Owner: Austrian Federal Property Administration, Vienna
Architecture & Visualisation: Marte.Marte Architects, Weiler, Austria
Contractor: Bauunternehmung Granit Gesellschaft mbH, Graz, Austria
Engineering and support: MEVA Formwork Systems Haiterbach (Germany) and Pfaffstätten (Austria)
Lower Austria’s College of Education is being renovated and extended by three new buildings arranged around the existing complex and following the plans of Marte.Marte architects. The old school building is demolished and a modern, much larger campus being built in its place. Three new buildings will be arranged around it: the largest is the new high school building with four levels, the second a two-level school practice facility and the third the new cafeteria.
Test pours are essential whenever high expectations are placed on the concrete finish. They allow the site to test the impact of facing, concrete type and mixture, setting behaviour, climatic conditions, formwork setup, pour speed and compacting. Sometimes, even small changes – such as a different concrete mixture or compacting method – can have a pronounced impact on the desired finish. This is the way the site proceeded on this project and after fine tuning the result was agreed upon.
The test pours showed very early on that standard formwork with plasticcoated wooden facing could not and would not deliver the required architectural concrete finish. Plywood panels do not sit flush in the frame and tend to swell and shrink with every pour. This leads to visible imprints that would have been unacceptable for a project with such high demands on the concrete surface as this one. MEVA employs an all-plastic, 100 % woodfree facing as a uniform standard in all its formwork systems. The all-plastic facing sits flush in the frame and neither shrinks nor swells, thus achieving an even high-quality concrete finish pour after pour. This convinced the owner and architects of this project. The formwork concept was discussed and, after a few minor changes, agreed upon.
Project and site management were now in a position to proceed with a clearly defined concrete strategy. As so often on projects with high demands placed on the concrete finish, the all-plastic facing alkus proved its superior performance and helped deliver a top concrete finish: It does not absorb moisture and remains stable even after many pours. It’s nonabsorbent behaviour and the use of only a thin film of release agent contributed to the even concrete surface as demanded by the architects. However, the right facing alone will not automatically guarantee excellent results. The way the formwork is handled on site is equally important. Cleaning the panels after each pour with a high pressure washer and repairing nail holes with identical material are but two measure that help achieve excellent results. Refer to the special article in Formwork-Press XII/2015, which you can order by e-mail to email@example.com.
The architects stipulated a symmetrical joint pattern in a 125 x 250 cm layout and a symmetrical arrangement of the tie hole imprints. The surface finish was to be totally even and without any panel frame imprints. Self compacting concrete was poured using panels with filling nozzles.
The Mammut 350 were equipped with a 20 mm thick all-plastic alkus facing that was attached from behind using 40 mm screws. This is easy to do with the alkus facing. The result was a joint-free concrete surface without any frame imprints. Since the tie holes are symmetrically arranged in the Mammut 350 panels, the ties were placed normally to achieve a harmonious concrete image. The high concrete pressure was catered for by using alignment rails, making the formwork setup stable and safe enough for the fast and high pours in one go up to a height of 6 m.
The high loads caused by suspended walls were supported through a shoring setup using MEP shoring towers and additional support beams underneath the suspended walls. The prop spacing was limited to 50 cm to account for the very heavy loads. The exceptional concrete finish achieved by contractor Granit on this project is mirrored by the results contractor Granit achieved on the University of Economics & Business project in Vienna. A special edition of FormworkPress is dedicated to its breathtaking architecture and unique formwork solutions. Contact us on firstname.lastname@example.org for your personal copy.
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