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

Abstract

Bitumen is one of the most important materials used in roads. During asphalt pavement construction, workers can be affected by emissions, such as volatile organic compounds (VOCs), when bitumen is heated. Therefore, it is crucial to correctly identify and measure VOCs. This paper presents a novel, promising method to determine VOC emissions. The proposed method offers a way to standardize routine measurements on a lab scale, enabling reliable comparison across bitumen types and their modifications or additives. A proton-transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) was used to monitor VOC emissions from commercial unmodified bitumen and crumb rubber modified bitumen (CRMB) with heating of up to 180 °C. Results confirmed that the temperature range of 160–180 °C is a highly influential factor for VOC emissions from heated commercial bitumen and particularly CRMB. A significant increase in alkane and aromatic emission was detected when the binders were heated to 180 °C. Sulfur-containing VOCs were almost nonexistent for the base bitumen fumes, while a significant increase was detected in the fumes when two different types of CR were added to the bitumen, even at 120 °C. The additional CR in the bituminous binder contributed to the potentially harmful VOC emission of benzothiazole, which belongs to the class of sulfur-containing compounds. The concentration of benzothiazole was 65%, 38%, and 35% higher for CR1 in comparison to CR2 at 140, 160, and 180 °C, respectively. It is clear from the results that this method allows different bitumen sources or modifications to be quickly analyzed and their VOC emissions cross-compared. If adopted and confirmed further, the method could offer the asphalt industry a viable solution to monitor VOC emissions by analyzing samples in real time at different steps of the production process.

Rapid and Direct Assessment of Asphalt Volatile Organic Compound Emission Based on Carbon Fiber Ionization Mass Spectrometry

“…The MWD of the negative ion mode was located in the range of 10–600 Da. In previous research, headspace GC–MS was the most widely used asphalt fume analysis method, and the results of these works showed that the molecular weight of detected VOCs in asphalt fumes was below 400 Da. ,,,, In addition, none of the work has pointed out that the molecular weight of the compounds in asphalt fumes may be above 400 Da due to the limitation of the analysis method. However, the results obtained by the established method show that there are many peaks in the mass range of 400–800 Da, which indicates that the chemical composition of asphalt fumes is much more complex than the reported composition in previous literature.…”

“…As one of the most powerful analytical techniques, mass spectrometry has been widely used in the field of asphalt analysis. For example, thermal gravimetric analysis–mass spectrometry (TGA-MS), proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS), and gas chromatography–mass spectrometry (GC–MS) have been used to assess the VOC emission in different asphalt materials. Among them, GC–MS has been used most frequently in asphalt fume analysis. ,− For example, GC–MS has been successfully used to analyze polycyclic aromatic hydrocarbons, , oxygenated VOCs, nitrogen VOCs, sulfur VOCs, and carboxylic acids in bitumen.…”

Characterization, Properties and Mixing Mechanism of Rubber Asphalt Colloid for Sustainable Infrastructure

“…As shown in Figure 1 , the relevant peer-reviewed journal articles were searched through Pubmed and Embase [ 66 , 67 , 68 , 69 , 70 , 71 , 72 ]. The search expressions involved “rubber asphalt” and “emission” or “pollution” or “economic” or “energy consumption”.…”

VOC emissions by fresh and old asphalt pavements at service temperatures: impacts on urban air quality

“…The emission of atmospheric pollutants by hot asphalt mixtures at deposition temperatures above 120 °C is well constrained at least regarding polycyclic aromatic hydrocarbons (PAHs), [22][23][24][25] and volatile organic compounds. [26][27][28] It is therefore striking that VOC emissions by asphalt mixtures at service temperatures, i.e. below 70 °C, had never been investigated before the year 2020.…”