Anaergia Resource Recovery Equipment Used at a California Wastewater Treatment Plant

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For more than a decade, Urban Mining Industries, based in New Rochelle, New York, has offered a new use for recycled glass in the form of Pozzotive, a crushed glass pozzolan used in the production of concrete. Like other man-made pozzolanic materials such as coal fly ash, ground glass can assume cementitious qualities when reacted with a combination of water and cement. Patrick Grasso of the Grasso family, owner of Urban Mining Industries, says Pozzotive strengthens concrete and reduces CO2 emissions. By using locally sourced glass, Pozzotive also ushered in a circular economy for the glass industry in Connecticut, where it is now made.

Grasso, a partner at Urban Mining Industries, says his family has a long history of involvement in the construction industry. The Grassos’ story begins over 15 years ago, with the family first obtaining a block manufacturing facility in upstate New York. After rebuilding the factory, they used it to make gray building blocks. Louis Grasso Jr., Patrick’s nephew, wanted to find a way to distinguish their gray block from all the other gray blocks made in America. After advising Louis to include recycled content in the block, a series of trial and error tests were carried out to find a material that could achieve this goal. It was decided that glass was the best choice. After realizing that using large chunks of glass wasn’t the best approach, they eventually created a fine crushed glass powder that became Pozzotive.

“So through this block making plant, we were able to see the market back then, when no one else was willing to experiment with this kind of stuff,” says Patrick Grasso.

Pozzotive in action

The magic of the Pozzotive effect in concrete, says Patrick Grasso, begins with a chemical reaction when combined with water and cement. Before Pozzotive steps in, cement hydration introduces two key compounds. One is hydrated calcium silicate (CSH), which Grasso says is the “glue” that builds strength in concrete. The other product is calcium hydroxide (CH), which conversely weakens the concrete and causes porosity. When a crushed glass pozzolan is introduced, it gives up a silica atom and joins CH to become CSH. This pozzolanic reaction allows the crushed glass to acquire cementing properties and to partially replace cement. In most mixes, Pozzotive replaces 20 or 30% of the cement.

Photo courtesy of Urban Mining Industries

Pozzotive next to recycled glass

Initially, Pozzotive was produced in small quantities at a product validation facility in New York. Prior to 2022, the company was primarily focused on gaining a solid footing in the pozzolana market. It took four years, Grasso says, to get an ASTM 1866 standard that specifically confirmed the viability of ground glass pozzolans in concrete. This process involved a committee of industry professionals who reviewed and approved 3rd test part made with Pozzotive.

Since its inception, Pozzotive has been used in projects in various locations, most of which are in New York and Connecticut. Some of them include the ESPN Digital Center 2, the New York Police Academy, and the Second Avenue subway station in Manhattan. During the renovation of the United Nations General Assembly building, 60 tons of window glass were harvested from the building and used to create cobblestones with Pozzotive for the UN Plaza. Grasso says smaller projects in Connecticut that have used Pozzotive, including Ox Ridge Elementary School in Darien and New Canaan Library in Canaan, particularly demonstrate Pozzotive’s importance in building a local circular economy.

Industries with an impact

In addition to supporting a circular economy, according to Patrick Grasso, Pozzotive addresses other challenges in the glass recycling industry: the cleaning and separation of glass and the costs associated with transportation and logistics if a processor is not not nearby. A common route for recycled glass is to turn it into bottles, but complications can arise in this process as the glass must be separated by color and any ceramics must be removed due to their different melting temperature. Glass color does not affect Pozzotive, and ceramic pieces are welcome as they are also pozzolanic. Pozzotive can also use lead-free electronics glass, flat glass and demolition glass. The glass goes through a cleaning and separation process and is ground into a pozzolana that is 95% smaller than 325 mesh, Grasso says.

According to Mr. Grasso, one of the main problems in the cement industry concerns CO2 emissions. Cement production accounts for about 7% of all global carbon emissions, and the United States alone uses more than 100 million tons of cement annually, he says. Twice as much concrete is used in construction as wood, plastics and aluminum combined. Even though common post-industrial cement substitutes such as fly ash and slag, which are leftovers from steelmaking, can create low-carbon concrete, Grasso says he considers ground glass post- consumption as an even better replacement.

“A glass bottle is a glass bottle just about anywhere in the world in terms of chemical makeup…you can make a very consistent finished product because of the raw material you start with,” says- he.

Grasso claims that each ton of cement generates almost a ton of CO2. Urban Mining Industries has conducted tests to replace up to 50% of the cement in concrete with Pozzotive, reducing the carbon footprint by nearly a ton for ton of the cement it replaces, he says.

Photo courtesy of Urban Mining Industries

Manhattan’s Second Avenue Station

Pozzotive has other benefits that show how it improves the performance of concrete as well as its durable qualities. Concrete with higher percentages of Pozzotive exhibits a brighter white color, which means it can reduce the heat island effect in urban areas, where temperatures are higher due to greater abundance of fabricated surfaces that absorb heat. Grasso says Pozzotive does a bigger job of preventing efflorescence — when a white powdery substance bleeds from concrete — and shrinkage, which means fewer cracks. He says concrete with Pozzotive is five times more powerful at reducing moisture and chloride ingress than a pure cement mix.

“I think it’s a holistic solution, a climate solution, a health solution – avoiding heavy metals and some of these other alternatives…and the circular economy problem of just taking the regenerative waste streams at the regional level and to reinject them into these regions”, he says. .

The future of Pozzotive

Pozzotive has been used by different companies and organizations, including O&G Industries of Torrington, Connecticut. TJ Oneglia, vice president at O&G, says he thinks the use of pozzolans in general is likely on the rise in the concrete industry. Oneglia highlights recent trends to use more recycled materials and reduce the carbon footprint of buildings.

“I see support in our local market from designers, architects, engineers, but also owners and end users of concrete. [There is] a desire to build green, and therefore Pozzotive, by its very nature, in my opinion, is greener than other sources of materials,” says Oneglia.

Crushed glass pozzolans, in particular, could see higher demand due to potential supply issues with other pozzolans, Oneglia says.

He says O&G plans to continue using Pozzotive blends, which are starting to be specified on school projects and municipal projects.

“We intend to supply it as an ingredient in our concrete where and when it is specified,” says Oneglia. “And then, on top of that, we intend to use it as part of our daily concrete when we can.”

Patrick Grasso explains that Urban Mining Industries’ goal now is to continue to market Pozzotive and use it for larger projects. The first full-scale Pozzotive plant was established in Beacon Falls, Connecticut in 2021. Grasso says it is a good central location from a glass raw materials perspective and allows Urban Mining Industries to serve the New York metropolitan market while also expanding into the Boston market. . The new facility will allow the company to produce about 50,000 tons of Pozzotive, Grasso said.

“We had to go through this four-year process to get an ASTM standard. And we had to use this product for over 10 years to make sure it wasn’t something stealthy, it was real. We were supposed to have the first factory capable of producing it commercially, on a large scale, and so all of those steps are now in place. So any market where there is a need for a reasonably sized glass solution, we can be there,” he says.

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