1.How many constituents are there in the brick earth?
a) 5
b) 4
c) 6
d) 8
Explanation: For a good brick earth, 5 major constituents are needed. They are alumina, silica, lime, oxides of iron and magnesia.
2. Which one of the below is the most important ingredient in the brick earth?
a) Alumina
b) Lime
c) Silica
d) Magnesia
Explanation: The amount of silica present in brick earth is 50-60% and it prevents cracking and warping of raw bricks.
3. In what form should lime be present in the brick earth?
a) Paste
b) Lump
c) Clinker
d) Powder
Explanation: Lime should be present in the brick earth in the form of very finely powdered state so as to prevent the flaking of bricks.
4. Excess of oxides of iron makes the brick:
a) Red in colour
b) Black in colour
c) Dark blue in colour
d) Yellow in colour
Explanation: Iron oxide imparts the red colour to the brick. Presence of magnesia makes brick yellowish and manganese makes it black. Excess of oxides of iron makes the brick dark blue on burning.
5. What happens to raw bricks if an excess of alumina is present?
a) Becomes hard
b) Becomes brittle
c) Decay
d) Shrinkage
Explanation: Raw bricks develop shrinkage, cracks, warping in presence of excess alumina. Other three changes happen on burnt bricks or final brick product due to excess of other constituents.
6. What is the harmful effect of presents of alkali in brick earth on bricks?
a) Discolourises bricks
b) Efflorescence
c) Porous bricks
d) Flaking
Explanation: Alkali exists in the form of soda and potash. Alkalis absorb moisture and with a passage of time, it gets evaporated, leaving white powdery deposits called efflorescence.
7. Why do bricks become brittle when excess silica is present?
a) Pores are created
b) Flaking occurs
c) Thermal stability is lost
d) Cohesion is lost
Explanation: Silica is present is either free or combined form. It is usually present as sand, which is cohesionless in nature. So, excess of silica would lead to loss of cohesion between particles and this make the brick brittle.
8. Which of the following leads to the formation of small pores in brick?
a) Iron pyrites
b) Pebbles
c) Organic matter
d) Alkalis
Explanation: Organic matter aids in the burning process. If it does not get burnt completely, gases are released which will lead to the formation of small pores, making brick porous
9. The presence of which of the below renders clay totally unsuitable for brick manufacture?
a) Kallar
b) Kankar
c) Hay
d) Lime
Explanation: Kallar or Reh consists of sodium sulphate. Bricks do not burn properly in its presence. After burning, it causes the surface of brick to peel off and crumble later on.
10. Carbonaceous material in small amounts is good for the brick earth.
a) True
b) False
Explanation: It is a harmful ingredient that causes different colours in interior and exterior of brick. Their presence defaces the plastering by discolouration