Current distribution and throwing power of galvanic cathodic protection with discrete anodes in reinforced concrete beam or column elements

Abstract

Galvanic cathodic protection (GCP) of steel in concrete by means embedded discrete anodes is a commonly used repair method to reduce or prevent steel reinforcement corrosion. The design and efficiency of the system depends greatly on the corrosion activity of the steel reinforcement and electrical resistivity of the concrete. In this research, the influence of chloride concentration and cement type in the concrete on the current distribution and throwing power of GCP with discrete anodes is investigated for linear concrete elements such as beams or columns. Results show a high throwing power (> 500 mm) of the GCP system for concrete with a CEM I cement (low resistivity) and limited chloride contamination. For concrete with a severe contamination of chlorides (2 m% by mass of cement) or high electrical resistivity (e.g. by the use of CEM III/A cement), the throwing power is greatly reduced to values of 60 mm and 110 mm, respectively. Consequently, based on the 100 mV depolarization criterium (EN ISO 12696:2016), GCP with discrete anodes was found to be most efficient for concrete with relatively low resistivity and limited corrosion activity of the steel reinforcement (related to chloride concentration in the concrete).

Influence of various parameters on the current distribution and protection degree of impressed current cathodic protection for reinforced concrete with TiMMO mesh anodes

“…For a higher concrete chloride content, the reinforcement steel corrosion potential will be more negative. This is consistent with findings in [5,10,11].…”

“…The concrete resistivity is approximately 3 to 4 times higher for the concrete with CEM III/A compared to the concrete with CEM I cement, both with 1m% Cl by the weight of cement. The influence of the concrete chloride content is relatively small, where a small decrease in the resistivity value can be noticed with an increase in chloride content, as in agreement with literature findings [11].…”

“…For the layer An increase in chloride content, linked to an increase in corrosion activity, is accompanied by a decrease in the 24h depolarization values and a decrease in throwing power. This is confirmed by [5,11,14]. The 100 mV depolarization criteria is not met for the layers at a distance of 130 mm and 230 mm from the anode for prism 4 (2 m% Cl with ACT).…”