Institute for Transportation

Iowa is home to more than 71,000 miles of granular 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, an Iowa State University civil engineering graduate student with the Institute for Transportation’s Program for Sustainable Pavement Engineering and Research (PROSPER), is addressing the challenge of maintaining these roads by three-dimension (3D) printing geogrids. Their web-like geosynthetic structures are made from recycled plastic to improve granular road performance and longevity.

Hasheminezhad; his research mentor Halil Ceylan, director of PROSPER and Pitt-Des Moines, Inc. Endowed Professor in Civil Engineering; and the PROSPER team have monitored a field performance test of a full-scale composite geosynthetic system in Buchanan County, Iowa.

This system includes a geogrid made from 100% recycled plastic bonded to a nonwoven geotextile, manufactured in collaboration with the geosynthetics industry. 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 required to construct structurally sound gravel roads. These improvements could translate into major cost and time savings for counties.

“The composite geosynthetic is performing even better than we expected,” Hasheminezhad 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.”

Read more about Hasheminezhad’s efforts and this research project in the Iowa State University College of Engineering news article.