Corrosion Performance of Steel Reinforcement in Self-Compacting Concrete Exposed to Combined Sodium Chloride-Magnesium Sulfate Exposure Solution

Abstract

This study investigates the effect of binder type, w/b ratio, and exposure solution on the corrosion performance of steel reinforcement in self-compacting concrete (SCC). Prismatic specimens made from SCC were subjected to combined chloride-sulfate exposure solutions and chloride solution for an exposure duration of 690 days. Variations in total and free chloride concentrations and changes in the microstructure of concrete in the vicinity of steel reinforcement in SCC mixes were examined through X-ray diffraction and field emission scanning electron microscope coupled with energy dispersive X-ray analyses. Results showed that OPC (ordinary Portland cement)-based SCC mixes exhibited lower corrosion current density than PPC (Portland pozzolana cement)- and OFA20 (OPC+20% fly ash)-based SCC mixes during the early exposure period with opposite variation observed during a later exposure period. Corrosion current density in SCC mixes exposed to NaCl+MgSO4 solutions correspond to negligible to low corrosion levels, which may be due to the pore filling effect of magnesium hydroxide and ettringite formed in SCC mixes exposed to NaCl+MgSO4 solutions that decreased the penetration of chloride ions to the rebar level. Further, the rate of chloride-induced reinforcement corrosion in the SCC specimens exposed to NaCl solution was more than that in the SCC specimens exposed to NaCl+MgSO4 solution for all the binders.