Cold stabilization of montmorillonite-based materials using portland cement

Montmorillonite-based materials are not well-suited to the cold stabilization process of extrusion-shaped clay products. First, we sought to determine, from among the reasons which could explain the difficulty in stabilizing montmorillonite with Portland cement, if one of the main causes was this clay's capacity to exchange and absorb cations from its surroundings. Indeed, in the montmorillonite-cement mixture, the Ca2+ ions freed by the binder are exchanged and captured by the clay particles, which prevents hydration reactions of the cement. In a second stage, we treated mortmorillonite before mixing it with cement. The treatment consisted of saturating this kind of clay with Ca2+ ions. It then appeared that the expansive properties of this clay must be the major factor in the behaviour of montmorillonite-cement mixtures.