Environmental Chemist Invents Cement That Absorbs CO2 Like A Sponge

An Arizona inventor has created a innovative new type of cement that actually absorbs CO2, rather than emitting it.

Portland cement (the generic name for common cement) is the “glue” that holds concrete together while it hardens. The production of this cement releases a significant amount of greenhouse gases.

“This plant, if it’s making about a million tons a year of cement, will emit roughly 800,000 tons a year of CO2 carbon greenhouse gases,”

says Steve Regis of the CalPortland Company, one of the top 10 producers of cement in the United States.

Every year, roughly 4 billion tons of Portland cement are produced worldwide – that’s half a ton for every person in the world. If CalPortland’s emission levels are typical, that means global concrete production puts roughly 3.2 billion tons of CO2 emissions annually.

CalPortland mix factory in Kenmore, Washington (Photo: Joe Dyer/Seattle PI)

CalPortland mix factory in Kenmore, Washington (Photo: Joe Dyer/Seattle PI)

Enter David Stone. 13 years ago, Stone was a Ph.D. student studying environmental chemistry at the University of Arizona in Tucson.

At the time, Stone was trying to figure out a way to keep steel from rusting and hardening. He described one of his failed experiments in a recent interview with PBS NewsHour:

“It got hot. It started to steam. It was bubbling and spitting. And I thought, well, that — that didn’t work. The next day, when I came in and I found it and rescued it from the garbage, I realized, this just didn’t get hard. It got very hard, glassy hard.”


But the experiment was not completely in vain. After finding the glassy remains in the trash, Stone began to realize that this discarded mass could be the foundation of an alternative form of cement.

“The whole process is green,” said Stone. He started by collecting steel dust from local steel mills (this dust typically ends up in landfills). Then he added silica to the mix. The silica was extracted from ground up glass bottles. NewsHour’s Kathleen McCleery explained,

“Stone connected with the community college at the Tohono O’odham Nation, a Native American reservation the size of Connecticut in Southern Arizona. There, he met Richard Pablo, a recovering alcoholic looking to turn his life around. Pablo knew where to find plenty of used glass.”


David Stone with a block made out of his cement substitute Ferrock (Credit: PBS)

David Stone with a block made out of his cement substitute Ferrock (Credit: PBS)

The resultant material, which Stone calls Ferrock because of the iron it contains, is a virtual carbon sponge. Instead of producing CO2, Ferrock actually absorbs the greenhouse gas as it hardens.

What’s more, Ferrock concrete has been shown to be about five times stronger than concrete produced using conventional Portland cement.

Many people in the industry think Stone’s invention, while certainly innovative, is a niche product that will never make its way into large-scale construction projects. But Stone doesn’t seem to be bothered by the detractors:

“I’m doing my part, as best I can, to respond, so that when the time comes and the world wants to build with new materials that are carbon-neutral or carbon-negative, I will be able to step forward and say, yes, I have such a material,”

he says.

Read the full story from PBS NewsHour.


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