During the recent decades, the use of non-destructive tests has reached greater attention due to its high versatility and the possibility of extending the investigations on a great number of points. On the other side, the existence of a wide building stock realized in reinforced concrete, which is reaching the end of its service life, has increased the research on the assessment of their safety level.
In this field, one of the most important parameters for r.c. structure is the concrete compressive strength, which “classically” is evaluated by means of compression tests on drilled cores. However, usually the extension of such procedure to a high number of points is quite difficult due to logistic and economic reasons. The use of non-destructive tests may overcome these limits, but still needs further investigations to improve the calibration process of the relationship between the acquired data and the compressive strength. The present paper deals with this issue and discusses the results of the investigations on r.c. buildings in Bari (Italy) which make use of both destructive and non-destructive tests. The data are analyzed by considering several test scenarios and by evaluating the variability of parameters related to the calibration process.