October 2, 2010
FEATURE | Concrete & masonry
Edmonton aggregate recycling program reduces capital project costs
For more than three decades Edmonton’s concrete and asphalt aggregate recycling program has been making new roads out of old, providing an in-house resource for infrastructure materials.
Edmonton was the first municipality in Canada to implement such a program, accumulating 5,000 tonnes in 1979 as a trial project.
From there, the intake and output has increased over the years to the point where the city’s two aggregate recycling centres take in about 220,000 tonnes of material annually, crushing out approximately the same amount.
“The material went from being a waste product that nobody wanted to something that everybody wants now,” said Blair Buchholtz, general supervisor of aggregate recycling for the City of Edmonton’s transportation department.
“It’s gone from a disposal item to one that’s worth a fair amount of money.”
Buchholtz said that about 95 per cent of the material the facility takes in is concrete and asphalt rubble from Edmonton’s capital construction and rehab projects.
Once crushed and mixed, Buchholtz said the final product, which is used as a sub base for Edmonton’s roads and streets, is superior to other products.
“We range about 30 to 20 percent asphalt in our mix, which aids in the bridging and helps with the compaction,” he said.
“With that kind of a mix, we end up with a material that’s far superior to any natural product, just because of the angularity, the way the unused cement powder will actually reset once it’s crushed and compacted again and water is added.”
But not only is the end product of value to Edmonton’s road projects, saving the city between $5.5 million and $9.9 million annually in buying similar sized materials, it diverts 220,000 tonnes of construction rubble from the landfill each year.
With tipping fees running at about $75 a tonne, the diversion alone saves the city another $16.5 million per year.
The project also saves money by eliminating a lot of the costs of transporting the materials from the supplier and to the landfill.
“Instead of hauling that material in from an outside pit, which we’d have to do, we’re just utilizing something that would have to be hauled out anyways,” he said, adding that the in-house operation makes for shorter hauls.
“Our cost to crush it and provide it back for our projects is just over the $10 range (per tonne),” he said.
“So, we’re saving a fair amount of money that way.”
Although the west scale operation sits on four hectares (10 acres) of land, and the southeast facility is somewhat smaller, it is able to crank out 220,000 tonnes of material each year with six year-round and a couple summer employees.
The supervisor attributes much of the operation’s success to his workers.
“It’s not a huge crew,” he said. “It’s one of the smallest crews in the city, but our impact for projects, for cost savings, is huge. On a busy day, we can run 200 trucks through the yard.”
Buchholtz said the process begins in the spring when the city’s various removal contracts begin.
Contractors begin tearing up roads, sidewalks, bus pads and the underlying aggregates and transporting them to one of the city’s two depots for stockpiling.
“We basically have a loader that will feed it into our hopper,” he said.
“We have a jaw plant that’ll crush it down to a four-inch minus. From there, it goes across a screen deck and all the stuff that’s under the 63 mm size will drop through and go onto a belt, across our scale and up into the pile. Anything that’s oversized will feed into a cone. We have a cone unit as well, and that’s set to the 63 millimetre.”
The re-crushed material returns to the system, looping back through the screen deck and on up the stackers to the stock piles.
When winter comes, the entire operation moves from the west scale on 107 Avenue to the southeast scale on 17 Street. The operation’s equipment is portable and it takes about a week to move and be ready to operate again.
The city is looking to expand the operation to include a third location in northeast Edmonton.
Buchholtz said the project is currently in the design stages and he is hoping to have the third facility up and running in a couple years.
The hope with the northeast location is to provide access to outlying municipalities to have their contractors drop off construction materials.
They would then be able to sell the crushed material back to municipalities at a low cost.
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