Recycled Glass Improves Concrete for 3D printing

Brief 

Major improvements in both strength and thermal conductivity for 3D-printed concrete are possible with the use of recycled glass, according to researchers at Technische Universität Berlin and Brunel University. They achieved the superior results by using glass, limestone and plastic fillers to partly replace the sand typically used in portland cement.

Insight

Researchers at Technische Universität Berlin (TU Berlin) and Brunel University have come up with a way of turning 3D printing concrete into a more robust, eco-friendly building material.

By partially replacing the sand in the Portland cement used to make concrete with recycled glass, limestone and plastic fillers, the team has managed to drastically improve its strength and thermal conductivity. Having already deployed their novel material to 3D print chunks of wall, the engineers say that with further R&D, it could eventually be used to erect the better-insulated buildings of the future.

“Vast quantities of natural sand are currently used to meet the world’s insatiable appetite for concrete, at great cost to the environment,” the researchers told The Conversation. “Our new research suggests a way to curb this impact. Our research shows that an ultra-lightweight, well-insulated 3D building is possible – something that could be a vital step on our mission towards net zero.”

Generally, concrete is made from a mixture of cement, water and aggregates such as sand, but the latter is often sourced unsustainably from riverbeds and beaches. What’s more, according to the researchers, high volumes of expensive admixtures are often added to ensure that this cement has sufficient flowability and buildability for 3D printing, thus raising the cost of any structures it’s used to build.

To combat these drawbacks, a considerable amount of research has been poured into replacing the binder in cement with various different fillers or natural aggregates. In 2020, for instance, a team at the Tongji University proved it possible to add sand recovered from demolitions in place of cement, without impacting its printing properties, albeit at the cost of modifications that affected its workability.