As the world moves towards green energy intended to have less of a carbon footprint, we are looking into one of the most versatile plants on the planet: hemp. Humans have been using hemp since the very beginning of agriculture. It’s one of the world’s strongest and most versatile plants, with a long history of utilization. In fact, the U.S. government even made a short film called “Hemp for Victory” during World War II to encourage farmers to grow hemp to support military efforts.
One of the latest uses of hemp is for construction purposes in the form of hempcrete.
What is Hempcrete?
Hempcrete uses the core of the plant and is usually mixed with a mineral, such as lime. Hempcrete is far lighter than traditional concrete, and its technical uses are vast, according to an open access article from IOPScience.  These technical uses include insulation, varnishes made from hemp, as well as ropes and strands.
Mineralization of hemp hurds is usually completed with hydraulic lime, which converts it to an inorganic state. In fact, hydraulic lime is also the typical binder in hempcrete. This study probed a different binder: cement (CEM II/N-M 32,5 R). The researchers noted that cement may “prolong the time of hydration [of hemp], which would result in a lot of undesirable circumstances.” Thus, they still had to mineralize hemp and relied on a published recipe : 100 kg hemp hurds, 110 kg hydrated lime, and 565 kg water per cubic meter. This process required 7 days.
They then created a cubic meter of hempcrete using 380 kg mineralized hemp hurds, 775 kg cement, and 167 kg water per cubic meter. Compared to the typical hydraulic lime binder, the cement binder was declared stronger. The compressive strength was recorded at 1.13 MPa, in line with foam concrete (0.5-1.5 MPa). This makes the hempcrete suitable as a filler material in lightweight concrete. The authors suggest that the laborious process of mineralization makes hydraulic lime the better choice.
Is Hemp the Future?
Due to the federal illegality of cannabis for nearly 100 years, hemp has been drastically under-utilized. As more cannabis reform occurs in the U.S., we will hopefully see hemp being used more — it can reduce our carbon footprint and provide a source of green energy.
To read more about the myriad ways hemp can help humanity and our Earth, check out Jack Herer’s The Emperor Wears No Clothes, available online for free.
- Novakova P, Sal J. Use of technical hemp for concrete – Hempcrete. 2019 IOP Conf. : Mater. Sci. Eng. 2019;603(5):052095. [Impact Factor: n/a; Times Cited: 20 (Semantic Scholar)]
- Mikulica K, Hela R. Hempcrete – cement composite with natural fibres. Advanced Materials Research. 2015;1124:130–134.doi:10.4028/www.scientific.net/amr.1124.130. [Impact Factor: n/a; Times Cited: 1 (Semantic Scholar)]