Preparation of Al2O3-2SiO2/geopolymer powder by hydrolytic sol-gel method and its activity characterization and research on the reaction mechanism

Abstract

Herein, we report the application of sol-gel method for the preparation of a new type of highly active Al2O3-2SiO2 geopolymer precursor powder. The newly synthesized geopolymer precursor powder was characterized by SEM, XRD, TG, FTIR and MAS NMR. Experimental results showed that all the geopolymer precursor powders prepared by this method exhibited amorphous crystal structure and FTIR absorption peaks were consistent to typical aluminosilicate. TG analysis showed that G1-0-35 prepared with pure water as the aluminum source solvent had higher weightlessness rate, and with the increase of water quantity, the layered structure appeared, the resonance peak of hexacoordination Al(VI) was enhanced and the coordination of silicon was changed. ICP test results showed that the G1-0-35 precursor powder with pure water as the aluminum source solvent dissolves more quickly in the NaOH, and the relative crystallinity was the highest (84%) after alkali activation. The changes in conductivity of different geopolymer precursor powders during the reaction at different temperatures and the changes in the concentration of aluminum and silicon ions with time in the geopolymer reaction were explored, which showed that the activity of geopolymers powders increased with increasing the amount of water. The geopolymer precursor powder prepared in this study are in line with the requirements of green production, and prompts great advantages in the study of geopolymer reaction mechanism.