Monitoring corrosion in concrete by means of Electrical Resistance Probes

Carbonation and chlorides are the main reasons for deterioration of concrete, caused by corrosion of rebars. Controlling the corrosion in concrete by means of a system able to monitor corrosion’s parameters, such as potential, pH or corrosion rate, represents a powerful way to prevent concrete deterioration and to reduce restoration’s cost of the damaged structure. The aim of this work was to test Electrical Resistance Probes (ERP), usually applied to corrosion measurements in pipelines or tanks, by embedding them in concrete to monitor and estimate rebars corrosion rate. Five ERP probes were embedded into two cylindrical concrete samples, together with four steel rebars. The samples were exposed to chloride penetration and carbonation. Free corrosion potential and corrosion rate values of the rebars were monitored, by means of corrosion resistance polarization measurements, in comparison with the loss of metal provided by the ERP system. At first, samples were submitted to accelerated exposition to the aggressive agents, then the exposition was carried forward in “field” conditions and for long time. Comparing rebars corrosion rate with respect to ERP data, the effectiveness of using this kind of probes in concrete was estimated. ERP probes were able to register the start of corrosion with fair precision and good answer quickness.