This article was published by Engineering News-Record here.

By Nadine Post

The Chemistry Is Just Right for A Mineral Substitute for Portland Cement that Can Save One Ton of CO₂ Emissions for Each Ton of Cement It Replaces

Jan 24, 2024. Rouzbeh Savary became hooked on concrete as a youth in Tehran, when he would frequently tag along to jobsites with his developer-father Davood. Even as a 9-year-old, he was mesmerized by crews casting concrete for his father’s multistory buildings.

“I was very curious about how concrete sets,” and “how it changes from a liquid to a semi-solid and then to a solid,” says Savary, founder and president of C-Crete Technologies, San Leandro, Calif. “My father also introduced me to ceramics and plaster of paris,” other moldable materials that harden.

Little did Savary know that his father, who died in late December, was laying the foundation for his own life’s work. Savary’s fascination with concrete became a relentless pursuit to develop a way to reduce the ubiquitous building material’s considerable greenhouse gas emissions.

He has finally succeeded, after 13 years of trying. Using materials science, engineering, nanotechnology and manufacturing, C-Crete has developed two binders for portland-cement-free concrete. One replaces the cement with slag and the other with zeolite—a globally abundant mineral.

The secret in the sauce is that the binders are produced without heat. As a consequence, they save approximately one ton of CO₂ emissions for each ton of portland cement they replace, says Savary.

Despite his considerable progress, it’s still an uphill battle for Savary. “The portland cement we are reinventing is low-cost, ubiquitous and has been around for almost 200 years,” he says. “I’m fighting the wrong perception in the construction industry that portland cement is the only reliable binding material for concrete.”

Savary is getting help disproving that perception. In its November debut for a 20-ton outdoor slab on grade, the zeolite concrete “showed promise,” says structural engineer Don Davies, principal of sustainable building consultant Davies-Crooks, which showcased the zeolite in Hubbard’s Corner, a living laboratory for new reduced-carbon materials.

Earlier last year, Hubbard’s Corner also debuted the C-Crete concrete slag mix, when crews cast 100 tons for part of the structure. The zeolite mix behaved similarly to the slag mix, says Davies, also an ENR Top 25 Newsmaker (see p. 48).

Developing the binders required “a lot of chemistry,” says Savary. He first had to figure out how to reverse engineer portland cement, which he did while getting his doctorate at the Massachusetts Institute of Technology (MIT). Then, using different rocks, ashes and slags, his team tried some 2,000 recipes. “From each failure, we learned lessons and narrowed down the starting materials,” says Savary.

In 2010, Savary and another student took first prize in the annual student-run MIT $100K Business Plan Competition. As a result, C-Crete Technologies was born. Since then, the majority of the nearly $15 million for R&D has come from government grants, including from the Dept. of Energy’s Advanced Research Projects Agency-Energy (ARPA-E).

“What makes Rouzbeh’s work special is that he is not trying to reinvent the entire cement industry,” says Madhav Acharya, a business fellow with Breakthrough Energy. “He understands he needs to work within the existing industry to provide a drop-in replacement that can be cost-competitive with the legacy binder and available on a large scale,” adds Acharya, who met Savary when he worked at ARPA-E.

C-Crete’s pilot plant is producing 20 to 30 tons per day of mostly the slag binder. Orders include small-scale uses, such as for a high school, a museum and houses.

Savary’s next step is to scale up production. He says he is in discussions with an industrial partner for a binder plant that would produce 1 million tons per year—the output of a typical cement plant—but hasn’t finalized a business plan.