21. The minimum stripping time before striking of formwork in case of reinforced concrete (RC) column is

- 7 days
- 14 days
- 21 days
- None of the above options

22. Which of the following pairs in respect of ordinary Portland cement are correctly matched?

- Initial setting times: 30 minutes
- Final setting times: 10 hours
- Normal consistency: 10%

- i, ii and iii
- ii and iii
- i and ii
- i and iii

23. Bulking of sand is

- compaction of sand
- segregating sand of particular size
- increase in volume of sand due to presence of moisture up to certain extent
- type of sand

24. Grading of aggregate in the concrete mix is necessary to achieve

- better durability
- reduction in voids
- higher density
- adequate workability

25. The fineness modulus of the fine aggregates should be between

- 5 to 6
- 4 to 5
- 3 to 4
- 2 to 3

26. The aggregate which pass through 4.75 mm IS sieve and entirely retain on 75 micron IS sieve is called

- cyclopean aggregate
- coarse aggregate
- fine aggregate
- all in aggregate

27. Purpose of slump test in concrete is to ensure

- workability
- strength
- durability
- soundness

28. The compressive strength of concrete determined from 15 cm × 15 cm @ cylinder as compared to that from 15 cm × 30 cm @ cylinder is

- more
- less
- equal
- dependant on mix proportion

29. An aggregate is said to be flaky; if its least dimension is less than

- 3/4 of mean dimension
- 3/5 of mean dimension
- 2/4 of mean dimension
- 5/8 of mean dimension

30. In design of a concrete mix by Fineness modulus method the value of F.M. of coarse aggregated is 7.3, the value of fine aggregate is 2.8 and value of F.M. of combined aggregates is 6.4. The percentage of fine aggregate to combined aggregate is

- 50
- 25
- 65
- 75