Iowa is home to more than 71,000 miles of gravel county roads. Though these unpaved roads typically carry low traffic volumes, they are essential to local communities and routinely bear heavy loads from farm equipment, construction vehicles, and service trucks.
Araz Hasheminezhad (’24), a civil engineering graduate student with Iowa State University’s Program for Sustainable Pavement Engineering and Research (PROSPER), is addressing the challenge of maintaining these roads by 3D printing geogrids — a web-like geosynthetic structure made from recycled plastic — that are designed to improve granular road performance and longevity.
The PROSPER team, including Hasheminezhad and his research mentor Halil Ceylan, director of PROSPER and a Pitt-Des Moines, Inc. endowed professor in Civil Engineering, is monitoring a field performance test of a full-scale composite geosynthetic system in Buchanan County, Iowa, over the next two years.
The system includes a geogrid made from 100% recycled plastic bonded to a nonwoven geotextile. So far, the results have been promising: The geogrid’s webbed design enhances the stability of the road base, reducing rutting and lateral displacement over time, and significantly decreases the amount of base aggregate (the depth of finer gravel dirt underneath the gravel road) required to construct structurally sound gravel roads. These improvements could translate into major cost and time savings for counties, Hasheminezhad says.
“The composite geosynthetic is performing even better than we expected,” he says. “After a heavy rainstorm and snowfall, we visited the test site to assess its performance in wet conditions. We found that the geogrid also improves drainage and moisture management.”
Although the project’s primary focus is infrastructure stability, sustainability has remained a guiding principle. Traditional 3D printing involves plastic filament that generates waste through material testing and iterative design. To reduce this environmental footprint, Hasheminezhad and his team sought to create a filament entirely from recycled plastic.
“One of the most time-consuming parts of the project was determining whether a 100% recycled plastic filament was feasible — and then finding a supplier capable of producing it,” Hasheminezhad says.
After nearly a year of searching, the team reconnected with a manufacturer that had found a way to provide a recycled filament. Once delivered, the material underwent extensive testing for durability, strength, and reusability.
“A bonus to this solution is that we’re transforming plastic waste into engineered geosynthetics — materials that would otherwise go to landfills are getting a second life,” he says. “We even found a way to reuse the filament throughout the design testing process, reducing waste at every stage.”
Looking ahead, the team — supported by funding from the Iowa Highway Research Board and the Iowa Department of Transportation — plans to continue monitoring the test site and exploring scalable manufacturing solutions. Their long-term goal is to expand the technology’s reach to rural and urban roads across Iowa and beyond.
“These geogrids have the potential to save time, resources, and reduce plastic waste at local, national, and international levels,” Hasheminezhad says.