Heidelberg Materials to Supply 35,000m³ of Concrete for Sizewell C Cut-Off Wall

First phase of key containment structure begins as UK’s newest nuclear power station moves into main works

Heidelberg Materials UK has been awarded a contract to deliver 35,000 cubic metres of concrete over the next seven months for the Sizewell C nuclear power station in Suffolk. The material will be used in the construction of a deep cut-off wall—an essential component of the site’s early civil engineering works.

Designed to form a watertight barrier around the central construction area, the wall will be made up of concrete panels and a plastic membrane. It is set to extend more than 50 metres underground, enabling the safe excavation of approximately four million cubic metres of earth for the planned twin-reactor nuclear facility.

Although the contract value has not been disclosed, Heidelberg confirmed that initial deliveries will be made from its Ipswich plant, with a mobile batching facility currently being installed on-site to ensure consistent supply as the project ramps up. The on-site plant is expected to become operational by the end of 2025.

The concrete mix includes admixtures from Sika, selected to improve the durability and workability of the material under complex conditions. The additives are designed to extend the placement window, enhance compaction, and provide resistance to groundwater ingress, ensuring long-term performance for the sub-surface structure.

Sean Hunter, Head of Nuclear Operations at Heidelberg Materials UK, said the company had collaborated closely with Sizewell C and its partners over the past year to develop and rigorously test the specialist mix design. He noted that Heidelberg’s decade of experience supplying concrete to Hinkley Point C—another major UK nuclear project—is being transferred to Sizewell C through what he described as “intelligent replication.”

“We’ve been able to bring forward proven solutions from Hinkley while also tailoring the mix to meet the specific geological and engineering requirements of the Suffolk site,” Hunter said.

Sizewell C, a joint project between EDF and the UK government, reached a key milestone in July 2025 with a final investment decision confirmed. The approval has paved the way for full-scale construction of the £38 billion power station, with enabling works already well underway.

Once operational, Sizewell C is expected to supply low-carbon electricity to six million homes, playing a critical role in the UK’s net-zero energy transition.