Chloride-induced corrosion of steel reinforcement in mortars manufactured with alternative environmentally-friendly binders

Abstract

There is increasing interest in exploring the durability of structures manufactured with cements that are more environmentally friendly than traditional Portland. Accordingly, protection against chloride-induced corrosion of carbon steel reinforcement in mortars manufactured with environmentally friendly hybrid cements and alkali-activated materials (AAM) needs to be analyzed in-depth. Hybrid cements are innovative alternative binders with reduced amount of clinker in their formulation (20-30%). Their precursors are aluminosilicate wastes and they are very feasible in-construction implantation because they are not activated neither with liquid solutions of strong alkalinity nor external heating. In this research, AAM mortars were manufactured using slag from industrial by-products activated with sodium silicate. Hybrid mortars were manufactured either from fly ash or from slag, and activated with Na2SO4. Portland cement (CEM IV) mortars were also included in this study as reference. Chlorides were made to penetrate into the four different mortars under study by diffusion. The porosity and chloride penetration were evaluated and related to the different materials. The electrochemical behavior of the steel reinforced mortar specimens was monitored by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements. The corrosion rate values obtained for steel embedded in AAM were similar to conventional CEM IV mortars, and the morphology of the attack is less localized.