UAA professor floats concrete solution to Alaska’s road rut problem

For the past 15 years — and the past eight in Alaska — UAA professor of civil engineering Osama Abaza has been developing a road surface that can stand up to Alaska’s road-rut problem.

The concrete slab at UAA is the first practical test of the solution. Abaza plans to work with the Alaska Department of Transportation to install a 180-foot lane of the concrete on Abbott Road next summer.

“I’m not going to say we have the magic solution, but we’re trying,” Abaza said in a September interview.

Abaza is branching out from the traditional asphalt used to construct Alaska’s roads by considering concrete. The idea is that concrete is a more durable material than asphalt, but less adaptable to Alaska’s variable temperatures. Asphalt flexes, concrete doesn’t. That makes asphalt good for extreme temperature variables, but not great with studded tires that steadily crunch away at the soft aggregate rock embedded in Southcentral Alaska roads.

Abaza has been trying to figure out how to fix that. He developed a concrete mixture that includes a small amount of rubber crumb from recycled tires mixed with toothpick-sized pieces of steel. Abaza said the idea is the crumbs will make the concrete more flexible. The thousands of tiny steel pieces will act like miniature reinforcing bars, in turn protecting the concrete from micro-cracks.

The hope is that a concrete road could be developed that is more durable, in turn extending roads’ current lifespans of about four to six years to a longer 15 to 20.

DOT research engineer Anna Bosin said concrete roads are common in the Lower 48, but rare in Alaska. The only one she knows of is several blocks of Nordic Drive, a low-volume roadway in Petersburg.

Bosin said concrete comes with a host of challenges — cracking under variable temperatures, difficult installation — and is overall much more expensive than asphalt.

But road ruts are their own problem for the department. A 2013 report found that overall Alaska’s road conditions are listed as fair, but road ruts are hard to miss for Southcentral motorists.

“DOT always wants to be innovative but also cost-effective and the best way to do that is through research,” Bosin said. “And then try to implement something that’s cost effective further into the system. I think that’s where we’re at in concrete.”

The Abbott Road segment, when completed, will be embedded with sensors to watch for how the road deals with freezing and thawing. It will also be placed right next to a lane of freshly paved asphalt so researchers can compare the wear on the two.

Concrete critics
Abaza is quick to point out that his concrete is still being tested and the research doesn’t definitively prove whether the mix will help Alaska’s roadways.

Then there are others who think the mix won’t work at all.

Anchorage Sand & Gravel cement dealer Xavier Schlee co-chairs the DOT “cement alliance,” a group that meets quarterly to discuss concrete use in Alaska. Schlee said that concrete already has numerous applications in Alaska roads — in some intersections, portions of roads, and atop weight and motion scales. He said many of them work successfully and in some cases have outlived multiple asphalt roads around them.

And while Schlee advocates for more concrete roads, he remains unconvinced that Abaza’s formula is the right solution.

Schlee said the “exotic” additions to the concrete are expensive and don’t add much in terms of flexibility. He said concrete with other additives is already in production, is cheaper, and more durable than Abaza’s proposed mixture.

He worries that implementing the design on a roadway before it’s properly vetted could damage future hopes for concrete roads in Alaska.

“If the mix design goes out and fails it won’t be perceived as the ‘UAA concrete mix design’ that went out failed, it will be perceived as a concrete failure,” he said.

Rich Giessel, DOT statewide quality assurance engineer, doesn’t think concrete has any practical use on most Alaska roads. Giessel said concrete appears to have limited applications in intersections and some places in Alaska, but for concrete to work, it has to be in a place with no frost heaves — an almost impossible-to-find condition in Alaska.

He noted that improved runways at Ted Stevens Anchorage International Airport are concrete and avoided frost heaves. But they didn’t come cheap, at $60 million to complete the project that involved 2 feet of concrete on top of 7 feet of gravel.

Alaska roads would need a similar sort of infrastructure, something that is likely cost-prohibitive.

“(Abaza) has invested a lot of time and research into this,” Giessel said. “But to me, it’s not a solution to any of our problems.”

State materials engineer Mike San Angelo said the department is open to considering concrete, but that since it operates a public service, they’re cautious about implementing new materials until it faces a barrage of testing.

He said the department is always trying to figure out ways to deal with ruts, from looking at importing harder aggregates to adding new materials to road mixes. This summer it laid a section of road downtown on I Street and on the Glenn Highway that included Kevlar-like fibers mixed into the asphalt as another real-world test.

Abaza understands their concerns, but emphasized that it’s impossible to know what will work until its tried.

“We have to create solutions for our community,” Abaza said. “That’s why I’m here.”

Source

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