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SCM, aggregate processor Calera eyes concrete pilots for CO2-sequestering carbonate

Sources: CP staff; Calera Corp., Los Gatos, Calif.

Two years after outlining research aimed at commercial processes for carbon dioxide-capturing aggregate or cementitious materials, Calera has announced a series of prospective concrete applications testing a mix agent from its Mineralization via Aqueous Precipitation technology. An initial carbonate product, Partial Cement Substitute (PCS), is derived from the flue gas of the Moss power plant in northern California, coupled with naturally occurring, water-based calcium or magnesium sources.



With properties similar to fly ash, the precipitated carbonate is earmarked for a curb and gutter mix in Santa Cruz, near the power plant and Calera headquarters. Officials in the coastal town are receptive to a 400-ft. demonstration of concrete with a reduced CO2 factor; a proposed mix design calls for 30 percent replacement of portland cement from even PCS and fly ash doses. Scheduled for June, the delivery will be the first of perhaps 10 cast-in-place or manufactured-concrete applications Calera plans this year, each requiring 5–10 tons of the carbonate agent.

At the World of Concrete (January 18–21, Las Vegas), the company noted a refined processing technique from demonstration equipment yielding about 1 ton of PCS per day. The carbonate material was used in a late-2010 slab pour at the Moss plant, followed by trial concrete paving stone production. Representatives from Calera, along with established concrete-grade calcium carbonate processors Carmeuse Lime & Stone (Premiacal) and Omya Inc. (Betocarb), are pursuing guides or standards for their materials through American Concrete Institute and ASTM Committee C9 on Concrete subcommittees.