Effect of the Reactivity of the Alkaline Solution and the Metakaolin on the Geopolymer Formation

The choice of precursors is a key parameter in the geopolymerization mechanism since it governs the kinetic of the reaction as well as the working properties of the final materials. This study focuses on the effect of the alkaline solution reactivity and metakaolin properties on the geopolymer formation. For this purpose, several geopolymer samples were synthesized from two alkaline solutions and three metakaolins. The structural evolution of formed geopolymers was investigated using FTIR spectroscopy and the following of the pH value during the formation. The measurement of mechanical strength was tested by compression. The results allow to evidence that for a less reactive alkaline solution, the reactivity of metakaolin governs the geopolymerization reaction. However, the alkaline solution is the steering reaction when it is highly reactive. Therefore, the extent of depolymerization of the alkaline solution and the reactivity of the metakaolin seem to control the rate of polycondensation and the mechanical properties of the geopolymer materials.