CORROSION CURRENT DENSITY OF MACROCELL OF HORIZONTAL STEEL BARS IN REINFORCED CONCRETE COLUMN SPECIMEN

Abstract

Chloride-induced corrosion of steel bar in concrete is one of the main problems affecting the
durability of reinforced concrete (RC) structures. Expansive products are formed due to corrosion at the
interface between concrete and steel bar. In this study, the differences in the magnitude of the macrocell
corrosion current density in RC column specimens cast using copper slag fine aggregate and fly ash
replacement were examined. This study aimed at investigating corrosion formation with respect to macrocell
corrosion current density. The experimental study was carried out through dry and wet (NaCl 10%) cycles for
specimens with different cover depths, which was investigated by electrochemical measurements. The result
shows that the largest macrocell corrosion current density was measured in the steel bars located at the upper
part of reinforced column specimens for each case of the specimens with a cover depth of 30 mm. This could
be partly attributed to the loss of the integrity of the steel and concrete interface which is examined based on
the oxygen permeability in the upper and lower sides of segmented steel bars. The variation of oxygen
permeability contributes to the macrocell corrosion formation especially in the steel bars affected by bleeding
water. Besides the integrity between steel bars and concrete cover, the quality of concrete cover and
variations in chloride ion concentrations are significant factors contributing to the macrocell corrosion
formation.