Autostrade routine survey of the structural state of bridges and viaducts mainly consists of visual inspections normally carried out twice a year. Whenever an enhanced corrosion damage is foreseen, further examinations are requested, as chloride profile and carbonation depth. Recently, potential mapping and corrosion rate have been, as temptative, randomly determined. As concerns potential mapping, both over bituminous overlay and directly over concrete surface, the results show that there is a fairly good correspondence between the potential distribution values and the reinforcement corrosion state. Besides, the corrosion rate, measured by means of a Gecor equipment, gave results which can not easily be correlated to the potential values and to the visual examination. Only in one case, a small bridge on the Genova -Milano motorway, the corrosion rate values correspond to a passive state of the reinforcement, despite of the potential mapping showing a very bad situation: after the demolition of the bridge it has been confirmed that the upper layer of the reinforcement was in very good condition, thus confirming the low corrosion rate values, while the lower bars were severely corroded, thus confirming the potential mapping, which inevitably takes into account both reinforcement layers. More experimentation is needed, in order to evaluate the convenience of such investigation technique, which unfortunatly requires very long measuring times.
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