This set of Building Construction Questions & Answers for Exams focuses on “Lime – 2”.
1. Poor lime contains more than ________ of clay.
Explanation: Poor lime consists of more than 30% of clay. Poor lime slakes very slowly and is also known as lean lime.
2. Fat lime slakes slowly while hydraulic lime slakes vigorously.
Explanation: Fat lime slakes vigorously while hydraulic lime slakes slowly. Fat lime is used to prepare mortar with sand or surkhi while hydraulic lime is used to prepare mortar for thick walls and damp places.
3. Percentage of impurities in limestones should not exceed ________ for preparing fat lime.
Explanation: Fat lime is prepared by calcination of a comparatively pure carbonate of lime. It should be composed of about 95% calcium oxide. The percentage of impurities in limestones should not exceed 5% for preparing fat lime.
4. Clay content in feebly hydraulic lime is about ________
Explanation: There are three main types of hydraulic lime- feebly hydraulic lime, moderately hydraulic lime and eminently hydraulic lime. Clay content in feebly hydraulic lime is about 5-10% and that in moderately hydraulic lime is 11-20% and in eminently hydraulic lime is 21-30%.
5. Which of the following is not true about hydraulic lime?
a) Hydraulic lime consists of clay and some amount of ferrous oxide
b) Hydraulic lime can set under water
c) It has a perfectly white colour
d) It is also known as water lime
Explanation: Hydraulic lime consists of clay and some amount of ferrous oxide. It can set under water and is also known as water lime. It does not have a perfect white colour due to which it appears less sanitary than white lime or fat lime.
6. Pure limestones are indicated by _________ colour.
Explanation: Pure limestones are indicated by white colour. However, hydraulic limestones are indicated by brown, bluish-grey or some dark colour.
7. Time taken by hydraulic lime to slake is about __________
a) 3-4 hours
b) 7-10 hours
c) 12-48 hours
d) 60-65 hours
Explanation: Time taken by hydraulic lime to slake is about 12-48 hours while the time taken by fat lime is about 3-4 hours. Quantity of water needed to slake hydraulic lime is less than that required for fat lime.
8. Which of the following statements about kankar is false?
a) It is used to manufacture natural hydraulic lime
b) It is available in nodular and block form
c) Kankar in nodular form can withstand heat without disintegration
d) It is a pure limestone
Explanation: Kankar is an impure limestone which is used to manufacture natural hydraulic lime. It is available in two forms – nodular and block form. Kankar in nodular form can withstand heat without disintegration and contains a higher percentage of clay.
9. Which of the following is not true about clamp burning?
a) It is adopted for manufacturing lime on a small scale
b) Best quality of lime is produced by this process
c) It is uneconomical to manufacture lime by this process on a large scale
d) Quantity of fuel required in this process is more
Explanation: Burning of limestones to manufacture lime is generally carried out in one of the following – clamps, continuous kilns and intermittent kilns. Clamp burning is used for manufacturing lime on a small scale. It is uneconomical to manufacture lime by this process on a large scale because the quantity of fuel required in this process is more and quality of lime produced by this process is not good.
10. Hydraulic lime resembles natural cement with about __________ of clay.
Explanation: With an increase in the percentage of clay in hydraulic lime its hydraulic property increases and the slaking becomes difficult. With about 30% of clay, hydraulic lime resembles natural cement.
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