### Concrete Technology and Design

**11. **According to I.S. : 456, the number of grades of concrete mixes, is

- 3
- 4
- 5
- 7

**12. **According to IS : 382-1963, a good aggregate should be

- Chemically inert
- Sufficiently strong
- Hard and durable
- All the above

Correct answer: (D)

All the above

**13. **According to IS: 4561978, minimum slenderness ratio for a short column is

- Less than 12
- Less than 18
- Between 18 and 24
- More than 24

Correct answer: (A)

Less than 12

**14. **According to IS: 4561978, the column or the strut is the member whose effective length is greater than

- The least lateral dimension
- 2 times the least lateral dimension
- 3 times the least lateral dimension
- 4 times the least lateral dimension

Correct answer: (C)

3 times the least lateral dimension

**15. **According to IS: 4561978, the flexural strength of concrete is

- Directly proportional to compressive strength
- Inversely proportional to compressive strength
- Directly proportional to square root of compressive strength
- Inversely proportional to square root of compressive strength

Correct answer: (C)

Directly proportional to square root of compressive strength

**16. **According to IS: 4561978, the maximum reinforcement in a column is

- 2%
- 4%
- 6%
- 8%

**17. **According to ISI recommendations, the maximum depth of stress block for balanced section of a beam of effective depth d is

- 0.43 d
- 0.55 d
- 0.68 d
- 0.85 d

Correct answer: (A)

0.43 d

**18. **According to the recommendations of IS : 456-1978, the expansion joints

- Are provided where plane changes abruptly
- Are provided to ensure minimum resistance
- Do not carry reinforcement across them
- All the above

Correct answer: (D)

All the above

**19. **According to Water-Cement Ratio Law, the strength of workable plastic concrete

- Depends upon the amount of water used in the mix
- Does not depend upon the quality of cement mixed with aggregates
- Does not depend upon the quantity of cement mixed with aggregates
- All the above

Correct answer: (D)

All the above

**20. **According to Whitney's theory, depth of stress block for a balanced section of a concrete beam is limited to

- 0.43 d
- 0.537 d
- 0.68 d
- 0.85 d

Where d is effective depth of beam

Correct answer: (B)

0.537 d