Thermal Treatment of Kaolin: Effect on the Pozzolanic Activity

Abstract

Thermally activated clays, especially kaolinitic clays, are today revaluated as a source of supplementary cementitious materials to reduce the CO2 emissions and energy consumption originated in cement production. In this work, the influence of different thermal treatments on the pozzolanic activity of raw kaolin with 98% kaolinite and ordered structure was studied. Results show that pozzolanic activity of calcined kaolin decays when using a thermal treatment at high temperatures (800 ¡C) and high periods of residence (30 minutes). Furthermore, low calcination temperature (700 ¡C) must be corresponding with a residence time that guarantees a high dehydroxylation percentage. Sample treated during 10 minutes (94%DH) was less reactive than the one treated during 30 minutes (96%DH). Results contribute to the industry purposes to reduce the energy consumption, the CO2 emission and to contribute with new alternatives of sustainable development.