A research team at Montana State University (MSU) (Bozeman, Montana, USA) has embarked upon a research project that repurposes industrial hemp plant stalks in order to create a natural building material known as “hempcrete.”
The project combines the hemp plant’s tough, woody inner stalk—also known as hurd—with a lime-based binder. The result is a relatively light material “doesn’t really flow like normal concrete” and has potential applications as insulation and structure in walls, explains Drew McNally, a junior majoring in civil engineering at MSU.
To create hempcrete, McNally uses hydraulic pistons in order to measure the crushing strength of cylinders of hempcrete composed of different proportions of cement and lime. “I really like the hands-on side of it, seeing how each of the different mixes perform,” she says. The hempcrete project is funded in part by the Montana Farmers Union, while McNally herself is financially supported by MSU’s Undergraduate Scholars Program.
One of McNally’s key collaborators is Kirsten Matteson, an assistant civil engineering professor in MSU’s Norm Asbjornson College of Engineering. Her years of experience in materials testing made her a natural choice to lead the project. “We’re always exploring possible uses for what would otherwise be waste materials,” says Matteson. “When we use waste materials in these applications, we often sacrifice some strength, but that’s OK if we get other properties that are desirable.”
Other important members of the team include Michael Berry, an associate professor of civil engineering at the Norm Asbjornson College of Engineering, and Kirby Hancock, lead architect at Constructive Solutions, a design-build firm headquartered in Bozeman. Berry is responsible for measuring the insulating properties of hempcrete mixes, while Hancock, an MSU alum, conceived the research idea and secured funding from the multi-state Farmers Union Enterprises.
According to Hancock, hempcrete is commonly used on a global scale, particularly in Europe and Asia, and is an option for companies looking to minimize their environmental impact. Other benefits of the material include its resistance to fire, mold, and pests, and its viability as an eco-friendly alternative to foam-based insulation. Hancock believes that the MSU project could aid builders in creating stable hempcrete mixtures and provide building officials with the necessary data to use the material in structures.
Last year, more than 200 licensed growers in Montana planted 50,000 acres of hemp, which was double the amount from the previous year. One cause for this bountiful crop was the 2018 Farm Bill that legalized hemp cultivation in the US. Aside from its use as a building material, the hemp surplus could be used to create medicines, foods, and cosmetics.
“It just sits there and farmers have to figure out what to do with it,” says Justin Loch, a director with the Montana Farmers Union, in referring to the remaining hemp stalks. “Being able to use the whole plant would mean more revenue and more markets for growers.”
McNally will report the preliminary findings from the hempcrete project at the 2020 National Conference on Undergraduate Research, which will be hosted by MSU from March 26-28.
Source: Montana State University, www.montana.edu.