From Trash to Major Interstate Repair
How bottles and jars are changing the face of civil engineering projects and the testing needs behind it all.
How many recycled glass bottles would it take to build an emergency support for one of the busiest four-lane highways in the world? We honestly wouldn’t have a clue, but we know someone that does.
According to Theresa Andrejack Loux, Chief Technical Officer for AERO Aggregates, it took the equivalent of 6.5 million glass bottles.
When a tanker truck flipped and caught fire on I-95 in Philadelphia, PA in June 2023, it caused an exit ramp to collapse, crippling the major thoroughfare that runs from Florida to Maine. AERO Aggregates’ foamed glass aggregate (FGA) was used to build the supporting structure that quickly stabilized the road in an emergency repair.
AERO Aggregates is a Pennsylvania-based company with a second plant in Florida and another planned in California. The company takes empty bottles and jars from recycling plants and landfill sites, turning them into an eco-friendly aggregate for use in a myriad of civil engineering applications.
Lightweight and Heavy Duty
Foamed Glass Aggregate (FGA) has been used as backfill in numerous projects, primarily where the soil underneath is soft and compressible and cannot support too much excess weight, such as an overnight parking apron for airplanes at Philadelphia International Airport.
That’s why it was so effective to quickly build up the damaged section of the exit ramp on the I-95 interstate on the outskirts of Philadelphia. A staggering 215,000 cubic feet of FGA was used to support a temporary, six-lane highway while contractors rebuild the actual bridge.
“FGA is absolutely ideal for this type of project, as it only weighs around one sixth of regular soil due to it being full of air bubbles. In the case of I-95, this helped protect the ageing sewage lines running underneath the structure, as they simply couldn’t withstand the weight of another 20 feet of traditional soil material,” said Andrejack.
“It was an awful accident and caused a huge inconvenience to everyone in the Philadelphia area, so we’re just delighted we could help and get things moving again extremely quickly.”
Quality Standards when Manufacturing FGA
The manufacturing process of the aggregate starts with cleaning the glass, grinding it into a powder and then 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. Upon cooling, the material cracks into gravel-like pieces.
She continued, “We aim for the bulk density of our standard product to not be any heavier than 15 pounds per cubic foot, which corresponds to about 240 kilograms per cubic meter. We follow the ASTM C29 standard for this type of bulk density measurement.”
“The other test that we run on a daily basis is a confined compressive strength test, which is what we use our Tinius Olsen 150ST machines for in each of our Philadelphia and Florida plants, with one on order for California. The company’s experience and input has been invaluable in developing our FGA product from the get-go and being a local company to ourselves has been an even bigger bonus.”
“The test method used for these compressive tests is EN 1097-11 although we’ve started down the road of trying to get a similar test standard in place at ASTM, which will obviously take some time.”
Supporting a Circular Economy
But where does all the required glass come from?
“Most communities do have some type of recycling program in place. The trend in recent years has been that some communities have dropped glass from the materials that they’re collecting through single-stream programs, but certainly there’s still many programs that do collect glass.”
“We work with recycling entities that are local to our plants to source the glass product that we need. We generally take lower-value glass because it’s the mixed color, the smaller pieces that generally can’t be used by a bottling operation or even a fiberglass plant. The glass product that we use generally goes to a landfill if we don’t take it.”
“with the addition of our California plant, we’ll have the capacity to divert over 500 million bottles per year from landfill.”
It’s been an amazing journey for Aero Aggregates and a perfect example of how materials testing is vital to the development of any exciting new product. This is especially true with FGA, which can make such a huge difference to everyday life and Tinius Olsen looks forward to helping develop this material even further in the future.
