Effect of chloride content level on concrete CP criteria

The currently available Standards for cathodic protection (CP) of reinforcement in atmospherically exposed concrete structures nominate a set of performance criteria as a measure of corrosion protection to embedded reinforcement. The predominantly used CP criteria for steel in concrete is 100 mV potential decay in 4-24 hours period. An experimental program was undertaken to assess adequacy of this CP criteria and it\u27s dependence on chloride content in concrete. Chlorides in the form of NaCI were admixed with water in preparing the test specimens. The chloride content ranged from 1.2 kg/m3 to 9.5 kg/m3of concrete. Chloride differentials within the specimens were artificially created using higher chloride bearing macrocells in the specimens and thereafter connecting the macrocell steel and the main steel (of the specimen) through an external resistor. A current reversal technique was used to establish the protection level needed for control of reinforcement corrosion. It was found that a 100 mV potential decay in a four hour period was more than adequate for corrosion protection of reinforcement in chloride contaminated concrete. The study also revealed that the potential decay value required for corrosion protection did not change significantly with polarization time. © 2006 by NACE International