Influence of CaCl2 and NaCl from different sources on chloride threshold value for the corrosion of steel reinforcement in concrete

The influence of CaCl2 and NaCl from internal and external sources on the chloride threshold value for the corrosion of steel reinforcement in concrete has been investigated. The onset of active corrosion for the steel reinforcement has been detected by half-cell potential and linear polarization methods. Also, the threshold value with different indices, such as free chlorides, [Cl−]/[OH−], total chlorides and [Cl−]/[H+] has been measured. It has been found that the chloride threshold values for the corrosion of the specimens with CaCl2 and NaCl from different sources depend on the indices. Especially, the critical [Cl−]/[H+], i.e. the ratio of acid soluble chlorides to acid neutralisation capacity irrespective of the type and different sources of chloride salt approximately keeps constant at 0.02.