Strange weather causes road failures

MAT-SU -- When winter turns to spring without passing through the crucial breakup process, one might think it would alleviate the problems that accompany breakup. That's not the case, however, according to Mat-Su Borough Public Works and the Department of Transportation's Mat-Su district officials.

"We thought it was going to be a real easy breakup," said borough Public Works Director Jim Swing last week, adding that similar comments had been made by department officials publicly. He joked that the problems now facing the department could have been avoided if they hadn't been so optimistic. "You shouldn't say things like that."

Swing said the unusual winter has led to an even stranger spring, and the uncharacteristic weather has affected borough roads in ways he didn't expect.

"We had a lot of frost heaving with paved roads," Swing said, "more than I've seen in a few years."

He added that the borough has seen failures and serious breaks in gravel roads where they aren't generally seen, while areas that are often problematic may not need fixing this year. Department of Transportation officials said that's been the case with state roads as well.

"I don't know if we've had as many potholes, but we've had more major failures," said DOT's Mat-Su District Supervisor Curt Devan. "The major repairs are worse."

Devan said two state-owned roads, Edlund Road and Vine Road, have bad breakage problems that will take a little more than a little hot-mix asphalt to fix. Part of the problem, he said, could be that those two roads, along with other roads that have been problematic this spring, are already in need of work.

"They're older pavement that was deteriorating to begin with, and had some poor materials underneath," Devan said.

In a state where finding ideal materials for road construction can be challenging, Dr. Lufti Raad, director at the Transportation Research Center at the University of Alaska Fairbanks, is working to find ways to make existing materials strong enough to suffice.

Finding materials to withstand Alaska's weather extremes is a big part of Raad's research. Transportation Research Center researchers test how different materials behave under different weather conditions and different traffic volumes. Weather, Raad said, is likely a contributing factor in the road breakage that took place this spring.

Without snow cover, he explained, moisture was able to penetrate deeper under the surface of the road -- and with the warmer weather, that water was given more time to migrate upward into the upper pavement layers, where it could -- and did -- do significant damage.

"You lose a little bit of the insulation layer on the surface," Raad said. "Snow is a good insulating layer … Essentially, you're giving the water in the roads more time to migrate upward."

Most of the road problems challenging Alaska, Raad said, is related to moisture. In the Southcentral area, the roads are subjected to constant freeze-and-thaw cycles, which weaken the asphalt by making it expand and contract time after time. Conversely, in the Fairbanks area, the roads are subjected to very deep freezes, which also stress and weaken the road surface.

In his work at the research center, Raad said, he and other researchers focus on how materials used today hold up to Alaska's weather extremes. How road materials lose strength when they thaw and what kinds of materials are needed so that loss of strength is diminished are two areas of focus at the center. Traffic, Raad said, also plays a large part in how materials perform.

"In some cases, you may have extreme weather, but not a lot of traffic," Raad said. "In other areas, you may have high traffic in the same conditions."

Raad said researchers at the center are studying how marginal materials, or materials found in areas where the road is to be built that may not be typically used for road-building purposes, behave when used in roads.

"[Roadbuilders] have to haul this material for a long distance and it's very costly," Raad said of the materials currently used for roads in some areas of the state.

Raad explained that tidal materials or material found in and along rivers, for example, are being tested to see how they may affect the durability of the road surface.

"If we used this material, how would the use of this material affect the stability of roads in 15 years versus five years," Raad said. "Then how much improvement do we need to incorporate?"

Researchers at the center, Raad said, are currently working with adding polymers -- naturally occurring or synthetic substances made up of large molecules -- to asphalt to improve low-temperature behavior for roads. The polymers, he said, allow greater flexibility. The research center, Raad said, is hoping to find the right mix of local materials and additives to make inexpensive, durable roads for various Alaska applications.

"The degree of improvement depends on the type of performance we need. This is the kind of approach we try to work with to come up with cost-efficient means to build roads," Raad said. "Many times, we do not need the best material to build roads."