Abstract
In case of this study of washed kaolin (WK) from the locality Sedlec (CZ) water begins to release before the temperature attains 400 °C and the dehydroxylation process finishes at 750?°C. The specific surface area of washed kaolin (19 - 19.5?m2.g-1) starts to decrease at annealing from 200 to 450?°C. In the temperature range of 550 to 750?°C when the dehydroxylation conversion degree achieves the value of 0.4 to 0.9 the specific surface area stagnates at 16 – 17.5??m2.g-1. A marked decrease in the value of the specific surface area was observed at a temperature of 950?°C.  Thermal activated “kaolin”, converted from 80 -90 % to metakaolin , shows little decrease of specific area at the temperature of 550 °C for time 60  - 90 min. up to 650 °C but shorter time (30 min.). Specific surface area and reactivity are very difficult for geopolymeric binders.