Effect of corrosion inhibitor on service life of cracked and non-cracked concrete

Abstract

Corrosion of steel in reinforced concrete structures can cause damage and costs involved and attracts researchers to look for solutions that delay the onset of corrosion initiation or slow its development. The effectiveness of four corrosion inhibitors in cracked and non-cracked sections of reinforced concrete was studied: Migrating Corrosion Inhibitor (MCI-2005) based on amine carboxylate; CNCI 1.37 based on calcium nitrite Ca (NO)2 at a concentration of at least 30%; and two lab-made green corrosion inhibitors based on recycled materials – fluorosilicates obtained from fluorosilicic acid (H2SiF6), the by-product of the phosphate industry, and from LABS (Linear Alkyle Benzene Sulphonate), the by-product of the detergent industry. The study followed the guidelines of the ASTM G-109 standard which examines materials intended to inhibit chloride-induced corrosion of steel in concrete, and the ASTM C-876 standard which evaluates the electrical corrosion potential of uncoated reinforcing steel, for the purpose of determining the corrosion activity of the reinforcing steel. Controlled artificial cracks of different depth were created to speed up the corrosion process in the steel. Such cracks allowed a direct penetration of chlorides into the depth of concrete. As was expected, the cracked concrete samples exhibited a significantly higher level of corrosion than the non-cracked samples. In the non-cracked samples, the effectiveness of the CNCI 1.37 commercial corrosion inhibitor was the highest. However, in the cracked samples it appears that its efficiency has decreased, while the recycled corrosion inhibitor based on K2SiF6 has shown the best performance. This result can be explained by the fact that fluorosilicate reacts with calcium hydroxide present in concrete and creates a non-permeable protective layer that inhibits the movement of chlorides to the steel bar.