Foamed Concrete

Foamed concretes are made by blending a very liquid cement slurry into a robust foam, much like folding melted chocolate into stiffly beaten egg whites to make a lovely chocolate mousse. This process results in a much lighter and cheaper cement material, which can be used to fill large areas very quickly. The foam is either protein based, usually from animal sources like hooves, horns and skin, or from synthetic foaming agents, which sort of ruins the nice chocolate mousse analogy. The cement can include additives to give the material a required density, like ash, dust, sand or slag, which is a glassy by-product of smelting metals.

High density foamed concrete has good resistance to water damage, as the dense bubble structure won’t let cracks appear in the same way that solid concrete might. Low density formulations might work better when weight is an issue, for example the layers between floors in a high-rise building. This material is different from the aerated concrete that breezeblocks are made of, which is made by pumping gas into the cement prior to casting, giving a heavier, denser result.