ETH Zurich Reduces Concrete Use by 70% with Foam 3D Printing Technology

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A team from ETH Zurich’s Digital Building Technologies (DBT) unit is exploring the use of foam 3D printing in the construction industry.

By 3D printing complex formwork using mineral foam, researchers have developed a new method for casting geometrically optimized concrete slabs.

The printable foam, developed at ETH Zurich with help from insulation specialist FenX AG, is made from recycled waste. It can be used to print both permanent functional formwork and recyclable temporary formwork.

According to the DBT unit, its resource-efficient formwork can result in up to 70% less concrete usage compared to a conventional filled concrete slab. In addition to being much lighter, the optimized tiles would also offer improved insulation characteristics.

The DBT team has already cast a prototype concrete slab using 24 3D printed formwork elements. Photo via ETH Zürich.

Replacing the formwork with foam

The word formwork is used to describe the process of creating a mold or mold in which to pour concrete. Conventional forms are often made from wood, but it is also possible to use steel, glass fiber reinforced plastics and other materials. Age-old craftsmanship is great for casting simple shapes such as walls or columns, but as soon as larger and more intricate geometries are involved, it becomes extremely time-consuming and labor-intensive.

By opting instead for the path of 3D printing in foam, it becomes possible to manufacture geometrically complex formwork elements that were previously unnecessary or simply unfeasible. Beyond the performance benefits, there are also sustainability benefits, as the approach lends itself to less material and energy use, two common issues in the construction industry.

Plus, thanks to FenX’s specialization in turning mineral waste into high-performance, long-lasting insulation, the 3D-printed foam material can even be removed and recycled. This means it can be retrieved to print a whole new formwork, further reducing material usage in the circular workflow.

24 foam elements, 12 unique shapes

To demonstrate their new technique, the DBT team 3D printed a set of prototype formwork elements and used them to pour a concrete slab. There were 24 formwork elements in total, each of which came in one of 12 unique shapes. All foam elements were produced using a custom foam extrusion setup using an ABB robotic arm.

The team then placed the foam elements in a wooden perimeter and filled it with “ultra high performance fiber concrete”. When cured, the cast slab measured 2m x 1.3m and featured a ribbed structure with point supports at each corner.

The strip-like arrangement of the ribs actually followed the isostatic lines derived from the main stress pattern of the slab, which made it not too different from a topologically optimized part. Essentially, concrete was poured into the areas of highest stress, maximizing the compressive strength of the slab while keeping material usage to an absolute minimum.

Construction 3D printing has already made its way out of the academic sphere and is currently being used in industry. Earlier this month, Indonesia’s Ministry of Public Works and Public Housing (PUPR) began testing 3D concrete printing as a way to meet the country’s demand for affordable infrastructure. In tests conducted alongside construction company PT. PP (Persero) Tbk and start-up Autoconz, PUPR used the technology to erect structures layer by layer from mortar.

Elsewhere, in the Dutch city of Nijmegen, what is believed to be the world’s longest 3D-printed concrete pedestrian bridge has recently been unveiled. Spanning a length of 29 metres, the structure was fabricated by Rijkswaterstaat, the Dutch Directorate General for Public Works and Water Management, and designer Michiel van der Kley, in honor of the election of Nijmegen as European Green Capital in 2018.

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Featured image shows a concrete slab being poured using 3D printed foam formwork. Photo via ETH Zürich.

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