How Heidelberg Materials UK leads the production of nuclear grade concrete
Heidelberg Materials is the only heavy building materials manufacturer in the UK certified to produce nuclear grade concrete in accordance with BS EN ISO 19443 .
The accreditation puts the company in a unique position to capitalise on this growing nuclear sector, as Sean Hunter, Head of Nuclear Operations at Heidelberg Materials UK, explains:
The UK Government has reinforced its manifesto commitment to build more nuclear power plants to achieve energy security, and the latest evidence of this came in late 2025 when Sizewell C in East Suffolk reached financial close.
Among its plans are to open up more new sites by including new nuclear technologies such as small and advanced modular reactors, which can be built at a greater variety of locations while still adhering to robust criteria.
Building nuclear power plants is technically demanding and requires consistent delivery of the highest quality building materials in significant volumes over an extended period. This means the role of quarrying and the selection and production of aggregates is critical to the success of these projects.
Heidelberg Materials UK has a strong track record in this area, supported by a dedicated project delivery team and a robust, internally sourced material supply chain that has been central to the delivery of high quality nuclear-grade materials to Hinkley Point C (HPC) in Somerset for over 13 years. We are now using the knowledge and experience gained at the site through intelligent replication to supply Sizewell C , where we are already supplying nuclear-grade concrete as part of the plastic cut off wall supply.
Producing nuclear-grade concrete
The raw materials used to produce nuclear-grade concrete must be of the highest quality and in precise ratios to achieve the high strength and durability requirements as set by the Office for Nuclear Regulation . Achieving this at scale, and doing so consistently, is a huge challenge; one that the Heidelberg Materials team met at HPC by developing a bespoke quality management system focused on quality, efficiency, and repeatability.
The system provides a digital framework for monitoring and verifying each stage of material production and delivery. It tracks compliance against project specifications and regulatory standards, supports documentation, and enables real-time quality monitoring.
And, it contributes to compliance by integrating testing data, inspection records, batch histories, and certification to enable full traceability at every stage of production.
Quality assurance at every stage
Every material entering our nuclear supply chain is subject to extensive testing.
Concrete mixes are assessed through regular sampling for 28-day strength requirements and monthly reports document compressive strength, consistency, and temperature.
Quality data is reviewed continuously to detect trends, guide adjustments, and assist the client in conformity. All material is accompanied by documentation confirming origin, test results, and compliance with project specifications. Our testing regime is supported by its national laboratories, equipped with calibrated, UKAS-certified equipment.
The standards and learnings established at HPC have created a culture of quality assurance and accountability across the wider business. It is embedded in every site, with employees aiming to uphold the same level of rigour and attention to detail, regardless of project size or scope.
The Heidelberg Materials team based at HPC manages on-site batching, delivery scheduling, pour coordination, and quality assurance, operating as a single point of contact for the client, with shared responsibility across all aspects of delivery.
It uses real-time digital dashboards to monitor material properties, site readiness, and compliance and has built a reliable, resilient logistics network which uses fixed routines and strict oversight to make sure materials arrive safely, on time, and within specification.
Nuclear safety culture
A strong nuclear safety culture is essential to all operations at HPC, including fostering a questioning and challenging mindset among the workforce.
Employees are encouraged to raise concerns, challenge assumptions, and seek clarification whenever there is uncertainty. This approach reduces the risk of errors and supports continuous improvement. A clear, structured process for reporting and resolving concerns ensures that quality and safety are maintained at all levels.
Our nuclear team is now sharing best practice and lessons learned from our close involvement in supplying HPC with the team at Sizewell C.
Over the past 12 months we have worked to develop and trial the concrete mix needed for the first phase of the cut-off wall, a structure which will run around the perimeter of the Sizewell C nuclear power station. Made up of concrete panels and a plastic wall, the cut-off wall will reach more than 50 metres below ground, forming a watertight barrier. This will enable around four million cubic metres of earth to be excavated from the site and allow construction of the two reactor units.
We are supplying around 35,000 cubic metres of concrete which contains admixtures from Sika to ensure workability, allow a longer window for placing and compaction and inhibit the ingress of groundwater. The material is being supplied from our Ipswich concrete plant as well as a mobile batching plant installed at the Sizewell C site.
Supplying nuclear projects requires more than high-quality materials. It demands a controlled, repeatable system for delivering under strict nuclear standards. The team at Heidelberg Materials has met this challenge through a bespoke technical framework operated by a highly qualified team of experts. The result is a supply chain that delivers consistent, nuclear-grade concrete at scale, backed by rigorous documentation, real-time monitoring, and continuous oversight. Although developed to meet HPC’s nuclear requirements, these methods and systems set a benchmark for quality, consistency, and control that can be tailored to any client seeking the highest standards of performance and assurance.
Setting the standard
In 2023 Heidelberg Materials UK (then Hanson UK) became one of the first companies in the UK to be certified to the ISO 19443 standard, which seeks to drive nuclear safety culture.
BS EN ISO 19443 is the quality management standard for those supplying products and services that are important to nuclear safety. The system is based on ISO 9001, combining best practice in quality and applying its principles to the nuclear sector while enhancing many areas to ensure long term impacts are assessed to reflect this highly regulated sector.