Effect of chloride ion, sulfate ion and conjoint chloride-sulfate ions on corrosion behaviour of steel reinforcement and performance of concrete

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Reinforced concrete structures are affected by various durability problems during their service life. Deterioration due to corrosion of steel reinforcement and degradation of concrete due to sulfate attack are the most significant durability problems encountered in reinforced concrete structures and have major financial implications around the world. Concrete durability problems are the major cause of concern all over the world especially in the coastal areas where the structures are subjected to both chloride induced reinforcement corrosion and sulfate attack, and mechanism of deterioration may become more complex because of ingress of both chloride and sulfate ions. Chloride and sulfate ions can either be present in the concrete ingredients (internal) and/or penetrate into the hardened concrete from outside environment (external). The corrosion behaviour of steel reinforcement and the performance of concrete may vary significantly in the conjoint presence of chloride-sulfate ions as compared to that in the presence of only chloride and sulfate ions. In this research work, a comprehensive experimental investigation has been carried out to study the effect of conjoint presence of chloride ions and sulfate ions along with the associated cation type on corrosion behaviour of steel reinforcement in electrolytic concrete powder solution (ECPS) and in concrete by incorporating different types of binder, steel reinforcement and water-binder (w/b) ratio. In addition, to analyze the effect of chemical composition of the electrolytic concrete powder solution on corrosion behaviour of steel reinforcement, the ionic concentration, pH and conductivity of the concrete powder solutions were determined. Further, the performance of concrete by incorporating different types of binder and w/b ratio under different exposure conditions in sulfate and conjoint chloride-sulfate environment was assessed. To evaluate the changes in phase composition of hardened concrete in the presence of chloride and sulfate ions, various microstructural techniques such as X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopy analyses were also carried out.
Supervisor: Bulu Pradhan