AMES, Iowa – A train of heavy equipment slowly worked its way across 8.6 miles of a northeast Iowa county road last summer.

The corn growing along C14 just south of West Union was dark green and high. Farmhouses and outbuildings were on the horizon. The ditches along the roadway were freshly mowed. It was a good day to fix a rural road built in the 1960s, patched up and covered over ever since, now deteriorated and even crumbling beneath the surface.

The fix was soy pavement technology developed by Iowa State University engineers.

The repairs to C14 were part of a full-scale, 24-mile demonstration of “soy roads” in rural areas of Fayette and Clayton counties and the town of Volga. Four different road projects used soybean-based paving products developed by Iowa State engineers Eric Cochran, the Mary Jane Skogen Hagenson and Randy L. Hagenson Professor in Chemical and Biological Engineering, Christopher Williams, the Gerald and Audrey Olson Professor in Civil Engineering, and their research groups. The technology is now produced by their startup company, SoyLei Innovative Products.

A full-scale project, indeed:

Leading the paving train along C14 was a tanker truck carrying refills of asphalt pavement emulsion, including soy-based binders, for rehabilitating and bonding recycled pavement material. Next was a semi pulling a tank full of water to cool the sharp bits of the next machine.

That big yellow machine ripped up the top 4 inches of a lane of asphalt, ground it and put it on a conveyor to the next machine. That one chewed up more of the pavement and mixed it with emulsifier, including soy oil polymers that replaced petroleum-based ones. In prior tests and demonstrations, the soy alternative has been the better option for binding and boosting pavement flexibility and performance.

The mixing machine dumped the cold and raw asphalt on the stripped roadway, and a trailing paving machine picked it up and spread a new and dark base layer across the lane for a pair of rollers to smooth. Paving crews later covered the base layer with a layer of hot-mix asphalt, also containing a soy-based binder.

Related soy-based asphalt demonstrations fixed 14.7 miles of two county roads, B45 and X28, in Clayton County and nearly a half mile of Washington Street in Volga. 

The Iowa State engineers estimated the projects used 12,000 to 15,000 bushels of soybeans and eliminated the need for more than 40,000 barrels of crude oil.

As Cochran reported in a summary, “By replacing petroleum-derived asphalt modifiers with soybean oil polymers, the project effectively turned soybeans into part of the road.”

It takes partners

In response to a fiscal year 2023 federal funding opportunity, Cochran and Williams, who have worked for about 15 years to develop and demonstrate a soy-based biopolymer that extends the life of asphalt pavements, began working with local leaders in Fayette and Clayton counties and the town of Volga to identify paving projects.

By replacing petroleum-derived asphalt modifiers with soybean oil polymers, the project effectively turned soybeans into part of the road.

Eric Cochran

As they prepared a proposal for Community Project Funding from the congressional office of U.S. Rep. Ashley Hinson, they also built other project partnerships. Those included the Iowa Department of Transportation, the Asphalt Paving Association of Iowa, Mathy Construction Co., of Onalaska, Wisconsin, Iowa State administrators and the university’s Institute of Transportation.

The Iowa Soybean Association and the United Soybean Board also supported the paving project, adding to their investment in the early research of soy-based asphalt binders and rejuvenators.

Hinson’s office led the request for federal funding, which amounted to $4 million of the $7 million cost of the projects. The other partners contributed funding and other, in-kind support.

“They put their trust in Iowa State to deliver,” Williams said. “And I think we delivered a great product.”

Low-risk, promising soy pavements

Northeast Iowa leaders didn’t consider it a gamble to sign on to a research project. 

Casey Stickfort, the Clayton County engineer, said there were two key factors in the county’s decision to participate in the demonstration project: The amount of funding available and, after hearing the pros and cons, “how low-risk the soy-based product was.”

Joel Fantz, the Fayette County engineer, said he’s followed the soy-pavements project for years and has even toured the researchers’ pilot plant at Iowa State’s BioCentury Research Farm. He’s served on the Iowa Highway Research Board and understands how hard it can be for research discoveries to become commercial products.

To make that jump, he said new technology needs to “offer higher quality, longer life or lower costs.” In addition, novel road-building methods need detailed specifications that fit project plans, assure quality and don’t burden paving crews. All that helps new ideas gain acceptance with engineers and contractors.

They put their trust in Iowa State to deliver. And I think we delivered a great product.

Christopher Williams

Elaine Follon, the mayor of Volga, said the community was desperate to replace Washington Street and its potholes. The main street through the town’s business district “was putting a huge damper on new business development and creating problems for existing businesses.”

Plus, the small town didn’t have the tax base to afford such a large project.

“I don’t think anyone here gave a second thought to this being a risk due to new research,” Follon said. “For us, it’s a miracle.”

And the results?

Fantz said he sees three wins for Fayette County: soy in the hot-mix asphalt will help reduce cold-weather cracking; soy in the cold in-place recycled pavement lowered the need and costs for other materials; and soy in a sprayed-on rejuvenator should extend the life of pavement and striping.

“The quality was excellent,” he said. “Time will tell – but it could turn out to be the best hot-mix asphalt we have ever constructed in Fayette County.”

Stickfort said he’s also pleased with the results in Clayton County. There aren’t any noticeable cracks, the roads now provide an even surface for snowplows and the dark pavements dry quickly.

In Volga, Follon said, “The road work is excellent and such a pleasure to drive on, like floating on a cloud.”

Contacts

• Eric Cochran, Chemical and Biological Engineering, SoyLei Innovative Products, ecochran@iastate.edu, 515-294-0625
• Christopher Williams, Civil, Construction and Environmental Engineering, SoyLei Innovative Products, rwilliam@iastate.edu, 515-294-4419
• Mike Krapfl, News Service, mkrapfl@iastate.edu, 515-294-4917