Institute for Transportation

Asphalt Materials and Pavements Program (AMPP) Director Chris Williams has been studying the use of recycled and bio-based materials in pavement production and maintenance for more than a decade. In 2019, those long-time efforts to make more sustainable and cost-effective pavements have yielded some much-deserved attention.

Early in the year, Energy & Fuels, a publication of the American Chemical Society, published a paper and highlighted the results of research on a new technology developed by Williams and two researchers in Iowa State University’s Department of Chemical and Biological Engineering. Williams, with Eric Cochran and Nacu Hernandez, developed a method to reduce the separation of ground tire rubber (GTR) in asphalt by mixing the GTR with a polymer additive before blending it with asphalt.

The new technology has the potential to reduce carbon dioxide emissions and energy use while recycling thousands of metric tons of both discarded tires and rubber each year. Right now, the United States generates 270 million waste tires each year, about 10 percent of which is put in landfills and other disposal areas. The technology also has an economic benefit, as using GTR is less costly than asphalt alone and virgin styrene-butadiene-styrene (SBS) elastomers. Read more about the project here.

GTR is just one of the recycled materials that Williams has studied for use in asphalt pavements. He has also conducted previous and ongoing research on using other recycled materials, including asphalt pavement content and asphalt shingles.

In addition to his research on recycled materials, Williams’ work on using bio-based materials, particularly soybean oil, also earned recognition in 2019.

While his work on using bio-based polymers in asphalt is ongoing, Williams received local media attention, as well as that of agriculture circles, when the researchers held an open house to highlight a newly paved parking lot that used the soy-based binder. Williams also conducted the work with the bio-based material in concert with Cochran. Read more about the project here.

The project initially got underway in 2014 with special funding from the Iowa Highway Research Board and concluded with a ton-per-day pilot plant built at Iowa State University’s BioCentury Research Farm, the site of the bio-based parking lot. The second phase of the project that includes field trials on at least six test sites is ongoing.

This research could have substantial impact on the Iowa economy through job creation, future tax revenue, and the export of a high-value specialty product, which has also shown success in numerous other applications, including adhesives, coatings, and packaging materials.

“We’ve been at the forefront not only in Iowa, but nationally and internationally, in developing new materials derived from vegetable coproducts,” Williams said. “We can use those components to not only improve asphalt’s performance but make it more economical, and it’s something we can do here in Iowa that develops our economy in Iowa and creates value to the state of Iowa and the people that live here.”