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This paper assessed the electromigration behavior of ethanolamine and its efficiency as a corrosion inhibitor of rebar during the realkalization. Cylindrical concrete specimen (diameter 45 mm, height 20 mm) with steel rebar (6 mm in diameter, 35 mm in length) were artificially carbonated and corroded in an accelerated manner with impressed anodic current. The specimens were realkalized in the electrolyte solution containing ethanolamine, while the steel rebars were connected to the cathodic current (200 mA·h, 1 A/m2). After 25 days of monitoring the repair process, experimental data revealed notable changes in electrochemical parameters. The corrosion potential increased from −627 mV to −236 mV, signifying a reduction in corrosion activity. The cathodic exchange current density decreased from 4.9 μA/cm2 to 2.3 μA/cm2, showing a decrease in the corrosion rate. Also, the pH value of the solution dropped to a comparatively lower level, the ethanolamine and potassium ion concentrations decreased from 22 to 30.54 g/L to 3.22 and 10.23 g/L, respectively. Moreover, nitrogen detection on the steel surface and varied levels of ethanolamine concentration at different depths in the concrete were also measured, both indicating a clear migration of inhibitor to the steel surface to form a passive film.

The durability of concrete is determined by its pore structure and permeability. The present work examines the effect of pore structure and porosity on the permeability of concrete after nearly a century natural carbonation. The samples were cored from a concrete building built in 1931. X-ray diffraction analysis, phenolphthalein dye test, Mercury Intrusion Porosimetry (MIP) were conducted to ascertain the composition, the carbonation depth, the permeability, the porosity and pore size distribution of samples. The experimental results revealed that the front of core samples was completely carbonated. The fractal dimension was calculated using the Mandelbrot model to characterize the pore structure. The combined harmless and less harmless pore proportions exhibited a linear correlation with the fractal dimension. A relationship between permeability and fractal dimension is established. The increase in the fractal dimension resulted in a gradual decrease in the oxygen diffusion coefficient. The diffusion coefficient tends to plateau when the fractal dimension exceeds a critical value of the combined pore proportion. While the pore proportion of concrete was higher than 14.64%, there was no significant effect on the permeability. The results of this study can serve for future assessments of concrete durability.

This paper reports the corrosion inhibition effect of the realkalization and corrosion inhibitors combination treatment on steel rebars. First, the corrosion was studied in simulated carbonated concrete and simulated realkalized concrete environments and then compared with the corrosion, while realkalization-corrosion inhibitor treatment was applied. The corrosion inhibitors studied are monoethanolamine (MEA), dimethylethanolamine (DEMA) and triethylenetetramine (TETA). Through the electrochemical measurement; the potential of steel rebars in realkalized environment containing MEA and DMEA shifted in positive direction by 84 mV and 66 mV; the current destiny of each group decreased by 3.76 and 2.33 μA/cm2, respectively. Unlike the addition of TETA shifted the potential in negative direction by 281 mV and increased the current density by 27.72 μA/cm2. Comparing steel rebars surfaces, the realkalization-corrosion inhibitors groups showed a better inhibition effect than the two control groups (simulated carbonated concrete and simulated realkalized environments). Among the corrosion inhibitors used, MEA has the best corrosion inhibition effect in the electrochemical realkalized concrete environment, it can form a protective film on the steel rebars through physical and chemical adsorption, which can effectively inhibit the corrosion of steel rebars. The result confirms that, by the combination of MEA and electrochemical realkalization, the corrosion inhibition in carbonated reinforced concrete can improve significantly.