Researchers may have discovered a new method for creating cement that is more environmentally friendly, potentially transforming the construction industry. Over the past two decades, experts have been working to reduce the amount of carbon dioxide (CO2) released by cement factories. The production of one tonne of cement emits about a tonne of CO2 into the atmosphere, which is detrimental to the climate. To put it into perspective, if cement were a country, it would be the third-largest emitter of CO2, following China and the United States.
The primary component of cement is called clinker. While experts have been able to minimize the amount of clinker required by blending it with other materials, there is currently no cement without at least some clinker.
A team at the University of Cambridge came up with an innovative idea. One of the researchers, Cyrille Dunant, proposed that by crushing old concrete to separate the sand and stones from the cement, and then heating the cement, it could be transformed back into clinker. Additionally, they considered using steel, which is a significant source of pollution, to aid in this process.
Although steel is the most recycled material by weight globally, cement is not commonly recycled. Previous attempts to heat waste cement from crushed concrete in a kiln to produce new clinker have been challenging in practice. However, researchers at the University of Cambridge decided to heat waste cement in an electric arc furnace (EAF) – the same type used for recycling steel. In steel recycling, lime is added to bind with impurities and metal- and silicon-based oxides to form a removable by-product called slag.
The researchers replaced some of the lime with waste cement, which was found to perform the same function as lime. Instead of obtaining low-quality slag, they obtained a product with a composition nearly identical to pristine clinker. Although the material requires adjustments by adding small amounts of lime, alumina, and silica, the resulting slag can be dried, crushed, and used to produce new cement.
If sustainable energy is used to power the furnaces, this method of recycling concrete and steel could potentially produce minimal emissions. According to Cyrille Dunant, “This is proof that cement is a recyclable material, similar to steel and aluminum, and it is possible to recycle cement using an electrical process.”
In initial small-scale tests, the team produced a few dozen kilograms of this new “electric cement.” They are now scaling up the process and aiming to produce up to 66 tons of reactivated cement in two hours. A Spanish company, Celsa Group, is also working to replicate the process at scale in its electric arc furnace in Cardiff.
Scientists believe that this discovery could not only significantly reduce carbon emissions associated with cement production but also make cement much cheaper to manufacture. However, Professor Allwood, who led the study, cautioned that while this new method shows promise, it is only part of the solution. “Producing zero-emission cement is remarkable, but we also need to reduce overall cement and concrete usage,” he emphasized. “We simply use too much of it.”
Recent Comments