Lime-potassium carbonate as an alkali activator for untreated kaolinite

An alternative alkali activator is studied. Kaolinite can chemically react with alkaline solutions such as NaOH or KOH solutions. The use of these solutions is however not without safety risks if the material is intended to be used by workers in the field. Ca(OH)2 combined with K2CO3 or (Na2CO3) is found to be an alternative activator. Besides solving the problem of working with an alkaline solution, an advantage of this system is that all the reactive components can be mixed in the dry state and only water needs to be added to start the reactions, as what is done for ordinary Portland cement.
In this study first the reaction between Ca(OH)2 and K2CO3 in aqueous solution is studied since information on this reaction is scares in literature. Next to KOH a double salt is formed, containing Ca and K. This implies that using this alkali activator, a larger amount of K will be need to reach the same reactivity as when pure KOH is used. The reactions are pretty slow (timescale of days at room temperature).
Some preliminary results of the materials made with this activator combined with kaolinite will be shown. A compressive strength of over 30MPa can be obtained for dried specimen, but the strength drops by a factor 3 in wet conditions. This alkali activator is promising and further work will be done to optimize the properties of the obtained materials.