# Concrete Technology Questions and Answers – Sampling

This set of Concrete Technology Multiple Choice Questions & Answers (MCQs) focuses on “Sampling”.

1. Loss on Ignition (L.O.I.) is the loss in weight of cement after being heated to ____________
a) 1000°C
b) 100°C
c) 500°C
d) 1500°C

Explanation: It indicates the prehydration or carbonation due to prolonged or improper storage of cement & clinker.

2. On cooling below 1250oC, C3S decomposes ____________
a) Fast
b) Slowly
c) Never
d) Depends on the conditions

Explanation: On cooling below 1250oC, C3S decomposes slowly but, if cooling is not too slow, C3S remains unchanged and is relatively stable at ordinary temperatures.

3. If the moisture content of 5 to 10% by weight, then the bulking of sand is increased by __________
a) 20
b) 30
c) 40
d) 50

Explanation: With the moisture content of 5 to 10% by weight, the bulking of sand is increased by 50.

4. When sand is fully dry then it’s volume is _________
a) Equal
b) Less
c) More
d) Can’t say

Explanation: When the sand is fully dry then there is 0 bulking in it. Therefore, the volume of sand will be same.

5. The mineral oil if present in mixing for concrete ______________
a) Improves strength
b) Reduces strength
c) Gives more slump
d) Gives a smooth surface

Explanation: The mineral oil is present in mixing for concrete increases strength for the concentration up to 2%.
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6. To neutralize 200 ml of sample should not require more than 10 ml of __________ normal HCI using methyl orange.
a) 1
b) .1
c) 10
d) .01

Explanation: To neutralize 200 ml of water sample the value of 0.1 normal HCI using methyl orange as an indicator should not require more than 10 ml.

7. The loss in weight should not exceed ________ % when tested with Na2SO4 and ________ % with MgSO4 solution.
a) 12, 18
b) 18, 12
c) 10, 15
d) 15, 10

Explanation: The loss in weight should not exceed 12 percent when tested with sodium sulphate and 18 percent with magnesium sulphate solution.

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