Will The CarbonStrong Formula Decarbonise India’s Concrete Industry?

Clean tech or climate tech is not just about digital technologies, Internet of Things, sensors and software. A lot of the existing physical infrastructure as well as the buildings and the commercial spaces of the future need to be reshaped for a greener world. Which is why the scope of clean tech extends into areas that are typically not seen as technology in today’s world of  AI and industrial revolution. 

A clear example of this is the research and development in materials science and chemistries, where many startups are looking to create more eco-friendly alternatives to the existing building blocks of industry, whether it is in plastic mitigation, or as in the case of Carbonstrong, the cement industry.

Fossil fuel emission from an increasingly simmering planet is set to hit record highs this year, with nations projected to discharge roughly 38.1 Bn Tonnes of planet-warming carbon dioxide by burning oil, gas and coal for energy, manufacturing cement, and various other activities. 

India’s pledge to go carbon-free is set for 2070. But, are the initiatives strong enough to drive the world’s most populous nation to reach its net zero goal? 

Cement manufacturing makes up about 8% of global CO2 emissions. India, the world’s second-largest producer of cement, accounting for more than 8% of the global installed capacity, manufactures about 700 Mn Tonnes of cement, spewing out 177 Mn Tonnes of CO2 in the process.

Despite years of efforts to substitute a part of cement with fly ash, a byproduct from thermal power plants, in making concrete and other decarbonisation initiatives, carbon emissions from global cement manufacturing kept soaring. 

“Concrete is key to making building foundations, columns, and slabs, and cement is a key material in it. Though it’s just 10-15% by weight of concrete, it’s two-thirds of the total value of it, and contributes about 95% to its carbon footprint,” said Harsh Jain, who founded sustainability startup CarbonStrong to fight the menace.

CarbonStrong, which promises to bring an impactful shift in India’s 249.14 Mn cubic metres of ready mix concrete market, through a low-carbon binder that promises to replace cement in concrete by 40-50%. “Our technology not only reduces the carbon footprint of concrete but also reduces the cost while enabling more upcycling of fly ash from thermal power plants,” the CEO said.

Jain’s brainchild is not one of its kind, but the founder believes that there’s a need for multiple such players to bring down the carbon footprints of cement and concrete industries, as well as real estate and thermal power plants. 

Business Based On Sustainability

Jain said that if India has to achieve its climate-related goals, the country must focus on cement and steel because these two alone account for more carbon emissions than all ICE vehicles put together.

CarbonStrong’s low-carbon binder mixes fly ash with cement with a few proprietary additives, ensuring lower carbon emissions from concrete industries. The use of fly ash is also directly associated with reducing Scope 1 emission in the environment.

Fly ash, produced from the combustion of coal, poses health issues if left open in the air or seeps to soil or water due to its content of heavy metals like arsenic, cadmium, and lead. Despite India’s efforts to reuse fly ash (in producing bricks and cements), millions of tonnes of this hazardous material are mixed with water bodies across the country.

“We are producing this binder for concrete after receiving multiple feedback and seeing demand from industry stakeholders. Concrete producers and builders now want to replace cement with fly ash or blast furnace slag, which is a byproduct of steel making,” said Jain, an IIT Roorkee graduate and a post-graduate from the Indian Institute of Management Ahmedabad. 

He met Vikramaditya Singh, a mechanical engineer, during his stint at EY where they worked together in multiple consulting projects for various EV companies. They started tracking the early-day EVs in India and later went on to work together in other companies as well before founding CarbonStrong in December 2022.

The duo realised that a lot of good solutions to decarbonise electricity and transport were out there in the form of renewable energy. “We wanted to bring some impact, yet these sectors hardly had space for small and young startups. The other two frontiers were agriculture and heavy industry. In heavy industries, there was enough white space when we entered.”

Since it started operations in 2023, CarbonStrong has been engaged with R&D and product innovation. It has so far done pilots for 15 customers across India. The startup has also carried out three pilots with construction startup Infra.Market, IIT Madras Research Park, and Hyderabad-based Earth Pavers by supplying them with around 56 Tonnes of its proprietary fly ash-based concrete binder.

Cofounder and chief operating officer Singh said that IIT Madras Research Park’s laboratories were being built using CarbonStrong’s concrete binder where 30% of cement used in buildings would be replaced by its material. “Being trusted by IIT Madras has been a big achievement for us.”

The startup raised a small pre-seed funding from Momentum Capital and Bharat Founders Fund last year and plans a seed round soon to set up its first commercial manufacturing facility in Bengaluru with a production capacity of 100 Tonnes per day.

