The Future of Asphalt
How do we keep our streets from crumbling underneath us?
Illustration by Pop Winson
People like to say there are only two seasons in Edmonton: Winter and construction. At the heart of both are our city’s roads. When it’s cold, those 44 million square metres of asphalt freeze, crack and slowly crumble. When it’s warm, fleets of city workers take to the newly spongy streets, repaving and patching up a staggering 450,000 potholes every year, on average. The worst damage actually comes in between these two extremes, during the freeze-thaw cycles in spring and fall, as temperatures jump above the freezing mark by day, but dip back below at night.
Potholes are an ever-present, city-wide nuisance — so much so that pledging to solve the problem has become an easy and predictable tactic for many an aspiring politician. Councillor Kerry Diotte, for one, has already made it a going concern in his current mayoral campaign. Yet the ubiquity of our faulty asphalt means that it also provides Edmontonians with some (metaphorical, anyway) common ground.
“No matter what part of the city you live in, or what you do for a living, everybody deals with potholes,” says political blogger Dave Cournoyer. “It’s the complaint that unites us as a city, in a weird way. Kind of like the Edmonton Oilers not making the playoffs.”
But despite all the lip service that’s paid to the issue, I wonder how much Edmontonians really know about how our roads work, as well as how deep the problem actually runs. Are average citizens equipped to judge whether spending more than $14 million on pothole repair in a single year — as city council has in 2013, dumping an emergency $9 million on top of the $5.2 million included in the annual budget — is a long-term solution? Is it a solution at all? And why are we so confident asphalt is the best material for the job?
Bob Dunford is the City of Edmonton’s director of road maintenance. He has no illusions about the state of our roads; specifically, the 14 million square metres of heavy-duty arterial roads that carry Edmontonians from point A to point B on a daily basis. Approximately 18 per cent of those are currently in need of not just select re-patching, but total rehabilitation. “That’s where your potholes are right now,” he says. “That’s what we’re feeling. We need to get that percentage under 10 per cent.”
Right now Edmonton is the pothole capital of Canada, hands down. There is no competition. Our average of 450,000 repairs per year dwarfs even those of larger cities like Toronto (140,000 to 280,000), Montreal (35,000 to 50,000) and Calgary (30,000 to 40,000). Clearly, there’s something about Edmonton and asphalt that do not get along. To find out what, exactly, that X factor is, I turn to Hugh Donovan, a construction-services engineer for the city and manager of its Engineering Services Quality Assurance Laboratory. (He’s also, in Dunford’s words, “our asphalt nerd.”)
Like Dunford, Donovan is realistic about the impact his work can have on the city’s roads. “I’m not sure I can actually design and build a road in Edmonton that will never, ever have a pothole,” he says. “It doesn’t matter how good a mix I make. There are extenuating circumstances I have no control over.”
One of those circumstances is temperature. The oils used in Edmonton’s asphalt cements have a temperature range of close to 90 degrees Celsius: from 58°C to –28°C. “Below that,” Donovan says, “the road will crack.” But we all know that Edmonton can sit for long periods of time in temperatures –28°C and colder. So why use this type of oil at all?
Because the alternative would be far worse. The other available oil product has a range of 52°C to –34°C, which, Donovan says, would likely cover the bottom end, since asphalt takes up to a week to fully absorb the colder air temperatures. But in the height of summertime, Edmonton’s black, heat-absorbing roads routinely get past that 52°C upper threshold. In the absence of an oil that can handle our city at both its hottest and its coldest, Donovan has had to make a choice. “I can’t have an asphalt that flows off the roads in the middle of summer,” he says. “So we accept the cracking.”
This compromise doesn’t sit well with Kim Krushell, the three-term city councillor for Ward 2. (She is not seeking re-election this month.) Krushell says that what’s needed for Edmonton’s roads is not an unlimited budget, but a larger change in how we approach road materials in general. “I don’t disagree that we need to fix potholes,” she says. “But I don’t think the way to solve it is to just pour money into it. I think the way to solve it is to look at new technologies.”
I ask Donovan whether there are any serious alternatives to asphalt out there — materials that won’t create the same pothole breeding ground. In fact, there is one. And we’re already using it, for better or worse; and that’s concrete.
While slightly more expensive, Donovan readily admits that concrete doesn’t lend itself to potholes as easily as asphalt does. The problem, however, is that concrete is far more difficult to repair. Parts of the Anthony Henday were built with concrete, but when they need even minor maintenance, traffic grinds to a halt, as all concrete patches have to sit for up to a week before vehicles can drive on them. Asphalt, by contrast, can be patched up overnight. Donovan says that concrete tends to be used less often in municipalities in general, because city roads are often sitting atop water, gas and sewer lines, to which the city needs quick and easy access.
Until the 1970s, Edmonton experimented with a combination of the two materials, but this is actually causing some of the worst headaches of all. Donovan estimates that nearly one-third of our current roads were build in this hybrid mode, with asphalt layered on top of a concrete base; during inclement weather, these materials expand and contract at different rates, which only increases the likelihood of the road breaking down. According to Donovan, most of our current pothole problems stem from these outdated roads, some of which have had no work done on them in several decades.
The good news is that the roads we’re building today are much more durable than they were in the past. Pothole repair remains a kind of Band-Aid solution, but the city’s concurrent road rehabilitation projects are removing these rickety old concrete-asphalt hybrids and replacing them with asphalt that’s better designed than ever. It just takes time: In the five years Donovan and his team have been using asphalt with new anti-stripping chemicals, for instance, which help prevent pieces of the mix from chipping away under pressure from heavy traffic, they’ve repaved approximately eight per cent of the roads.
Research and development at the Engineering Services Quality Assurance Laboratory — the only municipal lab of its kind in the country — has produced other cutting-edge modifications, too, including using polymers and customizing the asphalt mix depending on the road’s traffic load. These innovations are largely still in the testing stages, but could soon be included in future asphalt mixes, costs permitting. “Over the last 10 years, the amount of research done on asphalt-related products [has] probably [increased] 100-fold,” Donovan says.
And after many years of not properly investing in municipal infrastructure, city council has started to once again treat road maintenance as the critical issue it’s always been. One area that’s already showing results is neighbourhood roads. In 2009, the city launched its long-term Neighbourhood Renewal Program, which uses localized tax levies to update and replace old infrastructure, including roads. When the program launched, 37 per cent of Edmonton’s neighbourhood roads were ranked as being in “good” or “very good” condition. Today, that number is up to 48 per cent and climbing.
But the future is still far from certain. The current budget cycle runs out at the end of 2014, and Dunford says that continuing the long-term investment in our arterial roads, over the next four-year cycle and beyond, is crucial. Edmonton’s share of provincial and federal fuel-tax revenue could also potentially be put towards arterial road maintenance. It’s clear that the materials, expertise and facilities to bring Edmonton’s asphalt roads into the 21st century — and to bring that arterial rehabilitation rate down to a manageable 10 per cent — are all already in place. The only remaining question is funding.
Despite her push for alternate materials, Krushell agrees. She points out that when projects like the Quesnell Bridge widening and rehabilitation ran over their budget, the difference was taken from the arterial roads budget among others. Until those kinds of numbers are stabilized, it will be difficult for any kind of long-term solution to take hold.
This is obvious from a citizen’s perspective, too. “We’re the one jurisdiction in Canada that can afford not to have these problems,” Cournoyer says. “But it needs to be a long-term strategy. If you want good public infrastructure — that’s roads, public transit, sidewalks, universities, hospitals — you’ve got to invest in it. Quality of life isn’t free.
“Frankly, we can do it. There’s really no excuse.”