The City of Edmonton is taking a scientific approach to tackling its growing pothole problem. Hugh Donovan, construction services engineer, said climate change is causing more extreme weather, which means more damage to the city’s road system.
"On average annually we used to have 122 freeze, thaw cycles," he said.
"In the past four years, I’ve seen that grow to 160 and 180. There has been a huge increase related to climate change."
He also noted lower average temperatures and freezing rains are becoming more common.
The result is potholes – hundreds of thousands of them.
Based on the average kilograms used on a single pothole, he estimated city crews filled 485,000 potholes in 2014 and 750,000 potholes in 2013.
This January and February, crews fixed more than 26,000 potholes.
"Some of our pavements are extremely old," he said.
"We don’t rehab as often as we probably should because it’s a money issue. You only have so many. What we do is we pick and choose."
The city is investing $55 million per year on arterial road rehabilitation over the next four years.
He said that while oxidation and traffic cause wear on roads, one off the main culprits is weather. Old roads get brittle and crack.
Water gets in those cracks and freezes, damaging it. The cracks get bigger and bigger until they become potholes.
Donovan and researchers are now studying the impact of freeze/thaw cycles on asphalt at Engineering Services Quality Assurance Laboratory and looking for ways to make paving materials more resilient to widely-varying temperatures.
The research includes putting various asphalt mix samples through multiple freeze/thaw cycles, then performing tests to see exactly how many cycles the samples can withstand before starting to deteriorate.
Donovan said that at just seven cycles he is seeing 50 per cent loss of pavement life with water saturation at 80 per cent.
He noted that researchers are still sampling city streets to determine what the actual water saturation conditions are.
"This test may be way harsher than what is happening in the field," he said.
He is also researching materials used to fix potholes.
The city created 50 potholes and fixed them with nine different products using standard procedures to determine performances. After two years into the study, some are starting to drastically fail.
Donovan said he plans to share the labs results in papers as the city has done in the past.
"If we find something out that is to our benefit we certainly like to publish it and make it known to all the other municipalities," he said.
He hopes the tests will help the city not only evaluate what products and mixes work, but when and where to prioritize resources.
"Unfortunately I suspect we are going to find we can’t afford to do as many as we need to do," he said.
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