Mechanism of dedolomitization and expansion of dolomitic rocks

Based on thermodynamic analysis of the dedolomitization reaction and calculation of the volume change associated with this reaction by the principle of the tightest pile of particles, the influences of pH value on alkali-dolomite reaction and expansion were investigated. Dedolomitization reaction and its expansibility were evaluated by examination of dolostone powder-cement compacts and dolomitic rocks containing few clays and quartz. Dolomite reacts with hydroxyl to form CO₃^2- ion, brucite and calcite, which are fine, generally smaller than 1 μm, and enclose many voids. It is confirmed by seveal means that dedolomitization reaction can directly bring about expansion. The rates of both the reaction and expansion depend markedly on the pH value of solutions. The higher the pH value, the larger the rates. When pH value is low enough, the reaction does not take place, thus no expansion appears.