Concrete repair
Railway bridge B472 Marktoberdorf

From old to new
Bridge renovation Marktoberdorf

In the past year 2020, we received an order from Deutsche Bahn AG to determine the current condition of the rail bridge over the B472 in Marktoberdorf, in particular its load-bearing concrete parts. This is a three-span prestressed concrete bridge built in 1966 with rail traffic over a total length of 28 meters. On the basis of an expert report in December 2020, the damage including carbonation depths and chloride profiles could be determined and a concrete damage survey could be prepared.

Our assignment was to rehabilitate the identified damaged areas. In addition to the abutments and the bridge soffit, the 4 supports in particular were highly damaged by chloride. Since we were only able to close one side of the road, we started with one side of the bridge first. The entire work was carried out while the railroad and road traffic continued to operate. The first step was to excavate to a depth of approx. 2.40 meters down to the column foundation. A scaffold was then erected around the columns, to which a protective device was attached. We needed this for the subsequent ultrahigh-pressure water blasting. A special challenge was that the HDW blasting was to expose the existing reinforcement, but that a maximum of 7 cm of concrete was to be removed, as otherwise there would have been a risk of collapse. This process was permanently checked and approved by the responsible engineering office, and at the same time we were able to start caulking the superstructures and abutments. After the HDW blasting was completed and the removal accepted by the engineering office, we were able to reblast with solid abrasive and start to install the additional iron reinforcement allowance according to structural specifications. Subsequently, subsequent reinforcement connections had to be made. The engineering office specified to us how the new column reinforcement, including the reinforcement cage, was to be carried out. Once this was done, the specially designed circular formwork for shotcrete could be attached. The column cross-section was increased from 85 cm to 105 cm. And indeed, the columns were still round even after our shotcrete application!

For the superstructures and the abutments, a PCC system was used for reprofiling. This was followed by the application of a fine filler and the application of a coating in accordance with Surface Protection System-C. This is intended to ensure thatCO2 entry is inhibited and that carbonation proceeds more slowly, so that existing reinforcing steel remains in the alkaline environment for longer.

Finally, to the first bridge side, the removed soil was reinstated and compacted, the basalt natural stone pavement was restored, and the claimed areas were cleaned. The leaking cap joints, which were located at the top of the track area, were repaired with the help of a securing plan and a securing company.

Once this work was completed on one side of the bridge, the traffic protection was moved to the other side of the road and the identical procedure was started on the opposite supports, abutments and superstructure.

The entire rehabilitation took approximately 8 weeks.

Mathias Schäfer

Mathias Schäfer

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