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Which of the following statements are correct with reference to ensuring minimum shrinkage of prestressed concrete? 1. The water-cement ratio and proportion of cement paste should be kept minimum to reduce shrinkage. 2. Aggregates of larger size, well graded for minimum void, need a smaller amount of cement paste, and attendant shrinkage will be smaller. 3. Harder and denser aggregates of low water absorptions and high modulus of elasticity will exhibit small shrinkage.

Which of the following statements are correct with reference to ensuring minimum shrinkage of prestressed concrete? 1. The water-cement ratio and proportion of cement paste should be kept minimum to reduce shrinkage. 2. Aggregates of larger size, well graded for minimum void, need a smaller amount of cement paste, and attendant shrinkage will be smaller. 3. Harder and denser aggregates of low water absorptions and high modulus of elasticity will exhibit small shrinkage. Correct Answer 1, 2 and 3

The shrinkage of concrete is defined as the contraction due to loss of moisture. Due to the shrinkage of concrete, the prestress in the tendon gets reduced with time. The following affects the shrinkage:

1. Water –Cement ratio: If the water-to-cement ratio is higher, it is a low grade of concrete; loss of moisture is high and hence, the shrinkage is also high.

2. Cement content: Higher the Cement content, higher will be shrinkage.

3. Ambient temperature: If the temperature increases, then the loss of moisture is rapid and the shrinkage strain increases.

Justification based on above points:

The water-cement ratio and proportion of cement paste should be kept minimum to reduce shrinkage.

∴ Statement 1 is true

Amount of cement paste required depends on the availability of surface area. Higher the surface area higher will be the amount of cement required. Well graded and larger size aggregates has less surface area as compared to fine size aggregates and therefore, they required less cement paste and hence, less shrinkage.

∴ Statement 2 is true

Modulus of Elasticity means how much ease a material can be elongated or contracted. Higher Modulus of Elasticity means contraction or elongation will be difficult or lower. Harder and denser aggregates and hence, have higher modulus of elasticity so they will exhibit small shrinkage.

∴ Statement 3 is true

Related Questions

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