Refractory Technology

41. Cold crushing strength of fireclay bricks is about _________ kgf/cm2.

1. 50-100
2. 100-150
3. 200-400
4. 500-1000

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42. Cold crushing strength of ordinary fireclay brick is about 950 kg/cm2. On exposure to a temperature of about 1500°C, its crushing strength may come down to as low as _________ kg/cm2.

1. 450
2. 250
3. 150
4. 65

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43. Cold crushing strength of refractories depends upon its

1. Composition
2. Texture
3. Firing temperature
4. All (A), (B) and (C)

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44. Colour of fireclay bricks is

1. Light buff to reddish buff
2. Yellow
3. Black
4. None of these

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45. Conversion of silica mineral to Cristobalite is accompanied by reduction in its

1. Volume
2. Specific gravity
3. Both (A) & (B)
4. Neither (A) nor (B)

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46. Crushing strength of a refractory

1. Increases with rise in service temperature
2. Decreases with rise in service temperature
3. Is unaffected with change in service temperature
4. Decreases with increase in porosity

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47. Dilatometer is used for the determination of _________ of refractories.

1. Modulus of rupture
2. Permanent linear change
3. Resistance to CO attack
4. RUL

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48. Dolomite bricks have good resistance to attack by

1. Molten steel
2. Iron oxide
3. Lime slag
4. None of these

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49. Dry mix hydraulic compositions of refractory aggregates with suitable bonding materialsare called refractory

1. Mortars
2. Cements
3. Castables
4. None of these

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50. Electrical resistor bars are made of

1. Silicon carbide
2. Alumina
3. Zirconia
4. Graphite

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