Ankur Shrivastava, managing partner at Momentum Capital, sees a massive, underfunded opportunity in the space where CarbonStrong may gain from India’s push for greener solutions.

What reaffirms CarbonStrong’s commitment to a sustainability vision is the technology and the many facets of the construction sector. 

The CarbonStrong Edge

The construction industry in India uses three types of cements – Portland Pozzolana Cement (PPC), Portland Slag Cement (PSC), and Ordinary Portland Cement (OPC). In PPC, 15-35% of the cement is replaced with fly ash. PSC has 30-70% slag, a byproduct of steelmaking. In fact, the government has been focussed on fly ash management for decades, which is why it is used in making concrete and bricks that are used in the construction of roads and flyovers. 

During 2024-25, NTPC said that 32% of 340.11 Mn tonnes of fly ash generated in the country was used in the construction of roads and flyovers, followed by 27% in the cement industry, and 14% in the manufacturing of bricks and tiles.

Experts, however, differ on the extensive use of fly ash in cement. “Fly ash mixed with cement gains strength slowly and has extended setting time, which increases the construction project timings. Use of fly ash at a higher percentage can lead to micro-cracking in the concrete structures. Besides, the quality varies depending on the types of fly ash mixed with cement. And, poor quality PPCs are finding their way into buildings, bridges, and roads in the highly unorganised construction market in India, often compromising the quality of the construction projects,” a Kolkata-based structural engineer, who provides consultation to corporate and hospitality projects, told Inc42, requesting anonymity.

Mixing fly ash with cement also gives a huge cost advantage to the concrete producers and builders. 

Jain agreed to the drawbacks of using fly ash and the thriving black market in the cement industry. However, he claimed that CarbonStrong doesn’t depend on fly ash alone and uses certain proprietary mineral additives to ensure that the problems of the material are mitigated. “About 80% of our binder is mechanically processed fly ash, which has been treated by removing unburned carbon, coarse particles, and all the impurities. The rest 20% is our proprietary cocktail of additives that we use so that it can react a lot faster.”

Over the last 12 months, the startup has spoken to more than 300 concrete producers, plant operators, site engineers, and structural consultants to understand how these materials behave. 

The founders also worked with professors at IIT Madras and IISc Bangalore to learn the chemistry of the materials like cement, slag, fly ash and design-specific interventions that can substitute cement by 40-50% in concrete, compared to 10-15% in other PPC mixes.

While slag, used in PSC, is a great material in terms of both usability and sustainability, Jain pointed out that the access to this material is limited as the top few steel producers like JSW, Tata Steel, ArcelorMittal, and Steel Authority of India Limited (SAIL) control this market. Fly ash, on the other hand, is available in large quantities across the Indian states that can be purchased by bidding for auctions.

The startup promises that its binder costs 30% less than cement when the production starts at scale. Cement sells for INR 5,000-6,000 a Tonne, slag costs INR 4,000-5,000 a Tonne, and fly ash costs around INR 2,000 a Tonne. At scale, CarbonStrong will price its product at INR 3,500 per Tonne, which would be slightly more expensive than fly ash, but by replacing more cement, it will save costs for concrete producers.

Cementing The Road Ahead

Making the concrete and steel we need doesn’t need to bake the planet we call home. The hunt for cleaner, greener alternatives goes full throttle across the world. 

While founders agree that the construction industry has many unethical players along the value chain, CarbonStrong is confident that it can capture a significant portion of the market by working with more transparent and established concrete producers.

Coming from a lineage where at least two of his earlier generations have been associated with the cement industry, Jain is confident that CarbonStrong will go to the factories of the right people who will do justice to the promises the startup makes.

In fact, companies around the world are trying to reduce the carbon footprint of concrete by replacing cement with other materials. CarbonStrong believes that it can make a difference by being a part of the global push towards decarbonisation in the construction industry. 

The Indian startup competes with Europe’s Hoffmann Green, US-based Terra CO2, homegrown Novacet, and tens of new-age companies world over. 

While this is just the beginning and a few pilots have refined the vision of CarbonStrong, the real utility of its product will be tested only when used at a mass scale for all kinds of construction projects – from smaller two-storey buildings to high-rises and bridges. 

Even as ESG considerations begin reshaping the construction sector, startups like CarbonStrong still face an uphill task of proving themselves in a market dominated by large conglomerates. But the urgency of climate action demands collective effort, not siloed progress. In that sense, CarbonStrong seems aligned to where the world needs to head.

[Edited By Kumar Chatterjee]