Corrosion of steel rebar embedded in natural pozzolan based mortars exposed to chlorides

Corrosion of steel is considered the most important durability problem of reinforced concrete. The application of supplementary cementitious materials has been proposed in order to mitigate this durability problem, reduce the production costs and control the emission of greenhouse gases. Mexico is rich in volcanic areas from which natural pozzolanic materials can be obtained. This paper examines the use of such natural pozzolans as a partial substitute of normal portland cement in reinforced mortar specimens. Compositions with substitution levels of 0%, 10% and 20% by mass of normal Portland cement of natural pozzolanas were investigated. The specimens were exposed to penetration of chlorides. Compressive strength, corrosion potential, polarization resistance, electrical resistivity, and chloride content of the mortars were determined in order to characterize the physical, mechanical, electrical, and electrochemical behavior of the mortar as well as the embedded steel. It was found that the use of pozzolan has resulted in a significant increase in mortar resistivity and corrosion initiation time for the same cover depth, and as a result, decreases the rate of corrosion of rebars once corrosion was initiated.