This set of Basic Civil Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Manufacture of Concrete”.
1. Which process comes after batching in manufacture process?
a) Transportation
b) Placing
c) Mixing
d) Compacting
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Explanation: Batching involves measuring the amount of raw materials required for the manufacture of concrete. The next step is to mix all these ingredients together.
2. Ready mix plant and central mix plant differ in:
a) Transportation
b) Setting time
c) Properties
d) Water addition
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Explanation: In ready mix plants, all the other ingredients are mixed, except water. While in central mix plants, water is also mixed along with other ingredients.
3. How many methods of batching are there?
a) 2
b) 3
c) 5
d) 6
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Explanation: There are 2 types of batching – weigh and volume batching. In volume batching, volumetric measure of materials is taken (1 bag cement-35 litre). In weigh batching, measurement is in terms of weight (1 bag cement-50 kg).
4. What is the maximum height through which concrete can be poured?
a) 0.1-0.6 m
b) 0.8-1 m
c) 0.5 m
d) 2 m
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Explanation: Concrete consists of coarse aggregates. If it is placed or poured from a height above 1 m, segregation of coarse aggregate will take place, leading to improper distribution. It affects the strength parameter.
5. How many types of machine mixers are available?
a) 2
b) 5
c) 6
d) 3
View Answer
Explanation: Based on the technique of discharging mixed concrete, there are 3 types of mixers available. They are tilting type, non-tilting type and pan type mixers.
6. In small works, concrete is transported using:
a) Conveyer belts
b) Pumps
c) Pans
d) Buckets
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Explanation: In small works, less quantity of concrete is required. So, workers carry it in a pan atop their heads. Conveyer belts and pumps are used for large construction works.
7. Compacting is done to:
a) Place concrete on flat surface
b) Remove air bubbles
c) Place concrete on sloping surface
d) Introduce air bubbles
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Explanation: While mixing of concrete, sometimes air gets trapped in it in the form of bubbles. These have to be removed to ensure strength parameters are met with.
8. Concrete is generally placed on a:
a) Form work
b) Stand
c) Mould
d) Platform
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Explanation: Form work is a mould in which concrete is poured and allowed to set. It should be properly oiled and cleaned before pouring concrete. It can be used to cast beams, slabs, columns, etc.
9. Which is the best method for curing flat surfaces?
a) Spraying water
b) Placing wet gunny bags
c) Applying curing compounds
d) Stagnating water
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Explanation: Curing is the process of maintaining moisture in freshly laid concrete to strengthen it. For flat surfaces like floors and slabs, ponding or stagnating water is the best method. Temporary bund can be made with mortar and filled with water to cure.
10. Excess vibration during compacting can lead to:
a) Bleeding
b) Segregation
c) High strength
d) Air bubbles
View Answer
Explanation: Over vibration may lead to a problem called segregation. The coarse aggregate is separated from the cement matrix. This leads to low strength.
11. Steam curing is adopted for:
a) Precast structures
b) Columns
c) Beams
d) Walls
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Explanation: The precast structures are placed in enclosed chambers. Then the steam is pumped into the chamber. It accelerates the hydration of concrete and it is left for the curing period.
12. A gap of 0.3m is to maintained between cement bag and wall, while storing cement.
a) True
b) False
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Explanation: The storage of cement is important. It should not be placed too close to the wall or other cement bags to avoid air circulation around bags. It may dampen the cement and make it useless.
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