1. What is the depth the needle in Vicat apparatus should penetrate into the cement paste in consistency test?
a) 33-35 cm from bottom of the mould
b) 33-35 mm from top of the mould
c) 33-35 cm from top of the mould
d) 33-35 mm from bottom of the mould
Discussion
Explanation: The best procedure has been clearly mentioned in IS 4031 Part 4. According to the code, 33-35mm depth of penetration is ideal.
2. What is the most dominant constituent of cement?
a) Silica
b) Lime
c) Magnesia
d) Alumina
Discussion
Explanation: Cement contains about 60-65% of lime. Silica constitutes 17-25%, alumina 3-8% and magnesia 1-3%.
3. Deficiency of lime in cement leads to:
a) Unsound cement
b) Disintegration of cement
c) Quick setting of cement
d) Expansion of cement
Discussion
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.
4. What effect does calcium sulphate have on cement?
a) Retards setting action
b) Acts as flux
c) Imparts colour
d) Reduces strength
Discussion
Explanation: Calcium sulphate is found in cement in the form of gypsum. Its slows down the setting time of cement.
5. Which of the following adds a quick-setting property to cement?
a) Magnesium oxide
b) Silicon dioxide
c) Iron oxide
d) Aluminium oxide
Discussion
Explanation: Aluminium Oxide or Alumina is present in small quantity in cement and it helps in a quick-setting property.
6. Which of the following imparts greenish grey colour to cement?
a) Calcium silicate
b) Calcium aluminate
c) Calcium aluminate ferrite
d) Calcium carbonate
Discussion
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.
7. Excess of Alkali in cement results in:
a) Dry cement paste
b) Efflorescence
c) Less plasticity
d) Unsound cement
Discussion
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.
8. What function does iron oxide perform in cement?
a) Increases strength
b) Makes cement sound
c) Increases setting time
d) Acts as flux
Discussion
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.
9. How many major ingredients are present in the composition of cement?
a) 8
b) 5
c) 10
d) 6
Discussion
Explanation: There are 8 main ingredients present in cement. They are lime, silica, alumina, magnesia, iron oxide, calcium sulphate, sulphur trioxide and alkalis.
10. 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
Discussion
Explanation: The presence of ingredients is expressed in percentage. Iron oxide is present in 0.5-6% and sulphur 1-2.5%.