2022 journal article
Molecular-based asphalt oxidation reaction mechanism and aging resistance optimization strategies based on quantum chemistry
MATERIALS & DESIGN, 223.
• The molecule with sulfur and cata-condensed polycyclic aromatic hydrocarbons (PAHs) has strong oxidation reactivity. • The oxidation rate of Ⅰ molecules is limited by hydrogen and hydroxyl radicals, Ⅱ molecules is limited by oxygen radicals. • The molecular models of aged asphalt are established considering the short- and long-term aging. Understanding the oxidation reaction mechanism of asphalt is critical to improving its aging resistance. Here, quantum chemistry (QC) was used to study the oxidation reaction mechanism of 12 typical asphalt molecules. On this basis, the molecular models of aged asphalt were established, and the aging resistance optimization strategies of asphalt were proposed. The results show that the oxidation sites for oxygen-containing or heteroatoms-free molecules are on aromatic carbons ( I molecules). Reducing hydrogen and hydroxyl radicals can improve its aging resistance. The oxidation sites for sulfur- or nitrogen-containing molecules are on heteroatoms ( I I molecules). Reducing oxygen free radicals content can improve its aging resistance. The molecules containing sulfur and cata-condensed polycyclic aromatic hydrocarbons (PAHs) (such as R5) have the strongest oxidation reactivity. Reducing its content can improve asphalt aging resistance. Combining the QC and experiment results, LH90 contains more I molecules, while UP70 and MM70 contain more I I molecules (especially As3 and R5). The aging resistance of UP70 and MM70 is poor than LH90. Reducing the content of As3 or R5 molecules or the content of oxygen radicals can improve the aging resistance of UP70 and MM70. These findings lay a foundation for designing and preparing asphalt with excellent aging resistance.