The rising global trend of urbanization and developmental initiatives has substantially increased the demand for Ordinary Portland Cement (OPC). However, the energy-intensive nature of OPC production has prompted the emergence of Geopolymer products as an environmentally friendly alternative, since waste ashes are efficiently used as precursors and no calcination is required in the production of geopolymer binders. Urbanization has also magnified the challenge of managing Construction and Demolition (C&D) waste generated from concrete structures. This research aims to explore the impact of incorporating Recycled Sand (RS) derived from C&D waste as a replacement for Natural Sand (NS) on the Compressive Strength (CS) and Split Tensile Strength (STS) of Fly Ash based Geopolymer Mortar (FAGM) at curing stages of 7 and 28 days. Furthermore, the study investigates the influence of substituting fine Silica Fume (SF) with Fly Ash (FA) and varying the Molarity of the activator within the range of 10 to 12 on the properties of FAGM. Employing a L9 Taguchi orthogonal array for analysis, the Signal to Noise (S/N) ratio results indicate consistent patterns in CS and STS variations with substitutions and alterations in Molarity. Overall, the research reveals that while substituting NS with RS may diminish the strength properties of FAGM, simultaneous substitution of FA with SF along with a slight increase in the activator. Molarity can partly compensate for the reduction in strength properties of FAGM.