Mechanism of polysialation in the incorporation of zirconia into fly ash-based geopolymers

Little attempt has been made to understand the chemical and physical consequences of incorporating non-aluminosilicate materials into geopolymers. In the present work zirconia was chosen as an inert reference to examine the effects of. non-aluminosilicate source on the chemical and physical properties of a geopolymer matrix. Fourier transform infrared (FTIR), X-ray diffraction, and compressive strength analyses were used to characterize the matrixes. Inclusion of only a small quantity of zirconia was shown to impart a substantial increase in compressive strength for fly ash-based geopolymers. The basis of this increase in strength has been hypothesized to be due to the formation of specific zirconia-associated, three-dimensional polysialate species, which reduce the mobility of sodium while maintaining the charge balance and structural stability of the matrix. Through a simplified study based on zirconium polysialate solubility and FTIR measurements, an attempt was made to rationalize and correlate the observed chemical and physical properties of the matrixes with established mechanisms of geopolymerization.