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An introduction to foamed concrete

Established in 1991, Propump Engineering was the UK’s first ‘foamed concrete’ specialists, at a time when the construction industry barely knew what foamed concrete was. Twenty years on and still many people still don’t know of its capabilities. So, Propump has put together a simple guide to explain exactly what foamed concrete is, how it’s made and what it can do for you.

In the last twenty years, the use of foamed concrete has grown faster than any other ‘special’ concrete product. Special concrete applications in the UK are now thought to be close to about 1,000,000m3 a year, with much of this made up by volumes of foamed materials. However, despite the recent rise in popularity, foamed concrete is by no means a new product.

Two thousand years ago, the Romans discovered that by adding animal blood to a primitive concrete mix of small gravel, coarse sands, hot lime and water, and then agitating the mixture, small air bubbles would appear and make it more workable and durable. There is also evidence that 5,000 years ago Egyptians were using this type of technology, with similar results.

So, in two thousand years, how has foamed concrete changed? In its most basic form, foamed concrete is now a blend of sand, cement and water, with the additional ingredient of a synthetic or protein based foaming agent comprising water and air. As the foaming agent is added to the base mix, the density of the mix decreases whilst the yield increases – resulting in a lighter material.

The definition of foamed concrete is one that has an air content of over 30%. Typically the densities of foamed concrete range from 200kg/m3 to 1700kg/m3, showing significant reductions from traditional concrete which can be anywhere between 1700kg/m3 and 2400kg/m3. Strength of foamed concrete is generally accepted as being anywhere between 1 – 10 Newton/mm2. Strengths of up to 25 Newton/mm2 at 1400kg/m3 have been produced in laboratory tests.

It may look like a grey milkshake to start with, but once hardened, foamed concrete is comparable to autoclaved gas concrete products such as a celcon or thermalite block. Like the autoclaved product, foamed concrete is also extremely lightweight and offers a quick and easy installation – making it ideal for a number of applications where traditional concrete isn’t feasible.

Increasingly popular with designers and engineers, foamed concrete is perfect for filling voids where access is difficult or when a lightweight mix is needed to meet restricted loading limits. Its most common applications include bridges, floor and roof screeds, pre-cast panels, sewers and tunnels,

From lightweight, thermally insulating screeds to large volume mass infill projects, foamed concrete offers a versatile and high performance solution to an extensive range of concrete projects. From its Roman and Egyptian beginnings, foamed concrete has evolved to become one of the most innovative and progressive concrete solutions available – and without a toga in sight.

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