The 7.6-Angstrom Reaction Product in Smectite Clay-Lime Mixtures

摘要

Several mixtures of hydrated lime with one of three smectite (swelling) clays and water were made. Some mixtures contained fly ash and a little calcite. The strength and mineralogical composition were followed by X-ray diffraction as a function of age. The intent was to grow usable single crystals of 7.6-Angstrom reaction product. When this proved impractical a pure sample of small crystals were hand-picked and studied. This showed that the 7.6-Angstrom material that formed in these mixtures was tetracalcium aluminate carbonate-11 hydrate (monocarboaluminate). The type of exchangeable cation in the clay had no effect on the reaction. On the other hand the presence of magnesium rather than aluminum in the octahedral layer of the clay mineral hectorite prevented the usual reactions because these mixtures never hardened. (Author)