Consider the following statements regarding the functions of admixtures : 1. It is to speed up the rate of development of strength at early ages. 2. It increases the strength of concrete. 3. It increases the heat of evolution and decreases the durability of concrete. Which of the above statements is/are correct ?
- A2 and 3 only
- B1 and 3 only
- C1 and 2 onlyCorrect
- D1, 2 and 3
Solution
Concept
Purpose of chemical admixtures
Step-by-step solution
1. Accelerators speed up early strength gain (true). 2. Water reducers and superplasticizers increase strength by lowering the water–cement ratio (true). 3. Admixtures are used to improve durability and reduce heat, not to increase heat or reduce durability (false).
Explanation
Admixtures are added to modify properties favourably, so a statement that says they reduce durability is incorrect.
Why the other options are wrong
Options with statement 3 are wrong.
Shortcut
Admixtures improve, not worsen, durability.
Common mistake
Accepting statement 3.
Correct answer: C) 1 and 2 only