This set of Basic Civil Engineering Interview Questions and Answers for Experienced people focuses on “Composition of Good Brick Earth”.
1. How many constituents are there in brick earth?
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 brick earth?
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 brick earth?
Explanation: Lime should be present in 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 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 excess of alumina is present?
a) Becomes hard
b) Becomes brittle
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
c) Porous bricks
Explanation: Alkali exists in the form of soda and potash. Alkalis absorb moisture and with 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
c) Organic matter
Explanation: Organic matter aids in burning process. If it does not get burnt completely, gases are released which will lead to formation of small pores, making brick porous.
9. The presence of which of the below renders clay totally unsuitable for brick manufacture?
Explanation: Kallar or Reh consists of sodium sulphate. Bricks do not burn properly in its presence. After burning, it causes surface of brick to peel off and crumble later on.
10. Carbonaceous material in small amounts is good for brick earth.
Explanation: It is a harmful ingredient that causes different colours in interior and exterior of brick. Their presence defaces the plastering by discolouration.
11. How many types of brick earth are there?
Explanation: The three types are loamy, mild or sandy clay; marls, chalky or calcareous clay and plastic, strong or pure clay.
12. Loamy, mild or sandy clay has __________ percentage of alkali?
Explanation: It does not contain any alkali contents. It contains 5% of organics matter, 1% of lime, magnesia and oxides of iron, 66% of silica and 27% of alumina.
Sanfoundry Global Education & Learning Series – Basic Civil Engineering.
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