research papers
One of the main phases formed at the beginning of the carbonation reaction of cementitious building materials is the calcium hemicarboaluminate (abbreviated as Hc). This AFm (shorthand for hydrated calcium aluminate phases structurally related to hydrocalumite) phase was synthesized, crystallized and then studied by synchrotron X-ray powder diffraction and micro-Raman spectroscopy. At room temperature and standard experimental conditions two major cementitious phases were detected, the Hc phase (as a major phase) and carbonated calcium hemicarboaluminate (abbreviated as cHc). By increasing the temperature the Hc form transforms into cHc. The crystal structures of these important AFm phases were successfully solved and refined in the space group of the trigonal crystal system. Hc has the unit-cell parameters a = 5.7757 (1) and c = 48.812 (2) Å, and cHc the unit-cell parameters a = 5.7534 (1) and c = 46.389 (1) Å. The two crystal structures are composed of positively charged main layers, [Ca4Al2(OH)12]2+, and negatively charged interlayers, [OH2n(CO3)1 - n·4H2O]2-. The structure of the main layers is typical of the AFm family. Conversely, the interlayer region has a characteristic structure built up from water molecules and statistically distributed anions. In the interlayer, the Hc carbonate and hydroxyl anions are distributed in a 0.25:0.5 ratio, whereas the ratio of the anions in the cHc interlayers is 0.4:0.2.
Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S010876811203042X/eb5017sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S010876811203042X/eb5017Hcsup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S010876811203042X/eb5017cHcsup3.hkl | |
Rietveld powder data file (CIF format) https://doi.org/10.1107/S010876811203042X/eb5017297Ksup4.rtv | |
Rietveld powder data file (CIF format) https://doi.org/10.1107/S010876811203042X/eb5017347Ksup5.rtv |
Computing details top
(cHc) Tetracalcium dialuminium dodecahydroxide hemicarbonate hydroxide n-hydrate top
Crystal data top
C0.4AlCa2O9.2 | Z = 6 |
Mr = 259.14 | F(000) = 774.0 |
Trigonal, R3c | Dx = 1.942 Mg m−3 |
Hall symbol: -R 3 2"c | Synchrotron radiation, λ = 0.8264 (3) Å |
a = 5.7534 (1) Å | T = 347 K |
c = 46.389 (1) Å | white |
V = 1329.84 (4) Å3 | ?, ? × ? × ? mm |
Crystal data top
C0.4AlCa2O9.2 | V = 1329.84 (4) Å3 |
Mr = 259.14 | Z = 6 |
Trigonal, R3c | Synchrotron radiation, λ = 0.8264 (3) Å |
a = 5.7534 (1) Å | T = 347 K |
c = 46.389 (1) Å | ?, ? × ? × ? mm |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Ca1 | 0.66667 | 0.33333 | 0.67930 (2) | 0.0231 (4)* | |
