# Floating Concrete II Year

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Tb17omv
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Quizzes Created: 8 | Total Attempts: 1,398
Questions: 15 | Attempts: 171

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• 1.

### The aggregate in which particle of all sizes are present in various proportions is called

• A.

• B.

All-in-aggregate

• C.

Single size aggregate

• D.

None of these

Explanation
Graded aggregate refers to an aggregate in which particles of all sizes are present in various proportions. This means that the aggregate contains a range of particle sizes, from large to small, rather than consisting of only one size or being a mixture of specific sizes. This type of aggregate is commonly used in construction projects as it helps to create a more stable and durable final product. The other options, all-in-aggregate and single size aggregate, refer to aggregates that consist of only one size or a mixture of specific sizes, whereas "none of these" implies that none of the given options are correct.

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• 2.

### The aggregate in which majority of particles are one and same size is called

• A.

• B.

All-in-aggregate

• C.

Continuous aggregate

• D.

None of these

D. None of these
Explanation
The correct answer is "none of these" because the question is asking for the aggregate in which the majority of particles are one and the same size. However, none of the options provided in the question accurately describe this type of aggregate. Graded aggregate refers to a mixture of different sized particles, all-in-aggregate refers to a mixture of fine and coarse aggregates, and continuous aggregate is not a recognized term in the context of particle size distribution in aggregates. Therefore, the correct answer is "none of these."

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• 3.

### The maximum size of coarse aggregate for the concrete in a column of size 400 x 400 mm should be

• A.

40 mm

• B.

35 mm

• C.

25 mm

• D.

20 mm

D. 20 mm
Explanation
The maximum size of coarse aggregate for the concrete in a column of size 400 x 400 mm should be 20 mm. This is because larger aggregate sizes can lead to difficulties in achieving proper compaction and can create voids in the concrete. A smaller aggregate size ensures better workability and helps in achieving a more uniform distribution of the aggregate throughout the concrete mix. Additionally, a smaller aggregate size can also improve the overall strength and durability of the concrete.

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• 4.

### As the size of coarse aggregate decreases, the workability of concrete

• A.

Decreases

• B.

Increases

• C.

First increases then decreases

• D.

First decreases then increases

A. Decreases
Explanation
When the size of coarse aggregate decreases, it means that the aggregate particles are smaller in size. Smaller particles have a larger surface area compared to larger particles, which leads to increased friction between the particles. This increased friction makes it more difficult for the particles to move past each other, resulting in a decrease in workability. Workability refers to the ease with which the concrete can be mixed, placed, and compacted. Therefore, as the size of coarse aggregate decreases, the workability of concrete decreases.

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• 5.

### Shape of crushed rocks is

• A.

Rounded

• B.

Irregular

• C.

Flaky

• D.

Angular

D. Angular
Explanation
The correct answer is angular because crushed rocks typically have sharp edges and corners, giving them an angular shape. This is often a result of the crushing process, which breaks the rocks into smaller pieces without significantly rounding their edges. The other options, such as rounded, irregular, and flaky, do not accurately describe the typical shape of crushed rocks.

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• 6.

### The shape of  laminated rock is

• A.

Rounded

• B.

Flaky

• C.

Irregular

• D.

Angular

B. Flaky
Explanation
The correct answer is "flaky." This suggests that the shape of laminated rock is characterized by thin layers or flakes that easily separate from each other. This can be observed in rocks that have undergone a process called lamination, where sediments or minerals have been compressed and layered over time. The flaky shape is a result of the rock's composition and the forces that have acted upon it, such as pressure and erosion.

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• 7.

### River gravel is

• A.

Flaky

• B.

Irregular

• C.

Angular

• D.

Rounded

D. Rounded
Explanation
River gravel is typically shaped by the constant movement of water, which smooths and rounds the edges of the stones over time. This is why river gravel is characterized as rounded. The other options, such as flaky, irregular, and angular, do not accurately describe the shape of river gravel.

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• 8.

### Following shape of particle is not desirable in aggregate

• A.

Rounded

• B.

Irregular

• C.

Angular

• D.

