OPTIMIZED CALCINATION TEMPERATURES AND TIME FOR CONVERTING KAOLIN TO METAKAOLIN
This paper presents the results for optimizing the calcination parameters for converting Malaysian kaolin to metakaolin as pozzolana. Kaolin was thermally treated at different temperatures and times under controlled conditions. Instrumental techniques which include Thermogravimetry/Differential Thermal Analysis (DT/TGA), Fourier Transform Infrared (FTIR) and X-Ray Diffraction (XRD) were applied to study the phase transformation of the treated kaolins from crystalline to amorphous. Furthermore, the pozzolanicity of the treated kaolins was evaluated using the Chappelle’s Test and the Strength Activity Index methods. Based on this procedure, it was observed that calcination at 650oC for 1 hour is sufficient for complete conversion of the kaolin to metakaolin. The compressive strength of mortar with up to 20% of the metakaolin replacing cement was comparable to the control (OPC). Therefore, metakaolin produced from Malaysian kaolin may be used as a supplementary cementitious material.