPAC) is a novel direction to dissipate RAP. The movement of RAP and fresh aggregates during mixing is known as migration. This study focuses on the blending behavior of RPAC, which includes aggregate migration and binder diffusion. First, a novel method was developed involving luminescent aggregates (LA) for tracking aggregate migration, and fluorescent microscopy for observing binder diffusion. Subsequently, digital image processing technology was utilized to capture the blending behavior of RPAC, and indices were proposed to analyze the influence of mixing conditions and material content on the degree of blending. Finally, principal component analysis (PCA) was used to reveal the blending states of RPAC. The results show that LA effectively characterizes aggregate migration within the mixture when used as fresh aggregates. Areas of agglomeration were caused by RAP clumping, which was the reason for the inhomogeneity in RPAC. Aggregate migration occurs primarily in the size range of 0–1.18 mm. As the mixing time and RAP preheating temperature increased, the degree of aggregate migration did not exceed 50 %, and the degree of binder diffusion reached 90 %. PCA reveals that the binder diffusion and the migration degree of 0∼1.18 mm aggregates were critical indices contributing to 89.1 % of the blending behavior. This study proposes a novel method to observe and track the blending behavior, and the technique offers a theoretical foundation for improving RPAC's construction and performance.
