striatus has been developed by the block research group at ETH zurich and zaha hadid architects computation and design group (ZHACODE), in collaboration with incremental3D (in3D) and made possible by holcim. it combines traditional techniques of master builders with advanced computational design, engineering, and robotic manufacturing technologies. 3D printing can be used to build load-bearing concrete structures that require significantly less material and no steel reinforcement or mortar, and this project showed how this works.

millions of new buildings all over the world are being constructed with reinforced concrete, generating large amounts of CO2 emissions. the steel used for the reinforcement and the cement for the concrete are especially problematic in this regard. ETH researchers have now presented a way to reduce both, in a real project. using an additive process, the construction dubbed striatus was built with concrete blocks that form an arch much like traditional masonry bridges. this compression-only structure allows the forces to travel to the footings, which are tied together on the ground. the dry-assembled construction is stable due to its geometry only.

the researchers, together with the company incremental3D, developed a new type of 3D-printed concrete. contrary to the traditional way, the concrete is not applied horizontally but instead at specific angles orthogonal to the flow of compressive forces. this keeps the printed layers in the blocks nicely pressed together, without the need for reinforcement or post-tensioning. the special concrete ink for the 3d printer was developed by the company holcim precisely for this purpose. the name ‘striatus’ reflects the structural logic and manufacturing process behind the project. concrete is printed in layers orthogonal to the main structural forces to create a ‘striated’ compression-only funicular structure that requires no reinforcement.

‘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 without producing waste.’ says ETH professor philippe block. since the construction does not need mortar, the blocks can be dismantled, and the bridge reassembled again at a different location. if the construction is no longer needed, the materials can simply be separated and recycled making this whole project more sustainable.