Mechanical properties of ettringite and thaumasite—DFT and experimental study

Ettringite and thaumasite are important hydrated phases of cementitious materials that contribute to the mechanical properties and stability of concrete. We have performed first principle density functional theory-based calculations in order to predict structural and mechanical properties of these two minerals. In addition, we have used Brillouin spectroscopy to experimentally determine, for the first time, the full elastic tensor of a monocrystal of thaumasite. Aggregate bulk, shear, and Young's moduli have been obtained from both calculated and experimental data. A very good agreement was observed between DFT-predicted and experimental elastic constants of both minerals. Although thaumasite and ettringite have very similar crystal structure, the comparison of their elastic properties shows that thaumasite is stiffer than ettringite due to the lower amount of water molecules in its structure.