Portlandite

Formula : Ca(OH)2

Family: 
Hydroxides
Space group: 
Trigonal - Hexagonal ScalenohedralH-M Symbol (3 2/m) Space Group: P 3m1
Dana class: 
6.2.1.4 (6) Hydroxides and Oxides Containing Hydroxyl (6.2) where X++ (OH)2 (6.2.1) Brucite group (Rhombohedral: P3m1)
High temperature: 
From hydration of quicklime (CaO)and from leaching of "cement" minerals.
Geological context: 
Contact metamorphic mineral in limestone. Skarns along the contact of a magmatic intrusion .

Dernière mise à jour le 25.01.2021

THERMODYNAMICS

Individual properties (298.15 K)
M
g·mol-1
 V°
cm3·mol-1
 ΔGºf
J·mol-1
 ΔHºf
J·mol-1
 Sº
J·mol-1·k-1
 CP
J·mol-1·K-1
74.093 33.056 (Ref.: 95rob/hem) Robie R.A., and Hemingway B.S., 1995. Thermodynamic properties of minerals and related substances at 298.15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. U.S. Geol. Survey Bull., 2131, 461 pp. -896886 (Ref.: 10abla/bou) Blanc, Ph.; Bourbon, X.; Lassin, A.; Gaucher, E.C. 2010 - Chemical model for cement-based materials: Temperature dependence of thermodynamic functions for nanocrystalline and crystalline C-S-H phases. Cement and Concrete Research, 40, p. 851-867 -984552 (Ref.: Internal calculation) 83.390 (Ref.: 98cha) Chase, M.W.J., 1998. NIST-JANAF Thermochemical Tables, Journal of Physical Chemistry Reference Data, Vol. 9, 4th Edition. National Institute of Standards and Technology, Washington DC, 1951 pp. 87.49 (Ref.: 99aki/zot) Akinfiev N. and Zotov A., 1999. Thermodynamic description of equilibria in mixed fluids (H2O-non-polar gas) over a wide range of temperature (25-700C) and pressure (1-5000 bars). Geochimica et Cosmochimica Acta, 63, 2025-2041
CP(T) = a + b·T + ·c·T-2 (T in Kelvin)
a
J·mol-1·K-1
 b * 103
J·mol-1·K-2
 c * 10-5
J·K·mol-1
 Maier Kelley Ref.
89.26 33.11 -10.36 (Ref.: 99aki/zot) Akinfiev N. and Zotov A., 1999. Thermodynamic description of equilibria in mixed fluids (H2O-non-polar gas) over a wide range of temperature (25-700C) and pressure (1-5000 bars). Geochimica et Cosmochimica Acta, 63, 2025-2041
Reaction properties

Portlandite + 2H+ ⇌ Ca+2 + 2H2O

298.15 K, 1 bar log10K: 22.81 ΔH°r:-130108 J·mol-1 (Ref.: Internal calculation)
T(°C) 0 25 60 100 150 200 250 300
log10K 24.91 22.81 20.43 18.27 16.16 14.48 13.09 11.88
log10K(T) = A + B·T + C·T-1 + D·log10(T) + E·T−2 (T in Kelvin)
A B C D E
-284.929255 -0.044711 21380.115459 104.204551 -754249.169405