Flaky

D. Flaky
Explanation
Flaky particles are not desirable in aggregates because they have a flat and elongated shape. This shape can result in poor interlocking between particles, leading to a weaker and less stable aggregate structure. Flaky particles also tend to have a larger surface area compared to their volume, which can negatively affect the overall strength and durability of the aggregate. Therefore, rounded, irregular, and angular particles are preferred over flaky particles for better aggregate performance.

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• 9.

### Flaky shape is not desirable because it has

• A.

Lowest surface area for given volume

• B.

Highest surface area for given volume

• C.

Lowest perimeter for a given volume

• D.

None of these

B. Highest surface area for given volume
Explanation
A flaky shape is not desirable because it has the highest surface area for a given volume. This means that there is a greater amount of exposed surface area compared to the amount of space it occupies. This can lead to increased vulnerability to external factors such as weathering, erosion, and damage. Additionally, a high surface area to volume ratio can also result in increased heat loss or gain, making it less energy efficient.

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• 10.

### Flaky particle in aggregate

• A.

Reduces workability

• B.

Reduces durability

• C.

Hardened concrete looks like a stratified rock

• D.

All of these

D. All of these
Explanation
The presence of a flaky particle in aggregate can have multiple negative effects on concrete. It can reduce workability, making it more difficult to mix and shape the concrete. It can also reduce durability, as the flaky particles may not bond well with the cement paste, leading to weaker concrete. Additionally, when the concrete hardens, it may have a stratified rock-like appearance due to the uneven distribution of the flaky particles. Therefore, all of these effects can be observed when there is a flaky particle in the aggregate.

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• 11.

### The percentage of tricalcium aluminates in sulphate resisting cement is

• A.

More than 6%

• B.

Less than 6%

• C.

More than 16%

• D.

Less than 16%

B. Less than 6%
Explanation
The correct answer is less than 6% because sulphate resisting cement is specifically designed to have a low percentage of tricalcium aluminates. Tricalcium aluminates are highly reactive with sulfates, which can lead to the formation of expansive products that can cause cracking and deterioration of the cement. By limiting the percentage of tricalcium aluminates to less than 6%, the cement is able to resist the harmful effects of sulfates and maintain its strength and durability over time.

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• 12.

### Sulphate resisting cement is useful in structures

• A.

In river waters

• B.

Sea waters

• C.

In cold environment

• D.

In hot environment

B. Sea waters
Explanation
Sulphate resisting cement is useful in structures in sea waters because sea water contains high levels of sulphates, which can react with regular cement and cause deterioration. Sulphate resisting cement is specially formulated to resist the corrosive effects of sulphates, making it suitable for use in structures exposed to sea water.

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• 13.

### Portland blast furnace slag cement can be used

• A.

In under water structures

• B.

In structures in alkaline soils

• C.

In all places where ordinary Portland cement is used

• D.

All of these

C. In all places where ordinary Portland cement is used
Explanation
Portland blast furnace slag cement is a type of cement that is made by blending Portland cement clinker with granulated blast furnace slag. This type of cement has several advantages, including improved workability, reduced heat of hydration, and increased resistance to chemical attack. It can be used in all places where ordinary Portland cement is used because it possesses similar properties and can provide the same strength and durability. Therefore, it is a suitable alternative to ordinary Portland cement in various construction applications.

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• 14.

### Slag from blast furnace contains

• A.

Alumina

• B.

Lime

• C.

Silica

• D.

All of these

D. All of these
Explanation
Slag from a blast furnace contains all of these components: alumina, lime, and silica. Slag is a byproduct of the iron-making process in a blast furnace, where impurities in the iron ore combine with fluxes to form a molten slag. Alumina, lime, and silica are commonly found in the impurities and fluxes used in the process. Therefore, the correct answer is that slag from a blast furnace contains all of these components.

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• 15.

### Blast furnace slag has approximately

• A.

45% calcium oxide and about 35% silica

• B.

50% alumina and 20% calcium oxide

• C.

25% magnesia and 15% silica

• D.

25% calcium sulphate and 15% alumina