A Preliminary Assessment of Historical Changes in the United States Asphalt Paving Industry-Refining and Hot Mix Processes

• Published in: Journal of occupational and environmental hygiene 2007-01, Vol.4 (sup1), p.220-222
• Main Authors: Mundt, Diane J., Marano, Kristin, Nunes, Anthony, Adams, Robert
• Format: Article
• Language: English
• ISSN: 1545-9624; 1545-9632
• DOI: 10.1080/15459620701326273

The U.S. asphalt paving industry, which includes both the refining and hot mix sectors, has evolved over time to meet various performance specifications for asphalt (known as bitumen outside the United States). Additives to asphalt produced in the refinery, as well as changes in temperatures, equipment used, and materials added in the hot mix asphalt process-which are likely to vary by state-may affect exposures to workers in the asphalt paving industry. The purpose of this investigation was to document the changes in the refining, manufacturing, and hot mix of paving asphalt in the United States since World War II. The approach taken for the investigation of both the refining and hot mix sectors was similar. Historical documents, as available, were reviewed and individual experts in each industry sector were interviewed to identify current and historic practices. In general, of the refining facilities surveyed, the number reporting use of any material within a particular class ranged from none to more than half the respondents. Sixteen states were included in the review of the hot mix sector. All states reported addition of materials to hot mix asphalt currently or historically, but concentrations were generally small (less than 10% per unit weight of asphalt). Changes to paving asphalt in the United States over the past 50 years appear to have occurred, but are generally not consistent by geography or over time. Modifications that have been made to asphalt were to improve performance, and were dictated by state specifications.