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.
Highlights
Bitumen is a residue of crude oil refinery, which passes through a refinery process to be used as a binder
volatile organic compounds (VOCs) generated on-site during asphalt pavement construction can have a negative effect on the health of workers
The present paper introduces an innovative method to identify VOC emissions for
Summary
Bitumen is a residue of crude oil refinery, which passes through a refinery process to be used as a binder. Most lightweight compounds in crude oil are removed during this process, there is still some remaining in the final bitumen residue, which can be released as emissions during the production process of asphalt mixture at a high temperature (>150 ◦ C) [1,2]. Materials 2020, 13, 3659 compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), sulfur, nitrogen oxides, particulates, and carbon monoxide [3,4,5]. These components can be found in crumb rubber modified bitumen (CRMB). The rubber employed for the fabrication of tires is of high quality and resilient, leading to great potential for high-end recycling
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