The construction industry is highly unsustainable. In fact, 7% of global CO2 emissions result from cement production alone. In an effort to cut down construction-related carbon emissions, researchers in the Digital Building Technologies (DBT) department at ETH Zürich have created FoamWork. The project examines how foam 3D printing (F3DP) can be used in conjunction with concrete casting. The outcome is a less labor-intensive system that enhances material efficiency and lowers carbon emissions.

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Robotic arm setup with a 3D-printed foam stack on the table

Currently, cast-concrete structural elements use excessive material. Occasionally, engineers use hollow plastic forms to reduce concrete in standard slabs. For more complex systems, casting molds are made from timber or CNC-carved dense plastic foam. These labor-intensive systems overuse concrete or produce excessive waste from off-cuts. Conversely, using F3DP shapes within cast concrete formwork can save up to 70% of concrete, are significantly lighter and well-insulated.

Related: New eco-friendly, decomposing construction foam unveiled

3D-printed FoamWork components on a timber base

A slab prototype by the DBT team shows how versatile it is to combine concrete structures and 3D-printed foam. The slab uses ribs derived from isostatic lines, which indicate the directions of compression and tension. Based on the principal stress pattern, the geometry of this slab has 24 cavities for foam inserts of 12 different shapes.

Man operating machinery to remove the slab from framework

For the foam production, ETH Zürich has collaborated with FenX AG, a company that uses mineral waste to produce high-performance building insulation. A robotic arm fabricates the foam components using recycled fly ash, the waste from coal-fired power stations.

View of the cast concrete slab from above, half of the cavities filled with foam inserts while the other half remain empty

The foam components are arranged in timber formwork before poured in ultra-high-performance fiber-reinforced concrete (UHPFRC) to cast the structural element. Once the concrete cures, the foam pieces can either be left in for their insulative properties, or the raw material can be recycled and reprinted for other FoamWork projects.

Angled view of ribbed cast-concrete slab with cavities for foam inserts. Some foam components fill the holes further away from the viewer

This process can be replicated for other standardized or more intricate concrete structural elements. Calculating the principal stress patterns can be used to design and fabricate various material-efficient structural elements. These can range from standardized elements to customized slabs and walls.

Corner view of ribbed concrete slab with foam inserts in the cavities

Since there are no off-cuts created in using FoamWork, the whole fabrication system has the potential to be zero-waste. Alongside minimizing material waste, the lighter masses of the structural elements allow for easy transportation, handling and assembly on construction sites.

+ Digital Building Technologies, ETH Zürich

Photography by Patrick Bedarf