CUBE CASTING III YEAR

2.

Bleeding of concrete may be due to1. excess of water2. too much finishing3. coarse aggregates

1 and 2 only
2 and 3 only
1 and 3 only
1,2 and 3

Correct Answer

A. 1 and 2 only

Explanation

Bleeding of concrete refers to the excess water rising to the surface of freshly placed concrete. This can occur due to two reasons mentioned in the answer: 1) excess of water, which means that too much water was added during the mixing process, and 2) too much finishing, which means that excessive troweling or smoothing of the concrete surface was done. The third option, coarse aggregates, is not a cause of bleeding as it refers to the size of the particles used in the concrete mixture. Therefore, the correct answer is 1 and 2 only.

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3.

Minimum slab thickness as per IS 456:2000 is

25mm
15mm
20mm
10mm

Correct Answer

A. 15mm

Explanation

According to IS 456:2000, the minimum slab thickness is 15mm. This means that any slab constructed must have a minimum thickness of 15mm to meet the standards set by the Indian Standard code for reinforced concrete design.

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4.

Segregation can be prevented by

Properly grading the aggregate
Controlling water content in a mix
Using correct handling procedures
All the above

Correct Answer

A. All the above

Explanation

Segregation, which is the separation of coarse and fine particles in a mixture, can be prevented by properly grading the aggregate. This means ensuring that the different sizes of particles are distributed evenly. Controlling water content in a mix is also important as excessive water can cause the finer particles to separate from the coarser ones. Finally, using correct handling procedures, such as avoiding excessive dropping or sliding of the mixture, can also help prevent segregation. Therefore, all of the above options are correct ways to prevent segregation.

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5.

Bleeding can be prevented by

Controlling water content
Using finely ground cement
Controlling compaction
All the above

Correct Answer

A. All the above

Explanation

All the given options - controlling water content, using finely ground cement, and controlling compaction - can contribute to preventing bleeding in concrete. Controlling water content helps in achieving the desired consistency and reduces the risk of excessive bleeding. Using finely ground cement improves the particle packing and reduces water demand, which can also help in preventing bleeding. Controlling compaction ensures that the concrete is properly consolidated, reducing the chances of bleeding. Therefore, all the above options can play a role in preventing bleeding in concrete.

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6.

Concrete grows with age. This statement is

True
False
Debatable
Given by Duff Abrams

Correct Answer

A. True

Explanation

Concrete is a material that continues to gain strength and durability over time. As it cures, the chemical reactions within the concrete cause it to harden and become stronger. This process, known as hydration, can continue for several years, resulting in concrete that is stronger and more resistant to damage as it ages. Therefore, the statement "Concrete grows with age" is true.

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7.

The ease with which concrete can be compacted fully without segregation is called

Bleeding
Segregation
Workability
None of these

Correct Answer

A. Workability

Explanation

Workability refers to the ability of concrete to be easily mixed, placed, and compacted without any segregation. It is a measure of how easily the concrete can be worked with and manipulated. A concrete mix with good workability allows for proper placement and compaction, ensuring uniformity and strength in the final product. Bleeding refers to the separation of water from the concrete mix, while segregation refers to the separation of coarse aggregates from the mix. Therefore, the correct answer is workability.

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8.

When shear stress exceeds the permissible limit in a slab, then it is reduced by

Increasing the depth
Providing shear reinforcement
Using high strength steel
Using thinner bars but more in number

Correct Answer

A. Increasing the depth

Explanation

Increasing the depth of a slab helps to reduce shear stress because a deeper slab provides more resistance to shear forces. As the depth increases, the lever arm for the shear force also increases, resulting in a higher resisting moment. This increased resisting moment helps to distribute the shear stress over a larger area, reducing the overall shear stress in the slab. Therefore, increasing the depth is an effective way to reduce shear stress in a slab.

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9.

Bulking of sand is maximum if moisture content is about

2%
4%
6%
10%

Correct Answer

A. 4%

Explanation

The correct answer is 4%. Bulking of sand refers to the increase in volume of sand when it is moistened. As the moisture content increases, the surface tension between the sand particles decreases, causing them to separate and occupy more space. However, there is a limit to this bulking effect. When the moisture content exceeds a certain point, the sand particles become too saturated and the bulking effect decreases. Therefore, the maximum bulking of sand occurs at a moisture content of around 4%.

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10.

