Fig. 3.  TG–DTA curves of the dried gel in air.
Fig. 3. TG–DTA curves of the dried gel in air.

Pure chemosynthetic Al2O3–2SiO2 geoploymers displaying positive alkali-activated polymerization properties and high compressive strength at room temperature were effectively fabricated utilizing a sol–gel method. The molecular structure of the precursor powder and resulting geopolymers were investigated by X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) analysis. In addition, the mechanical and alkali-activated polymerization properties of these materials were also studied. NMR data revealed that the chemosynthetic powders began to contain 5-coordinated Al atoms when the calcination temperatures exceeded 200 °C. These calcined powders were capable of reacting with sodium silicate solutions at calcination temperatures exceeding 300 °C, which is, however, much lower than the temperature required to convert kaolin to Metakaolin.

This article originally appeared in Journal of Non-Crystalline Solids 356(2), 2010, Pages 72-76