Mechanical and statistical performance of FA-MK geopolymers: alkali and curing conditions

Recent studies on geopolymers often focus on single-factor effects, such as alkali concentration or curing temperature, neglecting their synergistic influence on mechanical performance and statistical reliability. Existing literature rarely correlates strength results with experimental variability or statistical significance, complicating mix optimisation. This study addresses these gaps by experimentally evaluating metakaolin–fly ash geopolymers under varied curing temperatures (25°C and 50°C), sodium hydroxide molarities (6, 8, and 10 M), and sodium silicate-to-sodium hydroxide ratios (1:1 and 2:1). Mechanical properties were assessed at 7 and 28 days, and phase transformations via X-ray diffraction (XRD). Results were statistically validated using t-tests and ANOVA to confirm the significance of processing parameters. Findings show that elevated curing temperature (50°C) markedly increases compressive strength (maximum achieved by G-82-50), while flexural strength responds more modestly. XRD confirmed that thermal activation promotes mullite dissolution and the formation of a denser geopolymer gel. The integration of statistical and microstructural analysis provides deeper insight into mix sensitivity compared with conventional reporting. This study offers a multiparameter evaluation and statistical significance approach to geopolymer mix design, providing a reliable pathway for high-performance, sustainable cement alternatives.