After much research and experimentation with alternative technologies and processes, Boehmers Block has created a process that builds on the quality of its existing autoclave concrete block to create the carboclave block, says the company’s president.
The new process modifies concrete block manufacturing to allow it to additionally serve as a carbon sink, a reservoir that accumulates and stores carbon, and reduces the company’s carbon footprint, explained Paul Hargest, of Boehmers, operating under Hargest Block Ltd.
"I spent about 10 years going through different processes to see if I could replicate a block that would be as good as autoclaving and I never came up with anything that met that requirement," said Hargest. "Now with carboclave, we use zero gas so we have zero emissions. That’s a big win. Moving forward we’ll probably be in a position where we’ll be able to make a carbon neutral block."
Although there has been information out for years about the benefits of curing with carbon dioxide and what it can do for concrete, it was never perfected until now, Hargest said.
Boehmers currently manufactures nearly all its products using carboclave technology and that will increase to 100 per cent as soon as existing backlogs and inventory are depleted.
"About 70 per cent of our production right now is carboclave and we’re fulfilling our inventory and current job requirements — we’ve got to finish our current work before we start any new works with carboclave," said Hargest. "Autoclaving will be phased out by mid-summer. It will no longer be autoclaving, it will be 100 per cent carboclaving."
The Cambridge, Ont.-based Boehmers has been in the concrete block business since 1875 and has been manufacturing autoclave blocks since the ’60s. The autoclave process gained prominence in the early ’70s, when the North American Autoclave Association was created. It consisted of 205 producers.
"When that process of curing took hold (autoclaving), it made such a wonderful product so everybody started jumping on the bandwagon," said Hargest. "But due to the energy crunch and cost, capital cost and the safety requirements involved, it very quickly diminished across the market."
Conventional concrete is made from water, portland cement and heat which creates a calcium hydrate that hardens over time. For autoclave, portland cement and silica flour under high temperatures and over 100 pounds per square inch (psi) of pressure create calcium silicates that are stronger and create completed curing, unlike a calcium hydrate which requires 28 days for full curing.
With carboclave, the calcium ions from portland cement and carbon dioxide (CO2) react to create a calcium carbonate if properly introduced. Calcium carbonate is from the limestone or granite family, Hargest explained. Carboclaving uses industry-recovered CO2 for the enhanced curing of concrete.
"We all know these materials are very strong and durable," Hargest pointed out. "The end result being that we were successful in being able to meet production requirements and produce a product that exceeded our expectations of ‘as good as autoclave.’ "
The process allows Boehmers to reduce the company’s natural gas consumption of one million cubic metres by 90 per cent. Furthermore, Hargest added, as the technology grows, the process will allow the block industry to become a key carbon sink and industry contributor in helping both the federal and provincial governments reach their mandates of reducing CO2 levels.
The company partnered with McGill University in 2009 to research, develop and perfect the curing of concrete with CO2. The research led from small scale trials on site to full scale production. To facilitate the creation of the carboclave product, Hargest invested more than $200,000 to complement government funding as well as offered up the use of the Hargest manufacturing plant. Proof of concept was first carried out at the laboratory scale, then scaled up to pilot trials and finally implemented at the commercial scale.
"Because concrete block is the building material of choice for hospitals, arenas, schools etc., it will gain even more prominence in other markets as the technology spreads," Hargest stated.
Boehmers was recently named the recipient of the Excellence in Innovation Award at the 99th annual Canadian Construction Association Conference in Mexico.
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