HOW CONSTRUCTION CAN MAKE THE SWITCH TO LOW-CARBON CONCRETE PART 2

The headline statistic on concrete is stark, to say the least. The world’s most heavily used construction material is responsible for around 8% of the world’s carbon emissions. This is part 2 of a two-part article.

One of the problems with ‘greener’ concrete is scaling it up, although things are beginning to improve. In the UK, the High-Speed 2 (HS2) rail project is currently one of the world’s largest infrastructure undertakings.

At London’s Euston Station, the construction team of contractor John F Hunt has been utilising Earth Friendly Concrete (EFC), developed by the Australia-based materials provider Wagners.

At the heart of EFC is a geopolymer system that binds industrial waste to make zero-cement concrete. According to Wagners, 400kg of waste material is reused in every m3 of concrete, resulting in a 75% reduction in carbon emissions, compared with traditional concrete.

Daniel Sweeny, group sustainability manager for John F Hunt, said, “We have made significant progress in lowering our operational carbon within the Group; however, our greatest challenge now is working with our supply chain to reduce our embodied carbon.

“Collaborating with Capital Concrete to pour Earth Friendly Concrete at our HS2 Euston project allowed us to save over 30 tonnes CO2e as a direct result. The consequence of this saving is being applied throughout John F Hunt, and we will increase our use of EFC, viewing it as a necessary product to help the construction industry achieve net zero.”

This is a good news story. The not-so-good news is that HS2 could potentially have reduced its carbon footprint by 2.5 million tonnes, had EFC been used across the entire project – that’ the same weight as 38 aircraft carriers.

Scaling up, though, will take time, and it’s time we may not have.

‘Wonder product’

In another UK-based example, as part of a motorway improvement scheme, Skanska recently undertook a trial, using a low-carbon reinforced concrete.

Paul Cole, a chief engineer on the project, said, “We’re doing this innovation project to see if we can remove carbon from concrete and remove steel from our reinforced concrete structures.”

Cole says, “We’re using an alkali activated cementitious material, along with a fibre reinforced polymer,” which, put simply, means the concrete contains no high-carbon cement, nor steel rebar. The cement replacement – which Cole calls “a wonder product” – kick-starts the reaction required to make the concrete harden, but has a much lower carbon footprint than cement.

Cole is pragmatic about how challenging it is to make the seismic shift away from standard concrete. He says, “The solutions are not there for us to simply pick up and run with. We have to investigate them, we have to trial them, we have to test them, research them.”

Perhaps, most importantly, he says, “We have to convince our clients that what we’re proposing works and that it will be the appropriate material to use in their permanent works.”

Carbon capture

Talking of convincing customers that you mean business, the German materials company that used to trade as Heidelberg Cement recently changed its name to Heidelberg Materials – that’s how serious the firm is about its own sustainability credentials.

Dr Dominik von Achten, chairman of the company’s managing board, said, “Our future is sustainable. We will be the first company in the world to offer carbon-free cement at large scale as early as 2024. We are vigorously driving forward the scaling of our CCUS [carbon capture usage and storage] activities: by 2030, we will reduce our CO₂ emissions by 10 million tonnes with the projects we have already launched.”

One of these projects is the construction of a full-scale carbon capture installation at the firm’s Brevik cement plant in Norway.

A world first, the Norwegian facility is expected to capture approximately 50% of the carbon in its emissions by 2024, totalling around 400 000 tonnes annually.

In Slite, Sweden, Heidelberg’s subsidiary Cementa operates a plan four times the size of its Norwegian counterpart. This facility produces around 75% of the cement used for all concrete production in Sweden.

Here, Heidelberg is set to build a carbon capture facility, which is expected to be capturing 1.8 million tonnes of CO₂ by 2030 – equivalent to the plant’s total emissions.

Additionally, Heidelberg’s subsidiary Cementa will introduce biomass to the fuel mix, furthering the emissions reduction.

A feasibility study for the project has concluded that the plant’s harbour location means transporting the carbon to a permanent offshore storage site and placed several kilometres down in bedrock is a workable solution.

The last word in sustainability

The members of the Global Cement and Concrete Association are in the main materials manufacturers, so one might assume there is some bias towards the continued use of these materials in construction.

Yet Thomas Guillot, the organisation’s chief executive, says, “We are asking for support from policymakers to create market demand for low carbon products in construction and public procurement. Policy reforms and the promotion of low carbon products can make a big difference as public infrastructure accounts for almost 60% of all global cement and concrete demand.

Guillot says “It is critical that the industry has government support to expand the successful pilots across the world towards commercial scale deployment. “We also need the wider construction industry to work with us toward the ambition of net zero concrete. Construction professionals, working with us and policymakers, will be key to developing the design and regulatory framework that will drive efficient use of resources and products, use of reprocessed and recycled material and the re-use of elements, as well as other technology to reduce materials and extend the lifetime of whole projects.”