World News, Today World News, Latest International News, World Breaking News, Trending News of World - Times of India
· collected 2026-09-06 · by TOI World Desk
Arizona's Department of Transportation used foam glass aggregate, made entirely from recycled glass, at 19 locations along a 23-mile section of Interstate 17 north of Phoenix in 2024. The material was chosen for its high compressive strength, low weight, and environmental benefits to support the added traffic lanes without crushing existing drainage culverts. Approximately tens of thousands of tonnes of foam glass aggregate were used in the expansion project, which aimed to reduce regular traffic jams and meet growing travel demand on a major highway that carries over one million motorists each year. The use of foam glass aggregate was a cost-effective alternative to replacing or rebuilding the underground concrete box culverts, which would have been more expensive and time-consuming.
Written by the local model on 2026-09-06,
using this article's own text rather than the other coverage of the
same event (that is the story summary below).
Engineers in Arizona have used an unusual material to expand a major interstate: tens of thousands of tonnes of crushed recycled glass.
asserted
Engineers → use → glass
During the expansion of Interstate 17 north of Phoenix, construction crews used ultra-lightweight foam glass aggregate at 19 locations along a 23-mile section.
asserted
crews → use → section
The material, made entirely from recycled glass, provided a lightweight structural fill that allowed existing drainage culverts, built decades ago for a two-lane highway, to support extra traffic lanes without being crushed by the added weight.
asserted
culverts → make → weight
According to the Arizona Department of Transportation (ADOT), this was the first time foam glass aggregate had been used in a state infrastructure project.
uncertain
aggregate → accord → project
In an official agency publication, ADOT Communications representative Laura Douglas said the material was chosen because it combines high compressive strength, low weight and environmental benefits.
asserted
it → say → strength
Solving structural challenges on a busy corridor
The 23-mile section of Interstate 17 between Anthem Way and Sunset Point is one of the region's busiest major routes, carrying more than one million motorists each year.
asserted
section → solve → motorists
To reduce regular traffic jams and meet growing travel demand, state transport authorities began a major widening project.
asserted
authorities → reduce → project
The work included adding third travel lanes between Anthem Way and Black Canyon City, as well as building dynamic flex lanes through the mountainous area leading to Sunset Point.
asserted
work → include → Point
However, adding lanes meant widening the highway over old concrete box culverts built beneath the road.
asserted
adding → add → road
These underground structures play an important role by carrying stormwater underneath the highway.
asserted
structures → play → highway
The original culverts were designed to support only two lanes of traffic.
asserted
culverts → design → traffic
Adding normal soil, stone or heavy concrete fill above them to support wider lanes could have placed too much weight on the structures.
uncertain
Adding → add → structures
Replacing or rebuilding the culverts would have cost much more and caused longer delays in the busy construction area.
asserted
Replacing → replace → area
Engineers found an alternative in ultra-lightweight foam glass aggregate.
asserted
Engineers → find → aggregate
By using the glass material instead of traditional earth fill, workers reduced the weight placed on the underground concrete boxes.
asserted
workers → use → boxes
Manufacturing an ultra-lightweight fill
Although it is made from recycled glass bottles and containers, the finished material looks very different from ordinary glass.
asserted
material → manufacture → glass
"Foam glass is made by crushing recycled glass into a powder and mixing it with a foaming agent," Douglas detailed in the ADOT report.
asserted
Douglas → make → report
"The mixed powder is then sent through a kiln and softened.
asserted
powder → mix → kiln
During this process, the foaming agent creates bubbles within the softened glass, which in turn creates the foam glass, an inert, non-leaching, rot-resistant, non-flammable, durable construction material."
asserted
which → foam → glass
The heating process creates lightweight, porous, gravel-like pieces that weigh far less than standard stone aggregate while still being strong enough to carry heavy loads.
asserted
that → create → loads
Because foam glass is made of closed-cell glass, it is also waterproof.
asserted
it → make → glass
This prevents it from absorbing water and gaining extra weight over the underground structures during heavy rain.
asserted
This → prevent → rain
The foam glass used along the Arizona highway was made in Florida and transported to the project in large bulk bags.
asserted
glass → use → bags
The bags became a noticeable sight for motorists passing the construction area.
asserted
bags → become → area
Promoting sustainability in highway engineering
The use of foam glass also supports wider sustainability efforts by keeping large amounts of glass waste out of landfills.
asserted
use → promote → landfills
Glass collected through municipal recycling programmes can be difficult to turn back into new bottles because of sorting problems and mixed colours.
asserted
Glass → collect → problems
Using the material in construction provides another way to reuse it.
asserted
Using → use → it
"Foam glass is not only an innovative material for construction, it's sustainable and environmentally responsible as well," Douglas noted in the publication.
asserted
Douglas → note → publication
The use of foam glass on Interstate 17 is part of a wider trend among US state transport departments looking for lightweight and durable fill materials for soft ground, retaining walls and bridge supports.
asserted
use → look → walls
Similar materials have already been used in European infrastructure, while their use on North American highways has increased as transport agencies consider long-term costs and environmental effects.
asserted
agencies → use → costs
Progress across the I-17 expansion project
The I-17 Improvement Project combines traditional construction methods with specialised materials.
asserted
Project → combine → materials
Along with the foam glass, contractors recycled almost all of the rock removed during major blasting work in the surrounding mountains.
asserted
contractors → recycle → mountains
The blasted rock was crushed on site and reused for aggregate base, embankment support and paving materials, helping reduce waste.
asserted
rock → blast → waste
The project has a total investment of about $522 million (£395 million), funded through state highway money, federal infrastructure grants and local regional transport funding.
asserted
project → have → money
By using lightweight glass aggregate over the existing culverts, construction crews avoided costly structural demolition while keeping the widened road safe and stable for heavy commuter and freight traffic.
asserted
crews → use → traffic
The completion of the widening work and flex lane installation marks a major step forward for Arizona's transport network.
asserted
completion → widen → network
