15.  Pick up the incorrect statement from the following :
A. Admixtures accelerate hydration
B. Admixtures make concrete water proof
C. Admixtures make concrete acid proof
D. Admixtures give high strength

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16. The rock which is not calcareous, is :
A. lime stone
B. macl
C. chalk
D. laterite

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17. To obtain cement dry powder, lime stones and shales or their slurry, is burnt in a rotary kiln at a temperature between
A. 11000 and 1200?C
B. 1200? and 1300?C
C. 1300' and 1400?C
D. 1400? and 1500?C

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18.  The maximum percentage of chemical ingredient of cement is that of
A. magnesium oxide
B. iron oxide
C.- aluminium
D. lime

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19.  The minimum percentage of chemical ingredient of cement is that of
A. magnesium oxide
B. iron oxide
C. alumina
D. lime

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20.  Pick up the correct proportions of chemical ingredients of cement
A. Lime : Silica : Alumina : Iron oxide : 63 : 22 : 6 : 3
B. Silica : Lime : Alumina : Iron oxide : 63 : 22 : 6 : 3
C. Alumina : Silica : Lime : Iron oxide : 63 : 22 : 6 : 3
D. Iron oxide : Alumina : Silica : Lime : 63 : 22 : 6 : 3

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21.  Pick up the correct statement from the following :
A. Lime in excess, causes the cement to expand and disintegrate
B. Silica in excess, causes the cement to set slowly
C. Alumina in excess, reduces the strength of the cement
D. All the above

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