Will Lavelle of Atkins and Dr Philippa Horton from the University of Cambridge discuss what’s claimed to be the world’s first trial of zero emissions cement, which aims to develop ‘net-zero’ cement for the global construction industry
The decarbonisation of the built environment presents a phenomenal challenge to the construction industry, as the global 2050 deadline looms. And with an estimated 80% of 2050’s buildings already in use today, there has rightly been considerable political and public attention given to the operational decarbonisation of existing UK homes – through improved insulation, installation of heat pumps and a rapid shift towards a decarbonised domestic electricity grid.
But there is also a keen focus on the carbon footprint of construction itself, and a real need to ensure embodied carbon is not left behind in this drive. Which is why the recent launch of zero-emissions cement trials is such an important step in the construction industry’s net zero journey.
Cement 2 Zero is a UK demonstrator project to trial the world’s first zero-emissions cement on an industrial scale. This innovative project, which secured £6.5m of Government funding from UKRI (UK Research and Innovation) as part of the Transforming Foundation Industries Challenge, aims to further advance the construction, cement and steel sectors’ decarbonisation journey to net zero industries of the future, to help meet the UK Government’s commitment of achieving net zero by 2050.
Led by the Materials Processing Institute, and supported by the University of Cambridge, in collaboration with key players in the supply chain, Cement 2 Zero, the end goal of the project is to produce ‘zero carbon’ Cambridge Electric Cement (CEC) at scale. It is the first collaborative trial of its kind to address the global construction industry’s biggest challenge of decarbonisation, in response to the climate emergency.
Concrete is the most widely used material on earth, after water. The chemical and thermal combustion processes involved in the production of cement are a significant source of CO2 emissions. The more than four billion tonnes of cement produced each year accounts for around 7% of global CO2 emissions, according to the Global Cement and Concrete Association (GCCA).
Cement-based products can easily contribute more than 50% of the CO2e (‘Carbon Dioxide Equivalent’) emitted during construction of a traditional new-build home. Cement is of course found in many of the key elements including foundations, mortar and screed, but also blockwork and plasterboard, and in the UK, concrete and cement account for 1.5% of CO2 emissions.
Project methodology
The Cement 2 Zero project will investigate the technical and commercial aspects of ‘upscaling’ the existing production from CEC to produce 20 tonnes of zero emissions cement.
The first phase of trial ‘melts’ is being carried out by the Materials Processing Institute, initially in a 250 kg induction furnace, before being scaled up to 6T in an Electric Arc Furnace (EAF). Once the process has been substantially trialled, developed and de-risked effectively, industrial scale melts will follow in CELSA’s EAF in Cardiff.
The two-year industrial trial will test each stage of the production process and brings together the expertise of the Materials Processing Institute, the University of Cambridge and key supply chain partners – Atkins, Balfour Beatty, CELSA, Day Aggregates and Tarmac – before using the product in a live UK construction project.
If successful, it could not only further advance the cement, steel and construction industries, but influence how we recycle, construct and maintain our built environment and transport infrastructure, shaping the future of towns and cities, while simultaneously boosting economic development and reducing CO2 emissions.
If Cambridge Electric Cement lives up to the promise it has shown in early laboratory trials, when combined with other innovative technologies, it could be a pivotal point in the journey to a zero-emissions society. The Cement 2 Zero project is an invaluable opportunity to collaborate across the entire construction supply chain, to expand CEC from the laboratory to its first commercial application.
It also has the potential to make a significant contribution to achieving a zero-carbon society, secure and increase jobs in the UK cement and steel sectors and challenge conventional production processes, creating high-value materials from demolition waste.
The science behind CEC is truly innovative. Three researchers at the University of Cambridge; Dr Cyrille Dunant and Professor Julian Allwood, along with co-author of this piece Dr Philippa Horton, invented a process that converts construction and demolition waste to cement over molten steel (using an EAF, normally used to recycle scrap steel).
The Cement 2 Zero project aims to demonstrate that concrete can be recycled to create a Slag Forming addition which could, when cooled rapidly, replace Portland cement.
Dr Dunant has discovered that the chemical composition of used cement is virtually identical to that of the lime-flux used in the conventional EAF steel recycling process.
Traditional Portland clinker, one of the main ingredients in cement, is produced by firing limestone and other minerals in a kiln at extremely high temperatures (1,450°C) – the process that accounts for more than 50% of the cement sector’s emissions.
Cement 2 Zero takes a different approach – it will use recycled cement as the flux in the electric steel recycling process (in an EAF powered by renewables). The by-product of this, when cooled and ground, produces Portland cement clinker, which is then blended to make ‘zero-emissions’ cement.
With this in mind, this innovative cement product (CEC) could be produced using a virtuous recycling loop, that not only eliminates the significant emissions of cement and steel production, but also saves raw materials.
This is a project that aims to be transformational for the cement and steel industries, creating a zero-emission supply chain from demolition to construction.
And, when it comes to housebuilding, CEC represents a huge opportunity to massively reduce the impact of our industry. And when you combine this with the lower carbon steel technology which is also enabled by this trial, there is a real sense that we’re well on our way to real net-zero homes.
Will Lavelle is embodied carbon lead at Atkins and Dr Philippa Horton is a business manager in the Engineering Department of the University of Cambridge