Concrete admixtures for Europe's biggest building site

Potsdamer Platz is a very special piece of real estate in a very special city. In the Belle Époque of the 19th century, sophisticated venues frequented by international high society were built here; at the beginning of the 20th century, the Wertheim department store emerged as a crowd puller; and by the 1920s, it was the busiest plaza in Europe. After the Second World War, the dividing line between two social systems ran right across Potsdamer Platz, with the construction of the Berlin Wall literally cementing it for posterity.

The birth of a new centre

After Germany’s reunification, Potsdamer Platz became the new city centre of Berlin, with countless office and residential buildings, restaurants, leisure amenities and shopping centres. Internationally renowned corporations invested in their future at this historically significant square. The Daimler-Benz Group, for example, built an entirely new city district with a total area of 68,000 m² at the cost of around 4 billion euros. However, developments of such magnitude quickly led to problems with the urban groundwater balance due to the high groundwater table prevailing at Potsdamer Platz. And with half of these investments requiring underground construction measures, challenges were bound to arise, including for MC as a company called in to find viable solutions.

Foundations under water

Excavation of the construction pits below the water table eventually leads to the formation of artificial lakes. Consequently, for the first time in construction history, a back-anchored concrete foundation made of steel-fibre-reinforced underwater concrete (UW concrete) had to be laid with an excavation pit depth of 20 m over an area of approx. 24,000 m². As early as the tendering phase, proof had to be provided showing that a UW concrete with steel fibres could indeed be installed under such conditions. Since fibres in the concrete greatly reduce flowability, the concrete composition had to be fundamentally changed compared to “normal” concrete. Since only formwork-enclosed sections concreted “in one pour” could guarantee a UW concrete base of the required density, it had to be possible to delay pumping the concrete with steel fibres and superplasticiser for up to 20 hours if conditions – e.g. inclement weather – so dictated. Round-the-clock concrete delivery also had to be guaranteed.

Maximum performance – maximum success

Success in this unique undertaking required everyone involved to be right at the top of their game. At the bottom of the huge water pits, divers helped lay the UW concrete foundation slabs. Good application properties tailored to these conditions were, of course, essential. With MC’s expertise at the forefront, the concrete used was alloyed with around 250 tonnes of superplasticiser and 50 tonnes of concrete retarder – all products offering MC’s renowned quality and reliability.

The former Iron Curtain zone that was Potsdamer Platz was quickly transformed into the capital’s newest quarter, with 19 apartment and amenity blocks, ten new streets, a central plaza, Marlene-Dietrich-Platz, and a lake containing around 12,000 m² of water.