The highest point of the drainage basin of the Danube is the summit of Piz Bernina on the Swiss-Italian border, at 4,049 m. Located in Central and Eastern Europe, the Danube is the European Union's longest and the continent's second longest river (after the Volga).

International waterway and 2,872 km of length

Classified as an international waterway, it originates in the town of Donaueschingen in Germany’s Black Forest region. The Danube then flows southeast for 2,872 km, passing through four capital cities before emptying into the Black Sea via the Danube Delta in Romania and Ukraine.

Near round navigation to the Black Sea

Once a long-standing frontier of the Roman Empire, the river passes through or touches the borders of ten countries: Romania (29.0% of basin area), Hungary (11.6%), Serbia (10.2%), Austria, Germany, Bulgaria, Slovakia, Croatia, Ukraine, and Moldova.

Gabčíkovo Waterworks protect from flooding

The Gabčíkovo Waterworks were originally designed and built on the Danube near the Slovakian capital Bratislava and close to the borders with Austria and Hungary. The main purpose of the huge waterworks project was to protect the region against flooding from the Danube. The reservoir and massive locks are bigger than those on the Panama Canal and also provide year-round navigation to the Black Sea. The hydroelectric power station at the dam provides approximately 8% of the whole country’s annual electricity consumption.

Differences in water levels up to 22 m

The waterworks consist of the 16 km Hrušov reservoir, which is designed to hold accumulating river water and control the flow through channels into the hydro-electric power station’s turbine generators, before discharging back into the river further downstream.
The huge 32 m high lock system was built to overcome the major differences in water levels (up to 22 m) and control the release of potential flood water. Ships enter the lock chambers that then drain from the base. Every 15 minutes around 200,000 m3 of water are displaced.

Major refurbishment

Each lock chamber is 275 m long and 34 m wide – larger than those on the Panama Canal. After more than 20 years’ service, there was significant visible damage to the reinforced concrete structure. During this time there had been no major maintenance or repair works carried out. In 2013, the project engineer decided it was necessary to carry out major refurbishment, firstly focusing on the left lock chamber, including the overflow edges, inlet and outlet channels.

Sika Abraroc SR. as ideal product for the repair

The entire lock chamber had to be drained and thoroughly cleaned employing high water pressure jetting. The surfaces of the reinforced concrete structure were repaired using a special type of mortar - Sika® Abraroc® SR. The product is ideal for the repair and protection of load-bearing, reinforced concrete hydraulic structures against hydraulic abrasion and aggressive water, such as found in water and waste water treatment plants, dams, locks and harbors, plus many other civil engineering structures that are subjected to heavy abrasion and loads, including the floors in storage and loading bays, silos and other industrial facilities.

Sealing and bonding of repaired lock walls

The exposed areas of the repaired lock walls were coated with Sikagard® to further protect the surface and provide a uniform color. The structural movement/expansion joints in the concrete lock structure were repaired and sealed with the Sikadur® Combiflex® system to accommodate high movement and additionally to facilitate installation of the product.

The system consists of 200 mm Combiflex strips, 2 mm thick, bedded and bonded onto the prepared concrete on both sides of the joints using the Sikadur®. The free central ‘movement’ zone of the strip is not covered with adhesive or bonded to the surface and can accommodate high movement in any direction.

Sika Injection filling the cracks

Cracks in the concrete soffit of the water inlet and outlet channels had formed for different reasons over time. The project engineer decided that they needed to be effectively sealed to restore the structural integrity and prevent further water ingress to the structure.
The system selected for filling and sealing the cracks was Sika® Injection®.

Sika MonoTop fixes steel plates on concrete for additional protection

The water constantly overflows the edges, which are subjected to severe exposure, stress and loading. The surface was given additional protection with heavy steel plates fixed to its repaired concrete areas using Sika MonoTop®. The small void between the steel plates and repaired concrete surface was sealed with an injection pump using SikaGrout®.

The waterworks are now equipped in future to easily overcome differences in water levels of up to 22 m. Anyone who has witnessed this live from a tourist boat on the water will never forget the impressive sight!

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