Belay Zeleke Dilnesa - Eawag-Empa Library

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CHAPTER 4 FE-CONTAINING HYDRATES IN HYDRATED CEMENT The observations made in these synthetic Fe-cements concerning on the fate of iron are comparable to the observations made in commercial Portland cements. In the OPC and HS cements investigated (see section 4.1) the main hydrates were C-S-H, portlandite, Al- AFm and AFt phases. The formation of Al/Fe-siliceous hydrogarnet was also observed but not Fe-containing ettringite. The presence of aluminium in the OPC and HS cements led to the formation of stable Al-ettringite and Al-containing AFm phases while all Fe released from the ferrite was present as Fe-siliceous hydrogarnet in the long term time. The experiments with the synthetic Fe-cements confirmed the validity of the thermodynamic calculations in the synthetic cements and confirmed that the presence of silica suppressed the formation of Fe-containing AFm phases. 181
5. GENERAL CONCLUSION AND OUTLOOK 5. GENERAL CONCLUSION AND OUTLOOK 5.1. General conclusion Thermodynamic modeling of the hydration process allows the compositions of the hydration assemblages to be predicted under different conditions and to be extrapolated to long time scales. However, an important limitation of thermodynamic modeling was the lack of knowledge on the Fe speciation in hydrating cement, as Portland cements contain generally around 4-7 % iron oxide. No experimentally determined solubility products have been available for most Fe-containing hydrates. It was unclear to what extent Fe substitutes Al in AFm and hydrogarnet phases. In addition, there was little experimental evidence which Fe-containing phases form in hydrated Portland cements. This thesis aimed to fill these gaps by: i) determining the solubility of different Fe-containing hydrates, studying their crystal structure and solid solution formation with Al-containing hydrates. ii) investigating the speciation of iron(III) in hydrated cements. Fe-containing hydrates Possible Fe-containing hydrates (Fe-hemicarbonate, Fe-monocarbonate, Fe-monosulfate, Fe-Friedel’s salt, Fe-strätlingite, Fe-hydrogarnet and Fe-siliceous hydrogarnet) and their solid solution with their Al-analogues were synthesized at different temperatures. The Fe- containing AFm phases (Fe-monocarbonate, Fe-monosulfate and Fe-Friedel’s salt) are thermodynamically stable at 20 °C and 50 °C. At 80 °C, the Fe-containing AFm hydrates are unstable with respect to Fe-hydroxide/hematite and portlandite. Fe-hemicarbonate and Fe-AFm hydroxyl (C4FH13) are unstable in the presence of carbonate and converted to Fe-monocarbonate with time in all experiments. Fe-strätlingite could not be synthesised 182
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Fe-containing hydrates and their fa
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The measured composition of the liq
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ZUSAMMENFASSUNG Thermodynamische Mo
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konnten die Fe-haltigen Hydrate im
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I owe to thank all the laboratory t
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Table 19 Compositions of Al/Fe-mono
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LIST OF FIGURES Fig. 1 Calculated v
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Fig. 34 Calculated solubility produ
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Fig. 62 Calculated solubility produ
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Table of Contents TABLE OF CONTENTS
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TABLE OF CONTENTS 3. SYNTHETIC FE
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TABLE OF CONTENTS 3.5.4. Solid solu
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1 INTRODUCTION CHAPTER 1 INTRODUCTI
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CHAPTER 1 INTRODUCTION be formed. T
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cm 3 /100 g cement 85 80 75 70 65 6
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CHAPTER 1 INTRODUCTION 1.4 Characte
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CHAPTER 1 INTRODUCTION Fig. 4 Sampl
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CHAPTER 1 INTRODUCTION Identificat
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CHAPTER 2 MATERIALS AND METHODS han
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3CaOAl2O3 + 6H2O → 3CaOAl2O36H2O
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CHAPTER 2 MATERIALS AND METHODS Tab
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CHAPTER 2 MATERIALS AND METHODS 2.2
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CHAPTER 2 MATERIALS AND METHODS fil
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CHAPTER 2 MATERIALS AND METHODS at
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CHAPTER 2 MATERIALS AND METHODS the
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CHAPTER 2 MATERIALS AND METHODS 0 t
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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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Page 156 and 157: CHAPTER 3 SYNTHETIC FE-CONTAINING H
Page 172 and 173: CHAPTER 4 FE-CONTAINING HYDRATES IN
Page 182 and 183: (Al+Fe)/Ca (Al+Fe)/Ca 0.8 0.6 0.4 0
Page 188 and 189: k 3 (k) CHAPTER 4 FE-CONTAINING HYD
Page 200 and 201: differentiated relative weight Weig
Page 202 and 203: Early reaction CHAPTER 4 FE-CONTAIN
Page 204 and 205: weight loss in % differentiated rel
Page 208 and 209: 5. GENERAL CONCLUSION AND OUTLOOK a
Page 210 and 211: Speciation of iron(III) in hydrated
Page 212 and 213: 5. GENERAL CONCLUSION AND OUTLOOK
Page 214 and 215: Techniques XRD X-ray diffraction TG
Page 216 and 217: APPENDIX APPENDIX Appendix A: Addit
Page 218 and 219: Intensity (arb. Units) P Fe 2O 3 R
Page 220 and 221: APPENDIX Appendix B7 XRD patterns o
Page 222 and 223: REFERENCES REFRENCES [1] H.F.W. Tay
Page 224 and 225: REFRENCES [29] M. Vespa, R. Dähn,
Page 226 and 227: REFRENCES [54] M. Balonis, B. Lothe
Page 228 and 229: REFRENCES [81] H.F.W. Taylor, Cryst
Page 230 and 231: REFRENCES [107] K. Kyritsis, N. Mel
Page 232 and 233: REFRENCES [134] M. Wilke, F. Farges
Page 235 and 236: CURRCULUM VITAE Curriculum Vitae Na
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