Insulating Eco-Concrete

Posted on 15th July, 2010

A modern version of the typical ‘block-built’ wall system uses insulating blocks which are manufactured using aerated concrete, pumice, ash and other lightweight aggregates.

Insulating concrete is a different form of construction that has appeared over the years in various guises. Recent forms of this building method use an insulating mould or shuttering system for walls and normal concrete is poured into this to form the load-bearing part of the wall. A less well-known type of cast insulating concrete was tried in the USA after WWII.

Diatomite and Wood-Fibre Concrete The US version was an experimental mix of sawdust, wood-shavings, diatomaceous earth, cement and clay. The sawdust and wood shavings replaced the sand and gravel found in normal concrete and as diatomaceous earth is used in industry for its insulating and fireproofing properties, this provided the fire retardant element necessary for the mix. The resulting concrete was found to be not as strong as normal concrete but this could be solved by building a cavity or double skin type wall with one ‘leaf’ of the wall providing the structural strength.  

More importantly, the ‘sawdust’ concrete used less cement and was reckoned to have about 12 to 14 times the insulation value of ordinary concrete. It has proven to be long-lasting with no significant deterioration of the buildings which have been built with it. The product can be cast in relatively thin slabs and can be drilled and sawn; and also plastered or sanded to produce a finish suitable for painting. It is lightweight and suitable for internal walls, floors and even the internal part of roofs; and can be reinforced if necessary.

Availability of Materials       Sawdust and wood shavings are easy to come by if you live near sawmills, although the variety of timber and even the age of the sawdust can affect the quality of the finished product. The best known source of diatomaceous earth in Ireland is found in the Lower Bann Valley, and it can also be obtained from suppliers of industrial minerals. Note that there are some health and safety precautions associated with certain commercial varieties. Clay is a common feature in most areas and cement is obviously available from builders’ merchants anywhere.

The actual mix requires knowledge of the qualities and quantities of the various constituent parts and could benefit from the addition of other environmentally friendly materials.

If anyone is interested in experimenting with this interesting building material, please get in touch through the website and I will be keen to help and advise.

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