P R OJ E C T M A N AG E M E N T
Asphalt Creativity Solves Concrete Instability BY SARAH REDOHL
M
aine’s Bangor International Airport boards around half a million passengers each year on up to 20 daily departures. When the concrete beneath its runway began to buckle, making the repairs in a timely manner was of the utmost importance. Northeast Paving, a civil contractor headquartered in Bangor, Maine, was up to the task. “Throughout the years we have done a majority of the paving at BIA,” said Northeast Paving Engineer Devon White. In 2021, Northeast Paving won the bid to repair BIA’s Runway 15/33. Northeast Paving Chief Estimator Greg Schaub said that, prior to the start of the contract, there were two areas of the existing runway that had heaved as a result of an Alkali-Silica Reaction (ASR) in the concrete. Also known as “concrete cancer,” ASR is a swelling reaction that occurs in concrete over time. Given sufficient moisture, the concrete’s highly alkaline cement paste reacts with the amorphous silica found in many common aggregates. BIA’s concrete runway was placed in the 1950s as part of Dow Air Force Base.
“This reaction caused the existing concrete to expand and with no place to go it started to buckle,” Schaub said. To resolve the issue, Northeast Paving took a creative approach. During the course of a 48-hour shutdown, its crews demolished two 300-foot-long concrete strips running transversely across the runway where the heaving was most severe and replaced them with 14 inches of P-209 aggregate base and surface asphalt. “The P-209 blend of stone and asphalt will work as a large-scale expansion joint of sorts to relieve pressure and heaving due to pressure,” White said. Ultimately, the asphalt strips aim to reduce swelling caused by ASR.
BREAK CONCRETE, FAST
Because the runway upon which Northeast Paving would be working is BIA’s only runway, the entire airport had to shut down for the work to be performed. “Shutting down the entire airport isn’t an easy thing for BIA to do,” Schaub said, so having weekly meetings in the month leading up to the job provided an opportunity to discuss methods, timeframes and logistics. “They needed to feel comfortable that we could get the job done in a tight timeframe.” Schaub thinks that Northeast Paving’s history of working at the airport not only helped give the client confidence that they could perform the work, but it also gave Northeast’s crews “an idea of what we were up against.” The full airport shutdown did make traffic control a bit easier than it otherwise would have been, added Northeast Paving Engineer Marshal Deckers. 18 | MARCH/APRIL 2022
Northeast Paving hired Pavilion Drainage Supply Co. to use its Wirtgen CB 7000 Guillotine Drop Hammer on the underlying concrete.
“On a normal airport job, we’d have to block off every entrance point for aircrafts,” Deckers said. For this job, he added, it was more important to mark the runway as closed down in such a way that it was visible from the air, rather than setting up barriers on the ground. “If you have moving aircraft while you’re working, you need more barricades and better delineation.” White said this includes Notice to Airmen or Notice to Air Missions (NOTAMs) issued stating that the runway will be closed, as well as flashing trailer mounted Xs as a visual indicator of a closed runway for potential approaching aircraft. Not having to set up so many barriers on the ground ended up saving the crew a small amount of time, which was particularly precious given that the crew would have a mere 48-hour window to complete the project. During the estimating phase of the contract, Schaub said Northeast Paving evaluated several different options to remove the existing concrete. “Breaking up the concrete with traditional hoe rams on excavators was evaluated but determined to be too time-consuming of a process,” Schaub said. During a previous job Northeast performed at BIA in 2008 to rubblize the concrete Air National Guard’s heavy duty apron, the company tried to use a resonant breaker—particularly near the fuel tanks—with the hope that it would cause less impact to the subgrade. However, Schaub said, the resonant breaker was unable to break the concrete all the way through, so they ended up using a guillotine on that job anyway.
