Waste glass could be used in 3D-printed buildings after researchers showed that concrete made with crushed glass has better insulating properties than more traditional concrete mixes.
The researchers found that when they gradually replaced a conventional aggregate traditionally found in concrete with waste glass, the thermal conductivity of the concrete decreased. The results could prove timely for those interested in 3D printing in construction and wanting to prove the technology with better insulated, more environmentally friendly buildings.
“While much of our waste glass can be recycled to produce new glass products, a large amount is still sent to landfill,” says Dr. Seyed Ghaffar, Head of the Additive Manufacturing Technology in Construction Research Group at Brunel University London. “So to reduce the waste glass sent to landfill, several recycling strategies need to be explored.”
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dr. Ghaffar believes the construction industry could be a potential destination for the unrecycled glass, a partial replacement for the vast amounts of natural sand currently used to meet global demand for concrete.
The team estimates that about 2,000 recycled beer bottles can be used per square meter if used in 3D printing a building.
Published in the Construction Engineering MagazineThe study found that when used as a replacement for basalt aggregate, a substance that already provides good insulation, glass waste had a thermal conductivity that was almost a fifth lower.
“To be specific, the samples with 50 percent and 100 percent waste glass volume replacement had lower thermal conductivity by 11 and 17 percent, respectively,” says Dr. Mehdi Chougan, a Marie Curie Research Fellow at Brunel’s Department of Civil. and environmental engineering. “But it’s also worth noting that the thermal conductivity of soda-lime glass — the most common type of glass found in windows and bottles — is more than three times lower than that of quartz aggregate.”
According to Brunel, the team also found that the addition of “expanded thermoplastic microspheres” – spheres of polymer filled with gas – gave an extra boost to the thermal properties, while also increasing the viscosity of the poured concrete.
“They can be simply explained as micro-balloons, which exhibit enormous volume expansion when heated,” said co-author Dr. Pawel Sikora, associate professor of civil engineering at the West Pomeranian Technical University of Poland in Szczecin.
“Due to their properties and inertness, the material can be used as a lightweight filler in the cementitious composites, with amazing thermal insulation properties.”
The researchers will now begin scaling up the project and 3D printing demonstration walls to better understand their thermal and mechanical performance.
