Canadians disposed of 25-million tonnes of waste in 2018, most of which is sitting in a landfill. Sometimes, even recycling winds up in landfills too. According to Recyc-Québec, only 28% of the glass Quebecers attempted to recycle in 2018 was actually recycled. The other 72%? You guessed it — landfill.

So what's the solution? Due to climate change, this is one of the biggest questions of our time. Usually, "Just build a bridge with it!" doesn't come up as an answer.

But that's what the City of Montreal is doing with one of its latest projects: the Darwin Bridge on Nuns' Island where they're replacing the two existing overpasses with new structures.

The press release calls the technique a "world first." 

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Where did this idea come from?

Étienne Cantin Bellemare, lead designer and engineer, told MTL Blog that the idea stemmed from research done at the University of Sherbrooke surrounding "Novel Ultra-High-Performance Glass Concrete." 

The research is sponsored by the City of Montreal and the Société des alcools du Québec (SAQ).

It enabled the city to try integrating glass powder into the making of sidewalks — which they've been doing since 2011.

In 2017, Bellemare said they decided to start working on the first large-scale application of glass powder and the Darwin Bridge was chosen as a pilot project for the material.

This project will give a "second life" to the equivalent of 70,000 bottles of wine in addition to saving 40,000 kilograms of cement, says the release.  

How is glass used in constructing a bridge and is it safe?

The two concrete bridges will contain 10% finely ground recovered glass also known as "glass powder," says the release.  

Bellemare explained that not only is this good for the environment — it's good for the bridge.

"Using glass powder is going to increase the durability of the concrete — durability [against] freezing and thawing and resistance to ice and salt. The concrete is going to be a little more strong also," Bellemare said.

Using glass powder as a substitute for concrete has been officially recognized by both ASTM and CSA standards.

When will the bridge be ready? 

The northbound bridge construction will be finished in about two weeks. The southbound bridge construction will start in April 2021 and is expected to last six months, said Bellemare. 

Bellemare also stressed that, in addition to being sustainable, the team put a lot of effort into designing a bridge that is "good looking."

They worked with a Quebec architectural firm, Provencher_Roy, which designed the Samuel De Champlain bridge.

"[It's] a very elegant [...] structure," Bellemare said. "Everything is curved so it's going to be a unique bridge." 

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