Mechanical Properties and Reaction Kinetics of Alkali-Activated Metakaolin

Abstract

In this study, the influence of the physicochemical properties and proportioning conditions of metakaolin on the mechanical properties of the synthesized metakaolin geopolymers was comprehensively evaluated, and the issue of the reaction control mechanism for the formation of mechanical properties during the synthesis of geopolymers was addressed. The reaction mechanism was analyzed by SEM and FTIR, and the kinetic analysis of the geopolymerization process was carried out using isothermal calorimetry combined with the Jander model. The test results show that the physicochemical properties of the metakaolin and the proportioning conditions together affect the mechanical properties of the geopolymer, with the correlation between the active aluminum content of the metakaolin and the strength of the geopolymer reaching over 0.87. The early stages of the geopolymerization reaction are all controlled by nucleation–growth mechanisms (N < 1), and the variability in control mechanisms is mainly found in the later stages of the geopolymerization reaction. The low reactivity and slow exothermic hydration of metakaolin are more inclined to the nucleation-growth mechanism responsible for the hydration process due to the large amount of encapsulation.