Influence of chloride salt type on chloride ion diffusion performance of alkali-activated slag mortar

•Alkali-activated slag (AAS) mortar has better resistance to chloride ion corrosion.•Different cation types affect the Dapp of AAS mortar.•MIP and XRD was performed to show a decrease in porosity.•EIS was performed to show an inverse exponential relationship between Rc,d and Dapp. This work focuses on evaluating the influence of four cationic chloride salts (NaCl, KCl, MgCl2 and CaCl2) on chloride ion diffusion characteristics of alkali-activated slag mortar. The chloride ion concentration profiles of alkali-activated slag mortar were tested in single cation and combined cation source solutions. The hydration products and mechanism of action were analyzed by XRD and MIP, and the chloride ion transmission characteristics of alkali-activated slag mortar were further analyzed in combination with EIS. The chloride ion apparent diffusion coefficient Dapp related to the chloride salt solutions with the four cation types decreases in the order of Dapp (KCl) > Dapp (NaCl) > Dapp (MgCl2) > Dapp (CaCl2). The combination of monovalent cations can promote the chloride ions diffusion of alkali-activated slag mortar, and the results of the combination of monovalent cations and divalent cations are different. The hydration products of slag are mainly C-S-H gels with low calcium to silicon ratio, which reacts with chloride salt to form Friedel's salt, which can fill the internal pores, optimize pore size distribution, and improve the resistance to chloride ion corrosion.