Preventing emissions of hazardous organic compounds from bituminous composites

Abstract

This study introduces a novel method to sequester hazardous organic compounds that are continuously emitted from bituminous composites during the service life of roadways, airports, bridge decks, roofs, and other exposed bitumen-covered surfaces. It has been recently reported that such emissions are not limited to high temperatures during the production of asphalt mixtures or paving operation; there are continuous emissions at ambient temperatures, and the emissions significantly worsen when surfaces are exposed to solar radiation or high temperatures. The loss of these compounds from bituminous composites negatively impacts both air quality and the durability of bituminous composites. This study creates an inherent scavenging system to reduce hazardous emissions from bituminous composites by using two abundant urban wastes: waste cooking oil, and end-of-life plastics containing polyethylene terephthalate (PET). We hypothesize that the superior durability of PET can be exploited to extend the durability and service life of the built environment that is associated with increased retention of bitumen's volatile organic compounds. Oil treatment of PET enhances the compatibility of PET with bitumen and improves bitumen capacity to retain volatile compounds. Our laboratory experiment shows that bitumen containing oil-treated PET is more resistant than neat bitumen to solar radiation; after 200 h of accelerated laboratory aging, the chemistry-based aging index and rheology-based aging index were significantly lower for bitumen containing oil-treated PET compared to neat bitumen. Our modeling based on density functional theory (DFT) verifies the effective coating of the PET surface via oil treatment and the capability of oil-treated PET to retain some organic compounds in bitumen. DFT modeling performed on six small organic compounds of bitumen showed a better interaction energy between these organic molecules and PET-oil chains compared to PET-PET chains. This study's outcomes highlight the significant role of oil-treated PET in improving the durability of bitumen and in reducing the hazardous emissions of bitumen, thereby promoting better air quality, resource conservation, and sustainability in the built environment.