CarbonStrong Raises ₹12.5 Crore to Scale a Fly-Ash Cement Substitute for India's Concrete Industry
CarbonStrong has raised ₹12.5 crore to scale a fly-ash-and-slag binder that can replace up to half the cement in concrete, aiming to cut emissions from one of the hardest industries to decarbonise.
Manik Gupta
Founder and editor of DeepTech India. Manik writes about India's frontier technology ecosystem — AI, semiconductors, space, quantum, robotics and biotech — translating research and policy into clear, reliable reporting.
CarbonStrong raises ₹12.5 crore to turn industrial waste into cement India doesn't have to fire a kiln for
Cement is one of the hardest industries to decarbonise: manufacturing it means heating limestone to over 1,400°C, a process that alone accounts for roughly 7-8% of global carbon dioxide emissions. Bengaluru-based CarbonStrong is betting it can shrink that footprint by replacing a large share of the cement in concrete with a binder made from something India already produces in enormous, underused quantities — industrial waste.
The climate-tech startup has raised ₹12.5 crore (about $1.5 million) in a seed round co-led by IAN Angel Fund and Rainmatter, with participation from Social Alpha, Full Circle Ventures, and existing backers Momentum Capital and Spectrum Impact. The fresh capital will fund CarbonStrong's first dedicated production facility, expand its team, and move the company from customer trials and paid pilots toward commercial-scale output.
Fly ash, steel slag, and a binder built to replace half the cement in concrete
Founded in 2022 by Harsh Jain, who serves as CEO, and Vikramaditya Singh, the COO, CarbonStrong processes industrial by-products — primarily fly ash from coal power plants and slag from steel manufacturing — into a low-carbon, cementitious binder that can substitute for up to 50% of the ordinary Portland cement used in a batch of concrete. Both founders came from consulting and energy-sector backgrounds rather than materials science labs, and the company has said its formulation grew out of sustained industry research paired with real-world pilot deployments rather than a single lab breakthrough.
India produces well over 200 million tonnes of fly ash a year, much of which is only partially utilised and otherwise stored in ash ponds that carry their own environmental liabilities. By converting that waste stream into a marketable substitute for a material builders already buy in bulk, CarbonStrong is positioning its binder less as a "green premium" product and more as a straightforward cost and supply-chain play — a pitch that matters in a construction industry where margins are thin and buyers are conservative about anything that touches structural material.
Pilots across three cities, and a market under regulatory pressure
CarbonStrong says its material has already been used in demonstration projects across Bengaluru, Hyderabad and Chennai, moving the company past the stage of lab validation and into the kind of paid pilots that construction-material buyers typically require before committing to larger orders. That trial base is what the company says it will now use the new funding to convert into recurring commercial contracts, backed by its own production capacity rather than third-party manufacturing.
The timing lines up with a broader tightening around embodied-carbon accounting in Indian construction and infrastructure procurement, as both government infrastructure programmes and private developers face growing pressure to report and reduce the emissions baked into the materials they use, not just the emissions from a building's operation. Cement and concrete, as one of the largest material inputs into that footprint, are an obvious target for substitution technologies — a category that also includes rival approaches such as calcined-clay cements and geopolymer binders being developed elsewhere in India's climate-tech sector.
Why investors are betting on industrial waste
IAN Angel Fund and Rainmatter's decision to co-lead a round this early suggests confidence less in a single novel chemistry and more in the deployment path CarbonStrong has already proven: real pilot projects, in real cities, using material inputs that are abundant and already being generated at industrial scale rather than requiring new supply chains to be built. For a category of startup that often struggles to get past small-batch validation, having concrete already in the ground in three metros is a meaningfully further stage than most climate-materials seed rounds reach.
Whether CarbonStrong can scale its binder from pilot volumes to the tonnage that India's construction sector consumes will depend on production economics that only a dedicated facility — the explicit purpose of this raise — can properly test. If it works, the model offers a template that other Indian climate-tech ventures are watching closely: profitable decarbonisation that starts from the country's waste streams rather than from imported technology.
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