Zn2+ as a dopant to stabilize hydrated magnesium carbonates

The formation of solid solutions of Mg‑carbonates incorporating Zn²⁺ was investigated. The presence of Zn retarded the reaction of brucite at the early stages but increased its reaction in the long-term. The initially formed nesquehonite [MgCO₃·3H₂O] and brucite converted to dypingite [Mg₅(CO₃)₄(OH)₂·5H₂O] with time, both in the absence and presence of Zn, while dypingite remained stable throughout the duration of the study (1 year). Zinc forms a solid solution with dypingite with a maximum Zn/(Mg + Zn) molar ratio of 0.01. The solid solution was found to be thermodynamically more stable than pure dypingite. With further increase of Zn beyond 0.01 Zn/(Mg + Zn) molar ratios, the excess zinc precipitates as X-ray amorphous phases with a possible Zn/Mg atomic ratio of 2 at early reaction time. The findings reported here confirm the possibility of solid solution formation in HMCs enabling the improved stability of certain HMCs for safe utilization as construction materials.