Proposed criterion to assess the electrochemical behavior of carbon steel reinforcements under corrosion in carbonated concrete structures after patch repairs

Patch repairs for reinforced concrete structures using Portland cement mortar are widely used to reconstruct a geometric section of elements damaged by reinforcement corrosion. When using this type of intervention, it is common to verify the corrosion’s onset at a site adjacent to the repaired site which was intact up to then. This mechanism is known as macrocell corrosion and it results, among others, from the electrochemical incompatibility of the repair material with the original concrete. The present work discusses the electrochemical theory of macrocell corrosion of carbon steel bars at the interface of patch repairs and carbonated concrete and proposes a methodology and a criterion to prevent this mechanism in structures undergoing recovery, based on experimental results from the main author’s thesis. Such criterion permits selecting the repair mortar that presents the least electrochemical incompatibility with the substrate of a structure suffering reinforcement corrosion induced by carbonation.

► Patch repairs in carbonated reinforced concrete were studied.
► Seven industrialized and six laboratory-made repair mortars were studied.
► A rise in potential difference will increase macrocell corrosion.
► A criterion is proposed for predicting electrochemical incompatibility.
► A repair mortar selection guide is presented as appendix.