Optimised cathodic protection design for maximum bond performance in reinforced concrete

Abstract

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