Ceramics-Silikáty 69, (3) 469 - 476 (2025)

This study focused on developing high-performance geopolymers using kaolin from Lam Dong province, Vietnam. The main objective was to find the optimal calcination parameter, temperature and holding time, to achieve the maximum compressive strength, Lam Dong kaolin was heated to produce metakaolin at temperatures between 600 °C and 800 °C for durations ranging from 0.5 to 2 hours. The resulting metakaolin was then mixed with a 10M NaOH solution and silica fume in a 2:2:1 weight ratio to create geopolymer mortars. These mixtures were cured at 60 °C for 7 days and subsequently at room temperature for 28 days. The results showed that calcining kaolin at approximately 700 °C for one hour yielded the highest compressive strength, reaching 25.59 MPa. The regression analysis supported this, identifying an optimal calcination temperature of 711 ° °C with one hour holding time. The material characterisation indicated that an Si/Al ratio of roughly 2.4 at 700 °C was crucial for the enhanced mechanical properties. This research highlights the critical role of precisely controlled calcination parameters for the complete metakaolin transformation and the formation of high-performance geopolymers. Furthermore, the study suggests that the calcination time had a significant influence on the compressive strength than the firing temperature within the studied range.