Quantum chemical insights into molecular interactions within asphalt systems

Molecular aggregation significantly impacts the stability, rheology, and durability of asphalt binders. While previous research has mainly focused on asphaltenes, the quantum-scale mechanisms of aggregation for all asphalt components remain unclear. This study uses quantum chemical calculations on 50 asphalt molecules to analyze surface electrostatic potential, π-electron properties, LOLIPOP index, and weak interaction energies to identify favorable aggregation configurations. The findings reveal that π-π interactions drive asphaltene aggregation, resins act as modifiers, aromatics enhance solubility and dispersibility, and saturated hydrocarbons create steric hindrance. Additionally, the length of polycyclic aromatic hydrocarbons and alkyl chains play a critical role in determining intermolecular distance and polarity. SARA fractionation and^1H NMR analysis of four binders show that TH asphalt, rich in π-electron-dense components with long side chains, stabilizes the microstructure, resulting in optimal rheological properties. AFM imaging reveals a honeycomb structure primarily formed by asphaltene-driven aggregation. In summary, this computational-experimental framework elucidates the molecular origins of asphalt aggregation and the distinct roles of SARA components, establishes a clear composition-performance relationship, and provides mechanistic guidance for designing durable asphalt.