Is the asphalt formula a factor in Toronto’s cracking and crumbling roads?
Published Tuesday, March 26, 2019 8:37PM EDT Last Updated Tuesday, March 26, 2019 8:51PM EDT
As crews battle constant cracking in the roads – filling about 200,000 potholes a year – some engineering experts are questioning whether the roads would last longer if the city used less recycled aggregate in its asphalt.
The City of Kingston has been using pure asphalt since 2010 in an attempt to extend the lifespan of its roads, based on recommendations out of Queen’s University.
“It will age prematurely and then crack, so that's the reason we've moved away from recycled asphalt,” said the director of Kingston Engineering Services, Mark Campbell.
The City of Toronto allows for up to 15 per cent of reclaimed pavement in the asphalt used in the base layers of its roads.
“When we're doing the reconstruction, repaving of a road, when they grind up that old stone, they can put a certain percentage of that old asphalt back into the new mix,” said City of Toronto road operations manager Mark Mills.
Mills said roads are currently lasting about 15 to 20 years on average. The heavy volumes of Toronto traffic and the thaw-and-freeze cycle also play big roles in the longevity of the roads.
Toronto tops the list of recycled aggregate users, according to the Toronto and Area Road Builders Association. Cambridge and Markham are the next big users, while Oshawa and Mississauga use the least amount of recycled aggregate.
Peel Region has been piloting the use of reclaimed asphalt in its roads and officials characterize the early results as “reasonable,” saying they will continue to monitor its performance.
The Ministry of Transportation revised the rules in 2017 to allow recycled aggregates only in the base layers of provincial highways in order to improve the performance and durability of the surface layers.
“With regards to reclaimed asphalt, it's an issue we continually review,” Transportation Minister Jeff Yurek told CTV News Toronto.
However, the Ontario Asphalt Pavement Council continues to advocate for the use of reclaimed asphalt, saying that rutting and cracking can be managed through compatibility assessments and engineering.
Toronto infrastructure committee chair James Pasternak said he will be encouraging transportation staff to review the performance of the pavement.
“We've got to look at better ways, we've got to look at new technologies, new systems of asphalt and concrete and look at what other cities are doing,” said Pasternak.
In Kingston, Campbell says the results so far have been promising. The city is able to recycle old asphalt into mixes destined for driveways in order to keep it out of landfills.
The city pays a five per cent premium on pure asphalt but staff believe the roads will last longer as a result.
“If you’re getting twice the life out of your road, you're saving costs,” said Campbell.