Impact of induced rapid surface carbonation (IRS-C) treatment on the steel corrosion in reinforced concrete: a counterintuitive effect

Corrosion of steel reinforcement in concrete is one of the main issues plaguing aging infrastructure worldwide. While concrete’s carbonation is usually associated with an increased risk of corrosion, this study proposes a counterintuitive method that uses carbonation of hardened elements to reduce corrosion risk: the induced rapid surface carbonation (IRS-C) treatment. Besides, this study analyzes the impact of IRS-C on the corrosion resistance of precast reinforced concrete elements and explains the mechanisms behind it. The IRS-C treatment consists of placing the hardened samples in a vacuum chamber, filling it with CO ₂ after removing the air, and leaving them for 48 hours, which induces rapid carbonation of the samples' outer surfaces. 12 concrete beams, 8 with and 4 without reinforcement, and 12 cylinders were used. Half of the samples were treated with IRS-C, while the remaining served as a reference. ASTM G109 results showed that the IRS-C treated samples had lower total corrosion than the untreated samples. The phenolphthalein test confirmed that the treatment did not affect pH near the reinforcement and therefore did not lower the chloride threshold for corrosion. Furthermore, water absorption and titration tests confirmed that IRS-C formed a low-porosity surface layer that reduced water and chloride penetration. Thus, the IRS-C treatment is a promising method to improve the corrosion resistance of precast reinforced concrete elements.