Our "bridge volunteers" already worked 1.400 hours on the bridge since November! In the course of the recent weeks they reconstructed the inner concrete areas and prepared the sealing - this had not been planned from the beginning. We have to keep in mind: this is not some standard bridge, but a trailblazer regarding tampered concrete constructions. This construction method was replaced after just a few years by the reinforced concrete construction method. Mostly we see how they built back then and especially what materials they used just when we have it in front of us - and this is what makes planning really difficult.
The decision on the best suited sealing method was the result of numerous specialists talks. Regarding the application of the sealant we faced the problem that none of the sealants of the present got along with the tar layer that was used for sealing in the distant past. To avoid the risk of the new sealing layer being "eaten away" by the tar within a few years and made effectless by that even the most tiny piece of tar had to be removed from the brittle concrete in painful detail work. Here as well the colleagues demonstrated a lot of creativity when it came to solving the problems.
The new sealing material has to meet many standards: the concrete has to be protected against moisture for many decades. The sealing itself has to bear up against the pressure of the span's filling material from above or even has to be protected against the filling material itself. And the sealing material has to be easy to handle as we are talking about areas that cannot all be accessed by a small folding step. The method to have a flat area as substructure has proven best. After the removal of the tar a sort of plaster is now at first going to be applied. Then the actual sealant and the filling will follow. You can find photos of these works at the end of our bridge photo gallary.