The electrochemical assessment of corrosion inhibition effect of calcium nitrite in blended concretes

This study examined the corrosion inhibition effect of a calcium nitrite-based corrosion inhibitor (CN) by assessing an electrochemical way together with a strength development of concrete containing CN. As binders, ordinary Portland cement (OPC) alone, a mixture of OPC with replacement of pulverised fuel ash at 30% (30% PFA), and a mixture of OPC with ground granulated blast furnace slag at 65% (65% GGBS), respectively were used for testing of the strength development, rate of chloride transport and corrosion behaviour. As a result, CN was significantly effective in increasing the resistance to corrosion risk and thus an enhancement of chloride threshold level for corrosion was achieved with no detrimental effect of CN on the compressive strength of blended concrete. For transport properties of chloride ions, PFA and GGBS were effective in lowering chloride ionic diffusion through concretes, but an increase in the content of CN in concretes resulted in an increase in the diffusivity of chloride ions. Then, the corrosion-free life of concretes exposed to a salt solution was varied with the content of CN and binder type. For OPC concretes, an increase in the CN content resulted in an increase in the time to corrosion, due to increased threshold value, while the time to corrosion for 30% PFA and 65% GGBS concretes was less dependent on the content of CN. It is due to the fact that the beneficial effect of CN in inhibiting corrosion could be offset by the increased rate of chloride transport in concretes containing pozzolanic materials.