The Transrapid line in Shanghai, subway stations in Amsterdam or Berlin's main train station - the Max Bögl Group has already made all of these and many other major projects a reality. The company from Sengenthal in the Upper Palatinate was founded in 1929 as a bricklaying business and is still firmly in the hands of the third generation of the family.

A relatively young mainstay at Max Bögl is wind energy: The Upper Palatinate company supplies towers made of three-meter-high concrete rings in a modular system plus a metal tip. With the special feature that each ring consists of three individual parts, on which the construction company holds a patent. This makes the components much easier to move - a standard truck trailer is sufficient for their transport. Around 30 concrete rings are stacked on top of each other and braced before the metal tip, which weighs around 60 tons - a real heavyweight - is placed on top. For this reason, various rings are made of a special concrete which, thanks to its steel reinforcement, can withstand the loads in the long term.

Paint system for fresh concrete

Since March 2022, the family business has now been using a new coating system for the concrete elements. It comes from FreiLacke and is a very fast-curing polyurea-based material. "We were able to draw on a wide range of experience in the wind energy sector - and not just in terms of towers," explains Andreas Löffler, who is responsible for International Business Development at FreiLacke. At the Sengenthal plant, the concrete components are demolded after curing and transported directly to the paint shop. "Because there is still a certain residual moisture in the concrete, special paint systems are necessary. In addition, the parts could still be warm after demolding due to the reaction heat of the concrete," explains Bögl production manager Holger Roth. FreiLacke's polyaspartic polyurea-based coating systems meet precisely these requirements and enable immediate coating. The concrete rings are transported in the paint store at Max Bögl on platforms of an automatic conveyor system. Here, their concrete surfaces are first prepared and filled; the cycle time is currently still just under one hour. The task here is to close any pores and blowholes for the best possible paint adhesion. Among other things, the FreoWind filler in light gray is used. The next step is the top coat, which is applied by an airless or air-assisted process as standard. After the cycle, the coating is already dried and ready for all further steps.

Double coating against stress cracks

On the one hand, the painting serves to enhance the appearance of the components; on the other hand, the paint coating gives them high mechanical strength and dirt-repellent properties. Two further workplaces in the hall are reserved for finishing work on the heavyweights; the finished painted components are then stored outside. From now on, they are permanently exposed to wind and weather. With the changeover to the FreiLacke system, the construction company primarily wants to increase the throughput of its concrete components, because the demand for new wind turbines is high - the Ukraine war acted as a booster internationally, says Andreas Löffler. Thus, the construction company is planning a significant increase in production figures from summer 2022.

Rheological adjustment facilitates processing

The changeover to the new coating system went largely without a hitch, as reported by Andreas Löffler, who was on site in Sengenthal together with an application engineer. Only the coating supply via ring line required meticulous pre-planning. "In fact, the workers really like working with the system," says Löffler, "because the priming filler is particularly easy to process and fits very well with the existing application technology - FreiLacke tinkered with the rheological setting specifically for this purpose."

Incidentally, Max Bögl is also active in the field of wind energy itself: the most powerful wind power plant in Bavaria with a Bögl tower went into operation in 2011 on the Winnberg in the district of Neumarkt. With a total height of 180 meters and a connected load of 3.4 megawatts, the plant produces more than a third of the municipality's electricity consumption. In addition, the specially founded Max Bögl Wind AG has held the record for the world's tallest wind turbine together with turbine supplier GE Wind Energy since 2017: The Upper Palatinate company supplied the towers for four wind turbines in Gaildorf inBaden-Württemberg with a hub height of 178 meters and a total height of 246.5 meters.

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