January 26th’s New Scientist ran an article on E-Crete (p 28 – 29), which is sadly behind a paywall but which I shall do my best to summarise here.

Concrete is a very versatile building material, but it’s not very green. The production process for Portland cement, a key ingredient of concrete, involves heating limestone up to 1400C. This produces half a tonne of CO2 per tonne of cement, with another third of a tonne of CO2, or more, produced by fuel burning, transport, etc.

Not good.

Indeed, it’s estimated that 5 – 8% of global CO2 emissions come from cement production, and demand for concrete is predicted to double over the next decade. The construction industry isn’t the fastest moving industry on the planet, but change is happening.

Enter Australian company, Zeobond, and their more eco-friendly E-Crete, a geopolymer concrete which releases just 10% – 20% of the CO2 from traditional concrete. It’s made by taking silicates and aluminates from fly ash and slag – the waste from power stations and steelworks – and adding an alkali which reacts chemically and produces a long molecule called a geopolymer. This can then act like cement does, binding together any gravel and sand that are introduced. The polymerisation process requires no heating, and produces no CO2, which makes it much greener than traditional concrete.

Whilst geopolymers have been used for the last decade in things like catalytic converters, it’s only recently they’ve started to be used commercially for construction. There have been worries that they set too quickly, making them hard to handle, and are more porous than traditional concrete and so may decay faster. But changes in the production process and rigourous testing suggests that they’re just as strong as concrete. Now geopolymers are being used in construction and engineering, as railway sleepers and in buildings.

Yet it looks like it’s going to be a while longer before we see a wholesale movement to geopolymers as conservative industries like construction are very risk-averse and want to see new materials fully proved before they adopt them. E-Crete’s green credentials might speed up the process, as pressure builds for the industry to change its ways and reduce its carbon footprint.

For me though, I’m excited not just by a concrete that is so green, but also by the fact that it recycles waste from other industrial processes. We need to think a lot more about closing loops, making the waste from one process the raw materials for another.