In Siegen (Germany) a Lidl supermarket was built, which in particular distinguishes itself from other branches of the retail chain in one aspect: the façade is provided with a textured fair-faced concrete surface. This is rather unusual for such stores.
Runkel Fertigteilbau GmbH undertook the production and installation of these concrete elements. The company is specialized in manufacturing fair-faced concrete elements of high quality and has gained much experience in the construction of supermarkets and discount stores. Just within ten weeks, the precast factory manufactured columns with integrally molded bases and installed 90 sandwich wall panels. These were previously manufactured at the precast factory and comprise a 15 cm thick supporting concrete shell, a 10 cm thick expanded polystyrene insulating layer and an 8 cm thick fair-faced concrete shell. In order to texture the surface of the fair-face concrete shell, the company responsible made use of a formliner technique. For this purpose, a polyurethane formliner is inserted in the formwork and poured with concrete afterwards. After hardening of the concrete the positive relief of the textured formliner is visible at the concrete surface.
For the supermarket in Siegen, the persons responsible took a decision in favor of textured formliners of the supplier NOE-Schaltechnik. They are characterized by their good workability and material quality. The company sells the polyurethane formliners under the name NOEplast and provides a wide range of standard formliners. The company attaches great importance to a reliable reproduction of the design requested in an excellent way. A fiber glass fabric protects the textured formliners against deformation. The textured formliner “Sinus” was used for the Lidl supermarket. It is characterized by its wavelike texture and is available in the maximum dimensions of 1.30 x 7.50 m.
Corner formliners and other solutions
Most precast factories manufacture textured corners of a building by connecting two formwork boards together in an angle of 90 degrees and fixing a formliner to each board. In order to avoid that the cement slurries run out, they cut the formliners with a miter and seal the joint with silicone. Using thin formliners this technique leads to excellent results; however using a more and more thick formliner and relief depth respectively this method reaches its limits. The textured formliner “Sinus” is one of the thicker formliners of the NOEplast product range, which is attributed to the large distance of 18 mm from the highest to the lowest point of the wave. To use designs providing corner and/or connection formliners is another possibility to manufacture wall edges and/or wall connections. This means, for examples, that a connection is created with a masonry design, which does not differ from a brick wall at all. The corner design of this supermarket was constructed without corner formliners. For the door and window openings a formliner strip was inserted in a mirror-inverted way and an additional layer of a 4 mm thick surface-coated formwork facing applied. This resulted in a 10 cm wide smooth fair-faced concrete strip around the openings.
Useable up to 100 times
For the Lidl supermarket precast factory Runkel manufactured a total of 35 textured elements of fair-faced concrete with some of them having quite different dimensions. Dipl.-Ing. Frank Siedestein, production manager at Runkel Fertigteilbau, states, “It was an advantage here that the formliners of NOE can be used up to 100 times. We were able to manufacture all concrete elements with just four textured formliners”. Three formliners were necessary to manufacture one wall panel. Consequently, each formliner was used 35 times. Since some of the sandwich elements had different sizes, the staff of Runkel started with the larger elements, measuring 3.75 m in height and 7.68 m in width. After stripping the formwork they shortened the textured formliner according to the following smaller size and manufactured the corresponding wall panels. They continued in this way until even the smallest elements were manufactured. For cutting NOEplast it is recommended to use a trimming knife or a circular saw with a hard metal disk. The staff of Runkel decided to use a manual circular saw and a guiding rail. NOE-Schaltechnik offers a special cleaner for the formliners, “which however was not necessary for ‘Sinus’”, as Frank Siedestein states, “Alternatively we have cleaned the formliner with water and treated it very carefully with the special release agent offered and recommended respectively by NOE.”
Whether the textured formliner is preferably laid in the formwork or cemented depends on the job site. If the concrete element is manufactured at the construction site, it is necessary to cement the formliner in the formwork. If it is manufactured, on the contrary, at a horizontal tilting table of a precast factory, it is up to the processor to decide whether to cement or lay the formliner on the formwork. The staff of Runkel decided to use the latter version because the formliners had to be taken from the tilting table for cutting the smaller wall panel sizes accordingly.
The NOEplast formliners feature different dimensions depending on the design. The size of the respective formliner, textured formliners available as well as many examples of applying the technique can be looked up on the homepage of the supplier or in the newly issued NOEplast Handbook.
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Runkel Fertigteilbau GmbH
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