a thermodynamic approach to cement hydration - Eawag-Empa ...

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Due to the very low solubility and very fast precipitation of ferric solution under many conditions, the first hypothesis can be favoured. It is also confirmed by the very low concentration of dissolved Fe even for very short equilibration times (Table 2.2). Liquid phase of the time-series study The results of the analyses of the ion concentrations in the liquid phase after different ageing times are presented in Table 2.2. The calcium concentration increased after 90 days up to21 mmol/L but then decreased again to 15 mmol/L at 180 days when gypsum was not present any longer. The sulphur concentration increased slightly but steadily during 180 days ageing up to 17 mmol/L. The measured iron concentrations ranged from 0.08 to 0.1 μmol/L but without a visible trend. Until 90 days of duration the pH is about 12.5, but at 180 days it decreased to 12.0. The calculated charge balance errors showed large negative errors for the first three samples (7, 24, and 45 days), indicating excess anions, respectively deficiency of cations (Table 2.2). Those samples were not considered for thermodynamic calculations. On the basis of the solid characterization it became evident that after 180 days equilibrium was reached and that after 180 days the concentration of the ions in solution were determined by the solubility of Fe-ettringite. The very low concentration of iron confirmed the fast formation of amorphous FeOOH. 32
Table 2.2. Measured hydroxide (OH - ), calcium (Ca), iron (Fe), sulphur (S) and potassium (K) concentrations in the aqueous solution after different times. Equilibration Measured OH time in days pH - Ca Fe S K Charge balance [mmol/L] [mmol/L] [μmol/L] [mmol/L] [mmol/L] error a [%] 7 12.4 28 7.03 ± 0.03 0.097 ± 0.001 13.30 ± 0.08 17.11 ± 0.07 -27 24 12.5 35 6.94 ± 0.03 0.088 ± 0.002 13.96 ± 0.07 17.53 ± 0.11 -33 45 12.5 32 8.22 ± 0.02 0.095 ± 0.001 15.46 ± 0.02 17.52 ± 0.04 -30 90 12.5 29 21.37 ± 0.11 0.084 ± 0.001 15.65 ± 0.05 17.05 ± 0.07 -0.6 180 12.0 10 14.62 ± 0.13 0.089 ± 0.001 17.07 ± 0.14 17.71 ± 0.16 3.1 Detection limits: Ca: 0.02 mmol/L; Fe: 0.001 μmol/L; S: 0.2 mmol/L; K: 0.03 mmol/L. Blank (0.04 MKOH-solution): Ca: < 0.02 mmol/L; Fe: < 0.001 μmol/L; S: < 0.2 mmol/L. Standard deviation was calculated from repeated analytical measurements of single samples. ∑ zi ci − ∑ z jc j cations (a) Charge balance error = z c anions + z c × 100 ∑ i i ∑ cations anions 2.4.2 Precipitation and dissolution experiments Solid phase of the precipitation and dissolution experiments j j XRD analyses of the solid phases of the precipitation experiment indicated that Fe- ettringite was formed at pH-values from 11.6 up to 13.2 (cf. Fig. 2.4A). Above a pH of approximately 13.1 Fe-ettringite became instable with respect to Fe-monosulphate. At pH- values above 13.1, where Fe-monosulphate was present, portlandite precipitated as under these conditions an excess of calcium was present. At pH-values above 13.4 the formation of Fe-monocarbonate was observed. 33
Page 1: DISS. ETH NO. 17422 A THERMODYNAMIC
Page 5: “Lisa, in this house we obey the
Page 8 and 9: VI 3.3 Methods ....................
Page 10 and 11: aluminates (Ca3Al2O6) and the alumi
Page 13 and 14: Zusammenfassung Die Eigenschaften v
Page 15 and 16: Die Mischkristallreihe zwischen Al-
Page 17 and 18: 1 Introduction 1.1 Ordinary Portlan
Page 19 and 20: solution is dominated by K, Na, and
Page 21 and 22: notation AFt-phases (Al2O3 - Fe2O3
Page 23 and 24: 1.3 Admixtures Admixtures are liqui
Page 25 and 26: Retarding admixtures Retarding admi
Page 27 and 28: about their stabilities and possibl
Page 29 and 30: or diffusion R t 2 3 K 2 × ( 1 −
Page 31 and 32: and undersaturation. After equilibr
Page 33 and 34: Ecker, M. and Pöllmann, H., 1994.
