Sustainable utilization of kaolin has brought benefits to the conservation of mineral resources and economic alternatives to construction materials that rely heavily on commercial Portland cement. Industrially produced water-washed kaolin particles can be thermally activated to meet requirements as supplementary cementitious materials, depending on temperature and duration of calcination. In this study, samples were calcined at temperatures of 600-800°C and durations of 3-4 hours to determine the optimum conditions for the development of metakaolin as supplementary cementitious materials. Using techniques such as PSA, BET, SEM/EDX, FTIR and XRD, water-washed kaolin particles were analyzed and significant differences were observed between the properties of each sample. At 800°C and 3-4 hours, samples were successfully transformed from kaolinite to metakaolinite. This change increased the distribution of multimodal particle sizes, decreased BET surface area, and loss of hexagonal kaolinite morphology. Besides, the weight and atomic percentage of O, Al, Si and K decreased, but C increased. Al-O-H peaks also disappeared, while Si-O peaks were transformed into a single broad peak of amorphous silica. In addition, the kaolinite reflections vanished, but quartz remained. However, complete dehydroxylation of kaolinite was successfully achieved due to increased disorder and defective behavior of samples which were believed to facilitate further transformation into metakaolinite.
