The surprising construction materials that could help save Ontario’s green space

ANALYSIS: Forget cans and bottles — the next big thing in recycling may be concrete and asphalt, writes John Michael McGrath
By John Michael McGrath - Published on Oct 31, 2018
Recycled aggregate can be used for such humble jobs as filling trenches dug for water mains and creating gravel shoulders on the sides of highways. (



Whether it’s a road, a sewer, or the foundation walls of a new gleaming tower somewhere in the GTA, every major new building or infrastructure project starts in a quarry somewhere in rural Ontario. That’s where the sand and gravel that eventually become concrete are blasted out of the ground with explosives before being loaded on a truck, on their way to becoming part of something new and shiny in the city.

But the material, referred to as “aggregate” in the construction industry, can also be reclaimed from infrastructure and buildings that have been demolished and replaced. That’s not done as often as it could, though — thanks to rules in such places as Mississauga, Niagara, and Windsor that insist fresh “virgin” aggregate be used in municipal projects.

“Our industry’s looking at ways to get greener — there’s a lot of pressure on us for that,” says Rob Bradford, executive director of the Toronto and Area Road Builders’ Association. “And this stuff (reclaimed concrete and asphalt) is piling up in our yards … it’s all going to end up in landfill once there’s no room left, and that’s not a good thing.”

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A report released by TARBA earlier this month shows that some Ontario municipalities have adopted much stricter rules on public projects than provincial policy requires. Under provincial rules, builders can use recycled aggregate as long as they follow standard procedures for checking its quality and, when necessary, mix it in with new stuff to ensure its strength. The Ministry of Transportation uses reclaimed aggregate in provincial highways.

The province says one thing, but municipalities say another. City rules that restrict the use of recycled aggregate are motivated by quality-control concerns: stuff fresh from the quarry is a known quantity and has predictable strengths and characteristics. Municipal building officials don’t have the same confidence in aggregate that might once have been part of a busy road or held up a building for 40 years, and it’s not like the original builder can vouch for it.

But recycled aggregate can also be used for pretty humble jobs — filling trenches dug for water mains or buried power lines, for example, or creating gravel shoulders on the sides of highways, where material strength is less of a concern.

Some municipalities have adopted rules that encourage the use of recycled aggregate: Toronto allows it to be used either in part or in full for all but three of the possible uses TARBA surveyed. Right next door, though, Mississauga prohibits the use of reclaimed aggregates for anything other than paving bike paths or access roads.

“For communities that say they’re about building a green city and longer-term thinking, this is an opportunity to signal that those things are important, even when they’re working on contracts for road work,” says Kate Graham, the report’s author and a political-science professor at Western University.

It’s not just road builders who want to see more use of recycled materials: even quarry owners and operators — who, in theory, could see it as competition — are in favour of it.

Norm Cheesman, executive director of the Ontario Stone, Sand, and Gravel Association, told in an email that his organization “strongly supports” recycled aggregate in road-building projects and that recycling “is important in extending the life of Ontario’s aggregate reserves.”

If the only side effect of these municipal rules were that road contractors had to pay to dispose of construction waste, that may not seem like the end of the world. But the province is currently running out of landfill space, and 10 per cent of the waste that ends up there comes from construction, according to the Environmental Commissioner of Ontario.

Quarries have an even larger environmental impact. “Pits and quarries disrupt the existing movement of surface water and groundwater; they interrupt natural water recharge and can lead to reduced quantity and quality of drinking water for residents and wildlife near or downstream from a quarry site,” reads a Toronto Environmental Alliance report from 2009.

TEA argues that we should increase our use of recycled aggregate in order to help preserve green space around the province.

“One thing we know is that over 75 per cent of the aggregates used in the GTA come from the Niagara Escarpment and the Oak Ridges Moraine,” says Heather Marshall, campaigns director for TEA. “For us, ensuring that we preserve those natural resources as much as possible while meeting the demand in growing urban areas is to recycle these materials.”

The Niagara Escarpment has been protected by various pieces of provincial legislation since the 1960s, but a 2013 court ruling determined that none prevents the opening of new quarries, except in the outer edges of the escarpment. For its part, the OSSGA emphasizes that using pits and quarries closer to the major population centres of the GTA helps cut down on pollution, as there’s then no need to haul massive amounts of material across the province. It also notes that the amount of land in the Niagara Escarpment being used for mineral extraction fell nearly 20 per cent between 1991 and 2014.

For now, TARBA is focused on raising awareness of the issue among municipal officials around the province. Both Bradford and Graham say that support from Queen’s Park could be useful, although Bradford notes that the province doesn’t usually strong-arm municipalities on policy matters like this.

“It’d be great if they came out and said, ‘Municipalities have to do this,’” he says. “But I don’t think that’s going to happen.”

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