Zusammenfassung Die Nutzungsdauer von Brücken kann durch Korrosion des Bewehrungsstahles eingeschränkt werden, wenn durch Undichtigkeiten in der Abdichtung chloridhaltige Feuchtigkeit in den Deckbeton eindringt und zur Depassivierung und Korrosion des Bewehrungsstahles führt. In diesem Fall sind umfangreiche Instandsetzungsarbeiten erforderlich. Um Instandsetzungsarbeiten zu optimieren, wurde eine multifunktionale Zwischenschicht aus Textilbeton – SMART-DECK – entwickelt. Diese bietet drei Funktionen: Ein vollflächiges Echtzeit- Feuchtemonitoring, einen vorbeugenden kathodischen Korrosionsschutz und eine Querkraftverstärkung. Der Fokus dieses Artikels liegt auf der Funktionsweise der ersten beiden Funktionen. Der Betreiber des Brückenbauwerks soll über ein Monitoringkonzept in der Lage sein, den Zustand seiner Fahrbahnabdichtungen in Echtzeit zu überwachen. Die relevanten Daten können über Internet übermittelt werden. Sofern der Einsatz einer kathodischen Vorbeugung aufgrund von Undichtigkeiten erforderlich ist, wird mittels Gleichrichtern eine Gleichspannung zwischen Carbon und Bewehrung aufgeprägt und so die Bewehrung kathodisch vor Korrosion geschützt. Hierbei wird das Stahl/Beton-Potenzial soweit in negative Potenzialbereiche verschoben, dass das Lochkorrosionspotenzial Epit nicht überschritten wird und es zu keiner Korrosionsinitierung kommt.

The service life of bridges is often threatened by an insufficient shear force capacity in the transverse direction as well as by leakages in the sealing layer, which leads to chloride ingress and therefore corrosion damages. To prevent expensive repair work and traffic obstructions, a thin, multifunctional interlayer of textile-reinforced concrete called SMART-DECK was developed. This interlayer provides three functions: A full-surface moisture monitoring in real-time, a preventive cathodic corrosion protection, and an increase of the shear force capacity. The operator of the bridge is able to monitor the condition of the sealer in real-time. The relevant data are transmitted via the internet and show the condition of the sealer in a simple color scheme. If leakage occurs, the cathodic corrosion protection can be switched on to protect the reinforcement from corrosion damages.The renewing of the damaged bridge deck sealing has not to be carried out immediately but can be postponed over years, for example, to periods with little traffic. In this paper, the scientific approach for the realization of the system is presented, beginning with laboratory pretests on the materials and numerical simulations. The results are used to test the functions of the system in the laboratory and later on two demonstrators. An outlook will present the next research questions.

During the development of a carbon-reinforced mortar interlayer for bridges, the idea of an electrochemical chloride barrier arose. An electrical field is generated between two carbon meshes, and the negatively charged chloride ions are held on the polarized upper carbon mesh to prevent chloride-induced corrosion in the reinforcement. Laboratory tests unexpectedly showed that higher voltages lead to an increase in chloride ions for certain depths of the reference probes. This paper discusses the implementation of analytical and numerical models that finally explain the effect only by the acting diffusion and migration with the help of a finite differences model and finite elements simulations. The effect of the local minimum is limited to positions above the depth of the first carbon layer of the test specimens. It is caused by the lines of the electrical field between the first and second carbon layer. According to the experimental and finite elements simulation results, higher voltages lead to lower chloride concentrations for all positions below the first carbon layer only after sufficient time duration. Therefore, the intended effect of an electrochemical chloride barrier can in general only be observed and confirmed after a certain time depending on position, conditions and parameters.

In the context of a joint research project, a system for monitoring, protection and strengthening of bridges by using a textile reinforced concrete interlayer has been developed which consists of two carbon layers with a spacing of 15 mm and a special mortar. This setup led to the idea to build up an electrical field between the carbon meshes, which suppresses the ingress of chlorides into the concrete. This paper focuses on the question which voltages and electrical field strengths are necessary to prevent critical chloride contents at the reinforcing steel. For this purpose, extensive laboratory tests have been performed, followed by a numerical simulation study. By applying an electrical field, the negatively charged chloride ions are forced to move to the upper carbon mesh that is polarized as an anode. It has been investigated whether the voltages to implement an electrochemical chloride barrier are smaller than they have to be for the common preventive cathodic protection. One advantage of this chloride barrier is that because of the lower current densities the anodic polarisation of the carbon meshes can be reduced. Therefore, different voltages, electrical field strengths, anode materials and anode arrangements were investigated.