Controlling the reactivity of silicate solutions: A FTIR, Raman and NMR study

Alkaline silicate solutions are of great interest for several industrial applications. Previous studies demonstrated the influence of different parameters such as the Si/M (Na, K) molar ratio, the dilution level, the cation size and the manufacturing process on the silicate species. The aim of this study was to complete the data from previous works. This study focuses on the effects of these various parameters on the polymerization and the reactivity of silicate solutions. To evaluate the effects, several solutions obtained from various processes with different cations and Si/M ratios were studied. All the solutions were characterized using spectroscopic investigations (FTIR, Raman and NMR). FTIR spectroscopy was used to define the polymerization state of the various solutions. The experiments revealed that increases in the Si/M molar ratio, the dilution level and the cation size lead to the polymerization of the species. However, the effect of the cation is less pronounced. Moreover, Raman spectroscopy revealed an increase in oligomers for Si/M molar ratios less than 1. It was also shown that the manufacturing process causes a slight variation in the amount of the different silicate species responsible of the reactivity of the solution. Knowledge of these key parameters is important for different applications, including geopolymer fabrication. Moreover, it was shown a correlation between the results obtained by NMR and Raman spectroscopy. (C) 2016 Elsevier B.V. All rights reserved.