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Prescriptive concrete specifications make carbon reduction a hard sell

John Bleasby
Prescriptive concrete specifications make carbon reduction a hard sell

Given international commitments between more than 77 countries to limit the planet’s global warming between now and 2050, action must be taken by all players involved in the construction process.

According to a McKinsey Global report, cement production is a major contributor to global construction’s GHG output and is “almost exclusively responsible for the resulting CO2 emissions” related to concrete production.

Recognizing their industry is labelled a climate crisis villain, the Global Cement and Concrete Association (GCCA) has responded. The organization representing more than half the world’s cement production has developed a 30-year plan to achieve carbon neutrality by 2050 called the 2050 Climate Action Plan. It’s hailed as the first major step taken by the industry to address carbon emissions related to the world’s most ubiquitous building material.

Today, major cement and concrete manufacturers are upgrading older facilities and adopting new technologies, actions that they claim have already reduced energy consumption in North America alone by as much as 35 per cent since 1990.

Leading companies in North America and Europe have also made recent commitments to new processes that will result in further significant carbon emission reduction.

For example, CalPortland is using new processes that reduce CO2 emissions during the manufacturing process itself. Vicat, parent company of the National Cement Company in the U.S, will commercialize “Carbon8,” described as a lightweight aggregate derived from a process that captures carbon dioxide-heavy cement kiln emissions. The Cemex Research and Development Center in Switzerland has developed the Vertua series of products that matches the performance of traditional concrete while delivering a 70 per cent reduction in carbon footprint.

International giant LafargeHolcim will change processing, mix and batching to reduce C02 emissions by 30 per cent and use a minimum of 20 per cent recycled material content, initiatives to be marketed under the “Ecolabel” logo in more than 70 countries. The DB Group in the U.K. has even developed what they say is a “totally cement-free alternative to conventional concrete” that has been used in highway construction.

And of course, Canada’s own CarbonCure Technologies has formed international partnerships for their patented process that purifies and injects C02 gathered from industrial sources into cement and acts as a strengthening agent while embedding the carbon in the concrete itself. This can mean less concrete is required to meet a project’s performance mandate.

The ongoing demand for concrete forecast over the next 30 years requires widespread adoption of these exciting new developments in order to reduce the GHGs and carbons associated with new construction.

Yet, current use of carbon-reduced concrete represents only a small percentage of today’s new projects. For adoption to increase meaningfully, there needs to be both champions for the cause among project owners and developers, and recognition of the enhanced performance characteristics of these new products among legislators and regulators responsible for concrete specifications.

Unfortunately, the result is often a confrontation between out-dated prescriptive specifications based on the outlook that more cement means better concrete, versus performance specs that determine specific criteria for how the concrete needs to perform.

As an early adopter of CarbonCure, Canadian concrete manufacturer Butler Concrete and Aggregates in Victoria, B.C. has experienced this conflict first-hand.

“The challenge of the prescriptive model is that most of the prescriptions were written many years ago and have not kept pace with the changes that have taken place and are now rapidly taking place,” owner Travis Butler told the Daily Commercial News. “There are no incentives through government contracts to encourage greener, cleaner concrete.”

Prominent leaders in the drive to reduce carbons in the atmosphere include high tech companies such as LinkedIn. Being an environmental role model is something they see as essential to their nature.

For example, LinkedIn’s new headquarters in Mountain View, Calif. used CarbonCure technology in its construction, thereby saving 240,000 pounds of C02 emissions, the equivalent carbon absorption of 133 acres of trees.

“We have a presence globally, and that provides a perspective and understanding of what our global environmental impacts are,” says Jennifer Mitchell, LinkedIn’s senior manager of design build workplace. “That makes it a priority for us to advance solutions for climate change.”

Mitchell agrees with Butler that prescriptive concrete specifications are an obstacle to the adoption of carbon-reduced concrete.

“They create restrictions for optimizing a mix design that uses embodied carbon while maintaining concrete performance.”

“Over the years, I’ve always wondered why we have these prescriptive specs that end up making things like 70 per cent over-strength,” says Nancy Novak, chief innovation officer with Compass Datacenters. “I’ve always thought of it as a lazy way to design concrete to assure that you have a certain amount of strength. It was wasteful because it required way too much cement.”

“There is a misconception that more cement makes better concrete,” says Christie Gamble, senior director of sustainability of CarbonCure.

She says that, in fact, over-prescribed cement can result in poorer concrete and increase its embodied carbon content, the opposite of what can and should be achieved.

On the governmental side, Canada’s uptake is slow.

However, New York State may provide inspiration for change. Legislation recently passed now sits on Governor Andrew Cuomo’s desk for approval. This would instruct New York’s Office of General Services to set low-carbon guidelines for procurement and award future contracts based on climate performance, not just price. New Jersey is considering similar legislation.

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