News

Mar 27, 2023

Insulating

The 414-mile road from Fairbanks, Alaska, to the frozen tundra of North

The 414-mile road from Fairbanks, Alaska, to the frozen tundra of North America's largest oil field is remote and rugged with hills steep as roller coasters, polar bears nearby and wild weather featured regularly in History Channel episodes of "Ice Road Truckers."

Known locally as the Dalton Highway, this sometimes-paved, often-graveled road is the lifeline to transport supplies from food to heating fuel to modular housing to the 213,543-acre oil field near the Arctic Ocean and the few towns north of the Arctic Circle.

When the Alaska Department of Transportation needed to repair the 50-mile leg that ends just shy of the oil field by Prudhoe Bay, it gave a green light to using block-molded expanded polystyrene as insulation in the roadbed.

A contractor is installing two layers of 2-inch-thick EPS as part of the base for a gravel-surfaced section of the highway, which dates back to 1974 and originally serviced construction of the Trans-Alaska Pipeline. The insulation serves two purposes, according to Monte Hagerty, plant manager at a facility in Anchorage that manufactured 4 million cubic feet of InsulFoam 40-brand EPS for the project. The product keeps the permafrost frozen for stability and raises the roadbed above the flood level, Hagerty told Plastics News.

Freeze-thaw cycles have taken its toll on the road reportedly traveled by some 200 tractor-trailer rigs a day. Though average temperatures there are below-freezing much of the year, summer usually brings highs in the 50s, and a wide range of temperatures from -62° F to 83° F have been recorded. Melting permafrost causes the highway to settle and buckle.

Another problem is due to major flooding in 2015 caused by the rapid melting of the Sag River. Overflow ice and a spring flood eroded parts of the road.

Hagerty said in an email that InsulFoam 40 addresses these problems by "banking cold" within the roadbed in winter to keep the permafrost frozen in summer and by providing a lightweight structural infill that lifts the roadbed above flood levels without overcompressing the underlying soils.

Traditionally, the only product that could meet the project standard in terms of thermal value, water absorption and compression was extruded polystyrene foam board, Hagerty said. However, the Insulfoam Anchorage plant has "specialized manufacturing equipment" that produces EPS boards that meet standards of the American Association of State Highway and Transportation Officials. Hagerty said he could only identify the equipment as a block molding machine for proprietary reasons.

He described the InsulFoam 40 product it forms as a "high-performance insulation consisting of a superior closed-cell, lightweight and resilient EPS, manufactured in a plank mold."

Road crews have installed plenty of the product to date for the project, which is scheduled for completion in 2019.

"Picture a football field stacked about 70 feet high with insulation," Hagerty said of the volume manufactured so far.

Preparing the Anchorage production plant and its workforce to fill the huge order was a major undertaking, Hagerty added.

"This required the plant to solve a range of production challenges needed to operate 24/7 for three years, while still also meeting other local demands for insulation products," he said.

InsulFoam 40 has been around about 25 years, according to a product data sheet that says commercial, industrial and residential applications include foundations, drill pads, railroad bases, ice rinks and parking structures in addition to uses for roadbeds and permafrost protection.

The InsulFoam brand is owned by Carlisle Construction Material Co., which is based in Puyallup, Wash., and says it is the largest U.S. manufacturer of block-molded EPS. CCM is a $2 billion division of the publicly traded Carlisle Cos., which employs more than 2,400 people and operates 26 plants in North American and five in Europe.

In Anchorage, Hagerty said, "Specifically, the plant ramped up production to supply 3 1/2, 52-foot long flatbed trucks of EPS every day to meet the Dalton Highway construction schedule, and worked with the contractor to ship the materials more than 500 miles to the job site."

Once there, typically no cutting or trimming is needed because the plank-mold process yields individual panels with a hard, skin-like finish, the product data sheet says.

Road workers with the Palmer, Alaska-based Cruz Construction Inc. are putting down more than 3,000 individual sheets per 12-hour shift, according to a YouTube video about the project.

A 50-mile stretch of Dalton Highway in Alaska that ends just shy of Prudhoe Bay is being upgraded with block-molded expanded polystyrene insulation in the roadbed. Road crews are installing more than 3,000 sheets per 12-hour shift.

Chris Krieg, project manager for Cruz Construction, explains in the video how the product is installed.

"Adhering the insulation board to the road surface kind of looks like a pogo stick, but it's a giant stapler that uses 6-inch staples," he said. "A guy walks along, punches it in, drives through the insulation board and secures it to the gravel."

Veteran members of the road crew have commented about the board's durability, according to Krieg.

"A lot of the old-timers were surprised at how well the board held up once we started putting gravel on it and bulldozing over it with our equipment," he said. "It wouldn't break apart and crumble in pieces like the stuff they had used in the past."

Maintaining the full corridor from Fairbanks to Prudhoe Bay is critical, Krieg added. Airplane deliveries aren't practical, and shipments via the bay aren't possible most of the year.

"To barge in to Prudhoe Bay, you've got a tight window, about two months — so the Dalton Highway is the main source for these guys here, and we need to make sure it stays in good shape," Krieg said.

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