This study investigated the effect of sand to fly ash ratio on the hardened properties of geopolymer mortar. Geopolymer mortar cubes were prepared by varying the sand to fly ash ratio from 1:1 to 1:3. The cubes were heat cured at 850°C and 3000°C. Compressive strength was found to decrease with increasing sand content. Sorptivity, apparent porosity and water absorption were observed to increase with sand content, while apparent density decreased with more sand. The 1:1 fly ash to sand ratio produced mortar with the highest compressive strength and lowest sorptivity.