Effect of Calcination Processes on the Crystallite Size, Grain Size and Particle Size of Water-Washed Kaolin Particles

Abstract

Sustainable kaolin particles can be used as supplementary cementitious materials in the construction industry, helping to achieve the goal of promoting sustainability. To achieve it, kaolin particles must be calcined in order to change into the most reactive form of metakaolin. However, calcination processes can influence the crystallite, grain, and particle size of kaolin, affecting its reactivity degree. In this study, water-washed kaolin particles were calcined by using a general purpose furnace at various calcination processes (temperatures = 600°C, 700°C and 800°C, duration = 3 h and 4 h, and heating rate = 10°C/min). The effects of calcination processes to the crystallite, grain, and particle size of kaolin particles were investigated. The crystallite size was computed by using the Scherrer equation, the grain size was measured by using ImageJ software, and the particle size was determined using the Zetasizer particle size analyzer. The size of the crystallite increased from 302.94 nm to 680.93 nm, while the temperature was elevated from 600°C to 800°C for 3 h to 4 h. Similarly, as calcination temperatures and duration increased, the average grain size increased from 580.15 nm to 843.19 nm. Meanwhile, as calcination temperatures and duration increased, the average particle size increased from 4168.88 nm to 4295.35 nm. It can be seen that the gap value showed only a very slightly increase with increasing calcination processes in the crystallite, grain, and particle size of kaolin particles. However, this increased sizing can reduce the degree of pozzolanic reactivity of the kaolin particles.