Influence of corrosion inhibitors on two different concrete systems under combined chloride and carbonated environment

Abstract

This paper presents the performance of three generic compounds, 4-Aminobenzoic acid (ABA), 2-Aminopyridine (AP) and Salicyaldehyde (SA) as migratory inhibitor on hardened concrete surface to curb corrosion due to combined chloride and carbonated environment. Two types of cement viz. portland cement and fly ash blended cement were used to prepare concrete mixes. Electrochemical techniques (LPR and EIS), gravimetric analysis were applied to evaluate the corrosion performance. Percolation ability of the inhibitors was assessed by UV–visible spectroscopy. Also, chloride profile and carbonation depth was analyzed after definite durations of exposure to identify the dominant cause of corrosion and effect of inhibitor application on these two parameters. Electrochemical and gravimetric results conclude that steel in blended cement is more vulnerable to corrosion as compared to portland cement. Obtained carbonation depth and chloride profile revealed carbonation had significant impact on the corrosion during combined exposure. Degradation of reinforced concrete due to corrosion occurs in two phases in combined environment. In the first phase, chloride ions initiate the corrosion process causing pitting corrosion and carbonation dominates this process during the second phase by aggravating the corrosion mechanism. Application of CoI reduces the corrosion rate effectively, where ABA displayed highest inhibition efficiency of 79.64% in portland cement and 88.31% in blended cement concrete, followed by AP and SA. The inhibition order followed the order of its concentration at rebar level showing direct relation between the two parameters. Optical examination of exposed concrete surface and extracted rebar’s surface validated the inhibition effect of the inhibitors. Reduction in the crack width was noticed on the concrete surface with inhibitor application. Blended cement concrete system which was observed to be more vulnerable to corrosion before the application of inhibitors was seen to attain similar corrosion resistance as portland cement concrete after inhibitor application.