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 concret e to reduce the risk of corrosion of Embedded steel due to chemical action. In the late 1970s, numerous studies were conducted to evaluate the corrosi on-inhibiting properties of calcium nitrite. The mechanism of corrosion pro tection has been reported to be anodic inhibition. One of the calcium nitri te-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, t he rapid hydration of cement may cause larger crystals to be developed. Thi s tends to increase the concrete permeability, especially at early ages. Four different concrete mixtures, with and without DCI, were evaluated usin g the rapid chloride permability test after 33 days and 5 months of curing. The complex dielectric constant of these mixtures was also measured after 30 days of curing. The dielectric constant was measured using a parallel pl ate capacitor, operating at the frequency range of 0.1 to 40.1 MHz. The tes ted concrete mixtures are used to produce hollow precast concrete piles, an d have a very low water-cement ratio (w/c), The mixtures were also rapid-cu red in a steam room at 70 C for 4 h. It was found that mixtures with DCI ha ve higher chloride permeability values than the mixtures without DCI. It wa s also found that the DCI mixtures have higher complex dielectric constants , especially the loss part. A leash significant difference (LTD) statistica l analysis was performed on the chloride permeability values and on the com plex dielectric constant results. Significant differences between 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 chlorid e permeability test.