Long‐term Resistivity Monitoring of a Lock – Valuable Data for different Durability Issues

A better knowledge on the exposure conditions of structures can help to evaluate the transferability of lab tests results to practical application or to generate a basis for modeling of different durability aspects. About 20 years and 10 years ago, a monitoring system was installed in two locks to get information on the temperature exposure and the degree of saturation of the concrete cover zone by means of continuous resistivity measurements with the Multi‐Ring‐Electrodes (MRE) and Multitemperature Probes (MTP) at different distances to the concrete surface. Due to the fact that resistivity is influenced by many more parameters than just the degree of saturation it is very complex to determine the degree of saturation. Uncertainties remain as concrete properties develop over the years and the cover zone which is of mayor interest for durability is additionally affected by casting and curing and later on by the exposure conditions. A deficiency of the Arrhenius equation to compensate for temperature effects on resistivity under certain conditions finally helps to overcome that difficulty. A data evaluation concerning freeze‐thaw attack gives examples and indicates possible further applications like carbonation.