C2I 2024 Manufacturing Technology winner: Cement 2 Zero

Category: Manufacturing Technology
Project: Cement 2 Zero
Partners: Cambridge Electric Cement (now rebranded at Reclinker) with AtkinsRealis, Balfour Beatty, CELSA UK, Day Group, Materials Processing Institute, Tarmac, and Cambridge University

Concrete contributes seven per cent of global carbon emissions and numerous efforts are underway globally to decarbonise this foundation industry.

The Cement 2 Zero project is one such effort that is developing, scaling and delivering a low carbon, circular cement technology that takes demolished concrete and recovers recycled cement paste from it.

This cement paste is then introduced in place of lime to recycled steel in an electric arc furnace (EAF) where it bubbles through the molten steel to purify it. As it does so, it creates a flux that rises to the top of the molten steel to form a protective layer (slag) that prevents the steel being exposed to air.

The slag is then cooled quickly in air to form Portland cement.

The general principle sounds straightforward enough, but getting the recycled cement ready for market requires a collaboration involving several players from different industries, all of whom bring their own unique expertise to the project, which began in a lab at Cambridge University as part of the FIRES research programme.

This led to Concrete 2 Zero, an Innovate UK funded effort involving AtkinsRealis, Balfour Beatty, CELSA, Day Group, the Materials Processing Institute, Tarmac, Cambridge University, and Cambridge Electric Cement Ltd, a company formed to bring this innovative solution to the market. The partners, experts in concrete waste separation, steel recycling, cement and concrete production, engineering design, construction, and world-leading research, bring with them with the shared goal of speeding up commercialisation and sustainability impact.

In 2023, the Cement 2 Zero project demonstrated the technology at pre-industrial scale at the Materials Processing Institute’s seven tonne EAF on its Teesside campus. The process used the flux material containing end of life recycled cement processed by Day Group, using a variety of scrap steel inputs provided by CELSA.

Patricio Burdiles, the engineering and operations manager for Cambridge Electric Cement (CEC) company (now rebranded as Reclinker), explained that the resultant material from MPI then went back to the lab in Cambridge for further testing.

“And then if we’re happy with that, it is sent to Tarmac, [who] repeats the test and validates that the results that we’re seeing are actually repeatable,” he said. “Then that material is taken and used by a construction company, in this case Balfour Beatty, to produce some sort of construction.”

The project then moved onto industrial scale trials at CELSA UK in Cardiff where the same protocols were followed.

CELSA is the largest steel recycling company in the United Kingdom and can processes 150 tonnes of steel in less than an hour, with the opportunity to produce 20 tonnes of recycled cement in parallel.

Results from CELSA have been encouraging but further work will be needed.

“That material is being sent to a precast location owned by Balfour [and] they’re going to produce some piles with the material, said Burdiles.

“The key is that without the collaboration, and without having industrial partners that could effectively put value into the project and add their expertise into each step, this project wouldn’t have worked. The university by itself couldn’t have done it, [but] each of these players on their own couldn’t have done what we have done as a consortium. It’s [been] collaboration that has been key to getting us to the point where we are.”

Taking the process to an industrial scale has brought about its own challenges; CELSA’s process has enabled the project to develop a cementitious slag, but it isn’t quite Portland standard yet.

“What we’re getting today is good, but we’re compensating for the lack of performance by mixing with traditional Portland cement, so we’re using a 50/50 blend today and we’re quite happy with it,” said Burdiles. “We see good results, and we think it’s a very good first step into what can be developed in the future.”

Getting to this stage required the project to be structured around work packages and weekly meetings to ensure seamless integration of efforts across the supply chain. The collaboration has led to several key outcomes, including de-risking development by sharing knowledge and insights to reduce uncertainties at each stage of the process; identifying cross-industry synergies that standalone entities might overlook; utilising the collaboration’s combined resources and knowledge base to speed up the transition from lab to market; and to make informed decisions that consider the entire supply chain, balancing individual and collective interests.

Looking forward, Burdiles doesn’t see any issues around getting hold of the demolished concrete needed to produce CEC slags. In the UK alone, up to 20 megatons of waste is generated from demolition activities, although this number includes things like dirt, bricks and all manner of other materials.

CEC is mostly interested in what Burdiles calls ‘clean concretes’ that can be obtained from taking out a highway or an airport runway.

He said: “The cement fraction in concrete waste, the concrete that you recovered from demolition, is around 10 per cent. If we say that we’re getting 10 megatons of waste concrete you could, in theory, extract around a mega ton of cement from that. And now, because of the recycling process and how CELSA works, you can produce at the Cardiff plant around 150 kilotons of slags per year. What we see is that the available recycled material in the UK is far larger than what we can process at Cardiff alone. It’s around six to seven times larger, so we see that there’s a lot of room to grow.”

Burdiles continued: “We don’t see the availability of recycled material as the bottleneck here, it’s mostly the processing capacity of the furnaces, particularly here in the UK.”

Whilst the UK is currently lacking in processing capacity for CEC slags, the picture is different in Europe and beyond.

“Across Europe there are several. Spain has, I think, 10, large electric arc furnaces. France has around eight. There’s quite a lot on the northern countries, Norway, Sweden, and Turkey has, impressively, a very large number of them.”

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