Test: B.M.C Soil,Concrete- 1 - Civil Engineering (CE) MCQ

Definition of an unstratified rock:
An unstratified rock, also known as a massive rock, is a type of rock formation that lacks distinct layers or stratification. Instead, it appears as a solid mass without any visible bedding planes or divisions.
Analysis of the given options:
Out of the options provided, the unstratified rock can be identified by examining the characteristics of each rock type:
A: Sandstone:
- Sandstone is a sedimentary rock formed from sand-sized grains.
- It typically exhibits visible layers or stratification due to the deposition of sediment over time.
- Therefore, sandstone cannot be classified as an unstratified rock.
B: Limestone:
- Limestone is also a sedimentary rock composed mostly of calcium carbonate.
- It can exhibit layers or bedding planes, known as bedding structures or fossils.
- Therefore, limestone cannot be classified as an unstratified rock.
C: Marble:
- Marble is a metamorphic rock formed from the recrystallization of limestone or dolomite.
- It lacks visible layers or stratification and appears as a solid mass without distinct bedding planes.
- Marble can be classified as an unstratified rock.
D: Slate:
- Slate is a metamorphic rock derived from shale or mudstone.
- It typically exhibits visible layers or foliation, which are parallel arrangements of minerals.
- Therefore, slate cannot be classified as an unstratified rock.
Conclusion:
Based on the analysis, the rock that can be termed as an unstratified rock out of the given options is C: Marble.

Chemical Composition of Marble:
- Marble is primarily composed of calcium carbonate (CaCO3), which is a chemical compound consisting of calcium, carbon, and oxygen.
- It is formed from the metamorphism of limestone, which undergoes heat and pressure over time, causing the minerals in the limestone to recrystallize and form marble.
Classification of Marble:
- Marble is classified as a calcareous rock due to its high calcium carbonate content.
- Calcareous rocks are those that are primarily composed of calcium carbonate or similar minerals derived from the remains of marine organisms.
- Other examples of calcareous rocks include limestone and chalk.
Properties of Marble:
- Marble is known for its characteristic veined patterns and wide range of colors, which are the result of impurities present in the original limestone.
- It is a relatively soft rock, with a Mohs hardness scale rating of 3-4.
- Marble is often used in construction, sculpture, and decorative applications due to its aesthetic appeal and workability.
Conclusion:
- Chemically, marble is classified as a calcareous rock due to its high calcium carbonate content.
- It is formed through the metamorphism of limestone and exhibits characteristic veined patterns and a wide range of colors.
- Marble is a versatile material widely used in various industries for its aesthetic appeal and workability.

Plaster of Paris is obtained by calcining.
Plaster of Paris is a white powder that is commonly used for making casts, molds, and other art and craft projects. It is obtained by a process called calcining, which involves heating a specific mineral to a high temperature and then grinding it into a fine powder.
The mineral used for making Plaster of Paris is gypsum. Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4·2H2O). When gypsum is heated to around 150 degrees Celsius, it loses the water molecules attached to its crystal structure and becomes calcium sulfate hemihydrate (CaSO4·0.5H2O), which is the chemical composition of Plaster of Paris.
The options given are:
A. Bauxite
B. Gypsum
C. Kankar
D. Limestone
The correct answer is option b. Gypsum.
Explanation:
To obtain Plaster of Paris, gypsum is calcined by heating it to a high temperature and then grinding it into a fine powder. This process causes the gypsum to lose its water molecules and transform into Plaster of Paris. The other options listed (bauxite, kankar, and limestone) are not involved in the production of Plaster of Paris.

Explanation:

• Definition of a rejected stone: A stone is rejected if it absorbs water more than a certain percentage.


• Given options: The options provided are 5%, 10%, 20%, and 25%.


• Choosing the correct option: We need to find the percentage beyond which a stone is rejected.


• Criteria for rejection: If a stone absorbs water more than the specified percentage, it is considered unsuitable and rejected.


• Comparing the options: Among the given options, the highest percentage that a stone can absorb water without being rejected is 10%.


