Evaluation of Fumes Emitted During Laboratory Methods of Incorporating Post-Consumer Recycled Plastics in Asphalt Mixtures Via the Dry Process

Using recycled plastics in asphalt could be challenging because of possible composition variations and contaminants. Post-consumer recycled (PCR) and post-industrial recycled (PIR) plastics can differ in composition, consistency over time, amount of contaminates, and degradation potential. Additionally, PCR and PIR plastics may contain chemical additives from their manufacturing process and residues of other materials after recycling. Thus, significant health and safety uncertainties surround the occupational exposure of asphalt workers to hazardous air pollutants (HAPs) emitted during the production and construction of recycled-plastic-modified (RPM) asphalt mixtures. When subjected to elevated temperatures, certain recycled plastics may release HAPs, including polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs). This study examined fumes emitted during four laboratory methods of adding PCR plastics in asphalt mixtures via the dry process that simulated the production of these RPM mixtures at asphalt plants. The fume analysis followed the US National Institute for Occupational Safety and Health (NIOSH), the US Environmental Protection Agency (EPA), and the International Organization for Standardization (ISO) methods for collecting, characterizing, and quantifying PAHs. The chemical characterization of the utilized PCR plastics was performed using gas chromatography/mass spectrometry (GC/MS) analysis. Results indicated that the evaluated PCR plastics did not introduce new compounds to the fumes but may have changed the observed concentration of the compounds in the fumes. Nonetheless, the concentrations of the detected HAP VOCs were significantly below the US Occupational Safety and Health Administration (OSHA) threshold values.