Effect of Mg on xonotlite structure and stability
Serena Mingione, Daniel Jansen, Frank Winnefeld, Sergey V. Churakov, Barbara Lothenbach
Abstract
Minor constituents such as clays or dolomite might be present in the raw materials used for the synthesis of xonotlite (Ca 6 Si 6 O 17 (OH) 2 ). These impurities can introduce additional elements (e.g., Mg, Al, Fe) into the system, affecting the purity of xonotlite, or promoting the formation of secondary phases. This study focuses on the influence of MgO on the formation and stability of xonotlite. A combination of solubility experiments conducted at 7, 20, 50 and 80 °C, along with thermodynamic modelling and atomistic simulations, was employed to investigate Mg incorporation. Structural and phase characterization was performed using XRD, TGA, FT-IR, SEM and 29 Si MAS-NMR. Up to 13 mol% of Mg can be incorporated into the xonotlite structure and the derived thermodynamic properties indicate that this leads to a stabilization of xonotlite. Higher quantities of magnesium lead to a stabilization of other phases such brucite, which may compete with xonotlite crystallization.