Assessing the effect of sodium nitrite as corrosion inhibitor against the corrosion of steel rebar in alkali-activated concrete

Abstract

The aim of this study is to investigate the effectiveness of corrosion inhibitor against chloride-induced corrosion of steel rebar in fly-ash (FA) and GGBS (ground granulated blast furnace slag) and Nanofine-based alkali-activated concrete. The Alkali-Activated Concrete (AAC) was prepared from FA, ground granulated blast furnace slag (GGBS), and Nanofine with Sodium hydroxide (NaOH) and Sodium Silicate (Na2SiO3) solutions. The concentration of NaOH varies to 10 M, 12 M, and 14 M, and all the specimens were subjected to accelerated corrosion, to perform the non-destructive test after the corrosion of the steel rebars. Fourier Transform Infrared (FTIR), scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) were used to examine the microstructure of AAC in the presence of Nano-Fine GGBS (NF), Sodium Chloride (NaCl), and NaNO2 and to compare the strength and corrosion properties with AAC and OPC. The ratio of sodium silicate to sodium hydroxide was taken as 2.5 and the solution-to-binder ratio was taken as 0.5. The compressive strength and ultrasonic pulse velocity (UPV) test of the Nano-fine based alkali-activated concrete increases as compared to the control concrete. The increase in the dosages of corrosion inhibitor and nano-fine increases the compressive strength of the control concrete and alkali-activated concrete. The half-cell potential of the control concrete and nano fine admixed with alkali-activated concrete mixes with different molarities is uncertain. The increases in the dosages of corrosion inhibitors reduce the occurrence of corrosion in the steel reinforcement rebars.