The objective of this study is to develop aerated alkali-activated mortar based on electric arc furnace slag (EAFS) and class F fly ash (FA) and investigate the effect of these different by-products on the resistance of the mortar to chloride penetration. Three variations of lightweight alkali-activated binder mortars were prepared by partially substituting cement and sand with Moroccan local by-products, namely EAFS and class F FA. A 4 M sodium hydroxide (NaOH) solution was used as an alkali activator in the mixture. The mortar specimens were cured in water at 20 ± 2 °C for 28 days at room temperature, followed by exposure to a chloride solution (0.5 M of NaCl) for 10 and 30 days. Characterization of the mortars was carried out using the X-ray fluorescence (XRF) technique to determine the elemental composition and X-ray diffraction (XRD) to identify the phases present. The XRD results obtained after 28 days of curing indicated the presence of hydrated calcium aluminate silicate (C-A-S-H) and hydrated alkaline aluminate (N-A-S-H) phases in the mortars. The formation of these phases impacts mortar’s resistance to chloride ingress. The results obtained after 10 and 30 days of exposure to saline solution, revealing that a higher content of EAFS, which promotes the formation of the C-A-S-H gel, significantly enhances the mortar’s resistance to chloride penetration.

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