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.

中文翻译：

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再生沥青路面结块对热再生沥青路面性能的影响分析：扩散熔融视角

再生沥青路面（RAP）的团聚影响热再生沥青混合料（HAM）的低温性能和水稳定性。为了解决这个问题，采用了一种名为聚丙烯酰胺（PAM）的表面活性再生剂。采用宏观实验、分子动力学模拟、傅立叶变换红外光谱 (FTIR) 和扫描电子显微镜 (SEM)。结果表明，随着 RAP 团聚率的增加，HAM 的水稳定性先下降，然后略有上升。值得注意的是，当粗粒RAP团聚率为60%时，混合物的水稳定性最差，并伴随着低温稳定性下降。利用菲克的扩散原理，结合分子动力学模拟、FTIR 和 SEM 分析，观察到 PAM 有效地扩散并与老化沥青融合。这导致新旧沥青的扩散系数增强，从而减轻对老化沥青的老化影响。此外，再生剂促进了新旧沥青之间的扩散和融合过程，从而提高了HAM性能，减少了粗粒RAP团聚对热再生混合物路用性能的不利影响。