How to make concrete foam

Written by morgan adams
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How to make concrete foam
Smithy Bridge, infilled with foamed concrete to make it stronger (Parrot of Doom (Wkimedia Commons - public domain))

Concrete foam, also called foamed concrete or aerated concrete, is a porous building material with bubbles throughout the concrete. Foam concrete does not decompose and prevents the loss of heat when used as insulation in housing. Cement and foam alone produce sturdy floor material. Concrete, foam and sand mixtures are used as partition walls, thermal insulation and soundproofing.

Skill level:

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Things you need

  • Concrete mixer
  • Foam generator
  • Formwork or moulds
  • Fine sand
  • Cement
  • Water
  • Chemical foaming agent

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  1. 1

    Decide how much concrete foam you need. For a volume of 0.5 cubic meters, you will need: 200 kilograms of cement, 200 kilograms of dry sand, 100 kilograms of water and foam generated at the correct density depending on your needs.

  2. 2

    Make the foam. Use the foam generator to make stable foam from the chemical foaming agent. In general, 500 litres of foam will make 1 cubic meter of foamed concrete. Foam generators use an air compressor to generate the foam. Portafoam is an example of smaller foam generating equipment.

  3. 3

    Mix the dry ingredients. Mix thoroughly and add the water in small amounts until sand, cement, and water are well mixed.

  4. 4

    Add the foam to the mortar. Make sure the foam and mortar and well mixed.

  5. 5

    Check the density of the product while wet. The density of dry concrete will be less, so make sure you are calculating based on wet density for your specific needs. For example, a density of 600 to 900 kilograms per cubic meter (17.2 to 25.4kg per cubic foot) is best for false ceiling and thermal insulation. See the Foam Concrete Physical Characteristics link below for more density recommendations.

Tips and warnings

  • Foam materials alone can sell for as little as $3 per square foot of wall area. The cost may be greater than other building materials, but the soundproofing and insulation benefits are worth the price.

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