Towards Sustainable Utilization of Rejuvenated Bitumen: A Review with Emphasis on Secondary Aging, Aging Resistance, and Multiple Rejuvenation.

To further advance the recycling of pavement waste, the secondary-aging and multiple-rejuvenation processes of bitumen are first systematically reviewed. Beginning with primary-aging mechanisms, rejuvenator classification and physicochemical properties are summarized to aid elucidation of primary rejuvenation. Secondary-aging evolution of technical and physicochemical properties of rejuvenated bitumen (RB) is critically analyzed. The aging resistance of virgin bitumen and RB is quantitatively compared via extensive literature data. The background and progress of multiple rejuvenation cycles are also outlined. The existing literature shows that identical aging modes can induce distinct component variations, while degradation patterns remain consistent across modes. Among petroleum-based rejuvenators, those with aromatic content exceeding 60% are widely used, and the polar carboxyl groups of tall oil account for their high efficacy. RB aging resistance strongly correlates with both rejuvenator type and dosage. Most RB outperforms virgin bitumen in aging resistance, and post-aging variation amplitudes of softening point and high-temperature failure temperature are approximately 20% for both, while those of penetration and viscosity range from 60% to 120%. Multiple aging-rejuvenation trends resemble those of primary cycles, with progressive macro- and micro-property deterioration as cycles increase. Future work includes developing high-performance bitumen from aged feedstock, establishing molecular screening systems for fatty acid bio-oil rejuvenators, and advancing multiple rejuvenation via molecular dynamics.