CWU News

CWU Research Looks to Recycled Glass to Make Concrete Greener

For a variety of economic reasons, glass is not recyclable in some parts of the country. That means it ends up in the trash and landfills. Central Washington University student April Sheeley is among those seeking a different solution.

Through an academic internship with CWU Sustainability, the Ellensburg senior has been researching whether crushed glass “recycled sand” can be used to replace a portion of the mined virgin sand typically needed to manufacture concrete. Sheeley’s work could lead to more than simply eliminating glass from landfills.  

“Concrete is the second most used product in the world after water and it emits a certain amount of carbon, something like 7 percent of the world’s carbon dioxide,” she said. “If we can get people in architecture, engineering, and construction thinking about using alternate concretes, it could reduce the world’s overall carbon footprint, along with reducing the need to use as many natural resources.”

Sheeley had to travel to Manson, Washington, to find the equipment to crush the glass to the consistency needed for the project, which also required a 28-day curing period for the glass-infused concrete. Last Friday (October 30), Sheeley and CWU Construction Management Professor Warren Plugge put her premise to test. They conducted stress testing on concrete containing 25 and 50 percent post-consumer recycled glass to see how the composite’s strength fared against that of traditional concrete.

“We were looking for the 'fracturability' of the concrete and compression strength variability with the concrete sand replacement,” Plugge explained about the test procedure.

The tests determined that the glass-sand replacement would be suitable for use in a variety of uses, outside of heavy and commercial construction.

“Impressively, the results showed there was an 11 percent reduction in compressive strength going from the standard mix to a 25 to 50 percent reduction in virgin sand being replaced by the pulverized glass,” Plugge added. “The mix held compressive strengths above 5,000 psi (pound-force per square inch) over a cure time of 28 days.”

While the compression test concluded Plugge’s specific involvement in the project, he said the findings will be presented in the senior-level concrete and asphalt courses that are integral to the Construction Management curriculum.

He also noted that other Central students interested in Leadership in Energy and Environmental Design (LEED) have indicated an interest in doing an analysis to see if the use of pulverized glass in concrete could potentially produce cost savings for construction projects and provide an environmental benefit to the region.  

Sheeley will continue her recycling-promotion endeavors and she remains optimistic that glass could become recyclable in the not-too-distant future. As part of her work, a public recap of her research will be presented on Zoom Friday, November 6, at 10 a.m.  

“We will also talk about other end markets for this type of recycled glass,” she pointed out. “Representatives from the state Ecology and Commerce Departments will attend to discuss resources they provide for using recyclables in industry.”

Media contact: Robert Lowery, Public Affairs, 509-963-1487,