Single-crystal Elastic Constants of Natural Ettringite

The single-crystal elastic constants of natural ettringite were determined by Brillouin spectroscopy at ambient conditions. The 6 non-zero elastic constants of this trigonal mineral are: C-sub-11 = 35.1 ± 0.1 GPa, C-sub-12 = 21.9 ±0.1 GPa, C-sub-13 = 20.0 ± 0.5 GPa, C-sub-14 = 0.6 ± 0.2 GPa, C-sub-33 = 55 ± 1 GPa, C-sub-44 = 11.0 ± 0.2 GPa. The Hill average of the aggregate bulk, shear modulus and the polycrystal Young's modulus and Poisson's ratio are 27.3 ± 0.9 GPa, 9.5 ± 0.8 GPa, 25 ± 2 GPa, and 0.34 ± 0.02, respectively. The longitudinal and shear elastic anisotropy are C-sub-33/C-sub-11 = 0.64 ± 0.01 and C-sub-66/C-sub-44 =0.60 ± 0.01. The elastic anisotropy in ettringite is connected to its crystallographic structure. Stiff chains of [Al(OH)-sub-6]-sup-3- octahedra alternating with triplets of Ca2+ in 8-fold coordination run parallel to the c-axis leading to higher stiffness along this direction. The determination of the elastic stiffness tensor can help in the prediction of the early age properties of cement paste when ettringite crystals precipitate and in modeling both internal and external sulfate attack when secondary ettringite formation leads to expansion of concrete.

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  • Accession Number: 01103732
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 17 2008 1:48PM