Queen’s University leads research to reduce concrete’s carbon dioxide emissions

Reinforced concrete is a common construction material but a lesser-known polluter. The cement-steel mix accounts for almost 10 per cent of global carbon dioxide emissions, far exceeding the roughly two per cent produced by the airline industry.

At the beginning of 2022, researchers at Queen’s University launched a research project in collaboration with the city and industry partners to develop ways of reducing concrete’s emissions footprint.

“Where all the CO2 comes from is the processes of turning them from naturally occurring rock and naturally occurring iron into concrete and steel,” explains Neil Hoult, a professor in the department of civil engineering at Queen’s University.

Not to mention emissions produced by the mining of those materials.

With cities like Kingston building more high-rise apartments and infrastructure, protecting the earth from climate change is also becoming urgent.

Hoult, fellow professor Josh Woods and their graduate students are currently testing how the construction industry could cut those emissions through two main approaches.

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The first is shape optimization, or finding a way to design structures to use less concrete; the second is functionally grading the concrete.

“In a concrete structure, there is usually only a couple of places where we see the maximum stresses — in other words, where we need the maximum strength of material — and everywhere else we don’t actually need that material strength,” Hoult said.

“Now we are actually looking at something called functionally graded concrete where we actually put the strong concrete where we need it, and strong usually equates to more cement and therefore more CO2, and then where we don’t need that strength we can use much lower-cement concrete.”

Hoult and Queen’s have also teamed up with collaborators at the University of Toronto and the University of Cambridge; industry leaders, including Arup, Aecon and Lafarge; and the City of Kingston.

While current research is happening in the Queen’s civil engineering labs, it will move into the real world with help from the city. An actual structure with low environmental impact will be designed and built at the Kingston Fire and Rescue Training Centre.

“We feel that what we are going to learn today … through this project … with Queen’s will help us in the future and will help probably help a lot of other projects, nationally and internationally also,” Sparos Kanellos, director and facilities management and construction at the City of Kingston, told Global News.

Hoult says the team at Queen’s hopes the demonstration structure will be used in the future as a classroom and as a living lab to educate students about low-carbon structures. The team hopes to start building the demonstration next summer.