Durability assessment of LC3-based reinforced concrete under combined chloride-sulfate environment via the EIS technique

Concrete technology has significantly advanced towards alternative sustainable and eco-friendly cement-based materials. Accordingly, the durability of real-life blended concrete under realistic exposure aggressive conditions needs to be explored in depth. This study evaluates the effect of local raw clay on the durability performance of underground reinforced concrete in a simulated real-life aggressive environment with combined chloride-sulfate attack. Blended limestone cement (LC) containing calcined clay (LC3) or fly ash (LCF) with 40% replacement by cement mass, were prepared concurrently to compare the results with the traditional OPC. Assessment of durability performance of reinforced blended concrete was performed using non-destructive electrochemical impedance spectroscopy technique (EIS), and compressive strength. Characterization and elaboration of electrochemical phases were monitored by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), and SEM/EDS analysis. Electrochemical measurements showed that the diameter of the impedance semi-circle in both high and low-frequency regions of LC3-based reinforced concrete increases as corrosion progresses, while that of LCF and OPC decreases. LC3 showed the best corrosion resistance marked by a lower corrosion rate and comparable strength. Furthermore, LC3 binder exhibited a good hydration degree, with higher CH and Friedel's salt content. Ultimately, the LC3 technology improves the durability performance of reinforced concrete structures in simulated real-life conditions which could advance its application on the industrial scale.