Technical Paper
Raw Material Tabular alumina
Calcined alumina Reactive alumina Sintered MgO Silica Fume
Calcium Aluminate Cement
Deflocculant & Permeability Enhancing Active Compound
Deflocculant Retarder
(Permeability enhancer) Silica sol
Water (%) Vibration Flow T0 (%) Table 6: Model Alumina-Silica MCC and NCC formulations (m-%) Raw material
Tabular Alumina 0-5mm Calcium Aluminate Cement
Deflocculant & Permeability Enhancing Active Compound Water (%) Vibration Flow T0 (%) Table 7: Model Alumina RCC formulations (m-%) in the center reached close to 300ºC.
Since the A15 castable consists only of tabular alumina and CAC80 it has been chosen for a more detailed analysis of microstructural differences between the castable with and without MP20. Samples have been cast and cured 24h at 20ºC and 100% rH. Then they have been crushed with a hammer and sieved below 100 µm in order to remove the coarse aggregates and to enrich the binder phase for the XRD and SEM analyses (Figure 13 and Figure 14). The A15 matrix shows the expected crystalline calcium aluminate hydrates. CAH10
and the hexagonale plates of C2 AH8
have been identified. Very different to that, the matrix of A15-MP20 doesn’t show these characteristic crystalline hydrate phases but has formed a calcium aluminate hydrate gel. Microcracks are visible in the gel but might have been caused by dessication of the gel in the vacuum of the SEM.
EDX analyses of the gel phase indicate that it contains both aluminium and calcium oxide.
Summary
This investigation has shown exemplary with three new products from the REFPAC®
active compounds range that the robustness of deflocculated castables can be increased significantly.
The deflocculating active compound REFPAC® 100 has shown very good
robustness to a wide range of impurities from different raw materials. The robustness is specifically shown through a stable flow performance over a wide range of impurities in the aqueous pore solution of the castable. RP100 brings more robust to a large range of silica fume containing
110
Specification 0-5 mm
Secar® Refpac®
Plenium (CAC80) Mipore 20 (MP20)
A15 85
15 -
+5.7 100
A15-MP20 85
12.5 2.5
+5.7
Specification 0-5mm
AC44B4 P152SB
0-0.09mm
Elkem Microsilica® 71 (CAC70)
Secar® Refpac® Na-TPP
Citric acid (PP-fiber) 30% solid
Mipore 20 (MP20) 971U
AS10 80
5 - -
5 10 -
+0.03 +0.02 (+0.1) -
+5.2 110 (95)
AS10-MP20 80
5 - -
5 7.5 2.5
- - - -
+5.2 105
www.ireng.org
AS0 90
-
6.5 0.5 3 -
-
+0.03 +0.02 -
+7.5 -
130
Figure 7: Gas permeability of LCC [2] 18 ENGINEER THE REFRACTORIES
Figure 8: Steam pressure in MCC and LCC [3] September 2017 Issue
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