Effects of CO ₂ and chloride ion interaction on the durability of one-part nickel slag geopolymer

To investigate the interaction between carbonation and chloride ions on the durability of single-phase nickel slag geopolymer mortar, three experimental conditions were designed: (A) chloride ion penetration followed by carbonation, (B) carbonation followed by chloride ion penetration, and (C) carbonation, chloride ion penetration, and wet-dry cycles. Macro-performance was assessed through compressive strength, pH values, and chloride ion concentration, while microstructural mechanisms were analyzed using XRD, TG-DTG, and SEM. Results showed that chloride crystallization delayed carbonation, while carbonation products enhanced resistance to chloride penetration. The synergy of carbonation and wet-dry cycles accelerated chloride transport, thickening the surface convection zone. XRD and TG-DTG analyses confirmed the formation of hydrotalcite-like phases due to the high MgO content in nickel slag. No Friedel’s salt was detected, suggesting chloride ions were captured mainly through physical adsorption of the amorphous gel phase.HighlightsCarbonation was delayed by chloride crystallization, while chloride resistance was enhanced by pre-carbonation.Chloride transport was accelerated by the synergy between carbonation and cyclic wet-dry exposure.Hydrotalcite-like phases were identified, while chloride was primarily through physical adsorption.