Application of textile reinforced concrete at a silo rehabilitation
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Report in the yearbook 2015
Carbon concrete for caramel
Scaffold inside of silo 9, Nordzucker AG
On June 26, 2014, the silo No. 9 of the Nordzucker AG in Uelzen was damaged by fire. The silo had been put into operation the year before, and it is able to store 80,000 tons of white sugar. In addition to the disposal of the world-biggest caramel candy, the concrete surface had to be repaired at the internal silo wall from a height of +25 m up to +58 m, at the ring beam.
Within the project “Uelzen 2”, the industrial and general applicability could be shown, of the very first general technical approval (GTA) for the use of textile reinforced concrete (TRC) for strengthening of constructions. In 2012, a sugar silo in Uelzen already had been strengthened. This time, the restoration due to fire damage was needed. The extent of the licensing scope granted by the GTA would have been enough to carry out the project. However, compared to the existing permit, a material change in the reinforcement was necessary. Therefore, an additional approval had to be obtained, for individual cases, in anticipation of the increased scope of the existing general technical approval.
For the sugar silo, approx. 14,000 m² textile fabrics were produced within few weeks by the company V. Fraas and were applied by professionals of Implenia (formerly Bilfinger SE) in the ring direction of the silo. The renovation works started with the removal of loose or damaged parts of the concrete cover by high pressure water jets in the upper 2/3 part of the silo. On the so prepared, load-bearing concrete surface a levelling layer was applied, where necessary, and afterwards two to three layers of TRC were applied by spraying concrete very quickly. The pumping of the concrete matrix, made of standard Pagel TF10, to a height of approx. 60 m was a clear challenge. The full reinforcement layer was not more than approx. 1.5 cm thick. So, the useable volume of the silo had not nearly changed. At the end, the surface was merely polished and covered with a food-safe coating after dismantling of the scaffold.
Just in time for the new sugar season, the silo could be handed over to Nordzucker AG. Here, in contrast to the project “Uelzen 1”, the usability of the silo was restored by the textile reinforced concrete layers, a static strengthening was not necessary, and we could insure that no traces of concrete could be found in the sugar, because nobody wants to have concrete in the sugar.