Using post-tension in-tank installation
Prestressing application in water storage tanks and reservoirs is commonplace all over the world.
A compressive stress is applied to the concrete members through high-strength steel tendons. This additional compressive force increases the concrete members’ tensile strength, meaning it is more durable and less likely to crack once the tank is filled.
The additional benefit of this approach is that there is a reduction in the reinforcement quantity, which is typically used to enhance the tensile strength of a reinforced concrete section.
There are 3 common approaches to using post-tension in-tank installation:
- Internal Bonded post-tension tendons
- Internal Unbonded post-tension tendons
- Externally applied Unbonded post-tension on the rough concrete surface using double extruded Monostrand tendons
Overview of the Tank in Asse
Interspan Europe has been involved in the post-tensioning of a water tank in Asse, Belgium. The tank has been designed by Stael Constr. & Engineering Services, and is being delivered by Franki Construct NV.
A slipform system from Bitschnau was used to execute the water tank, where the formwork is continuously raised by hydraulic jacks. This is a typical construction, given that the use of a slip mitigates water-tightness issues associated with jointing.
Two platforms were used in the formwork system – the upper platform, the working level above the poured concrete, and a lower level, which provided access for concrete finishing. The total height of the slip in Asse was 16.5m.
Using a slipform system meant a continuous 24h work presence from the concreter, steel-fixer and post-tension subcontractors for the full 5-day duration.