Picture caption: Concrete waste from demolition projects is used to make cement clinker. Picture credit: Rumman Amin on Unsplash

What’s the most widely used material on earth, after water? That’s an easy one to answer if you work in architecture, construction or engineering; it’s concrete, of course.

So, it’s no surprise that the processes involved in producing cement make up a huge chunk of global carbon emissions. According to data published by Robbie Andrew, an emissions scientist working for the CICERO Centre for International Climate Research Project in Norway, and the Global Carbon Project, the cement industry’s CO₂ emissions doubled between 2002 and 2021. Emissions from cement production are 7% of total global CO₂.

Although alternative building materials are used on some projects, the need for cement isn’t going anywhere, so it makes sense to look at how we can reduce these emissions. That’s exactly what the Cement 2 Zero project is doing, here in the UK.

This demonstrator project is a collaboration between the University of Cambridge, the Materials Processing Institute and other industry partners. It began with a discovery by Dr Cyrille Dunant, that the chemical composition of used cement – from the demolition of old buildings – is virtually identical to the lime-flux used in steel recycling.

Concrete waste is crushed, to separate the stones and sand from the cement powder and water that bind them. The cement powder can then be used in the recycling process for steel. This flux floats on the liquid steel, protecting it from oxygen in the air. Once the recycled steel is tapped off, the liquid slag is cooled rapidly and ground into a powder. This powder – now known as Cambridge Electric Cement (CEC) – is almost identical to Portland clinker, one of the main ingredients in cement.

The clinker is usually produced by firing limestone and other minerals in a kiln at 1450^oC – a process responsible for more than half of the cement industry’s emissions. It’s clear that the trial’s alternative approach, if viable, will have a huge impact on reducing carbon emissions.

Not only does the new process reduce the energy needed to produce clinker, but it also saves on raw materials. Dr Dunant sums up the scale of the problem, saying, “We take the built environment around us for granted; new homes, schools, hospitals, workplaces, roads and railways, as well as infrastructure that provides us with clean water, sanitation and energy – all require cement which is an essential building material.

“It’s estimated that annual production equates to more than 500kg of concrete per person on the planet per year, and it is not currently possible to produce the material without creating CO₂ emissions.

“This breakthrough offers a positive move in cement production and will support the industry response to the UK’s legally binding commitment to bring all greenhouse gas emissions to net zero by 2050.”

The trial will run for two years, with the first phase already having been carried out in a 250kg induction furnace. After the success of this initial run, the process is being scaled up to 6T in an electric arc furnace, with the goal of producing 20 tonnes of zero-emissions cement to use in a construction project. Eventually, industrial-scale melts will follow.

It sounds like a promising breakthrough, and something that could certainly make a huge difference to levels of emissions once it’s been thoroughly tested.

Realistically, we need more of these kinds of trials. Should this trial turn out to be successful, then let’s hope the use of Cambridge Electric Cement is widely adopted. We need innovations like this to be implemented quickly in order to reduce the pace of climate change.

Meanwhile, if you need assistance with the structural elements of an upcoming project, please do get in touch.