An airfield pavement project at Philadelphia International Airport is using approximately 90,000 cu yd of foamed glass aggregate, which officials believe is the largest application of its kind in North America. The ultra-lightweight fill speeds placement and eliminates the need for piles.
Work on the $35-million contract started late last year, says Rick Foster, executive vice president at James J. Anderson Construction Co.
“It’s really a material replacement job,” he says. “We’re digging out heavy material and replacing it with lightweight aggregate.”
The scope includes 5,000 linear ft of storm pipe, 62,000 sq yd of subbase, 54,000 sq yd of 16-in. concrete pavement and 8,000 sq yd of 9-in. concrete overlay, Foster says. “The compaction efforts are significantly different than compacting typical aggregate. [FGA] is easy to move around. We’re compacting with a dozer versus a roller. We could shave a year off the job compared to using wick drains and surcharging.” The apron is expected to be completed by the end of 2021.
Larry Allen, senior project manager with the airport, agreed that FGA helped cut the construction schedule. Since the airport is near the Delaware River, “the conditions include a high water table and soft soils that have a high potential for significant settlement,” he says. Surcharging, wick drains or other methods were considered, but “the use of FGA saved a minimum of six months on the construction schedule from the next fastest option, surcharging with wick drains,” he says.
FGA has been used in Europe for over 25 years, says Archie Filshill, who founded AeroAggregates in Eddystone, Pa., in 2012. The company is now opening two more plants.
Recycling centers send glass bottles of any size or color to the plants, which convert them into the aggregate by milling them into a powder and mixing in a foaming agent.
One of the first major projects using FGA was an interchange reconstruction for the Rhode Island Dept. of Transportation. FGA ensured a 100-year-old brick sewer was protected against the weight of the embankment, with no settlement, according to a Federal Highway Administration report.
On the airport apron replacement, using FGA diverts the equivalent of over 83 million glass bottles from landfills, and reduced delivery truck trips by 6,000, says Filshill. Moreover, crews can place 3,000 cu yd a day instead of the typical 1,000 cu yd, regardless of weather, he adds.
Unlike other lightweight aggregates, typically styrofoams, FGA isn’t flammable or degradable, says Filshill.
One of the challenges using FGA is that “the material comes in 100-cu-yd trailers, so we have to be careful about access,” says Foster. “I see it having multiple uses as far as ground improvements, loading critical structures.”
He adds, “I see at some point this material potentially changing design concepts due to its lightweight nature.”