Arizona highway expansion uses recycled-glass foam to reinforce culverts on I-17
During the I-17 widening north of Phoenix, engineers filled the roadbed with foam glass made from 100% recycled bottles, allowing old culverts to support new lanes.
In a pioneering move, the Arizona Department of Transportation employed tens of thousands of tonnes of foam glass aggregate, a lightweight fill made entirely from recycled glass, to expand Interstate 17. The material was placed at 19 locations along a 23-mile corridor that carries over a million vehicles annually, enabling the addition of third lanes and dynamic flex lanes without overloading existing storm-water culverts.
Foam glass offers high compressive strength, water resistance and a fraction of the weight of traditional stone fill, eliminating the need to rebuild the decades-old concrete boxes. Produced in Florida and delivered in bulk bags, the aggregate also diverts glass waste from landfills, supporting sustainability goals. The project, funded by state, federal and regional sources, totals about $522 million and includes recycling of on-site blasted rock for other construction uses.
Why it matters
The technique shows how recycled materials can solve engineering challenges while cutting costs and environmental impact.
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