Which one of the following statements is correct regarding the factors influencing strength of concrete ?
- AIf the size of cube is decreased, the compressive strength tends to increase and modulus of elasticity decreases.
- BIf the size of cube is decreased, the compressive strength tends to decrease and modulus of elasticity increases.
- CIf the size of cube is decreased, the compressive strength tends to increase and modulus of elasticity also increases.Correct
- DIf the size of cube is decreased, the compressive strength tends to decrease and modulus of elasticity also decreases.
Solution
Concept
Effect of specimen size
Step-by-step solution
1. Smaller specimens show higher strength because of lower probability of weak flaws (size effect) and greater platen restraint. 2. Modulus of elasticity follows the strength, so it also increases.
Explanation
Smaller cubes give higher apparent compressive strength. Since E increases with strength, the modulus of elasticity measured also tends to be higher.
Why the other options are wrong
A larger strength cannot go together with a smaller modulus, and a decrease of strength with smaller size is the opposite of the size effect.
Shortcut
Smaller specimen → stronger and stiffer reading.
Common mistake
Assuming size has no effect on strength.
Correct answer: C) If the size of cube is decreased, the compressive strength tends to increase and modulus of elasticity also increases.