Hempcrete or hemp concrete being a carbon-negative (carbon consuming) material is a great alternative for contractors to use in construction works. Hempcrete is prepared by mixing hemp shives (the inner woody core of hemp plant), water, and lime as the binding agent. Hempcrete has low density and excellent thermal and acoustic insulation properties.
There are a lot of hempcrete products available in the market, but the one that stands out is Hempcrete block. Hempcrete blocks are produced by the pressing, ageing and packing of hempcrete through appropriate machinery. The product finally obtained is solid but light, durable, and with excellent insulation properties.
The main source of strength of hempcrete comes from the high silica content (approx. 70%) in hemp shives, which makes it easy for the raw materials to bind together.
Production of Hempcrete Blocks
Earlier, Hempcrete blocks were prepared right at the site by mixing the raw materials and placing the mixture in the formwork, or by using equipment that required a highly qualified workforce.
But today, with the increase in demand and technological advancement, factories have been set up to produce hempcrete-based materials. The production process is divided into three simple steps :
The raw materials (hemp shives, lime-based binder and water) of hempcrete are proportionately dosed and mixed together.
Hempcrete obtained is poured in the blocks of widths between 6 and 30 cm in a special press.
3) Open-air Curing
After a while, the frail blocks of hempcrete are placed on an automatic conveyor belt which takes them to a storage area for open air-drying. This brings strength and hardness to the blocks. Depending on the width of blocks, it takes around 6-10 weeks for the blocks to become ready to use.
Applications of Hempcrete Blocks
- As external and internal Wall insulation
- As floors and roof Insulation
- Underneath floors
- As Plasters
- New Builds
- For Insulating older buildings
Advantages of Hempcrete Blocks
- Hempcrete has a negative carbon footprint of -72.0 kg/m² of wall which makes hempcrete block construction energy efficient and eco-friendly technique.
- The construction doesn’t take much time and reduces the labour costs and results in a cleaner site.
- Hempcrete is a low thermal mass material which means that it absorbs the heat during the day and emits it out during the night thus providing energy-cost savings.
- The quasi ductile behaviour of hempcrete blocks makes it reusable without affecting its structural properties.
- Hempcrete is a microbe and parasite resistant material.
- Hempcrete blocks have a fire-rating of 60-120 minutes.
- The low U-value (thermal transmittance) and enhanced insulation of hempcrete blocks help deliver low operational costs through reduced heating and cooling requirements.
- Hempcrete blocks are light in weight and are easy to transport and handle.
- Hempcrete blocks have excellent heat and sound insulation properties.
- Hempcrete blocks help in constituting breathable walls.
Disadvantages of Hempcrete Blocks
- Hempcrete has a low compressive strength and elastic modulus which makes it unsuitable for bearing direct loads- It needs a frame to carry the loads.
- Hempcrete walls are thicker which risks the reduction in carpet area.
- The raw material hemp of hempcrete is illegal to grow at a lot of places which makes it necessary for you to have it shipped from some other place.
- Forms are needed which must be continuously raised as you build.
EDITORAkshay is a Civil Engineer who has experience in various Pile foundation projects. Civil Engineering intrigues him but what intrigues him, even more, is the implementation of hybridized materials in construction projects. He is the author, editor, and partner at theconstructor.org.