This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Hydration of Cement”.
1. What is hydration of cement?
a) Chemical reaction of cement with acid
b) Chemical reaction of cement with water
c) Chemical reaction of cement with base
d) Chemical reaction of cement with salt, and acid
View Answer
Explanation: As water comes into contact with cement particles, hydration reactions immediately starts at the surface of the particles.
2. As the hydration proceeds the deposits of hydrated products on the original cement grains makes the diffusion of water to unhydrated nucleus ________
a) Easy
b) Very difficult
c) Very easy
d) Average
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Explanation: It is difficult thus the rate of hydration decreases with time & as result hydration may take several years.
3. The development of first 28 days strength is on account of the hydration of __________
a) C2S
b) C3S
c) C3A
d) C4AF
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Explanation: Higher C3S→higher early strength-higher heat generation (roads, cold environments). Higher C
4. Which compound is liberates higher heat?
a) C2S
b) C3S
c) C3A
d) C4AF
View Answer
Explanation: C3S having a faster rate of reaction accompanied by greater heat generation developes early strength of the paste.
5. Which compound is liberates lower heat?
a) C2S
b) C3S
c) C3A
d) C4AF
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Explanation: C2S hydrates & hardens slowly so results in less heat generation & developes most of the ultimate strength.
6. Which compound may lead to a rapid stiffening of the paste with a large amount of the heat generation?
a) C2S
b) C3S
c) C3A
d) C4AF
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Explanation: C3A is characteristically fast reacting with water & may lead to a rapid stiffening of the paste with a large amount of the heat generation (Flash-Set)-(Quick-Set).
7. In order to prevent this rapid reaction _______ is added to the clinker.
a) C4AF
b) Gypsum
c) Water
d) Extra cement
View Answer
Explanation: In order to prevent this rapid reaction gypsum is added to the clinker. Gypsum, C3A&water react to form relatively insoluble Calcium-Sulfo-Aluminates.
Sanfoundry Global Education & Learning Series – Concrete Technology.
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