A slender surrealist staircase of concrete and glass has been created by ABT. It is only about five centimetres thick, but the staircase spans nearly six metres without supporting ribs. The glass balustrades, which are connected invisibly to the stairs, enhance the illusion of weightlessness. Together, the concrete and the glass create a strong, hybrid structure. The staircase demands the utmost from the materials used and from ABT’s craftsmanship.
The staircase, which is intended for ABT’s headquarters in Velp, was designed by JHK Architecten. It is made of a single piece and is four times thinner than usual. To make the staircase so slender, the concrete and the glass have to cooperate in creating the structure: the glass is bonded to the concrete, adding both rigidity and strength to the stair. Without the glass, the stairs would behave more like a springboard. ABT used special software to calculate the details of the structure.
Innovative pouring process
Because of the extremely high tensile forces in the staircase, ABT chose self-compacting ultra-high performance fibre-reinforced concrete and a special cement. The reinforcement ratio is very high. Pouring the concrete was particularly difficult because the staircase is so slender: the viscous reinforced concrete had to fill a mould that was just five centimetres deep, which required an innovative pouring process. In particular, dispelling the air at the bottom of the mould required unconventional solutions. Special air channels in the casing and a very fine-meshed compacting technique were the key. The staircase was poured in the Romein Beton factory.