Effects of nitrite-based corrosion inhibitor on concrete's rapid chloride permeability values and its dielectric properties

Nitrite-based corrosion inhibitors are currently used in reinforced concrete to reduce the risk of corrosion of embedded steel due to chemical action. In the late 1970s, numerous studies were conducted to evaluate the corrosion-inhibiting properties of calcium nitrite. The mechanism of corrosion protection has been reported to be adic inhibition. One of the calcium nitrite-based corrosion inhibitors, DCI, was marketed in 1979. It is used mainly in concrete exposed to seawater or in bridge decks where deicing salts are applied. Because calcium nitrite acts as a concrete accelerator, however, the rapid hydration of cement may cause larger crystals to be developed. This tends to increase the concrete permeability, especially at early ages. Four different concrete mixtures, with and without DCI, were evaluated using the rapid chloride permeability test after 33 days and 5 months of curing. Tlie complex dielectric constant of these mixtures was also measured after 30 days of curing. TJie dielectric constant was measured using a parallel plate capacitor, operating at the frequency range of 0.1 to 40.1 MHz. The tested concrete mixtures are used to produce hollow precast concrete piles, and have a very low water-cement ratio (We/ The mixtures were also rapidcured in a steam room at 70 Cfor 4 h. It was found that mixtures with DCI have higher chloride permeability values than the mixtures without DCI. It was also found that the DCI mixtures have higher complex dielectric constants, especially the loss part. A least significant difference (LSD) statistical analysis was performed on the chloride permeability values and on the complex dielectric constant results. Significant differences bet\veen the means were obtained in each test method. This suggests that measuring the complex dielectric constant at low radio frequency could be related to the chloride permeability test.