Pyrolysis kinetics and pyrolysis-generated VOC emissions characteristics of thermally aged asphalt

Styrene butadiene styrene (SBS) is widely used to enhance asphalt pavement performance. When road fires occur, asphalt quickly undergoes pyrolysis, releasing toxic volatile organic compounds (VOCs) that threaten life security. Many previous studies investigate the SBS modifier’s impact on mechanical characteristics, while quite rare of them address the pyrolysis kinetics with VOC formation of the SBS-modified asphalt, particularly when they experience thermally aged process. This study has applied the thermogravimetry-mass spectrometry technique (TG-MS) and distributed activation energy model (DAEM) to address these research gaps. Our analytical results present that the thermal stability of the SBS-modified asphalt (SBSMA) is significantly promoted with 5% higher activation energy (E) than that of unmodified asphalt (UMA), mainly attributed to the heat absorption of the SBS modifier which results in a slow temperature rise of asphalt. However, the VOC emissions of SBSMA are nearly 190% higher than those of UMA, which is owing to the thermal decomposition of the SBS modifier. Besides, thermally aged asphalt emits approximately 40% fewer VOCs than fresh asphalt, indicating that the organic-compositional loss occurs during the aging process. This work provides fundamental insights into asphalt combustion and alerts designers to re-design SBS-asphalt owing to its dramatic pyrolysis-generated VOC emissions.