This set of Basic Civil Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Ingredients of Cement”.
1. What is the most dominant constituent of cement?
Explanation: Cement contains about 60-65% of lime. Silica constitutes 17-25%, alumina 3-8% and magnesia 1-3%.
2. Deficiency of lime in cement leads to:
a) Unsound cement
b) Disintegration of cement
c) Quick setting of cement
d) Expansion of cement
Explanation: Presence of lime in sufficient quantity is necessary to form silicates and aluminates of calcium. Excess lime leads to expansion, disintegration and unsoundness of cement.
3. What effect does calcium sulphate have on cement?
a) Retards setting action
b) Acts as flux
c) Imparts colour
d) Reduces strength
Explanation: Calcium sulphate is found in cement in the form of gypsum. Its slows down the setting time of cement.
4. Which of the following adds a quick-setting property to cement?
a) Magnesium oxide
b) Silicon dioxide
c) Iron oxide
d) Aluminium oxide
Explanation: Aluminium Oxide or Alumina is present in small quantity in cement and it helps in a quick-setting property.
5. Which of the following imparts greenish grey colour to cement?
a) Calcium silicate
b) Calcium aluminate
c) Calcium aluminate ferrite
d) Calcium carbonate
Explanation: Calcium silicate and calcium aluminate are pure white minerals. Calcium aluminate ferrite is brown in colour, but due to absorption of light by magnesium, present as an impurity, greenish grey colour is imparted to cement.
6. Excess of Alkali in cement results in:
a) Dry cement paste
c) Less plasticity
d) Unsound cement
Explanation: Efflorescence is the formation of powdery substance on the surface of masonry or concrete work. Alkalis usually get carried away by flue gases during heating. In excess quantity, they result in alkali-aggregate reaction.
7. What function does iron oxide perform in cement?
a) Increases strength
b) Makes cement sound
c) Increases setting time
d) Acts as flux
Explanation: Iron oxide acts as a flux, in addition to being responsible for imparting colour to cement. If the temperature goes higher, then iron oxide reacts with aluminium and calcium and results in the formation of calcium aluminate ferrite.
8. How many major ingredients are present in the composition of cement?
Explanation: There are 8 main ingredients present in cement. They are lime, silica, alumina, magnesia, iron oxide, calcium sulphate, sulphur trioxide and alkalis.
9. Sulphur in cement is present in what amount?
a) 0.5 – 6 g
b) 1 – 2.5%
c) 0.5 – 6%
d) 1 – 2.5g
Explanation: The presence of ingredients is expressed in percentage. Iron oxide is present in 0.5-6% and sulphur 1-2.5%.
10. An excess of magnesium oxide after 5% is harmful to cement.
Explanation: Excess of magnesium causes problems in structures built with this cement. It causes cracks in both mortar and concrete after they harden.
Sanfoundry Global Education & Learning Series – Basic Civil Engineering.
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