#### Concrete Technology

1

Placing of concrete should preferably be done at a temperature of

A.  0^circ C
B.  10^circ C
C.  20^circ C
D. 23^circ C
E. 27 pm 2^circ C

2

For the construction of the retaining structures, the type of concrete mix to be used, is

A. 1 : 3 : 6
B. 1 : 2 : 4
C.  1 : 1 1/2 : 3
D. 1 : 1 : 2
E. 1 : 4 : 8

3

Pick up the incorrect statement from the following:

.
A. Tricalcium silicate (C_ 3 S) hydrates rapidly
B. Tricalcium silicate (C_3 S) generates more heat of hydration
C. Tricalcium silicate (C_3 S) develops early strength
D. Tricalcium silicate (C_3 S) has more resistance to sulphate attack
E. None of these.

4

If X, Y and Z are the fineness modulli of coarse, fine and combined aggregates, the percentage (P) of fine aggregates to combined aggregates, is

A.  P = (Z - X)/(Z - Y) xx 100
B.  P = (X - Z)/(Z - Y) xx 100
C.  P = (X - Z)/(Z + Y) xx 100
D.  P = (X + Z)/(Z - Y) xx 100
E.  P = (Z - X)/(Y - Z) xx 100

5

Wp and Wf are the weights of a cylinder containing partially compacted and fully compacted concrete. If the compaction factor (W_p/W_f)  is 0.95, the workability of concrete is

A. extremely low
B. very low
C. low
D. high
E. none of these.