A ternary optimisation of mineral additives of alkali activated cement mortars

The effects of binary and ternary combinations of ground granulated blast furnace slag (GGBFS), fly ash (FA) and silica fume (SF) on compressive strength, flexural strength, water sorptivity, permeable voids and drying shrinkage of steam cured alkali-activated cement (AAC) mortars were investigated within the scope of this study. Also, three-level full factorial experimental design and response surface method were used for the optimisation of the amount of mineral additives by maximising compressive and flexural strengths while minimising drying shrinkage, water sorptivity and permeable voids. The use of ternary blends in AAC provided significant decreases in drying shrinkage, water sorptivity and permeable void content. However, the mechanical performance of ternary blended AAC has been negatively affected compared to GGBFS mortar. Nevertheless, compressive strength values of all binary and ternary blends of AAC were higher than conventional Portland cement mortar. The optimum AAC composition was obtained with a ternary mixture containing 20.3% FA, 18.9% SF and 60.8% GGBFS.

► Drying shrinkage and permeability based properties of AASC are considerably higher than PC. ► Partial replacement of GGBFS with FA and SF is effective in improving the drawbacks of AASC. ► RSM were used for the optimisation by maximising strengths, and minimising shrinkage and permeability. ► AAC with the ternary combination of 19% SF, 20% FA and 61% GGBFS had the highest desirability.