The effect of heating, to temperatures between 400 and 1200ºC, on the dehydroxylation of kaolin and the pozzolanic activity of the resulting amorphous material were determined by a variety of analytical techniques. Mixtures of concrete containing variable amounts of kaolin calcined at 700ºC were analysed and the results compared with those for concrete samples containing two different types of imported metakaolin. As shown in this work, Colombian kaolin can be used effectively as a raw material to obtain a highly active product (metakaolin). The optimum heating temperature for the kaolin is between 700 and 800ºC.
