Rapid synthesis and strength development of NaOH-activated metakaolin–zeolite geopolymers under microwave curing

This study investigates the combined effects of the Metakaolin–Zeolite (MK–Z) ratio and microwave (MW) curing duration on rapid strength development in NaOH-activated geopolymers. Geopolymer specimens with MK–Z ratios ranging from 0% to 100% were cured at 400 W for 5–15 min, and strength was assessed via unconfined compressive strength (UCS) tests and the strength improvement factor (SIF), while microstructure was examined using SEM and XRD analyses. The results show that the MK25–Z75 exhibits the highest SIF (12.27), highlighting substantial relative gains in Z-rich systems. Stress–strain analysis indicates that longer curing duration and higher MK content enhance stiffness and peak stress. SEM and XRD analyses confirm matrix densification and reduced porosity, supporting accelerated geopolymerization. Overall, optimizing the MK–Z ratio under MW radiation enables a rapid and sustainable approach for producing high-performance construction materials suitable for industrial applications.