Einfluss der Bauteilgeometrie auf die Korrosionsgeschwindigkeit von Stahl in Beton bei Makroelementbildung

Abstract

The exposition of concrete members to a chloride containing environment can lead to depassivation and corrosion of the reinforcement. A special configuration is generated if the concrete structure is only partly contaminated with chloride ions, whereas the other parts of the reinforcement remain passive. The self corrosion of the active reinforcement is superposed by the effect of a galvanic element, which leads to high metal removal rates and therefore to relevant restrictions of the structure durability. The macrocell current is influenced by a considerable number of factors. One important factor is given by the ohmic resistance between active and passive reinforcement parts, which is dependent on the specific concrete conductivity and the geometrical arrangement of both electrodes. The investigations of the geometrical influence were carried out by a combined approach consisting of laboratory experiments and numerical analyses. The laboratory program covers a wide range of practical standard cases. In the course of the numerical simulations additional cases with varying boundary conditions like surface area ratios, driving voltages and concrete resisitivities were analysed. The results allow a direct comparison of different structural members and geometrical arrangements in terms of the corrosion risk and enable a quantification of the leading influencing parameters. Furthermore the resulting data base was used to show how parameters like controlling and cell factors can be derived to describe the geometrical influence. These allow an estimation of the resulting macrocell current in order to assess the remaining life time or the determination of target values, e.g. the necessary concrete resistivity, as part of maintenance strategies