Concrete is such a prominent feature of the built environment that it can be easy to take it for granted. However, the substance comes with a high carbon footprint.
This is partly because the process of making the cement, which is a key part of concrete, involves the breaking down of limestone through a process known as klinkering. Taking place in furnaces, which have historically been heated with fossil fuels, it causes carbon to be emitted as the limestone breaks down.
As a result, the production of cement and concrete accounts for 7.5 per cent of global emissions. However, researchers at Cambridge University have found an alternative that could all but eliminate this
This works by recycling cement by using it as a substitute for lime flux, which is used in steel recycling. The process, involving an arc furnace, produces the by-product known as slag when the lime flux is used. However, when cement is used the by-product is reusable cement, which can then go into new concrete.
The development promises to provide an abundant supply of cement for concrete repairs and construction without adding to emissions, a breakthrough hailed by Cambridge professor Julian Allwood as “an absolute miracle”.
Details of the research have been published in the journal Nature.
This development may be particularly significant in the UK construction sector. Professor Allwood suggested that despite the breakthrough, the use of concrete in construction should still be reduced.
Part of that aim could be achieved by reducing the use of demolition and rebuilding from scratch. In 2019, Architects Journal started a campaign on behalf of members of the profession that advocated reusing buildings more.
However, that still means keeping old concrete buildings, tunnels and other structures in a good state and carrying out structural repairs will become increasingly necessary. It is very good news for the environment, therefore, that this new technique could ensure such work is no longer carbon-intensive.