Repairs on the concrete apron surrounding Sawyer International Airport's commercial terminal building are underway, with expansion joints being placed. The repairs are needed because the concrete has been expanding and migrating, putting pressure on the terminal building and causing damages. (Journal photo by Cecilia Brown)

MARQUETTE — Repairs are underway on Sawyer International Airport’s 80-acre concrete apron that surrounds the airport’s terminal building.

The repairs are needed because movement and expansion of the concrete apron has led to intense stress on the terminal building and the surrounding pavement, airport officials said.

“A portion of the pavement surface, the concrete, appears to be migrating to the north, and what is happening is, the concrete is hitting our terminal building and the jet bridge and any structure that is stationary there, and it’s applying a lot of pressure,” Airport Manager Duane DuRay said at an August meeting of the Marquette County Board of Commissioners.

Sawyer Director of Operations Steve Schenden said the pressure from the concrete has been causing some damage — cracks caused by the pressure can be seen on the terminal building, on the concrete and even inside the building.

The damage caused by the pressure, Schenden said, will be repaired after the underlying issue is addressed.

“We’ll fix the cause first, then go back and clean up,” he said.

The exact cause of the concrete’s expansion or migration is unclear, Schenden said, but noted engineers have speculated freeze-thaw cycles and expansion cycles over the seasons have led to the migration. Furthermore, he said, extreme heat over the summer caused the problem to become more severe.

The concrete apron repair project, which is funded by a Federal Aviation Administration Airport Improvement Program grant of approximately $137,000, involves the removal of certain sections of concrete near the terminal building, the addition of expansion joints and repair of the concrete in the area, airport officials said.

“They’ll take out the sections, they’re going to cut a fairly wide trough in those areas that it’s applying the most pressure,” DuRay said in a previous Mining Journal article about the project. “They’re going to put expansion joints in there, and they’re going to repair the concrete in those areas, giving that concrete the valuable space to expand and contract and alleviate the pressure.”

Because the concrete apron, which is about 8 inches thick, must withstand the weight of commercial planes, the newly poured concrete for the project needs to be tested for strength, Schenden said.

“When they pour concrete like this, they make test cylinders and then they take them to a lab and they do a seven-day test and a 28-day break test to see what the concrete actually strengthened up to,” Schenden said. While the repairs won’t be a permanent fix, they will buy some time, airport officials said.

“The concrete is continuing to move, but at least this is going to give us a little bit of time,” DuRay said in a previous Mining Journal article about the project. “And when I say a little bit of time, we’re probably looking at eight to 10 years if it continues to migrate at its (current) rate.”

The total cost of the project is $137,042, with a $123,338 federal share, a $6,852 state share and a $6,852 local share. Engineering work was performed by the county’s engineering firm, Mead & Hunt.

The construction work is being done by J Ranck Electric, which was the lowest bidder for the repairs on the commercial apron pavement.