Consider the following statements regarding the characteristics of poor lime : 1. It requires less slaking time and hydrates very fast. 2. Setting and hardening is very fast. 3. The color varies from yellow to grey. Which of the above statements is/are correct ?
- A1 only
- B1 and 2
- C3 onlyCorrect
- D1 and 3
Solution
Concept
Properties of poor (lean) lime
Step-by-step solution
1. Poor lime contains more than about 30% clay and slakes slowly (statement 1 is false). 2. It sets and hardens slowly, giving poor mortar (statement 2 is false). 3. Its colour is dirty white, yellowish or grey (statement 3 is true).
Explanation
Poor lime (lean lime) has a high clay content. It slakes with difficulty, gives little heat and a thin paste, and is yellowish to grey in colour.
Why the other options are wrong
Statements 1 and 2 describe fast action, which is characteristic of quicklime that is rich in calcium oxide, not of poor lime.
Shortcut
Poor lime = slow slaking, grey/yellowish.
Common mistake
Assuming that it sets quickly.
Correct answer: C) 3 only