Background: Digital building culture and sustainability

The construction of the future faces major challenges: worldwide, mankind is confronted with an immensely growing demand for buildings in the context of urbanisation. As a result, it is becoming increasingly relevant to build sustainably and cost-effectively. The answers to this can only be found together with a radical digitalisation of architecture and the construction industry. Robotic additive manufacturing such as 3D printing are of great importance in this regard. At 30 metres high, including the base, the White Tower will be the tallest 3D-printed building in the world.

3D printing of concrete

The White Tower demonstrates the ground-breaking possibilities of computer-aided design and digital manufacturing, which will fundamentally change conventional buildings in the coming years. Digital manufacturing technology promises substantial innovation in the construction industry. Compared to conventional methods, the tower can be manufactured more cheaply and more precisely because time-consuming, repetitive or complex work is carried out by robots. The White Tower is made from concrete using a 3D printing process developed at ETH Zurich. In this innovative manufacturing process, a robot applies thin layers of soft concrete one after the other through a nozzle. The material is soft enough to bond and form homogeneous components, but hardens quickly enough to support the successive layers.

Automatic integration of reinforcement

In the White Tower, the printed concrete is used for the first time in a fully structural manner and the necessary steel reinforcement is inserted in the robotic production process – a significant milestone in the development of 3D printing of concrete. To ensure structural strength, the 3D-printed columns are reinforced both horizontally and vertically with reinforcing steel.

Efficient use of material

By using robot-assisted concrete extrusion processes, the concrete can be applied only where it is needed. This reduces material consumption. In the thin, hollow columns of the tower, concrete is used where it is structurally required, similar to the optimised structures we know from nature. The saving in mass and cement means a reduction in the CO2 emissions generated during its production.

Formwork-free concrete construction

As the concrete is not poured in 3D printing, but applied by a robot in extruded strips, formwork is no longer required, unlike in conventional concrete construction. The elimination of formwork opens up new design freedoms in terms of expressive shapes, surface details and cavities. It also enables the cost-efficient production of customised components.

Modular prefabrication, detachable connections and prestressing

In the spirit of the circular economy, dismantling is already designed at the planning stage so that the White Tower can be rebuilt elsewhere. The modular design makes it easy to assemble and dismantle the individual components. The elements are connected dry, i.e. without adhesives, using detachable screws. The prestressing in the elements is another strategy for using concrete efficiently.

3D printed formwork and casting for horizontal elements

The horizontal components, which are not suitable for concrete printing, are produced using a novel process in which 3D-printed formwork is combined with castings made from an innovative, sustainable concrete.

Lightweight façade solution

The tower’s weather protection is achieved via an ultra-light, innovative membrane construction that can be removed in the summer months.

Digital design

All project data is stored in a digital twin, which enables the coordination, simulation, evaluation and realisation of the tower without the need for conventional construction plans. Augmented reality, virtual and augmented reality are used extensively in both design and realisation. Digital technologies are also used in the design process. The entire structure of the tower is programmed and designed using customised software that allows precise definition of the geometry and can send the required data directly to the printing robots. This technology also enables the efficient production of customised elements.