Chloride binding behaviors of metakaolin-lime hydrated blends: Influence of gypsum and atmospheric carbonation

•Gypsum addition promotes the formation of monosulfoaluminate and ettringite is favored in an even higher gypsum addition.•Carboaluminate and monosulfoaluminate can transform to Friedel’s salt in a chloride-rich environment.•Delayed-ettringite is formed during exposing metakaolin-lime with gypsum to chloride solution.•Carbonation reduces chloride bound in chloroaluminate as well as those absorbing on C-S-H gels.•Thermodynamic calculation and experiment demonstrate consistent results.