<![CDATA[Fly ash-based geopolymer mortar is a promising alternative to Portland cement because it utilizes aluminosilicate-rich industrial by-products and reduces cement consumption. This study investigated metakaolin, calcined clay, and rice husk ash as supplementary precursors and four NaOH/Na₂SiO₃ ratios (1:1.5, 1:2, 1:2.5, and 1:3) on the density, water absorption, and compressive strength of fly ash-based geopolymer mortar. A full factorial experimental design (3 × 4) was employed, with five specimens for density and compressive strength testing and three specimens for water absorption testing. Raw materials were characterized using X-ray fluorescence, and mortar properties were evaluated at 28 days. The data were analyzed using Two-Way Analysis of Variance at a 5% significance level, preceded by the Anderson–Darling normality test. Tukey’s Honestly Significant Difference test was applied to significant main effects. The results showed that supplementary precursor type and NaOH/Na₂SiO₃ ratio significantly affected compressive strength and water absorption (p < 0.05), whereas neither factor significantly affected density. No significant interaction was observed between the two factors for any evaluated property. The highest observed compressive strength was obtained by the metakaolin mixture at a NaOH/Na₂SiO₃ ratio of 1:2.5, reaching 18.01 MPa. Although the calcined clay mixture at the same ratio exhibited the highest observed density (2.22 g/cm³), density was not significantly affected by either factor. These findings demonstrate that precursor type and alkaline activator ratio significantly influence compressive strength and water absorption, while their effects on density and interaction are not statistically significant.]]>
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