Mechanical performance optimization of SiC-reinforced aluminosilicate geopolymer concrete using RSM-based Box-Behnken design

This study explores the fabrication and optimization of the mechanical performance of SiC-reinforced aluminosilicate geopolymer concrete (GPC) using RSM with the Box-Behnken Design (BBD). Fly ash was used as the primary aluminosilicate precursor, while silicon carbide (SiC) particles were used as silicon-enriched reinforcement to enhance the mechanical properties of the geopolymer matrix. The effect of SiC content (Sc: 3–9 wt.%), NaOH molarity (Nm: 6–12 M), and Na2SiO3/NaOH ratio (Nr: 1.5–2.5) on Compressive strength (CS), flexural strength (FS), and splitting tensile strength (STS) was evaluated. Quadratic empirical models were developed and validated through ANOVA, demonstrating excellent predictive capability with R2 values of 99.95%, 99.13%, and 99.72% for CS, FS, and STS, respectively. Experimental results revealed maximum CS, FS, and STS values of 64.43 MPa, 7.67 MPa, and 4.72 MPa, respectively. The Na2SiO3/NaOH ratio was identified as the most dominant factor influencing mechanical performance, while notable interaction effects between the activator ratio and NaOH molarity were observed. Multi-response optimization exhibited an overall composite desirability of 0.9653 at Sc: 6.67 wt.%, Nm: 11.33 M, and Nr: 1.55. The optimized GPC exhibited improved mechanical performance and significant potential for sustainable structural applications.