Aesthetic architecture in concrete for a utility building

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Deutsche Bahn AG is building a continuous rail line between Nuremberg and Berlin. One of the structures along its route is Kulch Tunnel, whose shaft-top building was constructed with the help of NOEplast textured formliners in combination with NOEtop frame formwork manufactured by NOE-Schaltechnik, Süssen, Germany.

Deutsche Bahn AG is currently constructing a continuous rail line between Nuremberg and Berlin as part of the German Unity Transport Project Number 8. Starting in 2017, ICE trains will run along these tracks at 300 km/h. Rail passengers will be able complete the journey between Munich and Berlin in only about four hours instead of the present six. 25 tunnels are among the engineering works required to make this possible. One of these is the Kulch Tunnel near Lichtenfels. It was built by a consortium consisting of Hochtief Construction AG, Alpine Untertagebau GmbH, Alpine BeMo Tunnelling GmbH and Bickhardt Bau Aktiengesellschaft.

The consortium completed the part project to the architectural requirements of DB ProjektBau GmbH with great care and attention to detail. These high standards also applied to the shaft-top building above the Kulch Tunnel at the side of the road between Altenbanz and Rossach. The 8.60 x 8.60 m surface-level building provides ventilation to the tunnel, accommodates services cables and ducts, and is the exit from the rescue access shaft. The building was not intended to be of great architectural significance. However, the client thought it important that the building integrated well into the surrounding landscape. It was therefore decided to give the concrete facade of the building the outside appearance of a masonry wall. The solution chosen was NOEplast textured formliners in conjunction with NOEtop wall formwork from NOE-Schaltechnik, Süssen.

Formed with textured formliners

To give the outside walls of the shaft-top building the desired look, the designers opted for the "Murus Romanus" motif. This formliner leaves a concrete surface that gives the observer the impression of looking at a random rubble masonry wall. NOE markets the polyurethane (PU) formliners under the brand name NOEplast and has a large range of different motifs. The manufacturer also offers customers the opportunity of realising their own design ideas. These could range from a simple relief to the reproduction of a photograph, almost anything in fact.

Use of textured formliners

The consortium had to fix the textured formliners firmly to the formwork panels. In the precast concrete works, it would be enough simply to place them on the vibrating table. Whether the concrete element is cast on site or in the precasting works, it is always recommended that the formliner be coated with a release agent specially developed by NOE. This ensures that the formwork can be easily stripped after concreting. All subsequent steps in the construction of an in-situ concrete wall are as normal – and the same process can be applied for almost all types of concrete. As soon as the concrete has hardened sufficiently, the formwork panels are removed along with the formliners to reveal the relief.

Special service

NOE-Schaltechnik is the only manufacturer to offer formwork panels and textured formliners from the same source. Therefore it can also offer a special service: textured formliners and formwork panels supplied ready for immediate use on site. This is beneficial above all for in-situ concrete sites, where there are often no level, clean set-down areas and temperature fluctuations can make gluing the formliners in place problematical. This was one of the arguments that convinced the consortium's site team to have the textured formliners supplied attached to a supporting board by NOE. Another was the sizes of textured formliners required. The Murus Romanus motif has a standard width of 6.00 m. However, the textured formliners themselves can be extended by any amount in length and width. The textured formliners for this utility building at Kulch needed to be 8.20 m wide (2.20 m larger than standard) and have no visible joints. As a result, the formliners had to be shaped so as to interlock vertically and horizontally with one another for the concrete to appear as a continuous masonry wall.

Use on site

The formliners supplied by NOE already attached to supporting boards were fixed to NOE's standard NOEtop formwork panels by the consortium's site team. These panels are known for being especially robust and very versatile in use. The manufacturer supplies them in four heights up to 3.31 m. The tallest variant was used on the Kulch Tunnel site. In addition, several formwork panels had to be joined together to make a unit 9.00 m wide. The site team used a NOEtec girder as a spreader beam to ease the task of working with this relatively wide formwork unit. The NOEtec girder was attached to four NOEtop crane hooks to simplify operations. All the walls of the building were erected in a very short time. On close inspection, it is obvious that the consortium's careful planning paid off. Once the concrete walls have developed a little "patina", only an expert will be able to tell at first glance that they are made from concrete and not stone.

Well planned

The details were carefully agreed between the client's representatives, the construction engineer and the site staff before the works were planned, designed and carried out. For example, all wall ends and door openings are formed in smooth concrete. This was achieved by dispensing with the texture on these surfaces to create a pleasing, uniformly flat frame around the openings in the natural stone relief. The client also stressed that the walls should not have any visible working joints in the concrete. As a result, the walls were concreted up to top of ceiling slab level and bent-out bar connections used to join the ceiling slab to the walls.

Being able to call upon the experience and know-how provided by a one-stop-shop supplier proved to be a particular advantage for the consortium. In this case, it was the manufacturer's expertise in using formwork with textured formliners to create reliefs in concrete surfaces. This project – although only small – showed that a simple utility building can fit aesthetically into its immediate surroundings with just a small amount of carefully applied design flair.

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