Preparation of geopolymer precursors by sol–gel method and their characterization

Pure Al2O3–2SiO2 precursors (powders) for a geopolymer were prepared by a sol–gel method. The alkali-activated products derived from the precursors meet the general criteria for a geopolymer. The structure of the powders was investigated by NMR, XRD, and FTIR analysis, and their alkali-activation properties were studied. The data show that the powders when heat treated at 200 °C begin to contain 5-coordinated Al, those heat treated at 300 °C can begin to undergo alkali-activation, and those heat treated at 300–800 °C possess a number of structure characteristics similar to metakaolin, and the properties of their alkali-activated products are similar to those of the metakaolin geopolymers.