Tag Archives: Ca(OH)2

Portlandite – basis for a very important building material


  • Named portlandite because it is a common product of hydration of portland cement
  • Formula: Ca(OH)2
  • Space group: P-3m1 (No. 164)
  • Crystal system: trigonal
  • Crystal class: -3 2/m
  • Lattice parameters: a = b = 3.5918 Å, c = 4.9063 Å, α = β = 90°, γ = 120°

Picture (public domain): SEM image of fractured hardened cement paste, showing plates of calcium hydroxide and needles of ettringite

Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • CaO6 octahedra (blue)
  • Oxygen (red)
  • Hydrogen (white)

For a 3D interactive version on sketchfab, see here: