Alkali-activated materials (AAMs) have been widely used as an alternative to Portland cement. This production of AAMs emits lesser carbon dioxide by utilizing industrial waste products to make this cement binder technology greener and more sustainable. The conventional two-part system comprises solid aluminosilicate precursors with an alkali solution to activate the AAMs. However, higher alkalinity of the liquid activator is required to complete the geopolymerazation process, making the cementitious materials costly and sticky, and thus not convenient to handle on the construction site, affecting the worker’s safety. A one-part AAMs system was introduced to overcome the two-part system’s shortcomings. The alkali solution is now replaced with a solid alkali activator which is easier and more practical to apply at construction sites. This study was carried out to evaluate the mechanical performance of one-part alkali AAMs in the form of mortar by conducting compressive and flexural strength, modulus of elasticity, and tensile strength tests at 28 days of curing age under laboratory experiments in the tropical climate of Malaysia. A drying shrinkage test was also performed to detect its durability. Three types of solid admixtures were added to complete the composition of the novel mix design formulation. According to the results obtained, the mechanical strength of one-part alkali-activated mortar achieved the minimum requirement for Class R3 structural concrete repair materials as per EN1504-3 specifications. This eco-friendly cement binder has excellent potential for further engineering development, particularly to become a new concrete repair product in the future.