Page 35 and 36: Meller, N. and Hall, C., 2004. ESEM
Page 37: zur Strassen, H. and Schmitt, C. H.
Page 40 and 41: 2.2 Introduction Aluminium containi
Page 42 and 43: (0.001 - 1.0 M) for the precipitati
Page 44 and 45: were present in the liquid phases,
Page 46 and 47: presence of a second atomic shell a
Page 50 and 51: 34 counts counts A pH measured 1200
Page 52 and 53: Ca4[Al(OH)6]2(OH)2·6H2O is only st
Page 54 and 55: Table 2.3. Calculated ion activitie
Page 56 and 57: 2 0 14 2.047 7 - - - - - - - - 2.04
Page 58 and 59: From the loss of water of the solid
Page 60 and 61: Liquid phase of the precipitation a
Page 62 and 63: Table 2.6. Thermodynamic data of th
Page 64 and 65: solubility of Fe-monocarbonateis ca
Page 66 and 67: c(Ca, Fe, S) in mmol/L c(Ca, Fe, S)
Page 68 and 69: o The heat capacity C can be calcul
Page 70 and 71: (Babushkin et al., 1985). The condi
Page 72 and 73: Ecker, M. and Pollmann, H., 1991. P
Page 74 and 75: Lothenbach, B. and Winnefeld, F., 2
Page 77 and 78: 3 Solid solution between Al-ettring
Page 79 and 80: postulated a possible miscibility g
Page 81 and 82: HNO3 suprapur qualitiy, 65%, with h
Page 83 and 84: 114, 116 and 216, cf. Table 1), das
Page 85 and 86: The c-parameter of pure Fe-ettringi
Page 87 and 88: XAl,total = 0.5 and XAl,total = 0.0
Page 89 and 90: differentiated relative weight in %
Page 91 and 92: 3.4.2 Liquid phase of the solid sol
Page 93 and 94: Table 3.4. Thermodynamic data given
Page 95 and 96: Assuming a continuous solid solutio
Page 97 and 98: The calculated ion concentrations a
Page 99 and 100:
On the basis of the measured ion co
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experiments were simulated, conside
Page 103 and 104:
Emanuelson, A. and Hansen, S., 1997
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Moore, A. and Taylor, H. F. W., 197
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4 Thermodynamic modeling of the inf
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4.3 Materials and methods 4.3.1 Exp
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4.3.2 Thermodynamic calculations Th
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4.4 Results and discussion 4.4.1 Ca
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much less pronounced retardation in
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elative peak intensity 20 15 10 5 0
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elative weight [%] counts 100 90 80
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very low during the first day of hy
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During the first day the pore solut
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4.4.4 Citrate The amount of dissolv
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Table 4.4. Calculated concentration
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grains. The precipitated or adsorbe
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Schwarz, W., Sujata, K., Jennings,
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ettringite structure. But not a con
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6 Outlook With regard to the refine
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Appendix 1: Solubility of Fe-ettrin
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Table A1.3. Thermodynamically calcu
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Table A1.5. Thermodynamically calcu
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Table A2.2. Values of the a-paramet
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Table A2.6.Calculated concentration
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Table A2.9. Calculation of the theo
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Appendix 3: Influence of citric aci
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Table A3.4. Calculated relative pea
Page 157 and 158:
Table A3.8. Calculated saturation i
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g/100g solid 50 40 30 20 10 C 3 S C
Page 162 and 163:
Table A4.2. Normative phase composi
Page 164 and 165:
Table A4.4. Measured concentrations
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elative weight [%] 100 90 80 70 60
Page 169:
CURRICULUM VITAE Göril Möschner B
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