Civil Engineering Objective Questions { Concrete Technology }

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22. Efflorescence imcement is caused dim to an excess of

23. Pick up the incorrect statement from the following :

A. Tricalcium silicate (C3S) hydrates rapidly

B. Tricalcium silicate (C3S) generates more heat of hydration

C. Tricalcium silicate (C3S) develops early strength

D. Tricalcium silicate (C3S) has more resistance to sulphate attack

24. Di-calcium silicate (C2S)

A. hydrates rapidly

B. generates less heat of hydration

C. hardens rapidly

D. provides less ultimate strength to cement

25. Tricalcium aluminate (C3A)

A. reacts fast with water

B. generates less heat of hydration

C. causes initial setting and early strength of cement

D. does not contribute to develop ultimate strength

26. Pick up the correct statement from the following :

A. High percentage of CS and low percentage of C2S cause rapid hardening

B. High percentage of C3S and low percentage of C2S make the cement less resistive to chemical 'attack

C. Low percentage of C3S and high percentage of C2S contribute to slow hardening

D. All the above

27. Pick up the incorrect statement from the following :

A. The degree of grinding of cement, is called fineness

B. The process of changing cement paste into hard mass, is known as setting of cement

C. The phenomenon by virtue of which cement does not allow transmission of sound, is known as soundness of cement

D. The heat generated during chemical reaction of cement with water, is known as heat of hydration

28. For an ordinary Portland cement

A. residual does not exceed 10% when sieved through IS Sieve No 9

B. soundness varies from 5 to 10 mm

C. initial setting time is not less than 30 minutes

D. compressive stress after 7 days, is not less than 175 kg/cm2

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