Effect of organic corrosion inhibitors on the behaviour of repair mortars and reinforcement corrosion

Repairing concrete structures affected by reinforcement corrosion is vital to ensure their durability and safety.
Organic corrosion inhibitors (OCIs) are widely used in the construction industry to prevent steel corrosion due to
their effectiveness, sustainability, and health and safety benefits. However, the effects of these OCIs on different
types of repair mortars have not been extensively studied. This study evaluated the fresh and hardened prop
erties, as well as the corrosion resistance, of four types of repair mortars (polymer-modified, general cementi
tious, fine-grained, and alkali-activated) incorporated with two types of OCIs (amino alcohols and sodium
gluconate-based) at dosages of 0.5 %, 1 %, and 2 %. Additionally, the corrosion kinetics of mortars under the
influence of OCIs were analysed using the impressed current technique. The results indicated that OCIs generally
enhanced workability and increased void content across all repair mortars. The amino alcohol inhibitor increased
the drying shrinkage of general cementitious and fine-grained mortars by up to 33 % and 39 %, respectively, and
reduced compressive strengths by 47 % and 26 %. However, it did not significantly affect water absorption. In
contrast, the sodium gluconate inhibitor increased water absorption in all repair mortars but notably decreased
drying shrinkage by up to 47 % in polymer-modified mortar and 66 % in alkali-activated mortar. Despite the
variations in the properties of repair mortars, OCIs effectively resisted corrosion and delayed crack formation
time by up to 400 %. The resistance to corrosion improved with increasing amounts of the inhibitor. The results
of this study were used to develop a technical guide for the construction industry, facilitating the selection of
appropriate mortar compositions to effectively repair corroded concrete structures and reduce the risk of further
corrosion.