VOC Emission Analysis of Bitumen Using Proton-Transfer Reaction Time-Of-Flight Mass Spectrometry

Area of Science:

• Environmental Science
• Materials Science
• Analytical Chemistry

Background:

• Bitumen heating during asphalt production releases volatile organic compounds (VOCs), posing risks to workers.
• Accurate identification and measurement of VOCs are essential for road construction safety and material assessment.
• Existing methods may lack standardization for comparing different bitumen types and modifications.

Purpose of the Study:

• To present a novel and standardized laboratory-scale method for determining VOC emissions from bitumen.
• To enable reliable cross-comparison of VOC emissions across various bitumen types, modifications, and additives.
• To investigate the influence of temperature and crumb rubber modification on VOC profiles.

Main Methods:

• Utilized a proton-transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) for real-time monitoring.
• Heated commercial unmodified bitumen and crumb rubber modified bitumen (CRMB) up to 180 °C.
• Analyzed emissions including alkanes, aromatics, and sulfur-containing VOCs.

Main Results:

• VOC emissions significantly increased between 160-180 °C for both bitumen types, especially CRMB.
• Sulfur-containing VOCs, notably benzothiazole, were detected at lower temperatures (120 °C) in CRMB, absent in base bitumen.
• Benzothiazole concentrations were notably higher in CRMB compared to base bitumen, varying with temperature and crumb rubber type.

Conclusions:

• The proposed PTR-TOF-MS method provides a standardized approach for analyzing and comparing bitumen VOC emissions.
• Crumb rubber modification significantly alters VOC profiles, increasing potentially harmful sulfur-containing compounds.
• The method offers a viable solution for the asphalt industry to monitor VOCs in real-time during production.