RECYCLING ON THE JOB
By Adam FreillConcrete Construction Construction Materials Demolition Green Construction
Scratching the surface on the use of aggregate sourced from demolition.
As construction companies look for ways to hit carbon-neutral and Net Zero targets, finding novel ways to work with existing materials, such as pre-existing concrete structures at jobsites, is gaining interest. And while the use of recycled aggregate is on the rise, the segment is still just scratching the surface of its potential in the Canadian market.
“There is momentum to evolve the industry into a more sustainable path,” says Peter Sanguineti, vice-president of Aggregates at Lafarge Eastern Canada, producer of Aggneo, a 100 per cent recycled aggregate. “Our innovation teams have identified and developed multiple technologies; processes to not only recycle materials but also reclaim, and upcycle materials, further increasing the opportunities to use in new applications and increasing the percentage of reused materials in our offerings.”
“When I first got in this business, we didn’t crush a spec material. Usually, we would crush to a four- or five-inch material and then just push it into the hole, and then you would buy a spec material to place on top of it,” says Dave Wray, project manager at Priestly Demolition, which offers its customers an option to crush concrete materials on site. “Now, we crush the material right to a spec and then it’s reused on site. It helps us to not have to buy spec material because we can make it right on site.”
While the more hesitant in the industry may raise questions about the quality of performance of these materials, testing programs and even its use elsewhere in the world will help to ensure that the performance of the product matches to the requirements of the application.
“At a high level, recycled aggregates with strict quality control should perform as well as virgin materials in most applications,” says Sanguineti. “In some European countries, recycled aggregates are being used as up to a 100 per cent substitute for virgin materials in certain concrete mixes.”
Currently in Canada, most reclaimed crushed concrete materials are used as backfill or, in some jurisdictions, as base materials for roads.
“We usually crush it to a three-quarter crush or a two-inch crush, which can be used as a B gravel or an A gravel,” explains Wray, adding that this material has been approved by Ontario’s Ministry of Transportation for use on roads—a relatively recent development. “We can use this crushed material on roads, where you never used to be able to. The spec is that you can use it, providing that you have a proper grade plan for the drainage.”
To that end, his company has been involved on the resurfacing of some of the runways at Toronto’s Pearson airport, where the existing concrete was hammered, crushed and used as base materials below the new surface.
Sanguineti says that the OPSS 1010 Standards, which are used for Ontario’s provincial highways, allow for Granular A material to be produced entirely from recycled concrete rubble, as well as up to 30 per cent recycled asphalt pavement, although he adds, “Many municipalities are still reluctant to expressly incorporate this into their own regulations or tenders, even if the application, road base, is the same.”
“Currently CSA A23.1 allows for the use of Recycled Concrete Aggregate [RCA] as partial or total replacement of virgin coarse aggregate in non-structural and low risk concrete applications,” says Nicolas Ginouse, technical director, Ready-mix, with Lafarge Eastern Canada. “To be able to expand the utilization of RCA in different structural concrete applications, this would require a shift in the regulatory mindset from prescription focused to performance- based specifications. This would open the way to more applications using RCA concrete mixes while ensuring performance and durability are maintained.”
To help foster this change in approach, it would also be helpful to have more real-world examples to truly illustrate the performance of these materials in the Canadian market.
PERFORMING IN THE REAL WORLD
“In order for the regulators to change the standards and regulations they need reliable data from the laboratory and, more importantly, from the field, in order to make changes with confidence,” says Ginouse. “Even if we do have a lot of internal data, we should invite the infrastructure owners to actively participate in more pilot projects in collaboration with the supplier, designer and even academic experts.”
“The key for increased adoption is to tie the recycled offering to an existing standard to bring reassurance of the performance to the end user without having the customer go through individual testing and the related risk,” adds Sanguineti. “If regulators would open the possibilities for recycled aggregates use in concrete, the RMX producer would work with its recycled aggregates supplier to develop mixes that use recycled aggregates and meet standard performance specifications for strength and durability requirements.”
MAKING DOLLARS AND SENSE
Of course, for a business case to be made for expanded applications of recycled aggregate, most company owners will want to know more about its impact on a project’s bottom line.
“Although Lafarge Eastern Canada has set the target to double recycled volumes in five years as part of our path to Net Zero, we recognize that in order for sustainability initiatives to be successful over time, they need to be profitable,” states Sanguineti. “The case for recycled aggregates is solid, as logistics costs are a significant component of the total aggregates supply cost and recycled aggregates are typically supplied from urban depots, which are usually much closer to market than the pits and quarries located outside the city boundaries.”
“It wouldn’t make sense to ship all the concrete off site and then turn around haul crushed concrete back, or an aggregate back,” says Wray. “It helps to control the cost.”
With shipping being such a significant portion of aggregate costs, Priestly has even come up with creative solutions for sites too small or difficult to access with its large crushing units.
“A lot of times in downtown Toronto, there isn’t the room to bring the crusher in,” says Wray. “What we have done in the past is rent a lot down by the lake, truck concrete to that site, crush it, and then turn around and truck it back to the lot that we demoed and use the crushed concrete to backfill the void.” That shorter trip makes logistics much easier, and it saves on both fuel and the associated greenhouse gases.
Beyond saving on the cost of transport, the materials themselves tend to be less expensive than virgin product as well. “If you have the opportunity, or the ability to use it, it totally makes sense,” he adds. “If it meets all the specs, and you can buy it for a few dollars a ton cheaper, you’re going to save money. To me, it makes total sense in a business aspect, to use it.”
While the financials make sense, perhaps more important is the performance of recycled aggregate, and a reputable supplier will ensure that the materials serving as source product is cleared of anything that could contaminate the end product so that the performance of the supplied recycled materials will live up to expectations.
“Any contaminants are cleaned prior to coming to the crusher,” says Wray, explaining that any materials that contain contaminants will not be included in the recycled products it sells to its customers. This concern about working with quality source materials is core to Lafarge’s recycled aggregate products.
“Making sure that the right type of feed is used in the Aggneo production process is critical to ensure its performance and consistency and is one of the main differentiating factors of our offer, and the reason behind its branding,” explains Sanguineti. “The feed typically comes from both our internal and external RMX customers as well as major infrastructure projects like roads and bridges.”
His company will also consider concrete rubble from construction demolition projects but adds that Lafarge uses a thorough screening process to ensure that the recycled raw materials will deliver on the brand’s performance expectations.
Along with the ability to help a project’s budget, and the potential to deliver at a performance level comparable to virgin aggregate, the use of recycled aggregate is also compelling from an environmental perspective, especially with today’s focus on CO2 reduction.
“In some specific applications, like cement production for example, recycled aggregates can offer incremental benefits versus virgin materials from a CO2 emissions perspective, as it minimizes emissions from the calcination process,” explains Sanguineti, adding, “We significantly reduce transportation related CO2 emissions, preserve natural resources and divert materials from landfills.”