Concrete Technology MCQ Question Answers

Concrete Technology MCQ 1

The test essentially done for quality control of portland cement is,

1. Setting time
2. Soundness
3. Tensile strength
4. All of the above

Answer

4. All of the above

Solution

For quality control of portland cement, the following tests are essentially done:

• Le-Chatelier test: The Le-Chatelier test is used to determine the soundness of OPC when it has been exposed to lime. The cement’s soundness is determined by two primary compounds: lime and magnesia.
• Blaine air permeability: Blaine air permeability is a metric for determining the fineness of the cement.
• The Vicat apparatus: The Vicat device is used to determine how long concrete takes to set and how consistent it is.
• Tensile testing machine: This machine is used to determine the concrete’s tensile strength.

Concrete Technology MCQ 2

If 1500 g of water is needed to make a cement paste with a regular consistency of 1875 g, the water percentage is,

1. 20%
2. 25%
3. 30%
4. 40%

Answer

2. 25%

Solution

Weight of water = 1500 g

Weight of cement paste = 1875 g

Weight of cement = 1875 – 1500 =  375 g

Percentage of water = weight of cement/weight of water=(375/1500)×100= 25%

Concrete Technology MCQ 3

The time it takes to remove the formwork under normal conditions with regular cement is:

1. 7 days for beam soffits
2. 14 days for bottom slabs spanning over 4.6 m
3. 21 days for bottom beams spanning over 6 m
4. All of the above

Answer

4. All of the above

Solution

According to clause 11.3.1 of IS 456: 2000

Type of Formwork	Minimum period before striking Formwork
Vertical formwork to columns, walls, and beams.	16 – 24 hrs (1 day)
Soffit formwork to slabs	3 days
Soffit formwork to beams	7 days
Props to slabs Spanning upto 4.5 m Spanning over 4.5 m	7 days 14 days
Props to beams and arches  Spanning upto 6 m Spanning over 6 m	14 days  21 days

Concrete Technology MCQ 4

The weights of a cylinder containing partially compacted and fully compacted concrete are Wp and Wf, respectively. If the compaction factor wp/wf is 0.95, the workability of concrete is

1. Medium
2. Very low
3. Low
4. High

Answer

4. High

Solution

Workability of concrete: Concrete’s workability refers to how easily it can be mixed, transported, molded, and compacted. It is also known as the energy required to overcome friction while compacting. Concrete’s workability is determined by:

• Slump test
• Compaction factor test
• Vee-bee consistometer
• Flow table test
• Kelly ball test

Degree of workability	Compaction Factor
Very low	0.78 – 0.80
Low	0.80 – 0.85
Medium	0.85 – 0.95
High	0.95 – 1.00
Very high	–

Concrete Technology MCQ 5

For given water content, workability decreases if the concrete aggregates contain an excess of

1. Thin particles
2. Flat particles
3. Elongated particles
4. All of the above

Answer

4. All of the above

Solution

Thin particles, flat particles, and elongated particles have more surface area, therefore more water is needed to get the workable paste of concrete. As a result, in the preceding situation, workability reduces for given water content.

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