Studies on the aspects of chloride ion determination in different types of concrete under macro-cell corrosion conditions

In the present investigation various extraction methods have been carried out for the estimation of free chloride and total chloride contents in different types of concretes, namely ordinary Portland cement (OPC), Pozzolana Portland cement (PPC) and Portland slag cement (PSC). Macro-cell concrete specimens were cast and subjected to severe alternate wetting and drying cycles of 10-months exposure. Concrete core samples were collected from the above specimens under different depths, namely 20, 40 and 60 mm. Six extraction methods for determination of free chloride and two extraction methods for determination of total chlorides in concrete have been carried out. Boiling water method was found to be a suitable for the determination of free chloride contents in concrete. As the depth increases the amount of chloride ion decreases. Filtration method is found to be not suitable for the determination of chloride ion in concrete. There is no quick method for determining the chloride concentration in concrete either in the field or in laboratory. Water-soluble chloride alone is a good indicator of the concentration of chloride ion in concrete. ISE method appears to be most convenient but it requires lot of calibration before analysis.