Potentials of direct material testing on existing structures – Strength reserves of a prestressed concrete viaduct. Recurring questions regarding the selection of appropriate populations in the context of material testing for reinforced and prestressed concrete bridge, as well as the strength reserves of existing concrete, were investigated through a special case study of a prestressed concrete viaduct with in-section construction on formwork carriage. In this scope, 141 drill cores were taken from Unterrieden Viaduct, which is to be dismantled, and tested for either compressive strength, splitting tensile strength or Young's modulus. The data sets were statistically analyzed. The results impressively demonstrate the potential of the direct determination of material parameters on existing structures. In particular, the anticipated compressive strength values were surpassed by 40 %, and the characteristic values from material testing even exceed the assumptions based on as built documents by over 100 %. Furthermore, an investigation of potential populations on the superstructure is carried out in order to develop recommendations for future sampling. For this purpose, the sample taken is divided into different potential populations and statistically analyzed. The result shows a very uniform structure with a dispersion well below the normative assumptions. This hardly provides any arguments for subdividing the superstructure into different populations.