Quiz: Civil Engineering
Exam: DFCCIL
Topic: Concrete Technology
Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. The entrained air in concrete ……………..
(a) Increases workability
(b) Increases strength
(c) Increases the unit weight
(d) Increases the effect of temperature variation
Q2. The bottom diameter, top diameter and the height of a slump mould are …………
(a) 30 cm, 20 cm, 10 cm
(b) 10 cm, 30 cm, 20 cm
(c) 20 cm, 30 cm, 10 cm
(d) 20 cm, 10 cm, 30 cm
Q3. No fines concrete is prepared by _
(a) By adding no fines material from normal concrete
(b) By increasing its strength
(c) By decreasing its strength
(d) By omitting no fines material from normal concrete
Q4. The cement concrete, from which excess water and entrained air are removed after placing it in position, is called _
(a) Vacuum concrete
(b) Prestressed concrete
(c) Sawdust concrete
(d) Low weight concrete
Q5. Too wet concrete may cause _:
A. Segregation
B. Lower density
C. Weakness of concrete
D. Increase strength of concrete
E. Decrease shrinkage
(a) A, B & D
(b) B, D & E
(c) A, B & C
(d) A, D & E
Q6. Which among the following is not a non-destructive test for concrete?
(a) Ultrasonic pulse velocity test
(b) Rebound hammer test
(c) Falling weight Deflectometer
(d) Core test
Q7. An excess of flaky particles in concrete aggregates.
A. Decrease the quantity of water and sand
B. Reduce the durability of concrete
C. Increase workability of concrete
D. Reduce the strength of concrete
(a) Only A & C
(b) Only B & D
(c) Only B & C
(d) Only A & D
Q8. According to IS 456 : 2000, what is the modulus of elasticity (E) of M25 concrete?
(a) 18000 N/mm²
(b) 20000 N/mm²
(c) 25000 N/mm²
(d) 35000 N/mm²
Q9. Calcium chloride and Tri-ethanol amine are the examples of___________
(a) Accelerators
(b) Retarders
(c) Plasticizers
(d) Air entraining agents
Q10. Consider the following statements:
Admixtures are added to concrete to
1. Increase its strength.
2. Reduce heat of hydration.
3. Delay the setting of cement.
4. Reduce water-cement ratio.
Which of the above statements is/are correct?
(a) 1 only
(b) 1 and 2
(c) 2 and 3
(d) 3 and 4
Solutions
S1. Ans.(a)
Sol. Air entrained agent increase the workability of concrete and also increase in resistance to freezing and thawing while decrease the strength of concrete. There are some examples of air entrained agent like wood resins, animal fatty oils, steric acid etc.
S2. Ans.(d)
Sol. Mould for slump –
Slump test is performed for measurement of workability.S3. Ans.(d)
Sol.
- No fines concrete is a type of light weight concrete.
- It is prepared by omitting no fines materials such as sand from normal concrete.
- In no fines concrete, Aggregate cement ratio varies from 6:1 to 10:1.
S4. Ans.(a)
Sol. Vacuum concrete is the type of concrete in which entrained air and excess water is removed with the help of vacuum mats connected to a vacuum pump. It improves the strength of concrete.
S5. Ans.(c)
Sol. Too wet concrete reduces the strength of concrete, excessive laitance and it may cause segregation and increase the shrinkage of concrete.
S6. Ans.(c)
Sol. Falling weight Deflectometer test is a destructive test while ultrasonic pulse velocity test, rebound hammer test and core test are non-destructive test for concrete.
S7. Ans.(b)
Sol. Flaky aggregates are not suitable for concrete works as they –
1. Reduces the durability of concrete.
2. Increases the quantity of water and sand.
3. Reduces the strength of concrete.
4. Reduces the durability of concrete.
S8. Ans.(c)
Sol. As per IS 456 : 2000
Modulus of elasticity (E) = 5000 √fck
= 5000√25
= 25000 N/mm²
S9. Ans.(a)
Sol. Accelerator → These are the admixtures which is used to accelerate the process of hydration. They decrease the setting time of cement, increase shrinkage and accelerate setting. They are commonly used in cold weather conditions.
Ex. Calcium Chloride (〖CaCl〗_2), Tri-ethanol amine, Sodium hydroxide (NaOH), Silicates etc.
S10. Ans.(d)
Sol. Admixture are added to concrete →
- To delay in setting of cement
- To reduce water-cement ratio.
- To accelerate hydration.
- To improve durability & workability.
- To reduce segregation & bleeding.
- To decreases the density of concrete.
