New York based mining company 'Urban Mining Industries' has been advancing a new use for recycled glass in the form of Pozzotive, a ground glass pozzolan used in concrete production.

Like other artificial pozzolanic materials, ground glass can assume cement-like qualities when it reacts with a combination of water and cement. Pozzotive strengthens concrete and lowers CO2 emissions, according to Patrick Grasso of Urban Mining Industries.

Grasso says that the magic of Pozzotive's effect in concrete starts with a chemical reaction when it is paired with water and cement. Prior to Pozzotive being involved, the hydration of cement introduces two key compounds in calcium silicate hydrate (CSH) and calcium hydroxide (CH). When a ground glass pozzolan is introduced, it gives a silica atom and joins the calcium hydroxide to become calcium silicate hydrate. This pozzolanic reaction allows ground glass to gain cementing properties and act as a partial replacement to cement. Pozzotive replaces approximately 20 to 30 percent of most mixes.

Pozzotive has been used in various large projects, mostly in New York and Conneticut. During the UN's General Assembly Building's renovation, 60 tonnes of window glass were harvested from the building and used to create pavers with Pozzotive for the UN Plaza.

Grasso says that Pozzotive, in addition to supporting a circular economy, addresses other challenges in the glass recycling industry including the cleaning and separating of glass and costs associated with transporting and logistics if a processor is not nearby.

A primary issue within the cement industry is carbon dioxide emissions, however common postindustrial cement replacements such as fly ash and slag are used as cement replacements to lower emissions. Despite this, Grasso believes that postconsumer ground glass is an even better replacement. Urban Mining has been tested to replace up to 50% of cement in concrete with Pozzotive.

The future of Pozzotive is bright, according to several different companies in Conneticut. T.J Oneglia, vice president at O & G, say that he believes the use of pozzolans in general is likely on the rise in the concrete industry.

"I am seeing support in our local market from the designers, the architects, the engineers and also the owners and the end users of the concrete. (There is) a desire to build green, and so Pozzotive, just by its very nature, in my opinion, is greener than the other sources of materials", Oneglia says.

Pozzotive is sure to lead to an increase in demand for ground glass pozzolans, in addition to potenital supply issues with other pozzolans.