Large-scale use of reclaimed asphalt pavement (RAP) is limited by strong gradation variability, uneven recovery of aged asphalt (AA), and an incomplete understanding of the rejuvenation mechanism. This study combines source evaluation, composite rejuvenation, and multi-scale analysis to improve AA recovery. A gradation variability model was developed using the t-distribution, and a reliability-based method was proposed for reclaimed material selection and mix design. Rejuvenator 1 (R1) was identified as the best option, and a ternary composite rejuvenation system was formed using R1, SBS-modified asphalt, and base asphalt (BA). AA performance was assessed using physical and rheological tests, supported by Fourier-transform infrared spectroscopy, fluorescence microscopy, and gel permeation chromatography. The t-distribution guarantee rate method quantified RAP gradation fluctuations effectively. At a 90% guarantee rate, the deviation in key sieve pass rates was below 3%, indicating stable sources. In the composite system, 10% R1 restored AA high temperature performance, while adding 30% SBS modified asphalt and BA improved low-temperature crack resistance. The micro analyses showed no new functional groups after rejuvenation. Recovery was mainly driven by physical blending, dilution, and optimisation of the molecular-weight distribution.
Li et al. (Sun,) studied this question.