EVALUATION OF CORROSION IN REINFORCED CONCRETE STRUCTURES USING HALF CELL POTENTIAL FOR VARIOUS EXPOSURES

Abstract

Reinforced Cement Concrete (RCC) structures are most widely used in infrastructure development across the globe. One of the main causes of deterioration is Corrosion of the Reinforcement in Concrete Structures. Thus, it becomes necessary to access the probability and severity of corrosion in structures so that it can be addressed before ultimate state is achieved. Half Cell Potential (HCP) Test is most widely used nondestructive technique used in Reinforced Concrete Structures for predicting the possibility of corrosion of steel bars. The limits of Half-cell values are prescribed by standards ASTM C876-22b and IS 516-part 5 section 2 for corrosion probability, but the exposure in which these limits hold true have not been described clearly. Also, during field investigations, it has been observed that these criteria are not followed. Thus, there is a need for further investigations in this area and to establish Half Cell Potential values for predicting corrosion under different exposure conditions. A statistical approach is therefore applied to establish the HCP criteria for corrosion evaluation for various structures in different exposure conditions. The HCP data was taken from various structures located across India where corrosion of steel occurred because of either carbonation or the combined effect of chloride and carbonation. The statistical approach used here takes advantage of the fact that the mean HCP of corroding and non-corroding bars differ significantly being more negative for corroding bars. The assumption made here in this approach is that the HCP data for corroding and non-corroding follows different normal distribution curves. An experimental initiative was devised to ascertain the thresholds of Half-Cell Potentials (HCP) in instances where corrosion is induced by cast in chlorides. The HCPs of the samples were consistently monitored, and visual inspections were conducted to detect corrosion. However, the planned experimental determination of the mean and standard deviation for corroded and non-corroded Reinforced Concrete (RCC) elements exposed to cast-in chlorides could not be carried out due to the absence of corrosion till writing of this thesis.