Recycling aged bitumen using bio-based rejuvenator tall oil: A molecular perspective on fusion, deagglomeration, and regeneration

The regeneration of asphalt pavements is essential for advancing green, circular, and sustainable transport infrastructure. A major challenge lies in the reverse design of rejuvenators tailored to the aging mechanisms of bitumen, particularly in selecting effective bio-based alternatives and understanding their molecular interactions with asphaltene aggregations. This study compares a bio-based rejuvenator, tall oil (T-type), with a conventional aromatic oil rejuvenator (A-type). Rheological tests evaluated the high- and low-temperature performance of regenerated binders, while atomic force microscopy and Fourier-transform infrared spectroscopy examined microstructural morphology and functional groups. To bridge macroscopic and microscopic observations, molecular dynamics (MD) simulations and quantum chemical analyses were conducted. Results show that T-type molecules exhibit larger dipole moments and more heterogeneous surface electrostatic potential distributions than A-type rejuvenator, leading to stronger molecular polarity. This enhances affinity with asphaltene aggregations, enabling non-bonded interactions that disrupt π–π stacking and effectively increase stacking distances. With excellent diffusion efficiency, compatibility, and deagglomeration capacity, the T-type rejuvenator demonstrates superior regeneration effectiveness and surface repair of aged bitumen compared with A-type. These findings provide mechanistic insight and methodological guidance for reverse design of bio-based rejuvenators and support their selection in sustainable asphalt recycling.