In New York, 29 million discarded glass bottles were ground into concrete for JPMorgan Chase’s 60-storey headquarters; replacing 40% of its cement cut over 5,000 tons of carbon and enhanced concrete strength
A massive skyscraper rising in Midtown Manhattan has turned tens of millions of used waste bottles into part of its structural support. The project shows how city waste can replace carbon-heavy building materials on a large commercial scale. Workers used special concrete containing ground recycled glass in the foundation and floor slabs of JPMorgan Chase’s new 60-storey headquarters at 270 Park Avenue. By replacing 40 per cent of traditional Portland cement with ground-glass pozzolan, the project kept 29 million discarded bottles out of landfills while also strengthening the concrete. The change saved more than 5,000 tons of carbon dioxide emissions during construction. Traditional cement production uses energy-intensive kilns that release large amounts of greenhouse gases, making concrete one of the main sources of industrial emissions worldwide. According to technical coverage in Concrete Products magazine, the project used the processed glass mixture across the 2.2 million-square-foot tower to meet environmental goals while also meeting strict structural performance requirements.
Converting municipal glass into raw material
The ground-glass product, made under the trade name Pozzotive by Connecticut-based company Urban Mining Industries, tackles two environmental problems at the same time. Construction companies are looking for low-carbon building materials, while recycling programs across North America often struggle to process mixed-colour glass bottles. Because of contamination and sorting costs, much of this glass can end up in regional landfills. Urban Mining collects used bottles from local waste streams and processes them through a dry milling system without chemicals or water. The facility grinds the glass into a fine powder that is free of hazardous crystalline silica. When the powder is mixed into ready-mix concrete, the reactive silica in the ground glass reacts with calcium hydroxide, a weak byproduct of cement hydration. This chemical reaction turns that byproduct into dense calcium-silicate-hydrate, the main compound that gives concrete its compressive strength. Engineering analysis published in Structure Magazine found that adding the glass powder increased the concrete’s final strength and long-term durability while reducing the amount of moisture that could pass through the slabs.
Engineering around tight construction schedules
Using recycled materials in high-rise concrete can create problems with setting times. Reducing the amount of Portland cement can slow early curing, which could delay floor-by-floor construction on busy urban sites. Consulting engineering firm Severud Associates designed the structural specifications for the 270 Park Avenue tower. Engineers adjusted the mix so the high amount of pozzolan concrete could reach the required early strength. This allowed contractors to maintain a fast floor-pouring schedule. “When asked by JPMorganChase to envision 270 Park Avenue as a model for the 21st century workplace, we knew Severud Structural Engineers had to give our contribution,” said Fortunato Orlando, Principal at Severud Associates, in a statement about the project’s engineering specifications. “The building’s design included 52,000 cubic yards of concrete that substituted locally-sourced Pozzotive ground-glass pozzolan for 40% of the cement in all structural concrete except the 16,000-psi mix.” Orlando added that ground-glass pozzolan has now been added directly to the engineering firm’s standard master specifications for future structural projects.
Establishing scale for circular construction
The use of recycled-glass pozzolan at 270 Park Avenue is one of the largest single applications of the material in commercial real estate. Construction managers from AECOM oversaw the work at the site, working with ready-mix concrete supplier Smyrna Ready Mix to deliver thousands of truckloads of the custom glass-based mixture into central Manhattan. “Pozzotive was the centerpiece of a much larger strategy to deliver the greenest skyscraper in America, if not the world,” said Max Driscoll, Vice President of Sustainability at AECOM Construction Management, while discussing the project’s material supply chain. “We are extremely proud to have facilitated a market transformation for ground glass pozzolan as a leading decarbonization strategy for construction.” Beyond the carbon savings during construction, the lighter colour of the glass-based concrete reflects more light than standard grey concrete. Developers expect this quality to reduce heat absorption on exposed surfaces, lowering cooling needs inside the building and helping reduce the urban heat island effect around the base of the tower. The successful project in Midtown Manhattan has also encouraged wider use of the material in the region. After the structural work at 270 Park Avenue was completed, transportation authorities in Connecticut and New York began specifying ground-glass pozzolans for public rail infrastructure and highway projects. This helped establish a permanent industrial market for municipal waste glass across the North American Northeast.
