Hemp can also be used as a natural concrete. You mix the hemp shives with magnesite-containing limes (Grenoble lime). The mixture is tilted into a formwork and solidified on the outer sides by light stomping.
The formwork can be stripped after about 15 minutes or be switched to the next height. Formwork panels are used as formwork.
The application of hemp concrete on site must comply with the professional regulations.
The manufacturing company must follow the charter for the construction with hemp and the recommendations of the hemp book concerning the use of own lime with allowed hemp supplements according to the professional regulations.
==> The information provided here are not intended as an application manual, they are only introductory information.
If the material is processed professionally, there are no problems and excellent results. A consultation and a precise way of working are a prerequisite.
If builders themselves can contribute a lot of working time, stomping is quite inexpensive. If the order is given externally to companies, hemp stones might be cheaper because they take less time to produce.
The hemp supplement is obtained by cutting the hemp shives.
Its basic features include:
- Low weight: The density is 100 - 110 kg /m³
- Insulating ability: The thermal conductivity is 0,048 W*-1 K1
- Ability to absorb water: Hemp absorbs up to four times its own weight in just one minute.
The hemp supplement has the following characteristics:
- Length: 20 bis 25 mm
- Size: 1 bis 4 mm
- Density: 110 kg/m³
- Color: very bright beige
- Purity: fibre and dust percentage < 2 %
- Humidity: < 19 %
Hemp supplement: 100 l
Grenoble lime: 25 ,g
Water: 24 l (stirrer), 30 l (concrete mixer)
Consumption: 1150 - 1300 l hemp supplement
280 - 310 kg grenoble lime
Density: 450 to 550 kg /m³ depending on compression
Compressive strength: > 0,2 Mpa
Thermal conductivity: 0,07 W*m-1K-1 at 0% relative humidity
Hemp supplement: 100 l
Grenoble lime: 30 kg
Water: 25 lt (stirrer) - 27 lt (concrete mixer)
Material requisition for 1 m³ depending on compression:
1100 to 1200 l hemp supplement
330 - 350 kg grenoble lime
Walkable after 1 day
Minimum thickness: 10 cm
Room must be well ventilated
Temperatures: min. 5 ° - max. 30 ° C
Density: 500 - 600 kg / m³ - depending on compression
Compressive strength: > 0,3 Mpa
Thermal conductivity: 0,07 W*m-1J1 at 0% relative humidity.
Hemp supplement: 200 l
Grenoble lime: 25 kg
Water: 44 l
Consumption for 1 m³ depending on compression:
1000 to 1100 l hemp supplement
110 to 150 kg grenoble lime
Density: 280 to 320 kg / m³, depending on compression
Compressive strenght > 0,05 Mpa
Thermal conductivity: 0,05 W*m-1K-1 at 0 % relative humidity
Concrete mixer machine (compulsory mixer)