Chloride-induced corrosion of steel bars in concrete with presence of gap at steel-concrete interface

Corrosion of steel bars in concrete with the presence of gaps/voids at the steel-concrete interface is summarized herein based on the accelerated laboratory and several long-term exposure tests. For this, reinforced concrete specimens with a length of 12 cm, width of 23 cm, and height of 28 cm were made. Specially fabricated steel bars were embedded in the specimens to measure the macrocell and microcell corrosion. The specimens were exposed to an artificially created chloride-induced corrosion environment. Furthermore, corrosion of steel bars of 23-year, 10-year, and 16-month-old reinforced concrete specimens was also reported to verify the results obtained in the accelerated laboratory investigations. Generally, the presence of gaps/voids at the steel-concrete interface causes the complete loss of passivity with the presence of chloride. The regions with the gap become anodic locally. The degree of micro-cell corrosion is also higher at these regions. This phenomenon is very clear at the bottom half of the steel bars oriented perpendicular to the casting direction of concrete. It could not, however, be neglected for the steel bars oriented along the casting direction of concrete due to the poor compaction. From this study, the significance of making concrete without interfacial gaps/voids at the steel-concrete interface is clearly understood, which is necessary to ensure long-term durability of concrete structures.