Cocoon Carbon, a startup that converts steel industry waste into a high-performance cement substitute, has closed a $15 million Series A round. The investment was co-led by 2150 and Brick & Mortar Ventures, two investors focused on built-environment technology. TVC (The Venture Collective) joined as a new participant, while existing backers Wireframe Ventures, Celsius Industries, Gigascale Capital, and SOSV continued their support.
Concrete is, by volume, the most widely used material in the world after water. For decades, the construction industry has relied on supplementary cementitious materials (SCMs) — industrial byproducts used to partially replace Portland cement in concrete mixes. They reduce cost, improve durability, and lower the carbon footprint of the final product.
The traditional sources of SCMs are disappearing. Most of the supply historically came from coal-fired power plants and blast furnace steel mills. As both industries wind down across the United States and Europe, those byproducts are becoming scarce. In several markets, SCM prices have already doubled since 2017. Construction demand, meanwhile, is moving in the opposite direction — driven in part by the data center building boom, global infrastructure is projected to double over the next four decades. SCM demand is now growing at roughly 6 to 7 percent annually.
"The SCM market is facing a structural deficit at exactly the moment infrastructure demand is rising," said Eliot Brooks, CEO and Co-Founder of Cocoon Carbon. "We're focused on delivering a plug-and-play solution that gives concrete producers access to affordable, local materials - while improving the economics of electric steelmaking. Expanding supply is the fastest way to stabilize costs and lower carbon in concrete."
The Series A will fund Cocoon's first commercial demonstration facility in the United States, designed to validate the technology at industrial scale and establish the operational track record needed to finance a broader rollout. The target is more than 50 steel plants across the US and Europe. The company is also doubling its team, with hiring underway for process engineers, materials scientists, and commercial staff in the UK, alongside plant operators and technical personnel in the US.
Cocoon's process starts with slag from electric arc furnaces (EAFs) — steel mills that use electricity to remelt scrap, already a cleaner alternative to conventional blast furnace production. That slag has historically been an underused byproduct. Cocoon takes it molten and cools it approximately 100 times faster than existing methods, producing a material that works as a direct replacement for traditional SCMs.
The cooling technology retrofits into existing waste-handling infrastructure at steel mills. No standalone facilities, no prohibitive capital costs, no operational disruption. By sitting within existing systems and co-locating at mills, Cocoon also sidesteps the transportation costs that make up a significant share of what concrete producers actually pay for SCMs. The result is a product that competes on price without asking buyers to pay a green premium.
The material has been validated through third-party testing in concrete applications, and the company has already piloted at a major steel mill. Cocoon's R&D facility and concrete testing lab are based in London.
Jacob Bro, partner and co-founder of 2150, put the scale of the opportunity plainly:
"Concrete is one of the biggest value streams on the planet, providing the foundation of our civilization, from buildings to infrastructure to data centers. It consumes orders of magnitude more energy than AI and emits more CO2 than any other sector," said Jacob Bro. "Cocoon stands out in the innovation landscape with a product that is better and cheaper than cement and delivers a true drop-in replacement product for the industry."
Cocoon Carbon was founded by Eliot Brooks, Will Knapp, and Freddie Scott. The London-based company's existing investors — Wireframe Ventures, Celsius Industries, Gigascale Capital, and SOSV — all returned for this round alongside new participants 2150, Brick & Mortar Ventures, and TVC.
