Civil Engineering - Concrete Technology

11. 

Pick up the incorrect statement from the following:

A. Workability of the concrete mix decreases with an increase in the moisture content
B. Concrete for which preliminary tests are conducted, is called controlled concrete
C. Bulking of sand depends upon the fineness of grains
D. Concrete mix 1 : 6 : 12, is used for mass concrete in piers.
E. All the above.

Answer: Option E

Explanation:

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12. 

Sand generally contains salt if it is obtained from:

A. nala beds
B. river beds
C. sea beds
D. all the above
E. none of these.

Answer: Option C

Explanation:

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13. 

The impurity of mixing water which affects the setting time and strength of concrete, is

A. sodium sulphates
B. sodium chlorides
C. sodium carbonates and bicarbonates
D. calcium chorides
E. calcium bicarbonates

Answer: Option C

Explanation:

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14. 

Pick up the correct statement from the following:

A. Continuous grading is not necessary for obtaining a minimum of air voids
B. The omission of a certain size of aggregate is shown by a straight horizontal line on the grading curve
C. The omission of a certain size of aggregate in concrete increases the workability but also increases the liability to segregation
D. All the above.

Answer: Option D

Explanation:

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15. 

Di-calcium silicate (C2S)

A. hydrates rapidly
B. generates less heat of hydration
C. hardens rapidly
D. provides less ultimate strength to cement
E. has less resistance to sulphate attack.

Answer: Option B

Explanation:

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