Corrosion Behavior of Cement–Fly-Ash–Slag Ternary Mortars in CO2-Rich Water Containing Chloride Ions

This study investigated the corrosion behavior of cement–fly-ash–slag ternary mortars in CO2-rich water containing chloride ions and the impact of CO2-rich water corrosion on the redistribution of chloride ions in the mortars. Research results indicated that the pozzolanic reaction of slag significantly reduced compressive strength loss and the corrosion depth. The fly ash, in contrast, with inadequate activity, thereby failed to effectively enhance the mortar’s resistance against CO2-rich water corrosion. Additionally, CO2-rich water corrosion promoted the decomposition of Friedel’s salt, reducing the chloride ion binding capacity of the mortars. The precipitation and dissolution of calcium carbonate initially decreased and then increased the diffusion rate of free chloride ions. The interaction effect between CO2-rich water corrosion and chloride ion penetration is demonstrated by chloride ion diffusion, low-field nuclear magnetic resonance (NMR), and mineral composition analysis.