• Conclusion: Therefore, the correct answer is option B: 10%.

Water Absorption in Good Brick

• Definition: Water absorption in brick refers to the amount of water that can be absorbed by the brick material.



• Importance: Water absorption is an important property to consider in bricks as it can affect the durability and strength of the structure built with the bricks.



• Acceptable Water Absorption: The water absorption for good brick should not be more than 15% of its dry weight.



• Explanation: The reason for this limitation is that excessive water absorption can lead to issues like efflorescence, reduced strength, and increased vulnerability to freeze-thaw cycles.



• Testing: Water absorption is typically tested by submerging the brick in water and measuring the weight gain after a specified period of time.



• Quality Control: Manufacturers ensure the water absorption of bricks meets the standard requirements to maintain the quality and performance of the bricks.

Composition of Clay Bricks:

• Silica: Clay bricks typically contain 35-70% silica, which is responsible for providing strength and durability to the bricks.


• Alumina: Clay bricks also contain 10-20% alumina, which helps in enhancing the thermal resistance of the bricks.


• Lime: Although lime is not present in equal proportion, it is also a component of clay bricks. Lime helps in enhancing the workability of the clay during the brick-making process.

Importance of Silica and Alumina in Clay Bricks:

• Silica: Silica is a key component in clay bricks as it helps in reducing shrinkage and cracking during the drying and firing process. It also contributes to the overall strength of the bricks.


• Alumina: Alumina plays a crucial role in enhancing the thermal properties of clay bricks. It helps in retaining heat, making the bricks ideal for applications where high temperatures are involved.

Conclusion:

Therefore, the composition of clay bricks, with 35-70% silica and 10-20% alumina, ensures that the bricks have the necessary strength, durability, and thermal resistance required for various construction applications.

Explanation:

Modular bricks (bricks with mortar) are of nominal size 20 cm × 10 cm × 10 cm

No. of Brinks required in 1 m³ of brickwork

500 bricks are required for 1 cubic meter of brick masonry work.

Plasticity of Bricks and its Contributors:

• Alumina: Alumina is a key contributor to the plasticity of bricks. It helps in binding the particles together and providing the necessary strength and plasticity for moulding bricks in suitable shapes.



• Lime: Lime also plays a significant role in the plasticity of bricks. It helps in improving the workability of the brick clay mixture, making it easier to shape and mould the bricks into desired forms.



• Magnesia: Magnesia contributes to the plasticity of bricks by enhancing the binding properties of the clay mixture. It helps in creating a cohesive structure that can be easily shaped and formed into bricks.



• Silica: Silica is another important element that contributes to the plasticity of bricks. It helps in reducing shrinkage during the drying and firing process, thereby ensuring that the bricks maintain their shape and structure after being moulded.

Therefore, the plasticity of bricks is a result of the combined effects of alumina, lime, magnesia, and silica, which work together to provide the necessary properties for shaping and moulding bricks into suitable forms.

Crushing Strength of First Class Brick

• Definition: The crushing strength of a brick is the maximum load it can withstand without crumbling or breaking.


• Importance: This property is crucial in determining the quality and durability of the brick for construction purposes.

Crushing Strength of First Class Brick

• First Class Brick: First class bricks are high-quality bricks that are uniform in shape and size, with sharp edges and smooth surfaces.


• Testing: The crushing strength of a first class brick is typically tested by placing it in a compression testing machine and applying a load until it fails.


• Result: The crushing strength of a first class brick is usually around 10.5 N/mm².


• Conclusion: Therefore, the correct answer is B: 10.5 N/mm².

To solve this problem, we need to use the concept of water absorption by bricks.
1. Water absorption capacity: The water absorption capacity of a brick is defined as the weight of water absorbed by the brick expressed as a percentage of the dry weight of the brick.
2. Standard water absorption limit: According to the Indian Standard (IS), the maximum water absorption limit for first-class bricks is 20% by weight.
3. Immersion in water: When a brick is immersed in water for 24 hours, it absorbs water due to its porous nature. However, the absorption should not exceed the standard limit.
4. Calculation: Let's assume the dry weight of the brick is 100 grams.
- According to the standard limit, the brick should not absorb more than 20 grams of water (20% of 100 grams).
- If the brick absorbs water beyond this limit, it would be considered substandard.
5. Answer: Based on the above calculation, the correct answer is option C: 20%. The brick should not absorb water more than 20% of its dry weight when immersed in water for 24 hours.
Therefore, option C is the correct answer.