Al1 | 0 | 0 | 0 | 0.0127 (5)* | |
O1 | 0.3051 (3) | 0.0586 (3) | 0.52121 (3) | 0.0151 (5)* | |
O2 | 0.66667 | 0.33333 | 0.93091 (6) | 0.0630 (10)* | |
O3 | 0.220 (3) | 0 | 0.75 | 0.025 (2)* | 0.40 |
C1 | 0.66667 | 0.33333 | 0.083333 | 0.025 (2)* | 0.40 |
Geometric parameters (Å, º) top
Ca1—O1i | 2.374 (2) | Al1—O1iv | 1.890 (2) |
Ca1—O1ii | 2.450 (2) | C1—O3v | 1.266 (4) |
Ca1—O2iii | 2.619 (3) | ||
O1iv—Al1—O1vi | 180.0 | O1xiii—Ca1—O1xiv | 146.32 (5) |
O1vii—Al1—O1viii | 180.0 | O1xiv—Ca1—O1xii | 117.25 (3) |
O1ix—Al1—O1x | 180.0 | O1i—Ca1—O1xiv | 117.25 (3) |
O1iv—Al1—O1vii | 95.36 (6) | O1i—Ca1—O1xii | 117.25 (3) |
O1iv—Al1—O1ix | 95.36 (6) | O1xi—Ca1—O1xiv | 86.21 (6) |
O1vii—Al1—O1ix | 95.36 (6) | O1xiii—Ca1—O1i | 86.21 (6) |
O1vi—Al1—O1viii | 95.36 (6) | O1ii—Ca1—O1xii | 86.21 (6) |
O1vi—Al1—O1x | 95.36 (6) | O1xiii—Ca1—O1xi | 83.35 (5) |
O1viii—Al1—O1x | 95.36 (6) | O1xiii—Ca1—O1ii | 83.35 (5) |
O1iv—Al1—O1viii | 84.64 (6) | O1xi—Ca1—O1ii | 83.35 (5) |
O1iv—Al1—O1x | 84.64 (6) | O1xiii—Ca1—O1xii | 63.65 (8) |
O1vii—Al1—O1vi | 84.64 (6) | O1xi—Ca1—O1i | 63.65 (8) |
O1vii—Al1—O1x | 84.64 (6) | O1ii—Ca1—O1xiv | 63.65 (8) |
O1ix—Al1—O1vi | 84.64 (6) | O1xii—Ca1—O2iii | 80.35 (4) |
O1ix—Al1—O1viii | 84.64 (6) | Al1iv—O1—Ca1xv | 104.00 (7) |
O1xi—Ca1—O1xii | 146.32 (5) | Ca1xiii—O1—Ca1xv | 93.79 (6) |
O1ii—Ca1—O1i | 146.32 (5) | O3v—C1—O3xvi | 120 |
Symmetry codes: (i) −y+1/3, −x+2/3, z+1/6; (ii) −x+4/3, −x+y+2/3, −z+7/6; (iii) −x+4/3, −y+2/3, −z+5/3; (iv) y, x, −z+1/2; (v) x+2/3, y+1/3, z−2/3; (vi) −y, −x, z−1/2; (vii) x−y, −y, −z+1/2; (viii) −x+y, y, z−1/2; (ix) −x, −x+y, −z+1/2; (x) x, x−y, z−1/2; (xi) x−y+1/3, −y+2/3, −z+7/6; (xii) x+1/3, x−y−1/3, z+1/6; (xiii) y+1/3, x−1/3, −z+7/6; (xiv) −x+y+4/3, y+2/3, z+1/6; (xv) −y+2/3, −x+1/3, z−1/6; (xvi) −y+2/3, x−y+1/3, z−2/3. |
(Hc) Tetracalcium dialuminium dodecahydroxide hemicarbonate hydroxide n-hydrate top
Crystal data top
C0.25AlCa2O9.25 | Z = 6 |
Mr = 258.13 | F(000) = 771.0 |
Trigonal, R3c | Dx = 1.824 Mg m−3 |
Hall symbol: -R 3 2"c | Synchrotron radiation, λ = 0.8264 (3) Å |
a = 5.7757 (1) Å | T = 297 K |
c = 48.812 (2) Å | white |
V = 1410.14 (7) Å3 | ?, ? × ? × ? mm |
Crystal data top
C0.25AlCa2O9.25 | V = 1410.14 (7) Å3 |
Mr = 258.13 | Z = 6 |
Trigonal, R3c | Synchrotron radiation, λ = 0.8264 (3) Å |
a = 5.7757 (1) Å | T = 297 K |
c = 48.812 (2) Å | ?, ? × ? × ? mm |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Al1 | 0 | 0 | 0 | 0.0127 (7)* | |
Ca1 | 0.66667 | 0.33333 | 0.67796 (4) | 0.0214 (4)* | |
