99 Bottles of Beer in the Wall: Recycled Glass in Concrete

The decline in our reliance on coal is a big win for many in sustainability. In today’s green building industry, however, Amanda Kaminsky of Building Product Ecosystems (BPE) explained that less spent coal means less fly ash byproduct, a common ingredient in m­any project teams’ “green” concrete mixes. We discussed this and BPE building industry partners’ glass-infused alternative to fly ash and slag concrete mixes in an interview ahead of next week’s Dual Market Transformation: Recycled Glass in Concrete panel.

Longer transport distances and diminishing supply are cutting the environmental and financial benefits of using fly ash (and some teams have already been moving away from fly ash use in building products due to broader health considerations). So, when Sims Municipal Recycling approached Kaminsky to collaborate in finding a market for an overabundance of locally recycled glass, use as a cementitious material for concrete mixes seemed one of the most viable options.

Only 60% of NYC’s collected post-consumer glass is actually recycled (double the average rates across the U.S.), but the remaining chunk still often goes to the landfill due a lack of consistent end uses. One problem is glass color: while clear glass has a range of uses (think plate glass), colored glass is much less in demand. What BPE understood during testing with its industry Partners like Kingston and Urban Mining Northeast was like “magic” (in the words of Kaminsky’s daughters): the browns and greens of wine and beer bottles turn white when the glass is ground down into a powder. And that powder seems to be a well-performing fit for the cement replacement desired in concrete.

Recycled glass offers an ideal solution to increasing transport emissions impacts posed by fly ash and slag, according to Kaminsky. “We’re taking a material that’s being generated in massive quantities right here in urban centers”—discarded glass—“and seeking to use it as feedstock right here where we build with so much concrete.” Regional processing of the material could also benefit the local economy and increase jobs.

With performance very similar to fly ash and slag mixes, the glass-concrete mix has a clear upper hand: a more reliable supply, lower transportation emissions, and it even has a shorter cure time than fly ash on average though a bit longer than slag, says Kaminsky.

Still, the challenge of building the necessary infrastructure for cleaning, processing, and feeding the glass efficiently into concrete batch plants is compounded by the need to evolve thinking around sensible feedstocks in the industry, especially for such a fundamental building material. Pricing of the ground glass commodity will also have to be competitive with other cement replacement materials.

To help transform the industry and market, demonstration projects are in the works here in NYC and in Northern CA, with inspiration from success stories in Montreal and Europe. Here, the City is even considering glass in concrete mixes for sidewalks across the boroughs.

The need for local building materials is not only a national or even a global issue: researchers are investigating how to mix concrete on Mars with local soil (a cheaper alternative to loading up the space shuttle with cement).

Learn more about the development of this new concrete mix and growing interest in its use from Amanda and innovators of the BPE working group next Thursday, January 21, at Mohawk Showroom.


About the author

Rena Lee
Rena is the Communications Associate at Urban Green Council.