Tor Alva (“White Tower” in Romansh) is a new architectural landmark that is intended to revive Mulegns, a mountain village threatened by depopulation that is currently home to 11 people. The Origen cultural foundation led the work in collaboration with ETH Zurich, to celebrate culture and the arts and to give the village a new lease of life.
The tower was designed by architect Michael Hansmeyer and ETH Professor of Digital Building Technologies Benjamin Dillenburger. Instead of relying on traditional concrete formwork, they opted for an additive manufacturing process.
A specific concrete was developed for the fabrication process by Robert Flatt, ETH Professor of Physical Chemistry of Building Materials.
It had to be soft enough to bond the delicate structures, while hardening quickly enough to support the subsequent layers. Just before the concrete leaves the pressurized nozzle, two additives are blended into the mixture, allowing the characteristic droplet-like relief on the columns to be achieved.
Two robots working together
In addition to the industrial robot that applies the concrete layer by layer into free-form elements without any supportive casting moulds, a second robot were placing a ring-shaped reinforcement in the new structure every 20 centimetres.
This horizontal reinforcement in the form of rings is supplemented by longitudinal rebars that are added after printing. The researchers developed a new testing method which allows the load-bearing capacity of 3D-printed concrete to be reliably calculated for the first time. This is a key requirement to ensure that such buildings can in future be tested just as safely as conventional reinforced concrete structures.
Guided tours
It took five months to print the columns on the ETH Hönggerberg campus. The components were then assembled in Savognin and delivered to Mulegns via the Julier road in a heavy goods vehicle.
Since May 23, the White Tower will be open daily for guided tours. From July onwards, the space will also host staged performances. Tor Alva is intended to remain in Mulegns for around five years. It can later be dismantled and re-erected elsewhere.
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