Correct Statement: Lime is made from dolomite/calcium carbonate.
Explanation:
Lime is a chemical compound that is commonly used in various applications such as construction, agriculture, and industry. It is produced by heating limestone (which is primarily composed of calcium carbonate) or dolomite (which is a mineral containing calcium magnesium carbonate) in a kiln. The heating process, also known as calcination, causes the limestone or dolomite to undergo a chemical reaction, resulting in the release of carbon dioxide and the formation of quicklime (calcium oxide).
Here is a detailed explanation of each statement:
- A: Lime is available in free state: This statement is incorrect. Lime is not found in a free state in nature. It needs to be manufactured through the calcination process.
- B: Lime is made from gypsum: This statement is incorrect. Gypsum is a different mineral composed of calcium sulfate, and it is not used to produce lime.
- C: Lime is made from dolomite/calcium carbonate: This statement is correct. Lime is made by heating either limestone (calcium carbonate) or dolomite (calcium magnesium carbonate) in a kiln, resulting in the production of quicklime.
- D: None of the above: This statement is incorrect because statement C is the correct answer.
In conclusion, the correct statement is that lime is made from dolomite or calcium carbonate.

Proportions of raw materials for the manufacture of Portland cement:
A: Lime 63%, silica 22% and others 15%
- Lime: 63%
- Silica: 22%
- Others: 15%
B: Lime 70%, silica 20% and others 10%
- Lime: 70%
- Silica: 20%
- Others: 10%
C: Lime 40%, silica 40% and others 20%
- Lime: 40%
- Silica: 40%
- Others: 20%
D: None of the above
Explanation:
To determine the correct proportions of raw materials for the manufacture of Portland cement, we need to consider the composition required for its production. Portland cement is primarily made up of lime (calcium oxide), silica (silicon dioxide), alumina (aluminum oxide), iron oxide, and other minor components.
Based on the given options, the most suitable answer is option A: Lime 63%, silica 22%, and others 15%. This is because Portland cement typically requires a higher proportion of lime and a lower proportion of silica compared to the other options provided.
The reason for the specific proportions is as follows:
- Lime (calcium oxide) provides the cement with its primary binding properties.
- Silica (silicon dioxide) is responsible for the cement's strength and durability.
- The "others" category includes minor components like alumina, iron oxide, and other additives that enhance specific properties of the cement.
The correct proportions ensure that the resulting Portland cement has the desired strength, workability, and durability for various construction applications.
Therefore, option A: Lime 63%, silica 22%, and others 15% is the correct answer for the proportions of raw materials used in the manufacture of Portland cement.

Compound of cement which reacts immediately with water and sets first is Tricalcium aluminate (C3A).
Tricalcium aluminate is one of the main compounds present in cement and it reacts rapidly with water, leading to the initial setting of cement. The compound is responsible for the early strength development of concrete.
Here is a detailed explanation:
1. Tricalcium aluminate (C3A):
- Tricalcium aluminate is a compound in cement that reacts quickly with water.
- It accounts for only a small portion of the overall cement composition.
- When water is added to cement, tricalcium aluminate reacts to form calcium aluminate hydrates.
- This reaction is exothermic and generates a significant amount of heat.
- The rapid reaction of tricalcium aluminate with water contributes to the initial setting of cement.
2. Tricalcium silicate (C3S):
- Tricalcium silicate is another compound present in cement.
- It is the major compound and contributes to the strength and durability of concrete.
- However, tricalcium silicate does not react as rapidly with water as tricalcium aluminate does.
3. Dicalcium silicate (C2S):
- Dicalcium silicate is also a compound found in cement.
- It reacts with water at a slower rate compared to tricalcium aluminate but still contributes to the overall hydration process.
4. All of the above:
- While tricalcium aluminate (C3A) is the compound that reacts immediately with water and sets first in cement, all three compounds (C3A, C3S, C2S) play important roles in the hydration and setting processes of cement.
In conclusion, the compound of cement that reacts immediately with water and sets first is tricalcium aluminate (C3A). However, it is important to note that the other compounds present in cement, such as tricalcium silicate (C3S) and dicalcium silicate (C2S), also contribute to the overall hydration and setting processes of cement.

