29. The grade of reinforced concrete to be used in sea water or structures exposed to sea water should be

A.M10

B. M 15

C. M 20

D. M 30.

30. The maximum compressive strength on 15 cm cubes of M 20 grade concrete at 7 days, should be a minimum of

A. 7 N/mm2

B. 10 N/mm2

C. 15 N/mm2

D. 20 N/mm2,

31. The minimum compressive strength on 15 cm cubes of M 30 grade concrete at 7 days, should be a minimum of

A. 7 N/mm2

B. 10 N/mm2

C. 20 N/mm2

D. 30 N/mm2,

32. The ratio of minimum compressive strength on 15 cm cubes prepared with the concrete of M 20 grade and M 40 grade, at 7 days should be at least

A.3

B. 1/2

C.1

D. 2.0.

33. The test strength of the sample is taken as the average of the strength of

A. 2 specimens

B. 3 specimens

C. 4 specimens

D. 5 specimens.

34. If A is the deviation of the individual test strength from the average of n samples, the standard deviation of concrete of the given grade is

A. 10 mm

B. 20 mm

C. 30 mm

D. 40 mm

35. The concrete is deemed not to comply with the strength requirements if the strength is less than the greater of

A. characteristic strength minus 1.35 times the standard deviation

B. 0.8 times the characteristic strength

C. the average strength of all the samples is less than the hour

D.lead test, provided the maximum deflection in mm is less than

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