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Atlas Block, Basalite Concrete, Shaw Brick demonstrate carbon dioxide-based curing

Eastern Canada concrete masonry market leader Shaw Brick has scheduled a spring launch of CarbonCure block, a CSA-grade unit that uses carbon dioxide in the molding cycle to improve compressive strength development.

The Nova Scotia producer is the premier user of a system from Halifax-based CarbonCure Technologies in which concrete masonry units become CO2 sinks, sequestering the gas as they cure. The process enables producers to promote blocks’ carbon-capturing function and reduced energy consumption—hence, smaller carbon footprint —realized by lowering cement in mix designs and steam usage in curing. Compared to conventional block making, the CarbonCure system exhibits up to 20 percent net greenhouse gas emissions reduction.

“We are already seeing orders for the product and expect to announce a deal with a national builder for preferred block specification,” says CarbonCure CEO Robert Niven. “CarbonCure blocks are indistinguishable from standard gray block, and have commanded specification from architects and government agencies, along with encouraging building-owner response. Concrete masonry customers now have a green option for routine or LEED-rated projects without compromising quality, aesthetics, or cost.”

“The curing system is profitable without its green marketing or potential carbon credit value,” he adds. “Ultimately, we provide customers two sources of value—higher early strength and green product differentiation. This is achieved by lowering the cost of production but not at the expense of productivity or quality. Each plant operator may profit from higher strength differently. For instance, reducing cement content, cull rates, curing temperature, inventory time/handling, or achieving lower unit density. ”

CarbonCure is unlike past CO2-based curing equipment, since carbonation occurs in the mold box rather than in the kilns. The distinction is critical, Niven notes, since producers avoid kiln corrosion issues and achieve superior material performance. CarbonCure engineers customize and install systems for optimal performance, leaving existing equipment, operating standards and materials mostly unchanged.

As Shaw Brick eyes field deliveries, peers Atlas Block Co. in Hillsdale, Ontario, and Basalite Concrete Products in Dixon, Calif., are set for their own CarbonCure Block System demonstrations by mid-year. The technology is being demonstrated on a wide range of mix designs and block machines. CO2 supplier Air Liquide provides a skid-mounted gas delivery system that integrates with concrete plant controls; gas is fed into the production process through CarbonCure's proprietary molds—without impacting cycle times.

The CO2 gas is permanently sequestered in concrete as embedded carbonate minerals like limestone. While meeting CSA and ASTM product quality standards, the CarbonCure Block System can provide higher early compressive strength, cement and energy savings, and lower cull rates. Measured against conventional products, Shaw Brick’s CarbonCure blocks have exhibited up to a 10 percent strength gain at 24 hours and 20 percent at seven days. Strength development assessments show that 24-hour and seven-day measurements are maintained or increased upon 28-day or 56-day tests. Testing has centered on normal weight block, although CarbonCure anticipates similar strength development trends in lightweight CMU.

Shaw Brick has deployed pilot systems since 2008. As the technology approached commercialization in 2011, CarbonCure landed a $1.2 million grant from the federal government’s Sustainable Development Technology Canada program. The company is also backed by prominent industry investors, while a sister business, Carbon Sense Solutions, is a consultancy for cement and concrete producers, listing Lafarge North America among its clients. CarbonCure board members include Lafarge Director of Sustainability and Commercial Innovation Kevin Cail, P.E., and Shaw Group CEO Bert Frizzell.

Along with Lafarge Canada (Contempra limestone cement), CarbonCure joins “cleantech” companies like Calera Corp. (precipitated calcium carbonate aggregate, binder), Ceratech Inc. (100 percent fly ash binder, admixtures), and Novacem Ltd. (low temperature-milled magnesium oxide binder) seeking to reduce or offset the carbon factor in concrete stemming from energy-intensive portland cement production. — www.carboncure.com