The effect of type and concentration of activators on flowability and compressive strength of natural pozzolan and slag-based geopolymers

Materials resulting from the alkali activation of GGBF slag show a wide range of workability, compressive strength and permeability. The main objectives of this work are to determine the effects of alkaline solution type and concentration, modulus of sodium silicate, sodium silicate to alkaline solution ratio and natural pozzolan replacement on the workability and mechanical properties of alkali activated GGBF slag. Results reveal that the geopolymer paste specimens containing KOH solution have higher compressive strength when compared with the geopolymer paste specimens containing NaOH solution. The optimum concentration of the alkaline solution is 6-8 molar. It can be concluded that in the presence of 6 and 8 molar alkaline solutions the maximum strength could be reached with 5% and 10% replacement respectively. The optimum range for each factor is suggested based on the different effects of these factors on the compressive strength.