A Historical Review of Additives and Modifiers Used in Paving Asphalt Refining Processes in the United States

Abstract

The U.S. asphalt paving industry has evolved over time to meet various performance specifications for liquid petroleum asphalt binder (known as bitumen outside the United States). Additives to liquid petroleum asphalt produced in the refinery may affect exposures to workers in the hot mix paving industry. This investigation documented the changes in the composition and distribution of the liquid petroleum asphalt products produced from petroleum refining in the United States since World War II. This assessment was accomplished by reviewing documents and interviewing individual experts in the industry to identify current and historical practices. Individuals from 18 facilities were surveyed; the number of facilities reporting use of any material within a particular class ranged from none to more than half the respondents. Materials such as products of the process stream, polymers, elastomers, and anti-strip compounds have been added to liquid petroleum asphalt in the United States over the past 50 years, but modification has not been generally consistent by geography or time. Modifications made to liquid petroleum asphalt were made generally to improve performance and were dictated by state specifications.

Keywords:

• asphalt
• historical
• occupational exposure
• paving
• refining

ACKNOWLEDGMENTS

The authors would like to acknowledge the Asphalt Paving Environmental Council and its members and The Asphalt Institute and the National Asphalt Pavement Association for sponsoring this work. Also, we thank the participating companies for their time and willingness to provide information for the surveys.

Notes

^A Participants were asked about the addition of re-refined engine oil bottoms, as well as the addition of used engine oil that was not further refined.

^A Includes five hydrocarbon additives not listed in the original survey but reported by respondents as “other.”

^B Includes two anti-strip additives not listed in the original survey but reported by respondents as “other.”

^C SBS, Styrene butadiene styrene.

^D EVA, ethylene vinyl acetate.

^E NA, not applicable.