According to IS: 4561978, the column or the strut is the member whose effective length is greater than

The least lateral dimension
2 times the least lateral dimension
3 times the least lateral dimension
4 times the least lateral dimension

Correct Answer

A. 3 times the least lateral dimension

Explanation

According to IS: 4561978, the column or the strut is the member whose effective length is greater than 3 times the least lateral dimension. This means that the effective length of a column or strut should be at least 3 times its smallest lateral dimension. This requirement is specified to ensure the stability and strength of the column or strut, as a longer effective length can lead to increased buckling or bending moments. Therefore, the answer "3 times the least lateral dimension" is the correct choice according to the given standard.

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11.

Separation of cement paste from sand in the mortar allowing the water or cement paste to appear at the surface is called

Bleeding
Segregation
Honeycombing
None of these

Correct Answer

A. Bleeding

Explanation

Bleeding refers to the process of separation of cement paste from sand in the mortar, causing the water or cement paste to rise and appear on the surface. This occurs due to the settlement of solid particles in the mixture, leading to the upward movement of water. Bleeding can negatively affect the quality and strength of the concrete, as it can result in an uneven distribution of cement paste and reduce the bond between the concrete and reinforcement.

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12.

The temperature reinforcement in the vertical slab of a T-shaped R.C. retaining wall is

Not needed
Provided equally on inner and front faces
Provided more on inner face than on front face
Provided more on front face than on inner face

Correct Answer

A. Provided more on front face than on inner face

Explanation

The correct answer is "Provided more on front face than on inner face". The reason for this is that the front face of the retaining wall is more exposed to external heat sources, such as sunlight, compared to the inner face. Therefore, the temperature reinforcement needs to be increased on the front face to compensate for the higher temperature gradient and prevent cracking or other thermal-related issues.

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13.

Concrete in the structural member has to pass through

Plastic stage
Hardened stage
Both (a) and (b)
Neither (a) nor (b)

Correct Answer

A. Both (a) and (b)

Explanation

Concrete in a structural member goes through both the plastic stage and the hardened stage. In the plastic stage, the concrete is still malleable and can be molded into shape. It is during this stage that the concrete is poured and compacted into the formwork. Once the concrete starts to harden, it enters the hardened stage where it gains strength and becomes rigid. Both stages are crucial for the proper development and performance of the structural member.

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14.

Consider the following statements Sand in mortar is needed for1. decreasing the quantity of cement2. reducing shrinkage3. decreasing the surface area of the binding material4. increasing the strengthOf these statements

2,3, and 4 are correct
1,2 and 3 are correct
1,3 and 4 are correct
1,2 and 4 are correct

Correct Answer

A. 1,2 and 3 are correct

Explanation

Sand in mortar is needed for decreasing the quantity of cement, reducing shrinkage, and decreasing the surface area of the binding material. By adding sand to the mortar mixture, the amount of cement required can be reduced while still maintaining the desired strength. Sand also helps to reduce shrinkage by providing a filler material that can accommodate the drying and curing process of the mortar. Additionally, sand helps to decrease the surface area of the binding material, which can improve the workability and cohesion of the mortar mixture. Therefore, statements 1, 2, and 3 are correct.

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15.

Diagonal tension in a beam

Is maximum at neutral axis
Decreases below the neutral axis and increases above the neutral axis
Increases below the neutral axis and decreases above the neutral axis
Remains same

Correct Answer

A. Increases below the neutral axis and decreases above the neutral axis

Explanation

The diagonal tension in a beam increases below the neutral axis because the beam is subjected to compressive forces in this region, which causes the tension to increase. On the other hand, the diagonal tension decreases above the neutral axis because the beam is subjected to tensile forces in this region, which causes the tension to decrease. This pattern of tension distribution is due to the bending moment acting on the beam, which causes varying stress and strain along its cross-section.

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Cube Casting III Year

Separation of the coarse aggregate from mortar is called

Quiz Preview

Bleeding of concrete may be due to1. excess of water2. too much finishing3. coarse aggregates

Minimum slab thickness as per IS 456:2000 is

Segregation can be prevented by

Bleeding can be prevented by

Concrete grows with age. This statement is

The ease with which concrete can be compacted fully without segregation is called

When shear stress exceeds the permissible limit in a slab, then it is reduced by

Bulking of sand is maximum if moisture content is about

According to IS: 4561978, the column or the strut is the member whose effective length is greater than

Separation of cement paste from sand in the mortar allowing the water or cement paste to appear at the surface is called

The temperature reinforcement in the vertical slab of a T-shaped R.C. retaining wall is

Concrete in the structural member has to pass through

Consider the following statements Sand in mortar is needed for1. decreasing the quantity of cement2. reducing shrinkage3. decreasing the surface area of the binding material4. increasing the strengthOf these statements

Diagonal tension in a beam