Millions of new buildings all over the world are still being constructed with reinforced concrete, even though this type of construction causes very high CO2 emissions. Given the problems posed by the cement and the steel used for reinforcement, researchers at ETH Zurich have now demonstrated a way to make savings for both of these elements. The Block Research Group from ETH teamed up with the Computation and Design group at Zaha Hadid Architects to build a footbridge in a park in Venice measuring 12 by 16 metres and constructed entirely without reinforcement. The structure, dubbed “Striatus”, was built from concrete blocks made with an additive process that form an arch like an old stone bridge. The forces in the compression-only structure travel straight to the footings, which are tied together on the ground. The blocks are stabilised by the geometry of the structure itself.
One completely new innovation here is the type of concrete 3D printing that the researchers developed together with the company Incremental3D. The concrete is not applied horizontally in the usual way but instead at specific angles so that the layers are exactly orthogonal to the flow of compressive forces. This means that the printed layers in the blocks stabilise themselves. The special concrete for the 3D printer was developed specifically for this purpose by the company Holcim. As the construction does not need mortar, the blocks can be dismantled and the bridge reassembled again at a different location. If the bridge is no longer needed, the materials can simply be separated and recycled. Professor Philippe Block from ETH Zurich said: “This precise method of 3D concrete printing allows us to combine the principles of traditional vaulted construction with digital concrete fabrication to use material only where it is structurally necessary.”
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