Institute for Transportation

The transformation of nearly 25 miles of roadway in northeast Iowa from cracked and pothole-riddled to smooth and looking brand-new has many obvious benefits—improved ride quality, increased safety, and community revitalization—but these particular lane-mile improvements represent so much more.

The infrastructure projects—14.7 miles in Clayton County, 8.6 miles in Fayette County, and 0.4 miles in the City of Volga—successfully demonstrated a “full-circle” asphalt recycling approach that combines in-place recycling, new mixes with higher reclaimed asphalt pavement (RAP) content, and bio-based modifiers, all while reducing the dependence on raw and petroleum-based materials and boosting Iowa’s soybean industry.

The key stakeholders in the $7 million project, funded in part by federal Community Project Funding but ultimately a public-private partnership, recently got together for an open house and bus tour to discuss the projects and celebrate how seamlessly the innovations had moved from the laboratory to the local lane-mile.

“The Washington Street Project is one of the most important projects our community has ever undertaken,” Volga Mayor Elaine Follon said. “The newly paved Washington Street will not only tie progress and aesthetics together but will allow drivers to admire the restored buildings and notice the businesses without being distracted by a hazardous roadway.”

The celebratory open house brought together the county engineers and contractors involved in the infrastructure projects and the Iowa State University researchers—particularly Asphalt Materials and Pavements Program Director Chris Williams and Mary Jane Skogen Hagenson & Randy L. Hagenson Professor Eric Cochran—who’ve been working on the innovative and sustainable asphalt improvements. The event also included industry and association partners and congressional staff who supported the project.

Project Scope and Outcomes

Construction on the projects broke ground this spring, with paving completed by the summer and substantial completion by last month, after full funding was secured in 2023 and planning was conducted throughout much of 2024.

More substantial details on the projects in each community follows:

• Clayton County: The rehabilitation took place on 10.3 miles of County Road B-45 and 4.4 miles of County Road X-28, both of which have relatively low vehicle traffic. The projects involved high-RAP hot-mix overlays, with full-depth patching of the worst areas and milling the old surface, before placing about 4 in. of asphalt mix that used a soy-modified binder to maximize the reuse of the RAP from the milling.
• Fayette County (including West Union): The rehabilitation took place on about 8.6 miles of County Road C-14/W-25/210th Street. It involved a full-depth reclamation, using cold in-place recycling (CIR) of the top 4 in. of existing asphalt; mixing the milled material with a soy-based rejuvenating agent; and then topping with a 4 in. hot-mix asphalt overlay containing a soy-derived polymer binder.
• Volga: The rehabilitation of Washington Street, which serves as the small city’s Main Street, included drainage improvements, bringing the sidewalks and crosswalks into compliance with the Americans with Disabilities Act, and then milling and overlaying the street with a soy-based hot-mix asphalt.

All of the projects included the integration of startup SoyLei’s—founded by Cochran and Williams, among others—soybean oil-derived polymer in the CIR, overlay, and surface treatments. The benefits include recycling a higher proportion of old asphalt, saving an estimated 1,500 to 3,000 barrels of oil per mile, and using the equivalent of tens of thousands of bushels of Iowa-grown soybeans. Additional expected benefits include greater flexibility and cracking resistance in the pavement.

Fayette County Engineer Joel Fantz said that the project “demonstrate[s] the leadership of Iowa in sustainability, value-added agriculture, and economic development.”

Overall, the project had the following results and outcomes:

• Restored nearly 25 miles to like-new condition
• Offset an estimated 40,000 barrels of crude oil through reusing old asphalt and being rejuvenated using molecules from soybean oil
• Used an estimated 12,000 to 15,000 bushels of soybeans in the form of modified soy oil through an epoxidation process, demonstrating the potential for a new market for the crop
• Avoided lower value utilization of old asphalt by recycling on site
• Used less new aggregate that would have been quarried and hauled
• Provided a real-world case study for startup SoyLei Innovations, which provided biobased polymers, to refine their products and demonstrate their use

“In a broader sense, the project exemplifies how public infrastructure funding can drive rural economic development by both improving critical assets and seeding a new biobased industry,” said Williams.

Next Steps

With construction complete, the Iowa State researchers will continue to monitor performance during the next few years, though early indications are positive. The team is also conducting a detailed cost analysis, though again early estimates suggest the cost per mile of the projects compare favorably to conventional methods due to the material savings.

The immediate successes, however, are enough for the project’s key stakeholders to continue the work and continue to promote the work.

Some future plans include scaling up production of soy-based materials for use in asphalt projects, engaging partners to develop standards and specifications that incorporate the methods and products used in the project, seeking additional pilot projects in other parts of the state and throughout the Midwest where soy production is already high, and additional testing of the materials for its long-term benefits and adjacent applications.

Part of the work also includes telling the story of this project’s successes.

“We want to emphasize that this is an Iowa-born innovation—from Iowa State’s research labs to Iowa’s local roads—and illustrate the return on investment in research funded through public-private partnerships,” Cochran said.