reduce its shrinkage on heating.
impart greater spalling resistance.
enhance the strength of fired refractories.
all (a), (b) and (c).
✅ The correct answer is option D.
Refractory Technology MCQs
102. An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture ?
Cork
Saw dust
Sand
Chemically prepared foam
✅ The correct answer is option C.
103. Skull is not formed on the carbon blocks in the hearth of a blast furnace, when it becomes cold, becaus of its
non-wetting characteristic.
high thermal conductivity.
high crushing strength.
none of these.
✅ The correct answer is option A.
104. Fireclay refractories have
low co-efficient of thermal expansion.
poor thermal spalling resistance.
tendency to expand unduly high during firing.
very high cost.
✅ The correct answer is option A.
105. Dry mix hydraulic compositions of refractory aggregates with suitable bonding materials are called refractory
mortars
cements
castables
none of these
✅ The correct answer is option C.
106. Magnesite chrome refractories
have better spalling resistance than chrome magnesite refractories.
have very low thermal co-efficient of expansion.
are not at all resistant to the corrosive action of iron oxide.
have very low (50 kg/cm2 ) cold crushing strength (C.C.S.), and can not be used in metalcase form.
✅ The correct answer is option A.
107. High thermal conductivity of a refractory material is not important, when it is to be used in the
coke oven regenarators
muffle furnace
blast furnace
recuperators
✅ The correct answer is option C.
108. Which refractory must have controlled atmosphere (temperature and humidity) for its safe storage ?
Tar bonded dolomite bricks
Fireclay bricks
Mullite bricks
Magnesite bricks
✅ The correct answer is option A.
109. Insulating refractories should have
high porosity
low thermal conductivity
both (a) and (b)
neither (a) not (b)
✅ The correct answer is option B.
110. Maximum apparent porosity of magnesite bricks is about __________ percent.
8
24
44
58
✅ The correct answer is option B.