Hempcrete is a mixture of hemp hurds (shives) and lime (possibly including natural hydraulic lime, sand, pozzolans or cement) used as a material for construction and insulation. It is marketed under names like Hempcrete, Canobiote, Canosmose, and Isochanvre. Hempcrete is easier to work with than traditional lime mixes and acts as an insulator and moisture regulator. It lacks the brittleness of concrete and consequently does not need expansion joints.
The typical compressive strength is around 1 MPa, around 1/20 that of residential grade concrete. Hempcrete walls must be used together with a frame of another material that supports the vertical load in building construction, as hempcrete's density is 15% that of traditional concrete.
Continued research is leading to novel formulas for Hempcrete that are are being developed to have higher compressive strengths (thanks in part to the relaxing of regulations in the United States). Some of these formulas enable the new forms of hempcrete to act as structural elements, due to a reduction in hemp and lime particle sizes and greater density. If combined with alternative construction methods such as 3D printing, construction in the 21st century could potentially not only be much more sustainable, but virtually waste-less.
Like other plant products, the hemp crop absorbs carbon dioxide gas as it grows, retaining the carbon and releasing the oxygen. 165 kg of carbon can be theoretically absorbed and locked up by 1 m3 of hempcrete wall over many decades as the hempcrete petrifies.
- Allin, Steve. Building with Hemp, Seed Press, 2005, ISBN 978-0-9551109-0-0. (p. 146, 1st Edition).
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- "Tradical Hemcrete 2008 Information Pack". American Lime Technology. Retrieved 2010-05-15.
- Hemcrete application data from Limetechnology