The construction industry sector heavily relies on natural resources and significantly adds to CO2 emissions. With a growing focus on sustainability and resource conservation, there is a pressing need to update current construction methods. An emerging substitute for binder that employs industrial wastes or products as its constituents is geopolymer. In this study, a sodium hydroxide (NaOH) solution-based geopolymer mortar (GPM) was created using fly ash-based geopolymers. GPM’s strength and durability characteristics have been identified. The impact of molarity on GPM’s compressive strength has been studied. The results of the test demonstrated that when the concentration of alkaline activator increased, so did the compressive strength of GPM. GPM mortar has a more robust early strength development feature than Portland cement mortar, which is important in real-world applications. NaOH solutions can easily be used to provide high-strength GPM while enhancing durability during ambient curing. The enormous amount of pond ash that has accumulated close to thermal power stations continues to pose a threat to the environment. One potential alternative for its sustainable management is to use pond ash as building material. Determining if pond ash may be utilized in place of sand in GPM is the aim of the current investigation. The potential use of pond ash in place of sand in GPM is the main topic of this research. According to tests, GPM can provide more strength and durability when used as fine aggregate in place of up to 20% of sand. These results demonstrate how GPM can preserve good structural performance while promoting sustainable building practices and minimizing negative environmental effects.