Explanation:

• Length of Vicat plunger: The length of the Vicat plunger in Vicat's apparatus typically varies from 40 to 50 mm.


• Importance of Vicat plunger length: The length of the plunger is crucial in determining the consistency of cement paste or mortar.


• Measuring consistency: The Vicat plunger is used to measure the consistency of cement paste by determining the depth of penetration.


• Standard range: The standard range of 40 to 50 mm ensures accurate and consistent measurements across different samples.


• Quality control: Maintaining a consistent length of the plunger helps in quality control of cement products.

Specific Gravity of OPC

• Definition: Specific gravity is defined as the ratio of the density of a substance to the density of a reference substance.


• Specific Gravity of Ordinary Portland Cement (OPC): The specific gravity of OPC is generally around 3.15.

Importance of Specific Gravity in OPC:

• Quality Control: Specific gravity is an important parameter in quality control of cement as it indicates the density and strength of the cement.


• Construction: Specific gravity is crucial in construction applications as it affects the mix design, workability, and strength of concrete.


• Durability: Specific gravity also plays a role in the durability and performance of concrete structures over time.

Conclusion:

• Specific gravity of OPC is an essential property that influences the overall quality and performance of cement in various construction applications.

Random Rubble Masonry - Face Stones
- Random rubble masonry is a type of masonry construction where stones of irregular shapes and sizes are used without any definite pattern.
- In random rubble masonry, face stones refer to the stones that are visible on the exterior surface of the wall. These stones are typically dressed to some extent to enhance their appearance and create a uniform face.
- There are several types of dressing techniques used for face stones in random rubble masonry, including:
1. Chisel dressed: Face stones are chiseled or cut using a chisel to create a relatively smooth and even surface.
2. Hammer dressed: Face stones are shaped and dressed using a hammer to create a rough and textured surface.
3. Axe dressed: Face stones are dressed using an axe, creating a textured surface with parallel lines.
4. Plain dressed: Face stones are dressed to remove any irregularities or projections, creating a smooth and even surface.
- Answer: The correct option is A, "Chisel dressed".

Explanation:

• Counteract C₃A: Gypsum is added to cement to counteract the fast hydration of tricalcium aluminate (C₃A). C₃A is a compound in cement that leads to the early setting and rapid hardening of concrete. By adding gypsum, the reaction of C₃A is slowed down, allowing for better control of the setting time and reducing the risk of cracking in the concrete.

Explanation:
To determine the classification of the concrete based on its slump value, we can refer to the standard classification system provided by the American Concrete Institute (ACI).
According to the ACI classification system, the slump value of 6.5 cm indicates that the concrete is in the plastic state.
Here's a breakdown of the ACI classification system:
1. Dry: Slump value less than 1.25 cm. The concrete is stiff and lacks workability.
2. Earth moist: Slump value between 1.25 cm to 2.5 cm. The concrete has a low degree of workability.
3. Semi plastic: Slump value between 2.5 cm to 5 cm. The concrete has a moderate degree of workability.
4. Plastic: Slump value between 5 cm to 10 cm. The concrete has a high degree of workability and can be easily molded.
Since the given slump value is 6.5 cm, it falls within the range of 5 cm to 10 cm, which corresponds to the plastic state.
Therefore, the correct answer is D: Plastic.

Separation of water or water sand cement from a freshly mixed concrete is known as Bleeding.