O1 | 0.3012 (3) | 0.0484 (4) | 0.52040 (6) | 0.0224 (5)* | |
O2 | 0.66667 | 0.33333 | 0.93875 (8) | 0.063 (2)* | |
O3 | 0.219 (2) | 0 | 0.75 | 0.025 (4)* | 0.25 |
O4 | 0.565 | 0.474 | 0.094 | 0.025 (7)* | 0.08333 |
C1 | 0.66667 | 0.33333 | 0.08333 | 0.025 (4)* | 0.25 |
Geometric parameters (Å, º) top
Ca1—O1i | 2.346 (3) | C1—O3v | 1.265 (9) |
Ca1—O1ii | 2.467 (3) | C1—O4 | 1.324 |
Ca1—O2iii | 2.439 (4) | O3—O4vi | 0.745 (3) |
Al1—O1iv | 1.900 (3) | O4—O4vii | 1.456 |
O1iv—Al1—O1viii | 180.0 | O1i—Ca1—O1xiv | 116.50 (5) |
O1ix—Al1—O1x | 180.0 | O1i—Ca1—O1xvi | 116.50 (5) |
O1xi—Al1—O1xii | 180.0 | O1xiv—Ca1—O1xvi | 116.50 (5) |
O1xiii—Ca1—O1xiv | 148.60 (8) | O1i—Ca1—O2iii | 79.08 (8) |
O1xv—Ca1—O1xvi | 148.60 (8) | O1xiv—Ca1—O2iii | 79.08 (8) |
O1ii—Ca1—O1i | 148.60 (8) | O1xvi—Ca1—O2iii | 79.08 (8) |
O1xv—Ca1—O2iii | 128.85 (6) | O3v—C1—O3xvii | 120.0 |
O1xiii—Ca1—O1i | 86.29 (9) | O3v—C1—O3xviii | 120.0 |
O1xv—Ca1—O1xiv | 86.29 (9) | O3xvii—C1—O3xviii | 120.0 |
O1ii—Ca1—O1xvi | 86.29 (9) | O3xix—O3—O3xx | 60 |
Symmetry codes: (i) −y+1/3, −x+2/3, z+1/6; (ii) −x+4/3, −x+y+2/3, −z+7/6; (iii) −x+4/3, −y+2/3, −z+5/3; (iv) y, x, −z+1/2; (v) x+2/3, y+1/3, z−2/3; (vi) −x+y+1/3, −x+2/3, z+2/3; (vii) −x+4/3, −x+y+2/3, −z+1/6; (viii) −y, −x, z−1/2; (ix) x−y, −y, −z+1/2; (x) −x+y, y, z−1/2; (xi) −x, −x+y, −z+1/2; (xii) x, x−y, z−1/2; (xiii) y+1/3, x−1/3, −z+7/6; (xiv) −x+y+4/3, y+2/3, z+1/6; (xv) x−y+1/3, −y+2/3, −z+7/6; (xvi) x+1/3, x−y−1/3, z+1/6; (xvii) −y+2/3, x−y+1/3, z−2/3; (xviii) −x+y+2/3, −x+1/3, z−2/3; (xix) −y, x−y, z; (xx) −x+y, −x, z. |
Experimental details
(cHc) | (Hc) | |
Crystal data | ||
Chemical formula | C0.4AlCa2O9.2 | C0.25AlCa2O9.25 |
Mr | 259.14 | 258.13 |
Crystal system, space group | Trigonal, R3c | Trigonal, R3c |
Temperature (K) | 347 | 297 |
a, c (Å) | 5.7534 (1), 46.389 (1) | 5.7757 (1), 48.812 (2) |
V (Å3) | 1329.84 (4) | 1410.14 (7) |
Z | 6 | 6 |
Radiation type | Synchrotron, λ = 0.8264 (3) Å | Synchrotron, λ = 0.8264 (3) Å |
Specimen shape, size (mm) | ?, ? × ? × ? | ?, ? × ? × ? |
Data collection | ||
Diffractometer | Synchrotron Diamond I11 (Great Britain) diffractometer | Synchrotron Diamond I11 (Great Britain) diffractometer |
Specimen mounting | ? | ? |
Data collection mode | ? | ? |
Scan method | ? | ? |
2θ values (°) | 2θmin = ? 2θmax = ? 2θstep = ? | 2θmin = ? 2θmax = ? 2θstep = ? |
Refinement | ||
R factors and goodness of fit | Rp = 0.030, Rwp = 0.050, Rexp = 0.008, χ2 = 40.069 | Rp = 0.029, Rwp = 0.040, Rexp = 0.008, χ2 = 27.384 |
No. of data points | ? | ? |
No. of parameters | ? | ? |
No. of restraints | ? | ? |