Porosity of fireclay refractories is _______________ percent?

Related Mcqs:

1. With increase in the porosity, thermal spalling resistance of fireclay brick___________________?

   A. Increases
   B. Decreases
   C. Remain same
   D. May increase or decrease

2. Fireclay refractories have __________________?

   A. Low co-efficient of thermal expansion
   B. Poor thermal spalling resistance
   C. Tendency to expand unduly high during firing
   D. Very high cost

3. Porosity is induced in insulating refractories by adding________________?

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

4. With decrease in porosity, the ______________ of the refractories decreases?

   A. Strength
   B. Thermal conductivity
   C. Spalling resistance
   D. None of these

5. Faster rate of drying of moulded refractories results in high _____________ of refractories?

   A. Green strength
   B. Voids
   C. Shrinkage
   D. Both B. and C.

6. Porosity of silica bricks varies from ______________ percent?

   A. 5 to 10
   B. 20 to 30
   C. 45 to 60
   D. 60 to 75

7. Maximum apparent porosity of magnesite bricks is about _____________ percent?

   A. 8
   B. 24
   C. 44
   D. 58

8. Maximum shrinkage in volume occurring during burning/firing of dried refractories may be as high as ______________ percent?

   A. 10
   B. 15
   C. 20
   D. 30

9. Pure bauxite is the best raw material for the manufacture of high alumina refractories, in which maximum alumina content can be as high as _____________ percent?

   A. 55
   B. 70
   C. 80
   D. 90

10. High porosity refractory bricks have _______________?

    A. Poor resistance to the penetration of molten slag, metal & flue gases
    B. Poor heat conductivity & low strength
    C. Better thermal spalling resistance
    D. All A., B. and C.