When water separates from the mixture and rises to the surface, it is called bleeding. This phenomenon can occur due to the following reasons:
Causes of Bleeding:
- Excessive water content in the concrete mix
- Use of a high water-cement ratio
- Inadequate or improper mixing of the ingredients
- Insufficient fines in the mix, resulting in a higher proportion of larger aggregates
Effects of Bleeding:
- Reduction in the strength and durability of concrete
- Formation of an uneven or porous surface
- Increased water content on the surface, leading to longer drying time and potential cracking
- Weakening of the concrete structure due to the loss of cement and fines
Prevention of Bleeding:
- Use of the correct water-cement ratio to maintain the desired consistency
- Proper mixing techniques to ensure uniform distribution of the ingredients
- Adequate curing to prevent rapid water evaporation
- Use of well-graded aggregates with an appropriate proportion of fines
In conclusion, bleeding in concrete refers to the separation of water or water-cement-sand mixture from the freshly mixed concrete. It can adversely affect the strength and durability of the concrete, as well as result in an uneven surface. Preventive measures should be taken to avoid bleeding, such as using the correct water-cement ratio and proper mixing techniques.

Los Angeles Machine: Testing Aggregate for Abrasion Resistance

1. Introduction: The Los Angeles machine is a commonly used testing apparatus in the field of civil engineering to evaluate the quality of aggregates used in construction projects.


2. Abrasion Resistance: The Los Angeles machine is specifically designed to test the abrasion resistance of aggregates. Abrasion resistance refers to the ability of an aggregate to withstand the wear and tear caused by mechanical actions, such as rubbing, grinding, and impact, during transportation, handling, and usage.


3. Testing Method: The Los Angeles machine consists of a cylindrical drum that rotates at a specific speed, along with steel spheres or abrasive charge inside the drum. The aggregate sample is placed in the drum, and the rotation causes the aggregate to rub against the steel spheres, simulating the abrasion it may experience in real-world applications.


4. Test Results: The Los Angeles machine measures the degradation of the aggregate sample by calculating the percentage of material that passes through a specific sieve size after a specified number of rotations. A higher percentage of material passing through the sieve indicates higher abrasion and lower resistance.


5. Importance: The abrasion resistance of aggregates is crucial in determining their durability and longevity in various construction applications. Aggregates with good abrasion resistance are preferred for road construction, pavement layers, concrete production, and other infrastructure projects to ensure long-term performance and cost-effectiveness.


6. Conclusion: In summary, the Los Angeles machine is used to test the abrasion resistance of aggregates. It provides valuable information for engineers and construction professionals to select suitable aggregates that can withstand the harsh conditions and maintain their structural integrity over time.

Answer: C. Abrasion resistance

Grading of sand causes great variation in:
- Workability of concrete: The grading of sand refers to the particle size distribution of the sand. Proper grading of sand is crucial for achieving the desired workability of concrete. The workability of concrete refers to its ability to be easily mixed, placed, and compacted. When the sand is well-graded, it allows for better fillability and flowability of the concrete mix, making it easier to work with during construction.
- Strength of concrete: The grading of sand also has a significant impact on the strength of concrete. A well-graded sand with a balanced distribution of particle sizes helps to optimize the packing of particles in the concrete mix. This improves the interlocking between the particles, resulting in a denser and stronger concrete structure. On the other hand, poorly-graded sand can lead to voids and weak zones in the concrete, reducing its overall strength.
- Durability of concrete: The grading of sand affects the durability of concrete as well. Proper grading ensures that the concrete mix has a good balance of fine and coarse particles. This helps to reduce the risk of segregation and bleeding during placement, which can lead to the formation of voids and weak areas in the concrete. Additionally, well-graded sand enhances the bond between the cement paste and the aggregates, improving the resistance of the concrete to various environmental factors such as freeze-thaw cycles, chemical attacks, and abrasion.
- All the above: In conclusion, the grading of sand has a significant impact on the workability, strength, and durability of concrete. Properly graded sand helps to achieve a well-performing concrete mix that is easy to work with, possesses good strength, and is resistant to various external factors. Therefore, the correct answer is option D, which states that grading of sand affects all the above-mentioned aspects of concrete.

