Mechanism of VOCs Release from Asphalt Materials Based on Molecular Simulation

Abstract Volatile organic compound (VOC) emissions from bituminous materials pose environmental and health risks during application. In this study, molecular dynamics and quantum chemical simulations were integrated to construct a four‐component average molecular structure model of asphalt. VOC release models of SARA fractions were developed. The release pathways of VOCs from the SARA model under pyrolysis were simulated and predicted. The effects of heating temperature and SARA components on VOC emissions were further examined by pyrolysis–GC/MS (Py–GC/MS), and simulation results were validated with controlled pyrolysis experiments. Simulations indicated that the carbon skeletons in saturates and aromatics are mainly C─C bonds, whereas resins and asphaltenes contain aromatic ring structures with uniformly distributed electron density. Asphaltenes, with more aromatic rings and the lowest frontier orbital energy levels, were the most stable, while saturates, with the highest frontier orbital energy levels, volatilized most readily. Pyrolysis experiments showed that alkanes were the predominant VOCs in asphalt, largely originating from saturates, which exhibited the highest unit VOC release. Asphaltenes emitted the least VOCs, mainly polycyclic aromatic hydrocarbons (PAHs), while aromatics and resins were also major PAH sources. The pyrolysis results agreed well with model predictions, elucidating the release mechanisms of asphalt VOCs.