Alkaline activation of metakaolin - An isothermal conduction calorimetry study

The alkaline activation of metakaolin leads to high mechanical performance inorganic polymers. A JAF conduction calorimeter was used to follow the reaction of metakaolin with NaOH solutions. The alkaline activation of metakaolin to yield a cementitious material is an exothermic process involving three steps: an initial and very fast process of dissolution, which is strongly exothermic, followed by an induction period in which the heat exchange rate decreases, and finally an exothermic step of reaction reactivation in which cementitious materials precipitate and after which the heat exchange rate decreases. The calorimetric curves lead to the following findings: The induction period is lengthened as the NaOH solution concentration and the liquid percentage increase. The induction period is shortened as the temperature increases. The total heat increases as the liquid percentage and the NaOH concentration increase.