Alcune considerazioni sui metodi non distruttivi per la determinazione delle proprietà meccaniche del calcestruzzo

Since wide programs for seismic assessment of public buildings are currently ongoing in Italy, non destructive testing methods for evaluating mechanical properties of concrete in existing structures are more and more popular within the technical community. Although according to the provisions of the Italian code of standard they cannot be directly considered without a preliminary calibration with respect to the results of destructive tests on a reasonably wide number of concrete samples, they can be utilized to deriving relevant information especially about the quality of concrete in terms of homogeneity. Several non destructive techniques are currently available for concrete structures and comparing the accuracy of the results derived by those techniques is nowadays an issue of concern. The paper presents the results of experiments, consisting in both destructive and non-destructive tests, on concrete columns which have been already tested under cyclic actions. Comparisons in terms of mechanical properties derived by the various techniques are presented and further calibration of existing formulae for interpreting non destructive measures are also proposed. Considerations about the spatial variability of concrete mechanical properties, possibly related to both the casting process and the load history, are also reported.