What is blinding concrete

Visionary architecture made of white concrete

During the implementation by the Leipzig architect Harald Kern, major tasks awaited everyone involved. Not only was the planning of the extremely difficult formwork challenging, but also the production of the concrete. The tender was made of class SB 4 exposed concrete and white concrete, i.e. the ball should be as smooth and as white as possible. After numerous tests carried out in advance and the production of various color samples, the spherical shell was produced with pure white concrete of strength class C 30/37 in consistency class F5, which was specially colored for the project.

Since Oskar Niemeyer - completely inspired by the Brazilian sun - wanted a dazzling white structure in Leipzig too, the company Berger Beton from Passau, responsible for concrete production and delivery, paid particular attention to the precise use of the corresponding components. The Portland cement Dyckerhoff WEISS FACE with its high degree of whiteness was therefore used. In addition to a white filler, an extremely light, high-quality sand and the white pigment titanium dioxide were used. The concrete had to be expertly built into the 20 cm thin spherical shell in such a way that there were no defects.

The manufacture and installation of the curved glass eyes that characterize the sphere turned out to be challenging and demanding. The glass for the upper half of the sphere was supplied by the Darmstadt chemical and pharmaceutical company Merck, known for intensive research and innovative developments. According to Merck, the liquid crystal windows used in Leipzig are a world first. Because the glasses that are also in the new Merck Innovation Center, which was recently opened in Darmstadt, can deal with solar radiation much better than conventional windows. The reason is the liquid crystals used here, which are also used in the manufacture of smartphone screens.

It all started with a letter that Ludwig Koehne wrote to the Brazilian star architect Oscar Niemeyer as managing partner of the Leipzig Kirow-Werke in 2011. The art lover Koehne not only described the building task - "to build a dining and dance hall on the roof of the canteen building" - but also came out as an admirer of Niemeyer's work and wanted "a curved building shape". His wish was heard by the master in Brazil and so a visit to Rio de Janeiro soon followed and ultimately a design, although initially only sketched with a felt pen, by the hand of the world-famous architect himself called "Sphere".

In conclusion, it can be said that a piece of architectural history was created in Leipzig. The creative and innovative materials concrete and glass played a decisive role in optimally implementing what was probably Niemeyer's last bold architectural dream.