High Speed 2
Unlocking circular materials to decarbonise UK high-speed rail
High Speed 2 (HS2) – Britain’s flagship high‑speed rail project – is one of the nation’s most ambitious infrastructure programmes. As it carves a new route across the country, the railway is producing vast volumes of excavated clay while depending heavily on carbon‑intensive concrete to build critical assets.
HS2 asked us to investigate a wider market challenge: why was the UK struggling to adopt calcined clay, a proven low‑carbon cement material that could cut emissions, reduce costs, and strengthen resource resilience?
Together with HS2, the Department for Transport (DfT), National Highways, and industry partners, we built the evidence, mobilised industry demand, and worked to accelerate the arrival of calcined clay into the UK construction market, with the potential to achieve a 40 percent cost and 30 percent carbon reduction.
Proving the credentials of calcined clay
HS2 is Britain’s new high‑speed railway, linking London and Birmingham in 49 minutes and targeting economic growth.
As part of its major tunnelling and civils programme, large quantities of clay are being excavated. Traditionally, this would be treated as waste and transported to landfill. At the same time, the organisation relies heavily on concrete to build vital infrastructure. Concrete accounts for a significant proportion of global carbon emissions, driven largely by the energy-intensive, CO₂-producing cement used within it.
With the UK’s decarbonisation deadlines fast approaching, HS2 saw an opportunity to tackle a wider market failure: calcined clay was proven internationally, but not yet adopted at scale in the UK.
We needed a partner who could unpick a very complex picture and help us understand whether the UK could finally embrace a material that the rest of the world already knows works.”
Unpacking a complex challenge
HS2 valued our combination of deep materials expertise, strategic capability, and strong connections across the wider infrastructure sector — including National Highways and other major stakeholders. This blend meant we could validate the science, navigate the complex supply chain, and convene the right industry actors to drive change.
The technical question mattered: could calcined clay work in the UK? But the bigger challenge was creating confidence across a vast, fragmented, and risk‑averse construction market. Concrete supply chains span multinational producers, local batching plants, and countless contractors. Changing the materials used requires every link in that chain to trust the performance, cost, and availability.
The shift to calcined clay was hindered by a mix of systemic barriers – from incentives that favour premium cement, to limited familiarity with calcined clay despite its compliance with British standards. Suppliers were also reluctant to invest without clear demand, creating a classic chicken and egg dynamic, while growing reliance on imported cement and dwindling supplies of alternatives raised wider resource security concerns.
The status quo was holding the entire industry back. Everyone agreed something needed to change, but no one actor could make that shift alone.”
Mobilising an industry‑wide response
Our work began with a comprehensive scientific and market validation exercise. We brought together global evidence, academic studies, and UK specific testing to confirm that calcined clay cement is technically robust, commercially viable, and already embedded within existing British Standards. “This gave HS2 the confidence to move from concept to action,” explained PA’s Starkie.
Next, we examined the UK supply chain in detail, identifying the blockers and the levers for change. This included modelling the potential carbon and cost savings – up to a 30 percent reduction in emissions per block of concrete and as much as a 40 percent reduction in cost due to lower energy requirements.
Recognising that no single organisation could shift the market alone, HS2 helped convene a national task and finish group sponsored by the Department for Transport and National Highways. We brought together suppliers, buyers, policymakers, and infrastructure leaders to build a united case for future use.
“One of the most significant steps was demonstrating demand,” explained PA's Starkie. She continued, “we secured letters of support from around ten major infrastructure and utilities client organisations and contractors to specify calcined clay in their projects if it became available.” This created a first of its kind demand signal, giving suppliers the confidence to seriously explore UK production and import pathways.
Our industry summit brought 100+ senior leaders into the same room – from national infrastructure owners to global cement manufacturers – to agree what must happen next. “It was the first time the entire value chain was challenged to think differently about concrete and commit to doing something about it,”
Accelerating the transition to low carbon construction
The work has helped shift how the UK infrastructure sector thinks about materials. It has built the evidence, signalled demand, and identified a credible pathway to cut emissions, strengthen resource security, and reduce costs. For the wider ecosystem, it has shown how calcined clay could become part of the UK’s mainstream construction mix.
The momentum created is already influencing national debate, with new policy discussions underway and suppliers beginning to reassess UK production opportunities.
Most importantly, this work is still creating the conditions for sector-wide adoption – ensuring public investment today can contribute to a lower carbon, more resilient future for consumers across the UK.
The real value of this work is that it has mobilised an entire ecosystem. We now have the evidence, the demand signal, and the industry alignment needed to accelerate calcined clay into the UK market, helping us reduce emissions, cut costs, and build a more resilient construction supply chain.”
If the UK is to meet its 2050 goals, we cannot wait for incremental change. This work is helping accelerate a shift that simply must happen.”
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