This Zero Carbon Cement from Recycled Concrete will Change the Face of Modern Construction

Engineers at Cambridge University have invented the world's first-ever zero carbon cement, called the Cambridge Electric Cement, a real accomplishment in the modern age.

The team is part of UK Fires, an organization we covered for its Absolute Zero report. The team consists of Dr. Cyrille Dunant, Dr. Pippa Horton, and Prof. Julian Allwood.

The team identifies the basic problem of cement to be chemistry, where calcium carbonate is cooked at 1,450°C with heaps of fossil fuel producing clinker and lots of carbon dioxide (CO2), Treehugger reports.

Concrete, Clinker, Cement

Cement is made by grinding clinker into a powder and mixing it with other ingredients. After that, cement is mixed with aggregate, primarily gravel and sand, to make concrete, which is then reinforced with steel to create buildings and structures.

Although the emissions from the cooking of calcium carbonate can be reduced, the chemistry will not change. This is the fundamental reason why concrete is called the most destructive material on earth and recently complained about concrete icebergs.

The team developed Cambridge Electric Cement using a modified formula.

Dunant noticed that used cement separated from recycled concrete was nearly identical to the lime flux used to remove impurities from steel in both electric arc and basic oxygen furnaces, according to the press release.

It floats on top of molten steel to keep it from oxidizing and eventually turns into slag, which is usually considered a waste product but contains calcium oxide, which is a key ingredient in cement clinker.

The Cambridge Method

The Cambridge researchers ground the slag into a powder and discovered that it is nearly identical to the clinker used to make new Portland cement.

In the Cambridge method, you deconstruct the reinforced concrete structure and recycle the reinforcing steel in an electric arc furnace. The aggregate is separated from the cement, which is then used to replace the lime flux in the electric arc furnace, resulting in "novel slag," which is used to replace the clinker in the Cambridge Electric Cement.

Prof. Allwood stated that if Cambridge Electric Cement (CEC) lives up to the promise it has shown in early laboratory trials, it could be a turning point in the journey to a safe future climate.

Allwood further explained that by combining steel and cement recycling in a single process powered by renewable electricity, the supply of the basic materials of construction could be secured to support the infrastructure of a zero-emission world and enable economic development where it is most needed.

The professor that this scenario could change the situation for both the concrete and steel industries, with regards to emissions. Making lime for the steel industry produces a lot of CO2; as in making cement, it involves cooking limestone or calcium carbonate, which approximately doubles the footprint.

Read also: Underwater Glue From Mussels Inspires to a Synthetic Cement According to Researchers 

According to the Multidisciplinary Digital Publishing Institute (MDPI), about 40% of lime produced goes to the steel industry, which is between 140 and 160 million metric tons per year.

The team theorized that if the lime is replaced by the Cambridge process, the carbon will be dramatically cut down, thus creating zero carbon cement.

However, there is going to be a big problem of scale, as the scientists explained. There are not enough buildings being demolished, and the steel industry doesn't generate nearly enough slag to replace more than a fraction of the conventional cement industry.

Allwood confirmed that the total zero carbon cement production would be much less than the current cement demand.

Allwood added that with the material efficiency strategies that have been the core of their team's work for the past 15 years, they suggest that modern construction projects could be built with much less cement than is being used today.

Related article: Making Cement Green: How Decarbonizing Cement Will Help Achieve Climate Goals