Effect of activator types and concentration of CO2 on the steel corrosion in the carbonated alkali-activated slag concrete

• Published in: Construction & building materials 2020-11, Vol.262, p.120044, Article 120044
• Main Authors: Zhao, Kai, Liang, Yongning, Ji, Tao, Lu, Yue, Lin, Xujian
• Format: Article
• Language: English
• Subjects: Alkali-activated slag concrete; Carbonation; Corrosion resistance; Passive film; Pore structure
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2020.120044

•The steel rebars embedded in AASC show a thicker passive film with higher Fe2+/Fe3+ compared to OPCC.•Carbonation resistance and corrosion resistance of OPCC are higher dramatically than that of AASC.•Higher concentration of CO2 accelerates the corrosion rate of steel rebars embedded in AASC. Research on durability of alkali-activated slag concrete (AASC) has received great attention but there are considerably few studies on the effect of carbonation on steel corrosion. In this paper, effects of activator types (waterglass and sodium hydroxide) and exposed concentrations of CO2 (0.03%, 3% and 20% by volume) on steel corrosion have been investigated, in both AASC and ordinary Portland cement concrete (OPCC). The latter was used as the control group for comparative purposes. X-ray photoelectron spectroscopy (XPS) was used to confirm the composition of passive film of AASC and OPCC. Pore structure of specimens before and after carbonation were measured with mercury intrusion porosimetry (MIP). The corrosion state of steel rebars were monitored by open circuit potential (OCP), potentiodynamic polarization (PP), and electrochemical impedance spectroscopy (EIS). The results illustrate that AASC shows a thicker passive film with higher Fe2+/Fe3+ compared to OPCC. These two activators have similar effects on steel corrosion under the accelerated CO2 environment, showing the similar degrees of corrosion after 140 days of accelerated carbonation. This may be attributed to the same carbonation resistance of the AASC with two different activators. In addition, AASC shows worse corrosion resistance in comparison with OPCC. Higher concentrations of CO2 could accelerate the corrosion rate of steel rebars embedded in AASC.