Mechanical characterization of concrete from existing buildings with SonReb method

The evaluation of the concrete compressive strength is a fundamental step for the assessment of existing reinforced concrete (RC) buildings according to the last seismic codes. This valuation can be conducted by the use of both destructive and non-destructive methods. Non-destructive methods, although being minimally invasive and easily extensible to a large number of elements, are influenced by many factors. SonReb method, combining Schmidt rebound hammer and Ultrasonic Pulse Velocity methods, allows to compensate the limits and the uncertainty typical of each method. The use of the combined methods (SonReb) increases the accuracy of the estimation of the in situ concrete compressive strength. In this paper, a significant database of both destructives and non-destructives tests conducted on existing RC buildings located in the Italian Region of Tuscany and built between the 50’s and 80’s, is used to perform statistical analyses. In detail the paper evidenced the need to conduct a wide campaign of on-situ tests, useful to define the concrete compressive strength with a suitable reliability. The results show that the uses of formulations present in the technical literature provide results different from the actual values. Conversely the results of SonReb method, calibrated with the strength of cylindrical samples (cores) extracted from a single building, are close to the actual ones.