# Concrete Technology Questions and Answers – Process of Manufacture of Fresh Concrete

This set of Concrete Technology Question Bank focuses on “Process of Manufacture of Fresh Concrete”.

1. What is the moisture content in slurry for wet process?
a) 35-50%
b) 12%
c) 40-45%
d) 100%

Explanation: The moisture content in slurry for wet process is 35-50%. 12% is the moisture content for dry process.

2. The slurry, in its movement down the kiln, encounters a progressively higher temperature. At first, the water is driven off and __________ is liberated.
a) SiO2
b) CO2
c) Gypsum
d) CaO

Explanation: At 900°C limestone decomposes, CaCO3.CaO + CO2 (endothermic reaction) CO2 is swept away by current air.

3. For complete hydration of cement the w/c ratio needed is ________
a) More than 0.25
b) More than 0.25 but less than 0.35
c) More than 0.35 but less than 0.60
d) More than 0.60

Explanation: A mix with a ratio of 0.45 may not mix thoroughly, and may not flow well enough to be placed. More water is therefore used than is technically necessary to react with cement. Water–cement ratios of 0.45 to 0.60 are more typically used.

4. The minimum water to cement ratio for cement concrete to hydrate is _______
a) 0.65
b) 0.5
c) 0.38
d) 0.27

Explanation: Minimum water cement ratio is 0.38. It cannot be 35 kg. W/C ratio depends on the exposure condition of concrete but minimum water cement ratio is 0.38 for full hydration of concrete.

5. Approximate percentage range of A2O3 in OPC is _______
a) 17-25
b) 3-8
c) 3- 10
d) 4-15

Explanation: Percentage of A2O3 is 3-8, CaO has 60-67, SiO2 has 17-25, SO3 is 1-3, MgO has .1-4 and soda has .5-1.3.
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6. What is the percentage of iron oxide in white cement?
a) High
b) Very high
c) Medium
d) Very low

Explanation: As iron oxide gives the grey colour to cement, it is therefore necessary for white cement to keep the content of iron oxide as low as possible.

7. What is the percentage of air by volume in Air Entraining Cement?
a) 3-4
b) 10-11
c) 7-8
d) 9

Explanation: Entertainment of air also improves work ability and durability. It is recommended that air contents should be 03-04 % by volume.

Sanfoundry Global Education & Learning Series – Concrete Technology.

To practice Concrete Technology Question Bank, here is complete set of 1000+ Multiple Choice Questions and Answers.