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Currently there are two bridges older than 120 years under reconstruction in Slovakia. One of them is the Old Bridge in Bratislava, which has been built in 1891 and has a steel superstructure supported by concrete piers. The other one is the Monier Arch Bridge in Krásno nad Kysucou, which has been built in 1892. Since only limited information about the properties of such an old concrete is available, it was almost impossible for the designer to verify the load bearing capacity of these bridges and to design their reconstruction efficiently. To verify the properties of these concretes drill cores were made on both bridges, some of them being more than 20 meters long [17]. After that the measured concrete properties were used to confirm or modify the reconstruction method proposed in the preliminary design. Our paper deals with some mechanical properties measured on these more than 120 years old concretes.

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This article discusses the properties of concrete within the piers of the Old Bridge in Bratislava (former Franz Joseph Bridge). It was the first permanent bridge across the river Danube in Bratislava as well as within the present territory of Slovakia. Mechanical, physical and chemical properties were verified on core drills, some of them being almost 23 m long. The concretes were tested for dynamic and Young’s elasticity module and compressive strengths. Subsequently the fines of concrete specimens were studied by the X-ray diffraction, TG-DTA and mercury intrusion porosimetry techniques and also by chemical analyses and SEM observations. The piers were made from 5 different concrete kinds. The concrete in the caissons and in the piers does not fulfil the criteria for structural concrete defined in the present European standards. This finding seriously suggests that carrying capacity of the piers after the reconstruction of the bridge, without any strengthening would become questionable.