Brimstone carbon-negative cement meets ASTM standard

US-based climate technology company Brimstone has gained third-party certification of its carbon-negative cement, which the company says marks the first carbon-neutral or carbon-negative cement to meet one of the most commonly-used standards in the construction industry - ASTM C150. 

Instead of baking limestone, Brimstone has developed an alternative method for producing cement, starting with carbon-free silicate rock. Chemically extracting calcium oxide from silicate does not release CO₂. In fact, according to the company, a byproduct of the process is magnesium that can actually absorb CO₂ from the atmosphere. 

“The biggest barrier to entry in terms of either decarbonising cement or steel, or coming up with an alternative product that can be swapped in for one of those structural material, is typically the testing,” said Stacy Smedley, executive director at Building Transparency, a non-profit organisation focussed on decarbonising construction.

Brimstone commissioned engineering firm Twining Consultancy to test its alternative cement in terms of air content, setting time and strength. The test concluded that Brimstone’s cement meets the ASTM C150 standard, the same standard met by the typical cement that is used every day. The company now plans to construct a pilot production plant in Nevada before building a commercial-scale factory. Around US$60m in funding has already been raised for the project, with investors including Breakthrough Energy Ventures, which is backed by The Bill Gates Foundation.