Now, engineers at ETH Zurich have developed a more efficient method for building with the material, erecting an ultra-thin, curved prototype roof that's 5 cm (2 in) thick on average, and designed to support energy-saving systems in the building.
Although it's since been dismantled to make way for other test structures, the prototype stood 7.5 m (24.6 ft) tall and was ultra-thin, measuring 12 cm (4.7 in) at its thickest and just 3 cm (1.2 in) at the edges. It had a surface area of 160 m2 (1,722 sq ft) and covered an area of 120 m2 (1,292 sq ft), and that discrepancy was down to the fact that the roof arched over, forming shapes that concrete normally wouldn't be capable of without complex support structures.
Instead of using custom-built, single-use wooden or foam scaffolding, the engineers tested a new technique of their own design. A net of steel cables was stretched into the desired shape, and a polymer textile was laid over the top to create a flexible formwork. The shape was controlled by algorithms that distribute the force evenly between the cables and determined just how much concrete needed to be applied to each section. Afterwards, the cable net can be dismantled, reused and reshaped as needed.