Vita residua di strutture in calcestruzzo armato carbonatate: stima della velocità di corrosione delle armature mediante monitoraggio della resistività elettrica nel calcestruzzo

The residual service life of a reinforced concrete structure in which carbonation of the concrete cover occurred can be estimated if reinforcement corrosion rate is known. The direct measurement of this parameter is not easy to achieve on real structures. However, an estimation of the corrosion rate can be obtained by means of concrete electrical resistivity measurements, easier to get. Indeed, electrical resistivity and corrosion rate are correlated. Nevertheless, for a correct estimation of reinforcement corrosion rate is necessary to know the correlation, to perform the measurements in proper way and to carry out a monitoring. In this paper are reported the results of an experimental work aimed on the evaluation of different methods for the measurement of the concrete electrical resistivity to obtain a correct estimation of reinforcement corrosion rate in carbonated concrete. Initially, tests on concrete specimens manufactured in lab and exposed, after carbonation, in different exposure conditions were performed. On these specimens concrete electrical resistivity, measured with different internal and external probes, corrosion potential and corrosion rate were monitored. Thus, the relationship between resistivity and corrosion rate was analyzed. Afterwards, the procedure developed with the laboratory tests was applied on field. Probes for electrical resistivity and corrosion potential monitoring were installed in selected structural elements of the “G. Meazza” Milano stadium. Data obtained were used to estimate the propagation of the corrosion and thus to achieve information in order to plan maintenance works.