Microscopic insights into the rejuvenator-induced depolymerization of asphaltene aggregates in aged asphalt

Asphaltene aggregates depolymerization is a critical factor in aged asphalt rejuvenation, yet the impact of major rejuvenator components remains unclear due to asphaltenes’ complex structure. Unlike previous simulation-based investigations, this study employs various characterization techniques to reveal asphaltene aggregate behaver during oxidative aging and the microscopic depolymerization mechanism and structure-activity relationships of 10 representative bio-based and petroleum-based rejuvenator compounds. The results revealed that oxidative aging increased the stacking density and order of aromatic layers within asphaltene aggregates and promoted O-H···O hydrogen bond formation. Additionally, oxidation reduced the critical micelle concentration of asphaltenes and caused fluorescence quenching, resulting in the development of dendritic three-dimensional aggregates with equidistant, layered, and porous structures. However, the introduction of rejuvenators disrupted the stacking of aromatic layers but had minimal impact on the arrangement of aliphatic chains. Rejuvenators containing heteroatoms further promoted depolymerization by forming hydrogen bonds with asphaltene molecules, reducing the aggregate size and producing more dispersed and irregular structures. The bio-rejuvenators with heteroatom functional groups exhibited superior depolymerization efficiency. This study provides mechanistic insights into rejuvenator-induced asphaltene depolymerization and establishing a foundational reference for the molecular design of efficient rejuvenators in recycled asphalt applications.