Unraveling oxidative aging behavior of asphaltenes using ab initio molecular dynamics and static density functional theory

Abstract

Asphalt aging is a major cause of cracking failure in asphalt pavement. However, owing to the lack of understanding of the asphalt aging mechanism, research on asphalt-targeted antiaging technology has encountered challenges. To address this issue, ab initio molecular dynamics simulations and density functional theory calculations based on the quantum chemistry framework were conducted to explore the reaction pathway and thermodynamic driving force of asphaltene aging. The physical properties of asphaltenes were evaluated to determine the effect of aging on asphaltene performance. The results indicate that asphaltenes undergo aging subreactions at different temperatures, including aromatization of naphthenes, formation of oxygen-containing groups, and homolysis of alkyl side chains. The free energy barriers of these reactions can be ranked in ascending order as aromatization < oxygen-containing group formation < homolysis. The molecular polarity, intermolecular binding energy, and solubility parameter of the asphaltene molecule increased significantly with aging, leading to enhanced agglomeration and reduced compatibility of asphalt components, resulting in the deterioration of asphalt cracking resistance.