Using Hemp to Repair Deteriorating Kentucky Bridges

Peiris, a researcher at the Kentucky Transportation Center and one of Harik’s former doctoral students, supervises the repair projects.

Despite unprecedented success, CatStrong has been on a quest to find an even more reliable resource. When introducing a new addition to their family of products, Harik leaned on a growing industry in the Commonwealth — the hemp industry.

As part of an experimental study, the team recently repaired one of the piles on the KY 32 bridge over Blaine Creek in Lawrence County using hemp — marking the first time the natural fiber has been used as a construction material for bridge repair.

Hemp, which is biodegradable and has a small carbon footprint, offers many advantages. “The limitations are low strength, incompatibility with existing resins, manufacturing processes and it is seasonable,” Harik continued. “Some of the limitations can be overcome with ongoing and future research.”

If the timeline for a project is five days, Harik says the majority of the time will be spent preparing. “Once the structural member section is built back to its original shape, we mix a two-part resin or paste and spread it on the surface. Then we press CatStrong into it, add another layer of paste over it and that’s it. Once applied, it will gain 80 percent of its strength within 24 hours.”

Harik, who wants to give credit where credit is due, admits he doesn’t physically create the CatStrong wraps. Instead, that’s the work of dedicated students — who he lovingly refers to as “Mignons.” On any given day, you will find them working busily in the Structures Lab on campus.

From design to development, students are involved in every aspect of CatStrong. Their passion for the product — and its ability to make Kentucky bridges safer — is undeniable.  “It is very gratifying and exciting to analyze a product, fabricate it, test it and see it deployed in the field to solve a real problem — in short, it is amazing,” Ethan Russell, a UK engineering student, said.

For future deployments, CatStrong will experiment with plant, instead of epoxy, based resins to produce entirely plant-based biodegradable, flexible, lightweight and re-useable wraps.

The primary objective in the KY 32 bridge — and any repair project — is to optimize the use of taxpayers’ funds while enhancing the state’s infrastructure.

The lessons learned from each project are used in future projects to upgrade and extend the life of bridges and buildings,” Harik said. “None of the success achieved in these repair projects would have been possible without collaboration between UK, sponsoring agencies and industry.”