© 2021 Elsevier LtdInvention of a new and improved binding material has become an urgent need in order to reduce reliance on Portland cement while minimizing environmental pollution and energy consumption associated with its manufacture. Geopolymer could be a possible alternative in the future. This study investigated some mechanical and durability properties of pumice-fly ash geopolymer paste, including six pumice + fly ash percentages, six alkaline activating solution-to-binder (A/B) ratios, and three curing times in the oven at 60 °C for 2, 4, and 6 days. Several laboratory tests such as consistency, strength tests, and UPV tests were used to investigate the behavior of various geopolymer mixtures. The results confirmed that pumice powder with fly ash can be utilized to create good geopolymeric binders with optimum compressive strengths of 31.02 to 69.90 MPa and optimum flexural strengths of 6.14 to 9.40 MPa. The highest strengths were obtained during the 6-day curing time. The results revealed that the strength of P-FA geopolymer specimens increases by increasing the A/B to a certain value (representing the optimum-active A/B ratio for each type of mixture), the strength decreases more or less than this value. Furthermore, the compressive strength of geopolymer samples with a high content of FA was increased before and after exposure to elevated temperatures.