[Ec2] Lime Hemp concrete

AUTHOR: Anna Holdenlime hemp concrete
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CROSSLINKS:

Database:
[Ec1][In1][In2]
[Sh1]
Prototypes:
[Hw]
Scenario Games: Action Plan:
[AP1]
External

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ACTORS/AGENTS
Farmers

Hemcore

Construction Industry
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DESCRIPTION
In France, hemp hurds are now available commercially under several different brand names: “Isochanvré “, “Canabiote” and “Canomose”; and come in two forms; for construction or insulation.

The processing required is similar for both types of product. The bast fibres are mechanically removed in a dry process without chemicals or the need for a retting (rotting) stage leaving behind the interior core, or hurds. These are then “naturally stabilized” (with borax and boric acid?) to make them fire and water resistant . For insulation the product is used in a loose form and is either poured or blown into roofing, partitions, floors or in wall cavities. Isochanvré meets the “norms” of the CSTB (Scientific & Technical Centre for Building) criteria for a good insulating material. In this application it is probably similar to the cellulose-based insulation made from recycled newspapers currently available in Australia.

Unlike these products however, Isochanvré claims one major qualitative difference - a “high thermic capacity” .The term “thermic capacity” is presumably equivalent to thermal mass - an ability to store warmth and later give it back, due it is claimed, to the high proportion of silica within the plant. Chènovotte Habitat acknowledge this is unusual: “Original evaluation is in progress, as the current common insulating materials have no [thermal mass]”

Isochanvré (type of hemp hurd) can be processed for construction purposes. The product is mixed with natural lime (not cement) and water in a cement mixer. Sometimes plaster of Paris (pure gypsum) or 10% river sand is added. At this stage the compound resembles cement. It can be poured like cement, hardens and becomes mold and insect resistant. After drying the isochanvré is a lighter, tawny colour with a texture similar to cork. isochanvré claims good thermal and acoustic insulating properties.

It can be utilised in drywall construction between form work, as an interior and exterior insulation obe poured as a floor, or as an addition to the existing slab to raise the level of an existing floor. The forms can be removed within a few hours, whilst the petrification process continues . A big advantage of the material is the fact that it makes several layers of conventional building materials superfluous: Isochanvré can replace bricks or cement, a vapour barrier, insulation, and plaster board or Gyprock panelling . The only finish required on the exterior is a coat of whitewash, with or without added pigments, whilst the interior can retain the cork-like texture by either waxing or varnishing the finished surface.

http://environment.guardian.co.uk/conservation/story/0,,1881460,00.html
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RESEARCH AGENDA
Research lime hemp construction and possibility of casting it within hemp fibre formwork