239. Strength of concrete with passage of time
A. increases
B. decreases
C. fluctuates
D. remains constant
240. Concrete gains strength due to
A. chemical reaction of cement with sand and coarse aggregates
B. evaporation of water from concrete
C. hydration of cement
D. All the above
241. Pick up the correct statement the following:
A. Ordinary portland cement is susceptible to the attack of magneisum sulphate
B. In set-cement, sulphates reactwiththe free calcium hydroxide to form calcium sulphate
C. Solid sulphates do not attck the cement compound
D. all the above
242. For the preparaton of lowheat cement, the contents of
A. C3S and C3A are reduced and content of C2S is increased
B. C2S and C3S are reduced and content of C3S is increased
C. C3A and C2S are reduced and that of C3S is increased
D. C2S, C3S and C3A are reduced
243. Vicat apparatus is not sued for
A. normal consistency test of cement
B. initial setting time of cement
C. final seting time of cement
D. compressive strength of cement
244. Pick up the wrong specification of Vicat apparatus from the following:
A. Diameter of Vicat mould-80 mm
B. Height of Vicat mould-40 mm
C. Diameter of the Vicat plunger -10 mm
D. Length of the Vicat plungr-50 mm
245. The initial setting time of ordinary port land cement should be:
A. 30 minutes
B. less than 30 minutes
C. more than 30 minutes
D. None of the above
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