Porosity of fireclay refractories is _______________ percent?

A. 5-10
B. 10-25
C. 25-35
D. 35-50

Fusion temperature of pure silica (SiO2) is _______________ °C?

A. 1350
B. 1715
C. 2570
D. 2800

Bottom of basic open hearth furnace are constructed of__________________?

A. Dead burnt magnesite ramming mass
B. Porous fireclay bricks
C. Semi-silica bricks
D. Silicon carbide bricks

Addition of zircon to silica refractory brick improves its_____________________?

A. Crushing strength
B. Resistance to slag attack
C. Both A. and B.
D. Neither A. nor B.

Refractories subjected to alternate cycles of heating & cooling are liable to loose their resistance to__________________?

A. Thermal spalling
B. Slag attack
C. Fusion under load
D. CO attack

Refractory bricks with lower permeability is produced by using __________________?

A. Higher firing temperature
B. Higher moulding pressure
C. Finer grog size
D. All A., B. and C.

Pure oxide refractories are generally monocrystalline in nature and are self bonded _______________ bricks are generally used as moderator in nuclear reactors?

A. Beryllia
B. Carborundum
C. Corundum
D. Thoria

Ceramic recuperators used for waste heat recovery from high temperature flue gas going out of the furnace is made of________________?

A. Fireclay
B. Silicon carbide
C. Corundum
D. Siliceous fireclay

Refractory bricks having lower porosity have_________________________?

A. High insulating properties
B. Low heat capacity
C. Low thermal conductivity
D. Greater strength

Silica bricks are never used for lining the____________________?

A. Beehive coke ovens
B. By-product coke ovens
C. Dome of blast furnace stoves
D. Roof of open hearth furnace