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This is Prof. Pavement. He might have found a way to make roads nearly pothole-free

Carleton University prof causes a stir with his new paving technology — and he's got the province's attention

SUDBURY — After decades of roadblocks, a Carleton University professor is finally making inroads with his innovative road-paving method, a process he says will drastically reduce potholes and extend the life of roadways everywhere.

Dr. Abd El Halim, professor of transportation engineering, has gotten a lot of attention recently for his Asphalt Multi-Integrated Roller – AMIR for short, named after Halim's son.

Why do roads fail?

Rather than using multiple rollers to compact the asphalt directly, the AMIR method uses a wide rubber belt, similar to a snow machine. The current technology, Halim said, hasn't really changed — ever.

"We've used the same rollers for 200 years,” he said. “We've changed everything else you can imagine — the mix, the traffic, but it's the same rollers."

Roads fail because they crack, Halim said. In northern climates especially, tiny cracks in the asphalt get filled with water, which freeze and expand the road, making the cracks a little wider. When the thaw occurs, a bit more water fills the now larger cracks, and when it freezes again, it makes bigger cracks, and so on.

"It's like if you put a bottle of water in your freezer — what happens to the bottle?" he said. "That's why we see the potholes in the spring."

Current paving technology has contractors use three different sets of rollers to compact the asphalt – a big roller at first, then eventually smaller rollers for more fine compacting.

Halim says each time the rollers go over the asphalt, it causes cracking to some extent because of the vibrations and uneven pressure being applied to the road.

"But after the appearance of a crack, there is no way you can fix them," he said. "It's like glass — once it's broken, it's broken."

How to make roads live longer

The key to extending life of a road, then, is to reduce the initial cracks as much as possible to ensure as little water as possible gets inside. That's where AMIR comes in.

He explains the difference with an analogy: take an egg, put it on a sponge and tap the top of it with a knife to see how long before it cracks. Then do the same thing with another egg, but put your finger over the top of the egg and then try to crack it.

"And that's the difference between the two rollers," Halim said. 

With AMIR, the pavement is always in contact with the flat rubber track as it's being compacted. And while traditional rollers go over the asphalt as many as 20 times to get it flat, AMIR takes a maximum of eight passes, further reducing the chances of cracking.

"You want it like a carpet sitting on top of the pavement while you roll it, so you don't have the cylinders dipping into the asphalt, causing these cracks."

When he first published his work, Halim earned international recognition, winning innovation awards, as well as interest from the paving industry. Many offered him money for exclusive rights to his idea – not to use it, but to get it off the market. There was no incentive for them to make roads that last longer, since it would hurt them financially.

“So I refused to sell it to them," Halim said. "I found they wanted to take the roller, but they didn't want to produce it. They'll give me money, yes, and I'll be a bit richer. But those companies weren't going to sacrifice their own business. My rollers would reduce dependency on their rollers."

Roads that live 20 years

After a successful test on a 40-kilometre road in Australia during the 2000 Sydney Olympics, AMIR still failed to attract more interest, and Halim focused on other things — until 2010.

“I was giving a presentation in Quebec City and my friends in Quebec asked about the roller, because the roads in Quebec are as bad as your own roads," he said.

After that meeting, he got a call from a former student who attended the Quebec City event and now works at the Ministry of Transportation. The call breathed new life into AMIR. He received some funding for research and developed with Tomlinson, a major Ottawa paving contractor, a kit that could cheaply convert existing roller machines to AMIR versions. Tomlinson has used it on some limited jobs.

MTO estimates that finding a way to extend the life of a road by one year "will save the province $50 million," Halim said.

Test roads have been done in Ottawa, and are so far outperforming asphalt laid at the same time using traditional methods. The AMIR road is still crack free, while the other road is already deteriorating. The goal is to create roads that last 20 years with only minor maintenance. 

"With current rollers, you're lucky if you get seven years,” Halim said. “You can see that in any city."

Good news for northern roads

Tony Cecutti, Greater Sudbury's GM of infrastructure, said they have been monitoring tests being done with AMIR and are excited about the possibilities.

"(Halim's) work is all about placing and compacting asphalt, and from I understand it's all good work," Cecutti said.

One of the challenges in paving, he said, is when one layer of asphalt is laid beside another. If one new section has already cooled, it creates a “cold seam” and doesn't mesh together well enough to resist water. Crews will sometimes pave two sections at the same time to avoid the problem, or try to put down the next layer before the first one cools.

If AMIR can provide asphalt that has fewer cracks to begin with, Cecutti said that could have significant benefits in a city with a harsh climate and frequent thaw-freeze cycles.

"Asphalt is a flexible material and it is always going to develop cracks over time,” he said. “There's no way to avoid that. The older your road is, the more cracks are going to occur in it. That's why areas where we have the most potholes tend to be the older roads."

The city spends about $1 million a year patching potholes, as well as replacing badly pockmarked roads with a new layer of pavement. About $25 million is spent just on paving new roads, not including culvert and other related work.

"It's a very expensive process,” Cecutti said. “It's one of the more expensive things we buy at the city."

High hopes for AMIR

While he's unsure a road in Sudbury could last 20 years before significant maintenance is needed, if AMIR pans out as hoped, it could save residents tax dollars if it lengthens the life of a road by even a year.

"That is certainly the hope, and certainly we're hopeful that the work MTO is doing extends the time," he said. "An extra year is giving you something like a five or 10 per cent increase in the life of the road, and that's significant."

The key will be for the province to adopt AMIR as the new standard. Cities such as Sudbury can't afford to do its own research, or use unproven technology in road contracts without a guarantee it will be more effective, Cecutti said.

"The province has significantly more funding to do those experiments for us and to tell us when it's appropriate to make a change in the standards," he said. "And all the people in the paving business are going to use that equipment should it become industry standard."

How long will the process take? Cecutti said a gauge could be changes contractors have made to asphalt in recent years. After research showed using old motor oil in asphalt mix leads to premature cracking, it took about five years before the industry changed the mix on direction from the province.

"So that didn't take long at all."

For his part, Halim said he senses a growing understanding that everyone will benefit if his technology is widely used — contractors can complete their jobs in less time with less equipment, governments will save money and residents get better roads and fewer potholes.

"Everyone will be a winner."