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Hemp used as construction form in Kentucky

News International-French

23 Oct 2019

Repairs were completed on the KY 32 Bridge over Blaine Creek in Laurence County, KY, USA. Some of the deteriorated wood pier-piles required extensive repair or replacement.

Hemp used as construction form in Kentucky - Hemp wrap around pile

Hemp used as construction form in Kentucky - Hemp wrap around pile

Carbon fiber wraps are generally used by the University of Kentucky (UK) research team to repair the piles. One of the piles on the KY 32 Bridge was repaired using Hemp wraps as part of an experimental study. This is the first time that hemp has been used as a construction material in bridges.

Hemp, as a natural fiber, has many advantages. It is a renewable resource, biodegradable, and has a small carbon footprint compared to synthetic fibers, e.g. carbon, glass, and aramid fibers. The limitations are low strength, incompatibility with existing resins (e.g., epoxy, polyester), manufacturing processes, and it is seasonable. Some of the limitations can be overcome with ongoing and future research. Hemp chipped hurds (or shives), a waste product produced during the processing of hemp fibers, has been used in the production of Hemplime (of Hempcrete). Hempcrete, an insulation material, is a bio-composite of hemp hurds and lime.

Kentucky Transportation Cabinet District 11 Bridge Crew applying epoxy adhesive on the CatStrong Hemp Wrap

The hemp wrap, identified as CatStrong BHW 2500 (BHW = Biaxial Hemp Wrap at 0o/90o, and 2500 = 2500 pounds per foot (36 kN/m) capacity in the x and y directions) is produced by students in the Structures Laboratory at the UK College of Engineering. Replacement of bridge piles, whenever possible, requires bridge closure and shoring, and is very expensive and time consuming. In 2012, and in cooperation with the Kentucky Transportation Cabinet (KYTC) and the Federal Highway Administration (FHWA), UK developed the CatStrong Wrap system using carbon fiber fabrics. It was first deployed on a bridge near Paducah, KY.

“More than 35 bridges have been repaired in Kentucky using the CatStrong products to strengthen bridge beams, columns, and piles. They have included carbon fabrics with capacities reaching 120,000 pounds per foot (1750 kN/m), and rod panels with capacities reaching 195,000 pounds per foot (2550 kN/m). Hemp was added to the CatStrong family of products since it is a growing industry in Kentucky. All proceeds from all CatStrong products go to UK to support students and product development. Issam Harik, Raymond-Blythe Professor of Civil Engineering and Program Manager at the Kentucky Transportation Center (KTC) at UK, and Dr. Abheetha Peiris, Research Engineer at KTC, have been leading a team of researchers working on an Innovative Bridge Research and Deployment in cooperation with FHWA, KYTC, and UK.

Mr. Eric Brown, Undergraduate Civil Engineering Student at the University of Kentucky, Inspecting the CatStrong Hemp Wrap
Harik said:

“For future deployments, we will experiment with plant, instead of epoxy, based resins to produce 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 in enhancing our transportation infrastructure. The lessons learned from each project are used in future projects to upgrade and extend the life of bridges and buildings. None of the success achieved in these repair projects would have been without the cooperation between UK, KYTC, FHWA, and Industry.”