THE STABILITY OF DOLOMITE IN HIGH pH ENVIRONMENTS

摘要

The experimental data gathered indicates that the dolomite in the presence of alkalis transforms to Ca-rich phase (probably Mg-rich calcite according to EDX) and Mg-rich phase, brucite. The crystals of calcium carbonate appear to grow along fault regions at the dolomite surface.Further experiments using electron and x-ray diffraction or more simply micro infrared spectroscopy will be conducted to establish the polymorphic form of calcium carbonate. Brucite is also formed as a reaction product in AAR. Its crystal form is generally much smaller leading to a dense uniform finely woven blanket like layer concurrently with the CaCO_3 crystals.Future studies should include an investigation of the dependence of the rate of dedolomitisation on environmental parameters such as temperature, pressure and chemical composition of the alkaline environment.Fracture studies on reacted dolomite crystals could also be attempted to identify the nucleation sites involved. Such studies would be augmented by the application of high-resolution electron microscopy and x-ray photoelectron spectroscopy to identify early mechanisms.