Concrete Technology Questions and Answers - Quality of Water

1. Which of the following statement is incorrect?
a) Water is the most important and least expensive ingredient of concrete
b) Excess of water forms scum
c) Less amount of water may cause honeycombing
d) Mixing of water is used in the hydration of cement and provides lubrication between fine and coarse aggregates.

Answer: c
Explanation: Excess amount of water may cause honey combing and less amount of water gives high density to the concrete.

2. Which of the following statement is incorrect for mixing water?
a) Suspended particles of clay and slit < .02%
b) The quality of CaCl2 is restricted to 1.5%
c) The pH value of water should be between 6-8
d) Free vegetable oil is beneficial

Answer: d
Explanation: Free vegetable oil is harmful but mineral oil up to 2% is beneficial to concrete for making healthy structure.

3. The vegetable oil if present in mixing for concrete __________
a) Improves strength
b) Reduces strength
c) Gives more slump
d) Gives a smooth surface

Answer: b
Explanation: If vegetable oil is present in mixing of concrete then it will reduces the strength due to more lubrication

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

Answer: a
Explanation: The mineral oil if present in mixing for concrete increases strength for the concentration up to 2%.

5. With regard to the curing water, identify the incorrect statement.
a) Curing water shouldn’t produce objectionable stains on the surface
b) The presence of tannic acid and iron compounds is objectionable
c) Iron and organic matter are responsible for staining
d) Water is suitable for mixing is also suitable for curing

Answer: c
Explanation: With regard to the curing water, Iron and organic matter are responsible for staining.

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

Answer: b
Explanation: To neutralize 200 ml of sample should not require more than 10 ml of 0.1 normal HCI using methyl orange as an indicator and .1 and .01 is very slow process.

7. To neutralize 200 ml sample of water should not require more than _________ ml of 0.1 normal NaOH.
a) 1
b) 2
c) 3
d) 4

Answer: b
Explanation: To neutralize 200 ml water sample should not require more than 2 ml of 0.1N Caustic soda with more than 6 pH of the water.

8. What is the permissible limits for construction of organic matter in water?
a) 200mg/l
b) 2000mg/l
c) 3000mg/l
d) 500mg/l

Answer: a
Explanation: 200mg/l is the standard value for the permissible limits for construction of organic matter in water

9. What is the permissible limits for construction of inorganic matter in water?
a) 200mg/l
b) 2000mg/l
c) 3000mg/l
d) 500mg/l

Answer: c
Explanation: 3000mg/l is the standard value for the permissible limits for construction of inorganic matter in water.

10.What is the permissible limits for construction of suspended matter in water?
a) 200mg/l
b) 2000mg/l
c) 3000mg/l
d) 500mg/l

Answer: b
Explanation: 2000mg/l is the standard value for the permissible limits for construction of suspended matter in water.