The incorporation of ground granulated blast furnace slags (GGBS) into fly ash-based engineered geopolymer composites (EGC) was explored to enhance their resistance against chloride-induced erosion. An investigation was conducted to understand how variations in the slag content, the water-to-binder ratio, the quantity of alkali activator, and the inclusion of polyethylene fibers affect the EGC's ability to resist chloride erosion. The study found an enhancement in the chloride erosion resistance with an increase in the water-binder ratio from 0.32 to 0.38. Conversely, the resistance decreased when the proportion of slag was raised from 40% to 100%, when the alkali activator content went up from 4% to 6%, and when the percentage of polyethylene fibers grew from 1.0% to 2.0%. Microstructural analyses revealed that a higher water-binder ratio of 0.38 reduced the peak intensity of calcium aluminate silicate hydrate, increasing the porosity and, thereby, compromising the chloride erosi