Effect of Molar Concentration on the Compressive Strength of Red Mud and Phosphogypsum-Based Geopolymer Mortar

In this study, industrial by-products red mud (RM) and phosphogypsum (PG)-based geopolymer mortar are used as an alternative to cement mortar. Alkaline solutions of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as activators to develop geopolymer mortar. RM was replaced with 10, 20, 30, and 40% by PG to develop geopolymer mortar. The effect of molar concentration of NaOH on the compressive strength of geopolymer mortar was analyzed at 6, 8, 10, 12, 14, and 16 M NaOH. The compressive strength of the geopolymer mortar was tested at 3, 7, and 28 days of the curing periods. From this study, it has been analyzed that compressive strength increases as the molar concentration of the NaOH increases and maximum compressive strength was obtained at 12 M molar concentration of NaOH. Further molar concentration increases beyond the 12 M of NaOH then compressive strength decreases.