Electrochemical testing of corrosion process in a reinforcement of a cracked concrete

This paper presents the results of an extensive electrochemical research work that was aimed at reproducing as close as possible the corrosive processes that take place along the rebar which reinforces concrete elements as being treated by mechanical loads and aggressive chloride ions. The tests have been carried out both on cuboidal blocks, reinforced by a plain rebar and on identical blocks reinforced by a ribbed bar. Prior to the measurements each sample had been subjected to a cyclic action of the aggressive environment by being exposed through 3.5 hour's time to the 3.1% strong solution of sodium chloride, and then to a drying process through 68.5 hour's time at the ambient temperature. The electrochemical tests embraced the measuring of the distribution of stationary potential, and that of the electrochemical polarization using the method adapted to the conditions inside the concrete elements. They made it possible to specify among other things the density of corrosion current and the resistance of polarization, which are used for measuring the corrosion process rate. We did find out that portions with a decreased potential did appear around each crack of the covering concrete. The strongest stimulation of electrochemical processes occurred in the presence of several cracks. Values of the corrosive potential, corrosion current density and polarization resistance did not depend on a width of the cracks. Actual values of the corrosion current density were lower in the samples reinforced with ribbed rebars than in the samples reinforced with plain rebars. This result evidences better protective properties of a concrete covering if a ribbed reinforcement is used.