Corrosion performance of steel reinforcement in concrete admixed with magnesium chloride and sulphate

Abstract

Purpose Besides with a large amount of Na + and Cl − ions in seawater, the presence of Mg +2 and SO 4 −2 ions builds more complex corrosion mechanism. This paper aims to investigate the corrosion of embedded reinforcement in concrete with the environment of both Cl − and SO 4 −2 anions associated Mg +2 cation. Design/methodology/approach The concrete specimens were prepared by using ordinary Portland cement (OPC), and OPC blended with metakaolin (MK) for water to cementitious material ratio (w/cm) 0.48 and 0.51. The concrete mixes were contaminated with the addition of MgCl 2 alone and combined MgCl 2 and MgSO 4 in mix water. Reinforcement corrosion was evaluated by half-cell potential and corrosion current densities (I corr ) at regular intervals. Moreover, the influence of cementitious material type, salt type and w/cm ratio on electrical resistivity of concrete was also investigated. The statistical models were developed for electrical resistivity as a function of calcium to aluminium content ratio, compressive strength, w/cm ratio and age of concrete. Findings Although the corrosion initiation time increases in the concomitant presence of MgSO 4 and MgCl 2 as internal source compared to MgCl 2 , I corr values are higher in both OPC and MK blended concrete. However, electrical resistivity decreased with addition of MgSO 4 . MK blended concrete performed better with increased resistivity, corrosion initiation time and decreased I corr values. Originality/value This study reports statistical distributions for scattered I corr of rebar in different concrete mixtures. Stepwise regression models were developed for resistivity by considering the interactions among different variables, which would help to estimate the resistivity through basic information.