ETH Zurich researchers develop 3D knitted formwork for a concrete structure

Researchers at ETH Zurich (Zurich, Switzerland) have developed a new formwork technology for a five-tonne concrete structure in Mexico City. The researchers used a textile knitted using an industrial knitting machine as a formative element for curved concrete shells – stretched with steel cables. The structure is a collaborative effort with Zaha Hadid Architects Computation and Design Group (ZHACODE) and Architecture Extrapolated (R-Ex).

An industrial knitting machine produced the formwork using a digitally generated knitting pattern. In four laps, it knitted a finished 3D textile with two layers in 36 hours. The lower layer forms the visible ceiling, the upper layer contains the tunnels for the cables of the formwork system and pockets for conventional balloons, which then became cavities after concreting. 

Then the knitted formwork was stretched in a frame, sprayed with a specially developed cement mixture. This first layer is only a few millimeters thick, but sufficiently thick to create a rigid shape. Thereafter, conventional fiber-reinforced concrete was applied. The knitwear itself weighed 25 kg, the steel ropes about 30 kg. Both components could be transported as normal carry-on luggage in a suitcase by plane.

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