Evaluation of the optimal process of thermal activation of kaolins

Metakaolin is a pozzolanic material obtained through thermal activation of kaolin. This research aims to investigate the effect of degree and duration of heating on the pozzolanic properties and reactivity of the produced material. Two types of Iranian mineral raw material, namely, K1K1 and K3K3, and one by-product of the domestic kaolin beneficiation process, K2K2, were activated by heating in a furnace chamber at temperatures 650–900 °C for 1 and 2 h. The changes in the crystalline structure of these materials were evaluated using X-Ray Diffraction (XRD), and also compressive strength tests were carried out on the mortars containing metakaolin to study the reactivity of the produced materials. The obtained results indicated that 1 h is sufficient for thermal activation of kaolin, and the optimal activation temperature is between 750 and 850 °C. Moreover, it was observed that activated metakaolin has an appreciable influence on the increase in compressive strength of the mortars.