Effects of supplementary cementitious materials on concrete reinforcement corrosion in magnesium sulphate

In this study, electrochemistry and weight loss techniques were used to investigate the effect of supplementary cementitious materials (SCMs) on corrosion behaviour of concrete reinforcement immersed in magnesium sulphate solution. The blend of three different SCMs (fly ash (FA), silica fume (SF) and ground granulated blast furnace slag (GGBS)) were used; The change in the surface morphologies of the corroded reinforced samples was physically observed. The electrode potentials of the samples studied increased from more negative potentials to less negative potentials with the highest of −1029.6 mV recorded for blended SCMs sample and −1030 mV recorded for control sample. Although, electrochemical noise behaviour was exhibited by all the samples throughout the exposure period. Lowest corrosion rate of 0.018 mmpv was observed with 30% SF while the control sample has 0.072 mmpv corrosion rate. Physical observation showed that about 25 to 60 mm from the interface between the concrete and the reinforcement to the top of the reinforcement corroded. The results obtained from the weight loss analyses showed that steel reinforcements in concrete samples containing GGBS, SF, and FA generally exhibited corrosion resistance in sulphate solution. However, increase in FA and GGBS contents in concrete resulted in decreasing corrosion resistance of steel reinforced concrete samples.