Consider the following statements: 1.The viscosity-modifying agents allow the concrete to remain cohesive even with a high degree of fluidity. 2.Self-consolidating concrete can be used for beam-column joints in earthquake resistant structures. 3.Self-consolidating concrete is not recommended for precast prestressed concrete. Which of the above statements are correct?
- A2 and 3 only
- B1 and 2 onlyCorrect
- C1 and 3 only
- D1, 2 and 3
Solution
Concept
SCC flows and fills forms under its own weight without vibration. A viscosity-modifying agent (VMA) keeps it cohesive and stops segregation.
Step-by-step solution
1. Statement 1: A VMA increases cohesion, so a highly fluid mix does not segregate or bleed. Correct. 2. Statement 2: Beam-column joints in earthquake-resistant structures have very congested reinforcement. SCC fills them well without vibration. Correct. 3. Statement 3: SCC is widely used in precast and prestressed plants for speed, good finish and no vibration. So 'not recommended' is wrong. Incorrect. 4. Correct statements are 1 and 2 only, so the answer is B.
Explanation
A VMA keeps self-consolidating concrete stable even when it is very fluid. SCC is ideal for congested joints like seismic beam-column joints. It is also very popular in precast prestressed concrete work.
Why the other options are wrong
A: Statement 3 is wrong. C: Statement 3 is wrong, and statement 2 is correct. D: Statement 3 is wrong.
Shortcut
SCC is used most in congested sections and precast plants, so statement 3 is false.
Common mistake
Thinking SCC is not suitable for prestressed precast work, when it is actually one of its main uses.
Correct answer: B) 1 and 2 only