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A Century of Asphalt Emulsions

Aug 21, 2023
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A Century of Asphalt Emulsions

Emulsified asphalt, also referred to as liquid asphalt because of its liquid state at ambient temperatures, includes both cutback asphalt and asphalt emulsion. A cutback asphalt is made by adding a diluent, typically a petroleum distillate, to refined asphalt. Cutback asphalt has reportedly been used in road construction since the 1800s. And there was a major expansion of cutback asphalt from the 1930s through the 1970s. Although still utilized for various applications, new developments over time and ultimately a push to mitigate uncontrolled hydrocarbon emissions in the U.S. specifically led to a push for further development, education and use of the more sustainable emulsified asphalt — asphalt emulsion. Asphalt emulsion is a mixture of two normally immiscible components, asphalt and water, combined with an emulsifying agent often referred to as a surfactant. The following timeline of asphalt emulsion gives you a glimpse into its considerable advancement over the past century.

A Timeline of Asphalt Emulsion

The first reported use of asphalt emulsion in pavement construction was in 1903, with the first asphalt emulsion patents issued to Leonard Schade van Westrum in the United Kingdom and then in the United States in late 1903 and early 1904 (Ref UK No. 21,195 October 1903 and US No. 752,486 February 1904). Westrum was issued a later patent in 1911 as well (US No. 992,313 May 1911). Modern asphalt emulsions in use today were patented by Hugh Alan McKay with the UK patent No. 202,021 in August 1923.

Patented technology prior to 1923 primarily focused on oil emulsions for road applications; however, a distinction can be made. Westrum’s approach to emulsifying oil contained a greater component of water and a lesser component of oil/asphalt. In Westrum’s first work, the water component was more than 75%. Furthermore, the dispersed oil component was a blend of oil and asphalt, much like what is referred to as “road oil” today. The 1923 McKay patent describes in detail an emulsion consisting of 70% asphalt (bitumen) and 30% water. This is a bit more like the asphalt emulsion produced and used today. Hence, we celebrate 100 years since the birth of modern asphalt emulsions in road construction.

Emulsions – The Answer to Hydrocarbon Emission Reduction

Use of asphalt emulsion has grown considerably over the past century, more specifically in the last half-century. The primary reason is a response to the creation of the U.S. Environmental Protection Agency (EPA) by the executive order of President Richard Nixon in 1970. In 1975, the EPA estimated that uncontrolled hydrocarbon emissions from the use of cutback asphalt were 655 kilotons per year. With the 1977 EPA publication of a guideline series, “Control of Volatile Organic Compounds From Use of Cutback Asphalt,” a large-scale national conversion from use of solvent cutback asphalt to asphalt emulsions was initiated. The advantages of converting from cutback asphalt to asphalt emulsions in terms of conservation of energy and reduction of air pollution were, and are, accepted by all concerned.

Organizations Ergon Asphalt & Emulsions (EAE) personnel are part of today, including the Asphalt Emulsion Manufacturers Association, the International Slurry Surfacing Association and the International Bitumen Emulsion Federation, to name a few, are dedicated to facilitating research and dialogue among agencies, suppliers, engineers, those in academia and more, on how to adopt, refine and efficiently utilize asphalt emulsions to preserve and maintain roadways, with minimal harm to the environment.

With today’s environmental and social governance narrative, there is increased concern over environmental impacts from all facets of the road construction industry. Engineers, environmentalists and major companies are concerned with the impact of construction methods and materials on workers and the environment.

This is an exciting time for research and development of modern asphalt emulsions, and the opportunities are vast. Emulsions make up a highly diverse heterogenous system. It is understandable why numerous researchers from all industries have studied this type of material for centuries. Ergon A&E looks forward to continuing partnerships with companies, associations and universities to further contribute to the knowledge and advancement of this versatile material.

Happy Birthday, Asphalt Emulsion! Here’s to many more.

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Gaylon is Executive Vice President – Technical Operations and Development for Ergon Asphalt & Emulsions and currently serves as the President of the International Bitumen Emulsion Federation. Gaylon plays an integral role in product development for Ergon's Pavement & Coating Resources business segment. He earned a Doctorate in Civil Engineering from Mississippi State University in 2015.

Written by Gaylon Baumgardner

Aug 21, 2023
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