Belay Zeleke Dilnesa - Eawag-Empa Library

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The measured composition of the liquid phase was used to calculate the solubility products at 20 and 50 °C and to derive the data for standard conditions (25 °C, 1 atm). The solubility products of Fe-Fr was similar to the solubility product of Al-Fr, while the solubility products of Fe-Mc and Fe-Ms were about 3 log unit lower than that of Al-Mc and Al-Ms indicating that in Fe-Friedel’s salt is probably not stable in cements. The very low solubility product of Fe-Si-Hg (5 to 7 log units lower than that of Al-Si-Hg) implies that Fe-Si-Hg could be a stable phase in hydrated cements. Also the mixed Al- and Fe-containing hydrates were synthesized to study the extent of solid solution formation. Both XRD and thermodynamic modelling of the liquid compositions indicated that Al- and Fe-monosulphate and Al- and Fe-Friedel’s formed solid solutions with a miscibility gap, while Al- and Fe- monocarbonate existed as two separate hydrates due to their different crystal structure (Al-Mc: monoclinic, Fe-Mc: rhombohedral). The formation of solid solution between Al and Fe-siliceous hydrogarnet seemed probable. To understand to what extent the findings from the synthesised hydrates were relevant for real cements, the speciation of iron was determined in hydrating cement using EXAFS spectroscopy. Identification of Fe-containing hydrates and quantification of their contributions was achieved by combining principal component analysis with iterative target tests, and linear combination. The results show that several Fe species already contributed to the overall Fe K-edge spectra of cement pastes during the first day of hydration. While ferrite was the dominant Fe-containing phase in the unhydrated cement, Fe-hydroxide was detected shortly after starting the hydration process. With time the formation of stable Al/Fe-siliceous hydrogarnet was observed, while the amounts of Fe- hydroxide and ferrite clinker slowly decreased. The latter finding agrees with results from ii
thermodynamic modeling of the hydration process, which predicts formation of stable Al/Fe-siliceous hydrogarnet in cement system. The determination of the solubility products of these hydrates will help to extend the thermodynamic data base of cement minerals and establish whether and to which extent Fe-containing hydrates are stable in fresh and in leached cementitious systems. The results from this study on the Fe speciation in cementitious systems are important for a better understanding of cement-water interactions with a view to the durability of cementitious materials. Keywords: Fe-containing hydrates; solubility product; solid solution; crystal structure; thermodynamic modeling; thermodynamic data iii
Page 1: Fe-containing hydrates and their fa
Page 6 and 7: ZUSAMMENFASSUNG Thermodynamische Mo
Page 8 and 9: konnten die Fe-haltigen Hydrate im
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Page 12 and 13: Table 19 Compositions of Al/Fe-mono
Page 14 and 15: LIST OF FIGURES Fig. 1 Calculated v
Page 16 and 17: Fig. 34 Calculated solubility produ
Page 18 and 19: Fig. 62 Calculated solubility produ
Page 20 and 21: Table of Contents TABLE OF CONTENTS
Page 22 and 23: TABLE OF CONTENTS 3. SYNTHETIC FE
Page 24 and 25: TABLE OF CONTENTS 3.5.4. Solid solu
Page 26 and 27: 1 INTRODUCTION CHAPTER 1 INTRODUCTI
Page 28 and 29: CHAPTER 1 INTRODUCTION be formed. T
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Page 32 and 33: CHAPTER 1 INTRODUCTION 1.4 Characte
Page 34 and 35: CHAPTER 1 INTRODUCTION Fig. 4 Sampl
Page 36 and 37: CHAPTER 1 INTRODUCTION Identificat
Page 38 and 39: CHAPTER 2 MATERIALS AND METHODS han
Page 40 and 41: 3CaOAl2O3 + 6H2O → 3CaOAl2O36H2O
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CHAPTER 2 MATERIALS AND METHODS Tab
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CHAPTER 2 MATERIALS AND METHODS 2.3
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CHAPTER 2 MATERIALS AND METHODS The
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CHAPTER 3 SYNTHETIC FE-CONTAINING H
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a). b). CHAPTER 3 SYNTHETIC FE-CONT
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o layer thickness (A) 8.0 7.8 7.6 C
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Phase log KSo CHAPTER 3 SYNTHETIC F
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volume [cm 3 ] 700 600 500 400 300
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Intensity [arb. units] Fe-Fr CHAPTE
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CHAPTER 4 FE-CONTAINING HYDRATES IN
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(Al+Fe)/Ca (Al+Fe)/Ca 0.8 0.6 0.4 0
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k 3 (k) CHAPTER 4 FE-CONTAINING HYD
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differentiated relative weight Weig
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Early reaction CHAPTER 4 FE-CONTAIN
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weight loss in % differentiated rel
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5. GENERAL CONCLUSION AND OUTLOOK a
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Speciation of iron(III) in hydrated
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5. GENERAL CONCLUSION AND OUTLOOK
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Techniques XRD X-ray diffraction TG
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APPENDIX APPENDIX Appendix A: Addit
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Intensity (arb. Units) P Fe 2O 3 R
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APPENDIX Appendix B7 XRD patterns o
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REFERENCES REFRENCES [1] H.F.W. Tay
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REFRENCES [29] M. Vespa, R. Dähn,
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REFRENCES [54] M. Balonis, B. Lothe
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REFRENCES [81] H.F.W. Taylor, Cryst
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REFRENCES [107] K. Kyritsis, N. Mel
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REFRENCES [134] M. Wilke, F. Farges
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CURRCULUM VITAE Curriculum Vitae Na
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