Optimization of Fresh and Hardened Properties of Fiber-Reinforced 3D Printed Geopolymer Composites Using Response Surface Methodology (2025-11)¶

This study presents a data-driven optimization of fiber-reinforced geopolymer mixes tailored for 3D printing applications. Using response surface methodology (RSM), the effects of carbon fiber content (0-0.6% by volume), sodium hydroxide (NaOH) molarity (8–12 M), and sodium silicate-to-sodium hydroxide (SS-to-SH) ratio (1-2) were evaluated on key fresh and hardened properties, including flowability, initial setting time, shape retention, compressive strength, flexural strength, and split tensile strength. The research aimed to achieve a balance between printability and mechanical performance through the systematic adjustment of key factors: carbon fiber content, sodium hydroxide (NaOH) molarity, and the sodium silicate-to-sodium hydroxide (SS-to-SH) ratio. Results indicated that flow was negatively impacted by carbon fiber content and higher sodium hydroxide molarity, achieving a minimum flow of 12.8 cm with a desirability score of 0.949. Initial setting time was maximized at 92.8 minutes, Shape retention reached 0.94 %, driven primarily by carbon fiber content. Compressive strength was significantly influenced by SH molarity, achieving a peak value of 51.4 MPa. Flexural strength was enhanced by carbon fiber content and interactions between SH molarity and fiber, resulting in 8.5 MPa. Split tensile strength reached 4.56 MPa with a desirability score of 0.96. The findings demonstrate a trade-off between fresh and hardened properties, where higher SH molarity improved mechanical performance but reduced workability. This study provides a comprehensive understanding of optimizing 3D-printed geopolymer composites, offering a mix design suitable for large-scale additive manufacturing of structural components.