In case of an assessment of an existing structure, based on current standards, characteristic properties of materials used for construction are required. Those material properties can be gained for pre-dimensioning at least from documents from the construction period by conversion. Whereas, for an ensured recalculation, characteristic material properties have to be determined by a qualified structural investigation. The currently used methods according to DIN EN 1990 [2] and DIN EN 13791: 2008 [3] lead, especially for a small sample size, to doubtful results and a high rate of over-or underestimation. By application of the new approach according to E DIN EN 13791/A20: 2016 [4] with the modified methods A and B, the characteristic concrete compressive strength can be determined with only slight deviation to the real value of the concrete compressive strength of the population within the boundaries of application. Subsequent, weaknesses of the currently used methods according to DIN EN 1990 [2] and DIN EN 13791: 2008 [3] are demonstrated. Furthermore, background information on the new approach according to E DIN EN 13791/A20: 2016 [4] is given.
