Characterization of metakaolin treated at different calcination temperatures

This paper presents the characterization of chemical and physical properties of metakaolin obtained via calcination of kaolin at three different temperatures (650˚C, 750˚C and 850˚C) in comparison to that of pure or non-calcined kaolin. Chemical compositions and content of amorphous compound of the resulting metakaolin were assessed with the aid of X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Particle size analyser was used to study the physical properties of the resulting metakaolin produced in the laboratory from purified kaolin, in order to compare their properties. In thermally activated products, the calcination regimes have an important influence on the properties and long-term durability performance of the cementitious matrices. Further, the evaluation of amorphous material (glassy phase) of the metakaolin was undertaken. The results of chemical compositions for metakaolin using XRF technique showed that the composition of the major oxides (Si O 2 + Al 2 O 3 + Fe 2 O 3) was 94.86%, 97.93% and 95.30% for metakaolin treated at a temperatures of 650˚C, 750˚C and 850˚C, respectively. The XRD patterns show that some ingredients are insoluble for the three different temperatures of metakaolin that peaks at 2θ (between 17˚and 27˚). The percentage of SiO 2 as glassy phase from the total weight of the metakaolin at 650˚C, 750˚C and 850˚C is 36.79%, 41.57% and 39.24%, while, the total percentages of amorphous compounds (glassy phase) are 79.41%, 81.86% and 82.17%, respectively. The specific gravity of the metakaolin is 2.6. Hence, the calcination temperatures influence the chemical compositions as well as the content of amorphous compound in the metakaolin, which will affect the reactivity of the metakaolin.