Corrosion Behavior of Steel Embedded in Ternary Concrete Mixtures

Abstract

The main reason for the premature failure of reinforced concrete structures is corrosion of the reinforcements. The use of new mortars based on ternary mixtures, an alternative to ordinary Portland cement (OPC), requires extensive research in order to check its passivating properties for reinforcements and the instability or permanence of the passive state achieved. Pozzolans and slag extend the market for concrete by improving specific properties of concrete products, allowing them to be constructed with other materials or placed in environments that would have precluded the use of Portland cement alone. In properly formulated concrete mixtures, pozzolans and slag have been shown to enhance long-term strength, decrease permeability, increase durability, and reduce thermal cracking of bulk concrete. Steel reinforcements have been exposed for 13 months in mortars immersed in a 3.5% NaCl solution. The effect of mortar composition using ternary mixtures of fly-ash (FA), micro-silica (MS), and granulated blast furnace slag (GBFS) was tested. OPC was also tested as a reference. Electrochemical characterization was performed, measuring corrosion potential, linear polarization resistance, and electrochemical noise resistance. The best passivating properties were shown by the mixture of 10% FA and 10% GBFS.