Dissolution-Reorientation-Polycondensation Process of Metakaolin in Alkaline Solutions Related to Geopolymerization
Geopolymer is a novel type of inorganic cementitious materials, which has become a hot topic across the world. Geopolymerization process of metakaolin in alkaline solutions shows important effects on final properties of hardened geopolymer. In this paper all the possible reaction pathways involved in the dissolution-reorientation-polycondensation process of metakaolin in alkaline solution were studied according to thermodynamic theory. The corresponding reaction energy of every possible pathway was also calculated using computation chemistry methodsemi- empirical AM1 calculation. The optimum reaction pathway was analysized based on the energy-minimized principle. The calculation results showed that highly alkaline accelerated the dissolution of 6-membered tetrahedron rings of SiO4 or AlO4 tetrahedron representing the molecular structure of metakaolin during dissolution process. Si-Al hybrid reorientation should theoretically be primary reorientation pathway during reorientation process. Framework clusters should be primary polycondensation products during polycondensation process. The above studies enhanced our understanding of formation mechanisms of metakaolin in alkaline solutions related to geopolymerization.
Pietro VINCENZINI and Cristina LEONELLI
Y. S. Zhang et al., "Dissolution-Reorientation-Polycondensation Process of Metakaolin in Alkaline Solutions Related to Geopolymerization", Advances in Science and Technology, Vol. 69, pp. 41-50, 2010