THE FIRST 3D PRINTED AND UNREINFORCED CONCRETE BRIDGE

Engineers and architects from ETH Zürich in collaboration with Zaha Hadid Architects and other partners developed a 3D printed concrete footbridge, which thanks to the angle of material disposal, doesn’t need to be reinforced.

Buildings around the world are being constructed with reinforced concrete. However, both the production of steel and cement, an ingredient of concrete, generate large amounts of CO2. 3D printing concrete helps reduce these emissions, as it only deposits material where it is necessary. This project took it a step further by leaving out the reinforcement steel.

The Block Research Group at ETH Zürich teamed up with the Computation and Design Group at Zaha Hadid Architects to build a 12-by-16-metre arched footbridge in a park in Venice – entirely without reinforcement.

The bridge, dubbed ‘Striatus’, consists of concrete blocks that form an arch much like traditional masonry bridges. The secret of no reinforcement lies in the 3D printed concrete, which the researchers developed together with the company Incremental3D. The concrete is not applied horizontally in the usual way but instead at specific angles such that they are orthogonal to the flow of compressive forces. This way, the printed layers are pressed together nicely, without the need for reinforcement or post-tensioning. The concrete ‘ink’ was developed by the company Holcim for this specific purpose.

The compression-only structure allows the forces to travel to the footings, which are tied together to the ground. The bridge is stable thanks to its geometry. Because the construction is dry build, needing no mortar, the blocks can easily be disassembled and reassembled at a different location, or recycled if they are no longer necessary.