More than half a billion glass bottles… That’s how much glass a Pennsylvania firm has reclaimed from landfills and turned into an unusual construction material: recycled foamed glass aggregate, an ultra-light type of mechanically stabilized earth (MSE) that is gaining popularity for its insulating properties and environmental benefits.
Assuming an average weight of eight ounces each, those 500 million glass bottles have an approximate weight of 125,000 tons and could circle the Earth three times. So, we’re talking about a lot of recycled glass.
Innovative materials are a cornerstone of progress in construction productivity, enabling faster, more efficient, and more sustainable practices. Recycled foamed glass aggregate is gaining popularity for its lightweight, insulating properties and environmental benefits, as it shows off its unique properties to speed construction efforts, particularly in infrastructure projects like roads and highways.
What is Recycled Foamed Glass Aggregate?
Recycled foamed glass aggregate is made from post-consumer recycled glass, such as bottles and other glass products. The production process begins by grinding the glass to a powder, which is then mixed with a foaming agent, typically silicon carbide. This mixture is heated in a kiln, where the foaming agent reacts to the heat, creating millions of tiny bubbles within the glass, transforming it into a highly porous, lightweight material. Once cooled, this material is crushed into aggregate sizes that can be used in various construction applications like widening roadways, acting as fill under concrete slab foundations, and insulating electrical transmission lines, among others. The EPA gave the material the green light back in the 1980s, but it has just recently been gaining traction and has been approved for use in more than 22 states in the U.S.
Applications in Construction
The primary application of foamed glass aggregate is in construction projects where weight reduction on underlying structures is crucial. It is an excellent fill material for highway expansions, providing a solid yet lightweight substrate that can support heavy loads without compromising the integrity of existing underground utilities. The material’s light weight reduces the stress on underlying structures, making it ideal for projects over sensitive areas, such as water pipes and sewage systems.
The aggregate is also used extensively as backfill for retaining walls and as a base layer for roadways and foundations. Its drainage properties, resistance to weather conditions, and portability, coupled with its mechanical stability, can make it a solid choice for fill in areas prone to water retention and flooding.
Rather than requiring eight-inch lifts like topsoil or fill, the aggregate can be placed in 24-inch lifts, so you get faster vertical build, with much less compaction required and no need to wait for optimal moisture conditions before adding weight.
According to Aero Aggregates of North America, LLC’s CEO, Archie Filshill, you can “take away two feet of soil, install 12 feet of foamed glass, with no additional weight. It’s a six to one conversion.”
Environmental Impact & Sustainability
One of the most compelling aspects of recycled foamed glass aggregate is its contribution to environmental sustainability. The use of recycled glass helps divert waste from landfills and reduces the demand for virgin raw materials. Moreover, the energy required to produce the MSE is significantly lower than that required for traditional fill materials like crushed stone or sand.
And an unusual property of the material is that it can be easily deconstructed and repurposed into another construction project by simply scooping it out of its location and placing it at its next one, with no other reclamation processes required.
Insulating Properties and the R-factor
Recycled foamed glass aggregate is a closed cell foam, so it has an R-factor value of 11.5 to 15.7 and boasts excellent insulating properties. The R-factor indicates the material's resistance to heat flow; the higher the R-factor, the better its insulating capabilities. In the context of infrastructure, using glass aggregate can help improve the energy efficiency of buildings and roads by providing a thermal barrier. This is particularly beneficial in utility insulation, where maintaining temperature control is crucial, which is why it has been used as insulation for power transmission lines without fear of damage.
Impact on Highway Expansion & Construction
The lightweight nature of foamed glass aggregate has made it a game-changer in highway expansion and construction projects. It allows for the rapid deployment of infrastructure without the need for extensive groundwork or reinforcement that heavier materials might require. This was notably demonstrated in the rapid repair of Philadelphia’s I-95, where it was used to stabilize the ground swiftly and effectively, allowing the highway to reopen in record time after a catastrophic collapse caused by a fire.
Integration with Concrete Construction
The lightweight material can also be integrated into concrete construction as a lightweight aggregate and insulator. This integration not only reduces the overall weight of the concrete but also enhances its thermal and acoustic insulating properties. Its use in concrete is advantageous in urban settings where noise reduction and energy efficiency are priorities. For example, you can place a foot of aggregate instead of layers of stone and Styrofoam under a slab, and achieve a similar R-factor, with significantly less weight.
From a construction safety & utility infrastructure mapping perspective, the aggregate “reads” much like a layer of gravel for ground penetrating radar (GPR) and EM locators, so there is no concern about it interfering with subsurface utility as builts or mapping.
Future Prospects & Innovations
The future of recycled foamed glass aggregate in construction looks promising, with ongoing research and development aimed at enhancing its properties and expanding its applications. Innovations in the composition and manufacturing process could see it becoming a standard material in even more areas of construction and civil engineering.
Overall, this material signifies a significant step forward in the quest for more sustainable and efficient construction materials. Its unique properties, such as the R-factor and utility insulation capabilities, combined with its environmental benefits, make it a potentially valuable asset in modern construction, particularly in infrastructure projects like highway expansion and concrete construction. As the construction industry continues to evolve, the role of innovative materials like this will undoubtedly expand, paving the way for more sustainable and resilient infrastructure development.
Frequently Asked Questions
How does ground penetrating radar find underground utilities?
Ground penetrating radar (GPR) is one of multiple technologies that are used to find and map underground utility infrastructure. At GPRS, we use it along with other complementary technologies as part of the Subsurface Investigation Methodology (SIM) to achieve an industry-leading 99.8%+ accuracy rate for utility locating. Read about the technical side of GPR here.
Does ground penetrating radar penetrate concrete?
Yes, it does. In fact, GPR is one of the main technologies used to assess the interior of elevated concrete slabs. While it cannot be used as a structural analysis tool, it can, the hands of a professional concrete imaging specialize, map the entire interior of your concrete slab reinforcements, the data from which GPRS can use to provide an accurate 3D BIM model of post-tensioned, pan deck, or other types of concrete slabs.