The concrete pillars of the Libeň Bridge are corroding, showed a survey

Prague - The concrete pillars of the Libeň Bridge in Prague are damaged by corrosion, and the mechanical properties of the concrete are unstable. This was stated today to journalists by Jiří Kolísko, director of the Klokner Institute of CTU, and Petr Dolínek, deputy mayor (ČSSD). The Klokner Institute examined the third pillar of the bridge.

The bridge, which dates back to 1928, has been in a state of emergency for a long time. Last year, the Prague Council approved a reconstruction, but the start date is unknown. The city is awaiting a decision from the Ministry of Culture, which is negotiating the declaration of the bridge as a monument.

"The bridge is founded on a load-bearing substrate composed of slates, but the concrete has a non-homogeneous macrostructure, is very porous, and degradation processes known as sulfate corrosion are taking place," said Dolínek.

Sulfate corrosion can occur in cement in the presence of sulfate ions. Their sources may be groundwater, a substance that was introduced during the production of concrete, or materials from the Vltava River. "There is a chemical reaction occurring, where new crystals form that expand and have a greater volume than the original material. This creates pressure and causes damage to the concrete structure," Kolísko explained.

Prague, along with the Technical Administration of Communications (TSK), will have the remaining pillars and other technical parts of the bridge inspected. The subsoil of the other pillars will also be examined. The Klokner Institute should complete its work by the end of this year.

What will happen to the bridge next is still unclear. Prague is waiting for the ministry to announce whether it will declare it a protected monument and potentially which parts will be included. "The missing decision is starting to limit us, as we cannot begin preparations for repairs. However, we can start monitoring the bridge," said Dolínek.

TSK plans to have other bridges examined using the same method. Among them may be the Hlávka, Legion, Palacký, and Barrandov bridges.

Since the Libeň Bridge was put into operation in 1928, its load-bearing structure has never been repaired. The authors of the bridge, which connects Holešovice and Libeň, are architect Pavel Janák and constructor František Mencl.

The Klokner Institute was founded in 1921 under the name Research and Testing Institute of Materials and Construction Structures. It now has four specialized departments, a composites center, an accredited laboratory, and since 1986, a forensic expert workplace in the field of construction.