Porosity is induced in insulating refractories by adding________________?

A. Powdered naphthalene
B. Ammonium chloride/sulphate
C. Calcium phosphate
D. All A., B. and C.

Insulating refractories should have_______________?
A. High porosity B. Low thermal conductivity C. Both A. and B. D. Neither A. not B....
With decrease in porosity, the ______________ of the refractories decreases?
A. Strength B. Thermal conductivity C. Spalling resistance D. None of these...
Porosity of fireclay refractories is _______________ percent?
A. 5-10 B. 10-25 C. 25-35 D. 35-50...
Faster rate of drying of moulded refractories results in high _____________ of refractories?
A. Green strength B. Voids C. Shrinkage D. Both B. and C....
Hot face insulating linings of high purity alumina fused mullite are used, where_________________?
A. Very high temperatures are involved B. Highly reducing conditions are involved C. Presence of iron or silica is harmful D. All A., B. and C....
Which is required in an insulating refractory ?
A. High thermal conductivity B. Low porosity C. Both A. and B. D. Neither A. nor B....
Which is not a natural insulating material ?
A. Diatomaceous earth/kieselgur B. Asbestos C. Vermiculite D. None of these...
With increase in the porosity, thermal spalling resistance of fireclay brick___________________?
A. Increases B. Decreases C. Remain same D. May increase or decrease...
Porosity of silica bricks varies from ______________ percent?
A. 5 to 10 B. 20 to 30 C. 45 to 60 D. 60 to 75...
Refractory bricks having lower porosity have_________________________?
A. High insulating properties B. Low heat capacity C. Low thermal conductivity D. Greater strength...