Optimised cathodic protection design for maximum bond performance in reinforced concrete

The influence of the long term effects of impressed current cathodic protection (ICCP) on the bond strength is investigated. A total of 16 pull-out specimens were divided into four series and the steel bars pre-corroded to target degrees of 0 % (control), 1 %, 2 % and 5 % weight loss. Four levels of ICCP current density ranging from approximately 0 (control) to over 1000 µA/cm2 were applied to each series. These are considerably higher than the levels typically used in practice, which rarely exceed 2 µA/cm2, but were used to replicate long term application within a reasonable timescale. Following pull-out tests, the values of bond load were determined. The analysis accounts for the accelerated ICCP by relating the total charge to the steel reinforcement in coulombs (current x time) to the bond values and migration of chloride ions. The results show that although some loss in bond is evident from the ICCP, an optimised current density can be applied to a real structure without affecting the as-designed bond strength in the long term e.g. ≤ 0.65 µA/cm2 for an ICCP duration of 70 years. Application of the same current density reduces the chloride concentration from around the steel irrespective of the degree of corrosion.