Special formwork employed during tunnel construction for BUGA 23
alkus® SF Flex formwork panel used for tunnel construction at BUGA 23 site in Mannheim
As part of the preparations for the German national garden show, Mannheim has seen the construction of a bicycle highway – and a key feature along the route is the "Am Aubuckel" bicycle tunnel, designed to withstand a daily traffic load of up to 20,000 vehicles. Reif Bauunternehmung was contracted to provide construction-engineering services on the BUGA tunnel. The distinguishing characteristic of this project lies in the concave shape and the trumpet-shaped curves of the underpass. This was a particular challenge for Kiefer Schalungsbau, which was responsible for constructing the special formwork. Implementation of the distinctive curves was achieved by employing the flexible alkus® SF Flex formwork panel.
alkus® SF Flex for special formwork applications
The purely architectural requirement of a concave shape for the 40-metre-long underpass definitely posed a challenge. The coated multi-layer plywood panels commonly used in special formwork projects failed to meet the demands of this particular task. To achieve the desired special curves, a tight bending radius was essential, thereby surpassing the flexibility limitations of plywood panels. The special formwork contractor Kiefer Schalungsbau therefore decided in favour of alkus® SF Flex. "An enormous advantage of alkus® SF in comparison to multi-layer plywood panels is its remarkable ability to be bent almost limitlessly, making it significantly easier to shape," explains Arnold Kiefer of Kiefer Schalungsbau. "The water resistance of alkus® is yet another noteworthy benefit." This was particularly beneficial during the project, as there was a gap of several weeks between installation of the special formwork and concreting, during which the solid plastic panel was exposed to moisture and wet conditions. Due to its non-swelling properties, the panel could be utilised outdoors for weeks without adversely affecting the concreting result.
Smooth surfaces without gaps and holes
"alkus® SF Flex was purposefully designed to meet the unique demands of highly challenging special formwork projects. Thanks to its remarkable flexibility, it does not crack and leave marks on the formed surface, not even during extreme bending," says Michael Tschenett, CEO of alkus AG. "This ensures a smooth surface finish with SF Flex." alkus® SF Flex is available in thicknesses of 3, 4 and 5 millimetres. In collaboration with Kiefer Schalungsbau, alkus AG developed the 4-millimetre-thick SF Flex specifically to meet the requirements of the BUGA tunnel construction project. The availability of the panel in a large format was also a crucial factor for the special formwork contractor. alkus® SF Flex is available in a size of 4 x 1.5 metres. Kiefer Schalungsbau obtained the flexible alkus® formwork panel from the long-term alkus partner MEVA Schalungs-Systeme GmbH. Further, to accomplish the external formwork of the structure, the MEVA Mammut 350 system (panel formwork), equipped with 20-millimetre-thick alkus® AL formwork panels, was used. The MEVA formwork system is employed for both underground engineering and the construction of residential towers. It boasts an innovative combination tie system that allows flexible switching between three different tying methods, resulting in a 30 percent reduction in switching time.
The alkus® SF Flex panel is similar to multi-layer plywood panels in terms of its shape, durability, price and ease of installation. But besides its enhanced flexibility, it also presents a range of other advantages when compared to plywood panels. "Multi-layer plywood panels are typically imported, which can give rise to quality defects or delivery issues depending on the country of origin. Widely varying prices are not uncommon either. alkus® in contrast is produced exclusively in Europe, thereby avoiding these factors," claims CEO Michael Tschenett. "The SF Flex panel is thus highly reliable in addition to its exceptional properties."