Hot-mix asphalt pavement recycling is widely practiced for its economic and environmental benefits. Existing studies are mainly focused on the engineering properties of reclaimed asphalt pavement (RAP) materials, without considering their impacts on the generated asphalt fumes—a widely recognized environmental hazard. The effects of using RAP on asphalt fumes are systematically studied in this research. Asphalt binders from different sources were used to create RAP materials in three aging conditions. Asphalt fumes were generated and collected from non-aged asphalt materials as well as RAP materials, followed by gravimetric and chemical analysis of the collected asphalt fumes. RAP materials were found to generate greater amount of particulates in asphalt fumes as compared with non-aged ones. RAP materials are also associated with increase in the types and concentrations of polycyclic aromatic hydrocarbons (PAHs) in asphalt fumes, especially those PAHs with more than three aromatic rings. PAHs increase in asphalt fumes is particularly noticeable for RAP created in the natural aging condition. It is reasonable to conclude that asphalt fumes generated from RAP become more hazardous, hence deserving more attention from researchers and practitioners. The mechanisms of the increase in PAHs are discussed, in addition to field exposure studies and mitigation measures.

Introduction

The majority of paved roads around the world are surfaced with hot-mix asphalt (HMA) pavements (Mallick et al., 2017), which are also widely used for the construction of airport runways, parking lots, and other facilities. It is estimated that about 1.6 trillion metric tons of asphalt mixtures are produced annually for the construction, rehabilitation, and maintenance of the paved civil infrastructures (NAPA and EAPA, 2011). The life expectancies of HMA pavements range from a few years to several decades. At the end of their service lives, HMA pavements need to be demolished, creating a large amount of wastes. In the United States alone, for instance, about 100 million tons of asphalt pavements are milled off annually in road resurfacing and widening (MAPA, 2019). The demolished pavements, however, still contain valuable aggregate and asphalt binder. If unattended, they form a significant source of inert solid wastes. Therefore, asphalt pavement recycling has become a common practice for cost saving and environmental conservation (Alam et al., 2010; Wang, 2016).