Belay Zeleke Dilnesa - Eawag-Empa Library

Mass of the solids in grams
2.5
2.0
1.5
1.0
0.5
CHAPTER 3 SYNTHETIC FE-CONTAINING HYDRATES
Fe-hydroxide
Portlandite
C 4Ac 0.5H 12
0.0
0.0 0.2 0.4 0.6 0.8 1.0
(Al/Al+Fe) ratio
C 3 AH 6
Fig. 53 Calculated solids in the CaO-Al2O3-Fe2O3-H2O system in 0.1 M KOH using the solubility
products as given in Table 28.
3.5.5. Aluminum siliceous hydrogarnet, C3ASH4
The C3ASH4 system is more complex than the silicon free C3AH6 system. The presence
of two different hydrogarnets can be expected, a silica-poor and a silica-rich with a
miscibility gap in between. For hydrogarnets prepared at 95 °C, a miscibility gap between
C3AS0.42H5.16 and C3AS0.76H4.48 was reported [110]. In this study the synthesis of C3ASH4
(target composition) was carried out at both 20 °C and 110 °C. Fig. 54 shows the XRD
pattern of the Al-containing siliceous hydrogarnet synthesized at 110 °C (equilibrated for
5 days) and at 20 °C (equilibrated for 3 years). The peaks of the sample synthesized at
110 °C are relatively broad. A minor splitting of the peaks was observed at d-spacing ~
2.75 Å, indicating that the solid could be composed of two siliceous hydrogarnets with
different compositions. The peaks of the solid synthesized at 20 °C indicated the presence
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