Effect of Various Parameters on the Strength of Flyash and GGBS Geopolymer Mortar

Geopolymers are a special class of inorganic polymers that are now promising binders developed by the activation of solid-state alumina-silicate with alkaline solution. Due to their environmental sustainability, geopolymers have been shown to be effective substitutes for cement binders in recent times. Additionally, its performance in an aggressive environment is encouraging, and these binders are gradually replacing cement concrete as a preferred option in aggressive situations. Numerous binders, including flyash, GGBS, metakaolin, and Palm Oil Flyash (POFA), have been the subject of extensive research, either alone or in combination with one or both binders. The current study's goal is to ascertain how different Liquid-to-Binder ratios (LB Ratio), NaOH molarities (M), and sodium silicate-to-sodium hydroxide ratios (alkaline solution ratio) affect the compressive strength of geopolymer mortar based on flyash and GGBS. The molarities of NaOH used in the study are 10 M, 12 M, 14 M, and 16 M. The investigations are carried out by altering the liquid binder ratio of 0.4 and 0.45. The ratios of sodium hydroxide to sodium silicate are 1.5, 2.0, and 2.5. A total of twenty-four experimental mixes of flyash and GGBS are made for each geopolymer mortar. The qualities of the fresh mortar are ascertained, together with the compressive strengths. The effect of various molar ratios on the compressive strength of flyash and GGBS mortar is studied. From the above studies, the geopolymer mortar with GGBS has shown improved results compared to the geopolymer mortar with flyash. Among all the mixes the mix with 14M exhibited superior performance in compressive strength. The specimens with an LB ratio of 0.45, AL ratio of 2.0 and 14M yielded a maximum strength of 52.69 MPa.