Non-destructive testing for the evaluation of concrete properties in civil engineering structures. Extensive low-destruction and non-destructive structural investigations were carried out on the Unterrieden viaduct in connection with its demolition. A key objective was to evaluate the hardened concrete properties of the structural concrete. In addition to determining selected material properties using drill cores, the application of indirect methods such as rebound hammer and ultrasonic transit time measurements in accordance with DIN EN 13791 was tested. The results were processed iteratively, statistically evaluated, and assessed for plausibility. No correlation (rebound hammer measurement) or only a slight correlation (ultrasonic transit time measurement) could be established for the measurement data of the Unterrieden viaduct. The results of the investigations and the identified potential causes for the reduced correlation suggest that the use of indirect methods for evaluating the properties of hardened concrete in bridge construction is only possible to a limited extent or requires intensive interpretation.