In an Australian study, waste glass replaced up to 60% of river sand in concrete; the recycled mix gained strength and resisted chloride penetration

A group of engineers in Australia found that, in lab tests, a substantial share of that sand can be replaced with waste glass without weakening the concrete. In some tests, it became stronger instead. According to Tamanna, Tuladhar, and Sivakugan's 2020 study, "Performance of recycled waste glass sand as partial replacement of sand in concrete," published in Construction and Building Materials, replacing up to 60 percent of natural river sand with recycled glass sand made the concrete stronger. It also helped it resist chloride ion penetration, one of the main causes of corrosion in reinforced concrete structures. Chloride damage is one reason parking garages, bridges, and highway barriers break down sooner than they should.

Why America is quietly running low on the right kind of sand

Sand feels endless, but the kind that goes into concrete cannot be grabbed from any spot. It requires a specific type of coarse river or pit sand, and that type is becoming harder to find near expanding U.S. cities. The U.S. Geological Survey's 2026 mineral summary reports that the United States produced about 870 million tons of construction sand and gravel in 2025, of which an estimated 42 percent went into Portland cement concrete. This creates heavy demand for river and pit sand deposits near growing metro areas, from Phoenix to Austin to the outskirts of Atlanta. Local sand pits in some of these areas are running short, and hauling sand long distances by truck raises both costs and emissions. That is why a substitute material that works as well as, or better than, sand matters to builders and city planners alike.

What the researchers actually tested

The team did not simply assume that glass could replace sand. They carried out controlled laboratory trials, substituting natural river sand with glass sand at three replacement levels: 20 percent, 40 percent and 60 percent. The recycled glass sand came from color soda lime glass collected through a regional recycling program in Cairns, Australia. They measured three key properties: strength, resistance to chloride ion penetration, and expansion caused by the alkali silica reaction, a chemical process inside concrete that can crack it from within over time. All three measures improved when compared with the standard sand mix, an issue that had previously made engineers cautious about using glass in concrete at all.

The US already has enough waste glass to explore this at scale

The US generates a substantial amount of waste glass, but not enough ways to reuse it. According to the U.S. Environmental Protection Agency, Americans produced about 12.3 million tons of glass waste in 2018, the most recent year with full EPA data available. About 31 percent of that glass was recycled; the remainder was buried in landfills or burned and not used again. If even a portion of that glass could be turned into sand-like aggregate for concrete, cities could rely less on river sand and landfills could receive less glass. This is one case where an environmental fix also addresses construction supply.

What this study does not prove, at least not yet

Building codes, supply chains and construction standards move slowly for a reason. Concrete holds up bridges and buildings, and any new mix needs field testing across climates, freeze-thaw cycles and load conditions before it becomes standard practice. The study described above also relied on lab-scale mixes and glass sourced from a single regional recycling program in Cairns, Australia, a real limitation for any claim about scaling this to U.S. cities, since glass composition and collection systems vary widely by region. This is an early result, not a finished product ready for general construction use.

Why this is still worth watching

Many millennials and young adults who are buying homes and paying taxes that fund infrastructure may have a stake in research like this. Research is more than climate rhetoric. Research like this could eventually mean fewer new sand quarries, less glass in landfills, and sidewalks that resist corrosion for longer. Concrete made partly from discarded glass bottles, if it performs as well as or better than the standard mix, could quietly reshape how American cities build in the years ahead.