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Is glass coming to a concrete near you?

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Is glass coming to a concrete near you?

Is glass coming to a concrete near you?

As cities across the United States struggle with the question of glass recycling, some companies are envisioning a new future for old bottles and jars. Google and the Ellen MacArthur Foundation teamed up in 2010 to examine “circular economies.” A circular economy is one in which materials are used and re-used in ways that limit the need for truly raw materials.

One area that the MacArthur Foundation examined was concrete. Concrete is a common building material, but it has some environmental downsides. Cement – a primary component of concrete – generates a lot of CO2 during its production. Various concrete mixtures can also contain toxic heavy metals like cadmium, arsenic and lead. These toxic inclusions come from fly ash and slag, which are sometimes used in concrete mixtures as a substitute for some of the cement.

Ground glass is being considered as a substitute for fly ash, which is in short supply. Fly ash is a residue generated by coal-fired power plants. No one’s building coal fired power plants today, and as more plants convert to natural gas, the supply of fly ash dwindles further. At the same time, the demand for concrete is rising, so finding an acceptable substitute for fly ash is a priority.

Substituting glass for fly ash could solve a couple of problems. First, it could create a viable market for recycled glass. That’s big because so many cities struggle with glass recycling, and it could remove some of the 8 million tons of container glass from US landfills every year. Second, it could reduce the demand for cement, which could in turn reduce cement-related carbon emissions significantly. Each ton of cement that’s produced releases a ton of carbon into the atmosphere.

Right now, using glass powder (called pozzolan) in place of fly ash would increase the price of concrete slightly – less than 5% – but it would decrease the carbon footprint of concrete to about 10% of its current size by reducing demand for cement. It would also eliminate the need to import fly ash from other places, like China and South America. The Foundation estimates that a pozzolan plant needs about 40,000 tons of container glass each year to keep up with the demand for ground glass, and multiple pozzolan plants would be needed to meet the annual demand for concrete. That’s still significantly less than the amount of glass that gets recycled, but concrete production offers a positive market for recycled glass – something that has so far been hard to come by.

Glassprimer™ glass paint is a specialized glass coating that bonds permanently to glass surfaces. GlassPrimer also makes a glass surface molecular activator that is designed to work with UV-inkjet glass printing processes. For more information about Glassprimer™ glass paint, please visit the rest of our site. If you’d like to purchase Glassprimer™ glass paint, please visit our online store .

Photo Credit: Sparkle Motion, via Flickr.com

Could glass have a role in concrete?

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Could glass have a role in concrete?

Could glass have a role in concrete?

Sometimes, people use the words “cement” and “concrete” interchangeably, but in reality, cement is a component of concrete. Concrete is a combination of aggregate (small stones) and liquid cement that cures or hardens over time. The cement binds the aggregate together and makes what appears to be a uniform surface.

Glass powder could be used as a pozzolan

In cement production, additives (called pozzolans) are combined with the mixture to improve the performance of the cement or give it more desirable qualities. Typically, pozzolans are silica-based or aluminum-based. Pozzolans have been used for thousands of years to improve the performance of cement. In fact, pozzolans of volcanic origin have been found in cements made in ancient Crete and Rome.

Today, pozzolans can be natural or synthetic. Two common pozzolans are fly ash, a by-product of burned coal, and silica fume, a by-product of silica smelting. Coal-fired power plants are a major source of fly ash, but fly ash is becoming scarcer as more coal-fired power plants either shut down or convert to natural gas.

Engineering students at the City College of New York (CCNY) have been experimenting with glass powder as a replacement pozzolan for fly ash. The high silica content of glass gives it a high potential. The researchers used glass powder from colored glass that had no recycling value. Although glass is infinitely recyclable, some glass pieces are too small to recycle, and colored glass must be matched with similarly colored glass before being recycled.

Used as a pozzolan, glass powder has some interesting advantages. The cement production process generates CO2, which is released into the air. Substituting glass powder for fly ash reduces the CO2 emissions associated with cement production.

One question about the use of glass powder as a pozzolan is strength. What impact will the use of glass have on the finished product? The researchers have teamed up with the New York City Department of Design and Construction to test the substitute in action. In May, the Department laid down some concrete sidewalk in South Jamaica, NY that uses the new glass-based cement. The City and the researchers will observe the performance of the concrete over time.

CCNY researchers aren’t the only ones looking at the material strength of glass in cement. A research team from the University of British Columbia is experimenting with the combination of polymers, fly ash and glass powder as a potential replacement for some volume of aggregate materials in concrete. The team has determined that it may be able to replace as much as 25% of the aggregate with the glass powder mixture.

Innovative uses for glass can help keep the material out of landfills, even when recycling it back into container glass is no longer an option. We’re not sure what the decorating value of glass powder is, but if you’re considering working with larger pieces of glass and want some inspiration, please check out the rest of our site. If you’d like to purchase Glassprimer™ glass paint, please visit our online store .

Photo Credit: Hideya Hamano, via Flickr.com