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Working with waste: part 1

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World Cement,

World Cement profiles three semi-finalists in the NRG COSIA Carbon XPRIZE that offer solutions to reduce the carbon footprint of concrete.  In this first article, Robert Niven of CarbonCure Technologies profiles technology that injects CO2 into wet concrete, improving its compressive strength. 

CarbonCure Technologies (CarbonCure), based in Nova Scotia, offers global concrete producers an opportunity to utilise and recycle waste CO2 into concrete to increase its environmental, material, and economic performance. Not only is the CO2 permanently converted into a solid mineral within the concrete, but the addition of CO2 also improves the compressive strength of concrete. This allows concrete producers to achieve the required concrete performance, while reducing the amount of cement, which provides operational cost savings for the manufacturer.

CO2 is captured from existing industrial emitters, before being purified, stored, and distributed to concrete producers in pressurised tanks. The tanks are brought to the concrete producer’s facility, where CarbonCure’s technology injects controlled doses of liquid CO2 directly into the truck or mixer. When liquid CO2 is injected into wet concrete, it chemically reacts with calcium ions released from cement to form solid, nano-sized calcium carbonate particles that become permanently bound within the concrete. The nano-material catalyses the normal portland cement curing reaction using a crystal seeding mechanism to yield a 10 – 20% strength benefit.

The installation of CarbonCure’s technology at a customer’s concrete plant is a process that resembles the introduction of a chemical admixture. The concrete producer connects a tank of liquid CO2 to the CarbonCure injection system, which regulates the dosing of CO2 into the concrete while it is batched or mixed. Upon injection, the liquid CO2 converts into a mixture of gaseous and solid CO2 (snow), whereupon it reacts with the hydrating cement to form solid calcium carbonate particles.

CarbonCure has been optimising its technology over its 10 years of R&D, and through industrial installations across North America. Industrial data has demonstrated that the introduction of the CO2 does not impact the concrete’s workability, air content, freeze-thaw performance, pH, density, durability, air content, colour, texture, or finish.

CarbonCure’s retrofit technology can be installed in any existing concrete facility in less than a week, has no upfront CAPEX, and is licensed to customers on a monthly basis. The company’s solution integrates within the existing supply chain, and complies with applicable codes and standards. Given CarbonCure’s scalable technology and business model, and the fact that the technology provides both environmental and economic benefits to the customer, the company is poised to scale globally. The company will continue to grow from its customer base of more than 50 current installations, and will leverage relationships with global corporate strategic partnerships to achieve a worldwide impact. CarbonCure has demonstrated that the technology can allow a typical concrete producer to achieve annual CO2 reductions of at least 500 t. If the technology were implemented globally, then the concrete industry could achieve CO2 emissions reduction of over 700 million tpy.

Read the second and third parts of this series here and here.

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Construction news Concrete news