HEIDELBERGCEMENT AG

New construction of Gleesen Lock on
the Dortmund-Ems Canal, North Rhine-Westphalia

The Dortmund-Ems Canal is one of Germany’s most important waterways. The around 29 km long northern canal section contains six locks which guarantee that ships can overcome a height difference of around 29 m from Bevergern to Gleesen. Many locks along the canal are more than 100 years old by now and no longer fulfil the requirements of modern shipping. The “New Locks DEK-North” project was set up for this reason. The old locks along the northern section of the canal are being replaced with new constructions to make the route future-proof for inland waterway transport.

Gleesen Lock, built in 1914, is also being modernised for this reason. A completely new lock system 140 m in length and 12.5 m wide with a lifting height of 6.37 m is being built so that in future larger inland cargo vessels can travel through this canal section.

Datteln Waterways Construction Authority is responsible for planning and realisation of the project. The planning is being realised by the Johann Bunte construction company. The concreting works for the construction pit with base and the new lock construction form a major component of the building contract. In order to satisfy the different requirements of the structures, two types of low-clinker concrete from HeidelbergCement AG are being used: CEM III/A 32,5 N-LH (na) for the base and walls and CEM III/A 42,5 N for the construction pit with underwater concrete.

Bulky navigable waterway constructions are subject to stress from weather and water. They have to constantly resist these effects in order to achieve their expected service life of at least 100 years. This means that CEM III cements with low hydration heat development are generally used to keep the temperature development low during concreting.

A total of approximately 15 000 t of CEM III cement will be supplied by HeidelbergCement for this project. These have reduced cement clinker content. Normally, ground limestone (CaCO3) is burnt at high temperatures to make Portland cement clinker in cement production. The molecules are split and CO2 is released in the process - the process of deacidification. Depending on the type of cement, it is possible to reduce the cement clinker content and replace it with alternative cement-like materials – for example with slag sand, a waste product from the steel industry. The benefits are obvious: apart from recycling a waste product, the cement’s carbon footprint is also reduced.

Since the lock location in Gleesen is extremely narrow, the transport of the cement was first planned by road. However, with around 6 000 trips, this would have caused a considerable traffic impact. Two mobile concrete mixing systems were set up on-site instead. These systems offer optimum co-ordination and short distances when concreting. The mobile mixers reduce the traffic impact as no truck mixers are supplying concrete to the site. The aggregate is also being supplied to the construction site in an environmentally friendly manner by ship via the Dortmund-Ems Canal. The types of cement come by truck from the HeidelbergCement plant in Ennigerloh.

Björn Kranz, project manager for Johann Bunte, explains: “The interesting thing about building locks is the dimensions. The lock base is three metres thick and the walls are actually up to six metres thick in several places. When hardening the concrete there is an exothermic chemical reaction which arises with heat. The thicker the components, the more difficult it is to dissipate the heat. Stress cracks can form from high temperatures across the thickness of the component. This is why we used CEM III/ A 32,5 N-LH (na) cement from HeidelbergCement for the base. Heat development here is extremely slow and cracks can be avoided. After all, the lock is supposed to hold for at least the next 100 years”.

The construction pit has been finished since the middle of last year. Björn Kranz remembers: “First we produced a slotted wall as temporary shoring and then built the underwater concrete base in order to be able to build the lock in the dry. CEM III/A 42,5 N was used here as it has high compressive resistance. The underwater concrete base serves to seal the construction pit against underground water. The construction pit is up to 30 m wide, 200 m long and more than 17 m deep. The largest concreted section has a volume of 5 500 m3. Concreting took three days and continued around the clock. At times, there were actually three concrete pumps in use. Since the concrete for the underwater concrete base was inserted with the aid of divers, a free-flowing consistency was necessary. The concrete was then able to level off by itself. This is also the reason why it was constructed rapidly and in one pour”. After the underwater concrete base had been constructed, the water could be pumped out in order to form a dry construction pit. The lock base was then installed in seven concreting sections.

The lock walls are currently being concreted. The 3 to 6 m thick walls are concreted in individual sections of up to 700 m3. Depending on the geometry and required concreting speed, up to three concrete pumps are again in use. After concreting, the concrete generally remains behind the shuttering for seven days.

The shell construction of the lock should be completed in Autumn 2021. Insertion of the lock gates, drive and electrical technology begins after this. If everything goes according to plan, the lock will open its gates at the beginning of 2023 – also for larger inland cargo vessels.

www.heidelbergcement.de

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