In July 2023, in the dusty basement of a building in Seattle, Washington, about 60 tonnes of concrete were poured as part of the renovation of a historic building. To an outsider, it looked like just another job site. Even to the workers pouring and shaping the concrete that day, it was more or less business as usual.

In fact, the messy, decidedly unglamorous occasion marked a milestone in the race to reduce gigatons of global CO2 emissions. That’s because the concrete was made using a more sustainable binding material developed by the startup C-Crete.

For C-Crete founder and president Rouzbeh Savary PhD ’11, the fact that the work went on as normal was a huge success. That’s because cleaning up an industry as large and conservative as construction is going to require a seamless, inexpensive transition.

C-Crete, shown here, is being placed in a building foundation in Seattle. Image: Courtesy of R. Savary, C-Crete Technologies.

“I am glad that we didn’t start with a flagship building that may signal only wealthy corporations can afford it,” explains Savary. “Cement is so abundant and such a low-cost commodity that if a new product aims to impact its CO2 emissions, it must penetrate into mass market, where everybody can resonate with and afford it.”

Decarbonising concrete would make a truly meaningful reduction in greenhouse gas emissions. Although estimates vary, the International Energy Agency found the cement industry is responsible for about 7% of human-caused CO2 emissions across the globe.

Concrete is the second most-used substance in the world after water. Savary likes to say that even water use is inflated in that ranking because it is used to make concrete.

C-Crete’s patent-pending materials bind with locally available mineral feedstocks and industrial byproducts to make cement-free concrete. The materials can be manufactured without the high temperatures needed for Portland cement production, reducing energy requirements. The company says C-Crete’s binder also absorbs CO2 over time, further greening up the lifecycle of the material.

“Our vision is to be able to use local Earth’s crust composition to make cementitious binders,” says Savary. “Cement’s use is ubiquitous and there is no need to ship it across the globe.”

Now, with what Savary calls the first pour of Portland-cement-free concrete in the US under its belt in Seattle, C-Crete is hoping to capitalise on broad interest and partnerships to scale rapidly.

“A single material can have such a big impact,” says Savary. “We’re aiming to reinvent century-old Portland cement using local materials, and to get this adopted in construction.”

From the $100K to a product

In the late 2000s, Savary pursued his PhD in MIT’s Department of Civil and Environmental Engineering. But he also took courses in materials science, business, and physics in order to further his understanding of cement. He also joined the newly formed MIT Concrete Sustainability Hub while at MIT

“Cement science is an interdisciplinary area, so I had to educate myself through different fields,” says Savary. “That exposed me to technologies and startups in different disciplines. I met several companies trying to address issues with composite materials and energy efficiency, and I tried to wrap my head around how I could learn something from those problems and solutions and apply them to my own complex material.”

At the time, the concept of low-carbon cement was still in its infancy, but that didn’t stop Savary from proposing a lower-carbon alternative to the superabundant material at the MIT $100K Entrepreneurship Competition. Savary won the competition, which allowed him to further pursue the idea. He founded C-Crete in 2010, his last year at MIT.

“I am grateful to MIT for giving me the opportunity to dream big,” says Savary. “We’re not executing at the level we want yet, but we are on a good track. MIT was a big factor in seeding the idea, nurturing it in the beginning, and building the confidence to tackle this hard-to-abate, carbon-heavy industry head on.”

Over the next decade, Savary continued tinkering with material combinations. To make concrete today, workers mix Portland cement with water, which creates a paste that binds to materials like sand and rock. Cement production accounts for the expensive and carbon-intensive portion of concrete, so Savary wanted to find a set of molecules that could produce a cement-like binder.

“In our lab we probably identified about 2,000 formulas that didn’t work,” says Savary. “But after each failure over the years, we took the lessons and said, ‘okay, another one down.’ We were narrowing our options, though it was not quite Edisonian and we had some guidelines.”

The molecular combination C-Crete finally settled on is still under wraps as the company waits for its patents, but third-party testing has found that it meets the performance requirements of Portland cement, such as strength and flowability.

“Because the industry is so used to Portland cement, and also because of the liabilities involved in construction projects, if a new product is complicated to use or behaves differently, contractors and workers won’t switch,” says Savary.

“It had better be a drop-in technology that bears minimal to no changes in the current behaviour of concrete, from its dry mix components to its liquid and hardened stages. We wanted to make C-Crete as easy and as close as possible to conventional practices.”

C-Crete has received strong interest in partnerships, including from ready-mix companies, which operate the trucks with the spinning cement container in the back.

“All they need to do is get our binder and swap it with Portland cement,” says Savary. “The resulting concrete has the same mix design. It’s the same ratio of gravel to cement and sand to cement and admixtures.”

Making green cement a reality

C-Crete’s current production facility can produce tens of tonnes of its binder per day. A typical cement manufacturer can produce more than 2,000 tonnes a day. But the company plans to partner with manufacturers to scale up quickly, and Savary has received inquiries from architects, engineers, construction companies, and building owners around the world to use C-Crete’s binder.

“Because of the concern about carbon emissions, more and more people are interested in solving this issue,” says Savary.

C-Crete also continues to innovate on its materials. This month, the US Department of Energy awarded the company $2m to develop ways to use carbon dioxide captured from the air in its concrete, which would make it carbon negative. Earlier in September, C-Crete received another approximately $1m from the department to expand the types of materials it can use to make its cement-free concrete.

But for now, C-Crete is primarily focused on scaling the production and deployment of its existing technology. Fortunately, Savary believes the industry is starting to share his sense of urgency about the problem.

“Since my time at MIT, when we didn’t see as much interest from the market, everything has changed,” says Savary. “We seem to be at the tipping point. Now there’s a good product-market fit. Once we scale up and execute as planned, it will lead to enormous impact.”