The effect of carbonate and sulfate ions on chloride threshold level of reinforcement corrosion in mortar with/without fly ash

• The coupling effect of carbonate and chloride ions on reinforcing corrosion in mortar has been studied.
• The effect of sulfate ions on chloride threshold level of reinforcing corrosion in mortar has been researched.
• The effect of carbonate or sulfate ions on chloride binding capacity has been studied.

The aim of the study is to evaluate the effect of carbonate and sulfate ions on chloride threshold level of reinforcement corrosion in mortar with/without fly ash. The initiation of active corrosion for the reinforcement was detected by half-cell potential and electrochemical impedance spectra methods. The free chloride or total chloride by mass of binder was used to express the chloride threshold level. The results indicate that the presence of carbonate ions in the chloride solution shortened the time to initiation of reinforcement corrosion and decreased chloride threshold level in both the Portland cement mortar and fly ash mortar specimens. And compared with the single chloride solution, the concomitant presence of chloride ions and sulfate ions decreased the chloride threshold level, but did not influence the time to initiation of chloride-induced reinforcement corrosion. Besides, although the presence of fly ash decreased the chloride threshold level, it delayed the time to initiation of reinforcement corrosion.