Effect of Alkali Lignin on Adhesion and UV Aging Resistance of Recycled Asphalt Binder by Waste Engine Oil

A substantial quantity of reclaimed asphalt pavement mixture (RAP) is generated during the regeneration of asphalt binder pavement. The old asphalt binder (OAS) in RAP can be effectively reused after regeneration processing, while the utilization of waste engine oil can restore certain physical properties of OAS such as penetration and ductility. Recycled asphalt binder (RAB) by waste engine oil exhibits significant deficiencies in adhesion and antiaging properties. In this work, alkali lignin is introduced into RAB through physical blending. RAB containing 3wt% of alkali lignin (RAB-3L) improves ultraviolet (UV) aging resistance and adhesion property of RAB. Specifically, atomic force microscopy tests demonstrate that, after 12 days of UV aging, the adhesion of virgin asphalt binder decreases by approximately 47.8%, whereas the adhesion of RAB-3L only decreases by 33.7%. Fourier infrared spectroscopy reveals that, after 12 days of UV aging, the carbonyl index and sulfoxide index of RAB-3L increase by only 33.3% and 17.8%, respectively. Results from molecular dynamics simulations indicate that the adhesion works of RAB-3L with SiO2 and CaCO3 are approximately 19.47% and 23.16% higher than those of RAB, respectively. In general, alkali lignin shows promising potential for enhancing the adhesion and antiaging properties of RAB.