Analysis of the impact of reclaimed asphalt pavement agglomeration on the performance of hot-recycled asphalt pavement: A perspective on diffusion-fusion

The agglomeration of reclaimed asphalt pavements (RAP) affects the low-temperature performance and water stability of hot-recycled asphalt mixtures (HAM). To address this problem, a surface-active regeneration agent which named polyacrylamide (PAM) was employed. The effects of the coarse-grained RAP agglomeration rate, the alterations in the aged asphalt before and after the addition of PAM, and the degree of diffusion and fusion between old and new asphalt on HAM performance were investigated using macroscopic experiments, molecular dynamics simulations, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The findings revealed that the water stability of HAM first decreased and then slightly increased as the RAP agglomeration rate increased. Notably, at a 60% coarse-grained RAP agglomeration rate, the water stability of the mixture was at its poorest, accompanied by a declining low-temperature stability. Utilizing Fick's diffusion principle, in conjunction with molecular dynamics simulations, FTIR, and SEM analyses, it was observed that PAM effectively diffused and fused with the aged asphalt. This resulted in enhanced diffusion coefficients for both old and new asphalt, consequently mitigating aging effects on the aged asphalt. Furthermore, the regeneration agent facilitated the diffusion and fusion process between old and new asphalt, thereby improving HAM performance and reducing the adverse impact of coarse-grained RAP agglomeration on the road performance of thermally recycled mixtures.