Factors affecting the proportion of ingredients in concrete:

• Bulking of sand: The bulking of sand refers to the increase in volume of sand due to the presence of moisture. This can affect the proportion of sand in the concrete mix, as the bulking factor needs to be accounted for to ensure the correct ratio of sand to other ingredients.


• Water content: The amount of water used in the concrete mix is crucial in determining the strength and workability of the concrete. The correct water-cement ratio needs to be maintained to achieve the desired properties in the final concrete product.


• Absorption: The absorption capacity of aggregates like sand and gravel can also impact the proportion of ingredients in concrete. If the aggregates absorb too much water, it can affect the overall water-cement ratio and lead to a weaker concrete mix.

Importance of considering all factors:

• Each of these factors plays a vital role in determining the quality and performance of the concrete mix.


• Ignoring any of these factors can result in a concrete mix that is either too weak, too brittle, or too difficult to work with.


• By considering all these factors and adjusting the proportions of ingredients accordingly, a well-balanced and durable concrete mix can be achieved.

Conclusion:

• It is essential to carefully consider the bulking of sand, water content, and absorption of aggregates when determining the proportion of ingredients in concrete.


• By taking all these factors into account, a concrete mix that meets the desired strength, workability, and durability requirements can be achieved.

Explation: It depends on the design mix. It can also be a nominal mix. For, M20, it can be in the ratio of 1:1.5:3 with water cement ratio of 0.5.

To prevent segregation, the maximum height for placing concrete can be determined based on a few factors:
1. Workability of Concrete: The workability of concrete refers to its ease of handling and placing. If the height of concrete placement is too high, it may lead to segregation, where the coarse aggregates separate from the cement paste. To prevent this, the maximum height should be limited.
2. Size and Type of Aggregates: The maximum height for concrete placement also depends on the size and type of aggregates used. Coarse aggregates have a tendency to settle down faster than fine aggregates and cement paste. Therefore, the maximum height should be limited to prevent the segregation of aggregates.
3. Consistency of Concrete: The consistency or slump of concrete also plays a role in determining the maximum height for placement. If the concrete is too fluid or has a high slump, it will have a greater tendency to segregate. Therefore, the maximum height should be reduced for more fluid concrete.
Based on these factors, the maximum height for placing concrete is typically limited to around 150 cm (1.5 meters) to prevent segregation and ensure proper consolidation. This height allows for efficient placement and ensures that the concrete remains cohesive without significant segregation.
Therefore, the correct answer is A: 150 cm.

Answer:

While compacting the concrete by a mechanical vibrator, the slump should not exceed 5.0 cm.

Explanation:

Slump is a measure of the consistency or workability of fresh concrete. It indicates the flowability and deformation characteristics of the concrete mix.

Importance of Slump in Concrete Compaction:

• Proper compaction of concrete is essential to ensure its strength, durability, and overall performance.


• Slump is used as an indicator to determine the water content and workability of the concrete mix.


• If the slump is too low, the concrete may be difficult to compact and may result in insufficient consolidation.


• If the slump is too high, the concrete may be overly fluid and prone to segregation and excessive bleeding.

Maximum Slump Limit:

While compacting concrete with a mechanical vibrator, the slump should not exceed 5.0 cm. This limit is specified to ensure proper compaction without compromising the strength and quality of the concrete.

Reasons for the Maximum Slump Limit:

• If the slump exceeds 5.0 cm, the excessive flowability of the concrete may lead to inadequate consolidation.


• The excess water in the mix can also cause segregation, where the heavier aggregates settle down and the water rises to the surface.


• Excessive bleeding can occur, resulting in a weakened concrete structure.


• The excessive slump may also lead to difficulties in finishing and shaping the concrete surface.

Conclusion:

While compacting concrete with a mechanical vibrator, it is important to ensure that the slump does not exceed 5.0 cm. This limit helps to achieve proper compaction, minimize segregation and bleeding, and ensure the overall quality and performance of the concrete.