"Effects of chemical admixtures on permeability and apparent porosity of a low- cement castable refractory were studied. The low-cement castable refractory mix consisted of 85 wt.% tabular alumina aggregate, 5 wt.% calcined alumina and 5 wt.% silica fume as ultrafines, and 5 wt.% high alumina cement as hydraulic binder. Five additives were evaluated in two statistically designed experiments. The additives included Darvan 7S (polymethyl methacrylate based compound) and sodium hexametaphosphate as plasticizers, citric acid as retarder, and sodium carbonate and lithium carbonate as accelerators. A surface response methodology approach was used and two face-centered composite orthogonal designs for five factors at two levels were chosen to evaluate the effect of the two plasticizers separately. The level of additives were (low-high): Darvan 7S (0.03-0.04 wt.%), sodium hexametaphosphate (0.060-0.065 wt.%), citric acid (0-0.005 wt.%), sodium carbonate (0-0.0025 wt.%), and lithium carbonate (0-0.0025 wt.%).
Air permeability was measured using a vacuum decay permeameter. Apparent porosity was determined following ASTM C 830. In both experiments, it was found that the most significant effect was due to lithium carbonate. Lower permeabilities can be reached when lithium carbonate is used. In addition, it was verified that lower water content resulted in lowering the permeability. The plasticizers concentration was also found significant. Sodium hexametaphosphate allowed resulted in lower permeabilities than Darvan 7S while no significant difference in apparent porosity was observed. No definitive correlation between permeability and apparent porosity was established"--Abstract, page iii.
Moore, Robert E., 1930-2003
Hagni, Richard D.
Smith, Jeffrey D.
Kirchoff, Thomas J.
Materials Science and Engineering
M.S. in Ceramic Engineering
University of Missouri--Rolla
ix, 70 pages
© 1999 José María Soto Perdomo, All rights reserved.
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Soto Perdomo, José María, "Effect of chemical admixtures on the permeability of a castable refractory" (1999). Masters Theses. 1789.
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