How to inflate a concrete shell weighing 80 tons

© TU Vienna

Concrete shells for domed buildings are normally cumbersome and time-consuming as well as expensive. The Vienna University of Technology has developed a potentially cost-effective and resource-efficient alternative with a construction method it calls the "Pneumatic Forming of Hardened Concrete (PFHC)".

The functioning of the construction method is comparatively easy. At first a flat concrete plate with wedge-shaped outlets is casted with concrete. The precise geometric form of the plate is decisive for the subsequent form of the concrete dome. Subsequently it is formed into a double-curved concrete dome by inflating the air cushion placed underneath the plate. The post-tensioning tendons at the circumference are tensioned with the help of hydraulic presses in order to stabilize the dome. The method saves up to 50 percent of the concrete as well as 65 percent of the necessary reinforcement steel.

Recently the forming process was successfully tested on a test concrete shell in Carinthia. A concrete plate weighing 80 tons was lifted with air pressure of only 20-22 millibars to form the planned concrete dome. The particularly smooth surface form can be attributed to the sophisticated geometric optimization.