Corrosion of Steel Bars in Concrete with the Variation of Microstructure of Steel-Concrete Interface

An experimental investigation was carried out on chloride induced corrosion of steel bars in concrete under marine environment with the variation of micro-structure of steel-concrete interface. To create the variation of micro-structure of steel-concrete interface, steel bars coated with cement paste of different W/Cs and cement types were used. For investigation, cylindrical concrete specimens were made with steel bars (with and without cement paste coating). W/C ratios of cement paste coat were 0.3, 0.5, 0.7 and 1.0. The specimens were exposed to an accelerated seawater exposure controlled with automatic wetting and drying. The specimens were tested till 45 cycles in the exposure. Test items include compressive strength of concrete, chloride ingress into concrete, electrochemical evaluation of corrosion, microscopic investigations of steel-concrete interface by optical microscope, scanning electron microscope (SEM), and linear traverse. It is revealed that the initiation of corrosion is significantly influenced by the nature of micro-structure of the steel-concrete interface, such as size of voids at the steel-concrete interface.