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. 2014 Oct 29:2014:873215.
doi: 10.1155/2014/873215. eCollection 2014.

Low Temperature Synthesis of Belite Cement Based on Silica Fume and Lime

M A Tantawy  1 , M R Shatat  2 , A M El-Roudi  1 , M A Taher  2 , M Abd-El-Hamed  2
Affiliations

Low Temperature Synthesis of Belite Cement Based on Silica Fume and Lime

M A Tantawy et al. Int Sch Res Notices. .

Abstract

This paper describes the low temperature synthesis of belite (β-C2S) from silica fume. Mixtures of lime, BaCl2, and silica fume with the ratio of (Ca + Ba)/Si = 2 were hydrothermally treated in stainless steel capsule at 110-150°C for 2-5 hours, calcined at 600-700°C for 3 hours, and analyzed by FTIR, XRD, TGA/DTA, and SEM techniques. Dicalcium silicate hydrate (hillebrandite) was prepared by hydrothermal treatment of lime/silica fume mixtures with (Ca + Ba)/Si = 2 at 110°C for 5 hours. Hillebrandite partially dehydrates in two steps at 422 and 508°C and transforms to γ-C2S at 734°C which in turn transforms to α'-C2S at 955°C which in turn transforms to β-C2S when cooled. In presence of Ba(2+) ions, β-C2S could be stabilized with minor transformation to γ-C2S. Mixture of silica fume, lime, and BaCl2 with the ratio of (Ca + Ba)/Si = 2 was successfully utilized for synthesis of β-C2S by hydrothermal treatment at 110°C for 5 hours followed by calcination of the product at 700°C for 3 hours.

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Figures

Figure 1
Figure 1
Polymorphs of belite.
Figure 2
Figure 2
XRD patterns of (a) limestone and (b) silica fume (where C is calcite).
Figure 3
Figure 3
FTIR spectrum of silica fume.
Figure 4
Figure 4
SEM micrograph of silica fume.
Figure 5
Figure 5
FTIR spectra of lime/silica mixture hydrothermally treated at 110°C for (a) 2 hours (b) 5 hours.
Figure 6
Figure 6
FTIR spectra of lime/silica mixture hydrothermally treated for 2 hours at (a) 110°C (b) 150°C.
Figure 7
Figure 7
TGA/DTA thermogram of lime/silica mixture hydrothermally treated at 110°C for 5 hours.
Figure 8
Figure 8
FTIR spectra of lime/silica mixture hydrothermally treated at 110°C for 5 hours (a) before calcination, (b) calcined at 600°C, and (c) calcined at 700°C.
Figure 9
Figure 9
XRD patterns of lime/silica mixture hydrothermally treated at 110°C for 5 hours (a) before calcination, (b) calcined at 600°C, and (c) calcined at 700°C (where C is calcite, P is portlandite, G is γ-C2S, and B is β-C2S).
Figure 10
Figure 10
XRD patterns of (lime + BaCl2)/silica mixture hydrothermally treated at 110°C for 5 hours and then calcined for 3 hours at (a) 600°C and (b) 700°C (where C is calcite, P is portlandite, G is γ-C2S, and B is β-C2S).
Figure 11
Figure 11
SEM micrographs of mixture of silica fume and lime hydrothermally treated at 110°C for (a) 2 hours without BaCl2, (b) 2 hours with BaCl2, (c) 5 hours without BaCl2, and (d) 5 hours with BaCl2.
Figure 12
Figure 12
SEM micrographs of mixture of silica fume and lime hydrothermally treated at 150°C for (a) 2 hours without BaCl2, (b) 2 hours with BaCl2, (c) 5 hours without BaCl2, and (d) 5 hours with BaCl2.
Figure 13
Figure 13
SEM micrographs of mixture of silica fume and lime represented in Figure 11 after being calcined at 600°C (right) and 700°C (left).
Figure 14
Figure 14
SEM micrographs of mixture of silica fume and lime represented in Figure 12 after being calcined at 600°C (right) and 700°C (left).
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