State-of-the-art sports arena, state-of-the-art materials and processes: RAMPF develops a high-performance polyurethane system for the stunning exterior of the new Puskás Ferenc Stadium in Budapest.

The Puskás Ferenc Stadium in Budapest is to seat over 67,000 spectators, and one of the construction specifications was that the outer facades of the 30 staircases feature a special surface structure in the form of prominent ring patterns.

The individual staircases are 7.5 m wide and 30 m high. A total of 13 precast concrete components (2.2 × 7 × 0.24 m) had to be produced as cladding for each facade.

To keep assembly work to a minimum and ensure the large concrete components were as stable as possible, wetcast molds from the WASA PRECAST brand were used.

WASA PRECAST molds are large-format molds made from high-quality polyurethane that are used as master models (negative molds) when manufacturing concrete. These master models exhibit a high level of detail, stability, and mechanical strength.

The polyurethane molds required for the stadium’s facades weighed approximately 1,800 kg, which posed a number of technical challenges with regard to material, modeling, and handling.

To avoid casting errors – which would be very expensive on this scale – WASA Compound and RAMPF Polymer Solutions developed a polyurethane system specially tailored to the plywood model of the mold. Due to the large quantity that had to be cast, it was essential that the casting resin exhibit a long pot life, low heat generation, and minimal shrinkage. In other words, it was vital that the reactive casting resin system remain workable for as long as possible before curing.

Changes in the volume or dimensions of the cast resin mold were to be avoided wherever possible.

Due to the size of the mold, the resin had to be cast in several layers, while also ensuring that the contours of the individual layers were not visible. An alkali-resistant, plasticizer-free system was developed to prevent changes to the mold while casting concrete.

Moreover, the viscosity of the polyurethane system had to be adjusted so it would level out evenly and thus ensure optimum filling of the individual ring cavities.

The individual, tailor-made elements fit almost seamlessly into the staircases. The interplay between flexible molds and high-performance concrete in the staircase architecture is crucial to the stadium’s overall look.