When chemist David Stone was a PhD student at the University of Arizona in the United States, an experiment that went wrong allowed him to create an eco-friendly alternative to cement that will be brought to the market through his company, Iron Shell, this year.

Initially looking for a way to keep iron from rusting, he said in a recent PBS report that he didn’t think his experiment worked after it started “bubbling and spitting”. However, when he came in the next day he realised a “very hard, glassy hard” product had been created.

Called Ferrock, the product has since been tested to be about five times stronger than Portland cement and features iron as its key ingredient, which Stone gets from steel mills. This steel dust, he says, isn’t recycled and typically goes straight to the landfill. Silica is also added to the mix, which comes from ground up glass.

What really sets Ferrock apart, however, is that it acts as a type of carbon sponge – Ferrock only hardens when it is exposed to high amounts of CO2, which is diffused into the wet mixture and reacts with iron to create iron carbonate.

“This is a carbon negative process that helps trap the greenhouse gas, carbon dioxide,” explains Stone.

But, is Ferrock practical for large-scale operation? Steve Regis from Calportland Company says Stone’s invention is great for non-structural applications, but cannot meet the scale needed for large infrastructure and building projects. However, Doug Hockstand, Director of Tech Transfer at Tech Launch Arizona, who is collaborating with Stone to commercialise Ferrock, says the future is promising.

“The formation of Iron Shell promises to be very exciting,” he said. “The technology stands to impact the world in a variety of ways, including both reduction of carbon dioxide production and sequestration of other carbon dioxide production, as well as recycling of waste products such as steel waste and in some cases, recycled glass.

“For all that, this represents an amazing engineering achievement that has the potential to create a great, positive impact on the environment.”

Geraldine Chua

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