How recycled glass bottles will be used to rebuild I-95

Most of the glass bottles we put in curbside recycling bins end up in a landfill or an incinerator, as the mix of colors and any contamination by other materials can often make glass recycling impractical.

Unless Archie Filshill gets his hands on it.

Filshill’s Eddystone-based company, Aero Aggregates of North America, turns discarded glass into a lightweight, gravel-like material that contractors will rely on in rebuilding the damaged section of I-95.

Called foamed glass aggregate, it is being used to build up the damaged section of the Cottman Avenue exit ramp. Workers will deposit 15,000 cubic yards of the stuff to support a temporary, six-lane highway while contractors rebuild the bridge that collapsed in a tanker fire Sunday, said Filshill, the company’s chief executive officer.

He said project engineers chose to use his company’s lightweight material, which weighs one-sixth as much as regular soil, to protect aging sewer lines beneath.

“Those things aren’t designed to hold another 20 feet of soil on top,” he said.

For those who picture shards of beer bottles along the highway, fear not. Glass aggregate looks nothing like glass.

The manufacturing process starts with grinding glass into a powder and subjecting it to a three-phase cleaning and filtering procedure. Workers then add a proprietary, mineral-based foaming agent and heat the powder in a kiln at 1,650 degrees Fahrenheit.

The material emerges from the kiln looking like a long, gray sheet of cake, said Robert Swan Jr., a Drexel University engineering professor who has studied the material’s properties. Upon cooling, the material cracks into gravel-like pieces, and is further broken down in a tumbler into one- to two-inch chunks.

“It’s not like putting glass bottles under the roadway,” he said. “It’s an engineered material.”

The company’s glass aggregate has been used as backfill in several other Philadelphia-area projects, primarily where the soil underneath is soft and compressible and cannot support too much excess weight. One example was an overnight parking apron for airplanes at Philadelphia International Airport, Filshill said.

It also has been used in highway projects along the East Coast, and is approved by 23 state departments of transportation, he said.

At a news conference Wednesday morning, Gov. Josh Shapiro touted the fact that the material was sourced locally.

“Pennsylvania fill!” he said.

Aero Aggregates is expanding beyond its Delaware County roots. In addition to its main 97,000-square-foot plant in Eddystone, on the site of the old Baldwin Locomotive Works, the company opened a second facility last year in Dunnellon, Fla., and it plans to open a third later this year in Modesto, Calif.

Once the third plant is running, Filshill projects that the company will find new uses for more than half a billion glass bottles a year.

“If we didn’t use it,” he said, “it’d be going to landfills.”