Green Builder Media CEO Sara Gutterman talks with Craig Szabo about how post-consumer curbside glass is milled into an ultrafine pozzolan that replaces cement in concrete. Szabo explains the carbon reductions, strength gains, and durability improvements the material delivers across the building sector.
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Sara Gutterman: Tell us how at a high level up the glass works.
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Craig Szabo: So we take in essentially blue box glass. So your your curbside recycling glass, which, is not clean glass by any stretch of the imagination. So it goes to a municipal recycling facility for for primary processing, basically to remove some of the non glass components. And then that gets shipped here. And we go through a series of steps to essentially remove everything but the glass and make it into a, a fine powder at about 3 to 5 microns.
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Craig Szabo: So a 10th the size of flour. That's, essentially pure glass. So 99.8% pure.
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Sara Gutterman: Are you able to quantify how much carbon reduction is possible with the glass.
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Craig Szabo: At your base? So if you replace cement with with our up to glass product or glass porcelain, which is the primary source or primary market for our material, you can reduce your carbon footprint footprint by a factor of 20. So we we, we can play a substantial role in, in helping concrete get to its goal of being, essentially carbon neutral, by 2050.
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Sara Gutterman: So how does the inclusion of crushed post-consumer glass affect the compressive strength, durability, and lifecycle performance of the final of the final concrete product?
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Craig Szabo: We're one of those green products that can say they're actually, you know, green and you know, and performance in the context that, if you replace cement with our ground glass in a regular concrete mixture, you will get better, better strength. So, so, and strengths are measured by what? Compressive, you know, is measured p.s.i you get at 28 days of, of a mix.
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Craig Szabo: So that will improve by a factor of 20% using our glass. And you will get improved, corrosion resistance, sulfate resistance, three star resistance. So the durability, the overall durability of the concrete will be improved substantially using glass and as a replacement for cement grade.
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Sara Gutterman: And I'm assuming the same is true for things like thermal performance, shrinkage, and long term cracking potential. All better, or at least comparable to traditional concrete formulations.
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Craig Szabo: Exactly. In fact, the the the the code or the buzzword of durability, which, which leads to a lot of what you just referred to. Sarah, is much better. We're, you know, we're much better at that than a traditional concrete mixture.
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Sara Gutterman: So is up to glass best suited for certain types of projects, like low rise or infrastructure, or is it scalable across the entire building sector?
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Craig Szabo: And it's scalable across the entire building sector, with actually, exceptional results. Seen in all the high performance concrete. So all concrete that's used in bridge decks, you know, especially road, structures, special building structures, where you replace steel with, with high performance concrete. If you use our glass in those mixtures, you you can get, very substantial performance, improvements in those mixtures.
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Sara Gutterman: Are there any logistical or cost considerations when incorporating optic glass into existing concrete manufacturing processes?
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Craig Szabo: A single, provision is to maintain it, you know, maintain it dry. I mean, when you ground glass that fine it likes it likes water. So but that would be no different than any other. The materials used in, in making concrete up to the point of actually making concrete where you add water.