Effect of mix proportion parameters on chloride erosion resistance of fly ash/slag-based engineered geopolymer composites

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 erosion resistance of the EGC. In contrast, increasing the slag content, alkali activator, and polyethylene fiber percentage generated the reverse effect, reinforcing the material's resistance to chloride penetration. The optimized EGC demonstrated promising chloride erosion resistance with a low chloride diffusion coefficient of 0.0661 × 10−12 m2/s, paired with robust mechanical properties including compressive strength ranging from 70 to 80 MPa, ultimate tensile strength between 5 and 6 MPa, and ultimate tensile strain reaching up to 8%.