Wallis, Switzerland

Amidst the Swiss mountains in the Canton of Wallis in the western part of Switzerland close to France, a hydropower plant was built underground. It is one of the most powerful pumped-storage hydropower plants in Europe, with a yearly power of 900 MW which produces around 2.5 billion kWh of electricity.

The whole power station was built underground in order to protect the mountain scenery. 17 km of tunnels were built and therefore around 1.7 million m³ of rock was excavated, which was then partially used as aggregates for the in-situ and sprayed concrete.

Project Requirements

The mix-design for the self-compacting concrete was developed during a phase of lab trials as well as 1:1 trials on site. The owner wanted fairfaced concrete quality. Further requirements on the concrete resulted from the concrete pumps, pipelines and filling of moulds.

There were two different mix designs for the concrete. One mix design OB24-SCC was used for fair-faced concrete parts and the second mix design OB27-SCC was used for backfilling of steel tubes.

Sika Solutions

After preliminary trials, Sika was able to offer tailor-made products for the concrete systems. The requirements on both, fresh and hardened concrete, have been quite demanding. The use of excavation material as aggregates for the self-compacting concrete was an added challenge for the fulfilment of this task.

Sika impressed the contractor with different products, which enabled the manufacturing of self-compacting and conventional cast-in-place concrete as well as project-specific special concrete. The construction site was visited regularly by our technical personnel and Sika concrete service technicians carried out quality checks.

Products Used

Sika® ViscoCrete® GTC 1: Superplasticizer for concrete
Sika® ViscoCrete® GTC 2: Superplasticizer for concrete
Sika® FroV 5 A: Air void entrainer
SikaRetarder®: Retarder