In this present experimental study, high calcium fly ash was utilized in the production of one-part alkali activated mortars. The HCFA was activated with anhydrous sodium metasilicate powder at 10 - 20 percent of the total precursor materials and cured at ambient condition. In this study, granular anhydrous sodium metasilicate has been successfully utilized to produce one-part alkali activated mortars. Thirteen mixes of one-part geopolymer mortar were designed using RSM central composite design with percentage of alkali activator and w/b ratios as parameters. Hardened density, workability, and, compressive strength was envisaged. The results showed that increasing the granular activator beyond 15 by weight of the fly ash reduces the strength and workability of the one-part alkali activated mortars. The RSM investigation helped in advancing the level of granular activator as far as acquiring ideal qualities and they were observed to be ideal at 16 of the granular activator and 0.3 w/b proportion. The model conditions were created, and the outcomes were approved through ANOVA by witnessing the model noteworthiness level of more than 95. One-part alkali activated mortars exhibited highest compressive strength of almost 40 MPa at 28 days curing. The density of the one-part geopolymer mortars is almost the same regardless of the mixes. © Published under licence by IOP Publishing Ltd.