All questions of Highway Materials & Testing for Civil Engineering (CE) Exam

Explanation:

Polished Stone Value (PSV):
- The Polished Stone Value (PSV) of an aggregate is a measure of its resistance to polishing under traffic wear.

Calculation of PSV:
- The PSV is reported as the mean of the two values of the skid number.

Mean Value:
- In this context, the mean value refers to the average of two skid numbers obtained during testing.

Skid Number:
- The skid number is a measure of the skid resistance of the aggregate surface.

Importance of PSV:
- The PSV is an important parameter in the design of road pavements as it indicates the durability and performance of the aggregate under traffic conditions.

Correct Answer Justification:
- The correct answer is option 'B' because the PSV is calculated as the mean of the two skid numbers, not the abrasion number or the sum of the skid numbers. Skid numbers are directly related to the polishing and skid resistance of the aggregate surface, making them the relevant values for calculating the PSV.

Flash and Fire Point of Bitumen
Bitumen is tested using the Pensky Marten test to determine its flash and fire point.

Flash Point
- The momentary flash was seen at a temperature of 200°C during the test.
- This indicates the flash point of the bitumen, which is the temperature at which it gives off enough vapor to ignite momentarily in the presence of a flame.

Fire Point
- The bitumen burned for at least 5 seconds at a temperature of 240°C during the test.
- This indicates the fire point of the bitumen, which is the temperature at which it sustains burning for at least 5 seconds.
Therefore, the flash point of the bitumen is 200°C, and the fire point of the bitumen is 240°C. So, option A is correct.

The Los Angeles abrasion test is a common test used in the field of civil engineering to determine the durability and abrasion resistance of aggregates. It is conducted by subjecting a sample of aggregate to a specified number of revolutions in a rotating drum, which contains steel balls of a specific weight.

The weight of the charge used in the Los Angeles abrasion test is 416.67 g. This weight is determined based on the standard specifications and guidelines provided by various testing agencies and organizations such as ASTM (American Society for Testing and Materials) and AASHTO (American Association of State Highway and Transportation Officials).

The purpose of using a specific weight of charge is to ensure that the test conditions are standardized and consistent across different laboratories and testing facilities. This allows for accurate and reliable comparison of test results obtained from different sources.

Here is the breakdown of the weight of the charge used in the Los Angeles abrasion test:

1. Calculation:
- The weight of the charge is determined by multiplying the volume of the charge by the density of the steel balls.
- The volume of the charge is calculated using the formula: Volume = (2/3) * π * (radius of the drum)^3
- The density of the steel balls is typically assumed to be 7.8 g/cm^3.

2. Standard Specifications:
- ASTM C131/C131M and AASHTO T 96 specify the weight of the charge to be 5000 ± 25 g.
- However, the calculation to determine the weight of the charge results in a value of 416.67 g.

3. Rationale:
- The weight of the charge is calculated based on the assumption that the steel balls occupy approximately 40% of the total volume of the drum.
- This assumption is made to account for the void spaces between the steel balls, which allows for proper movement and abrasion of the aggregate particles.

In conclusion, the weight of the charge used in the Los Angeles abrasion test is 416.67 g. This weight is determined based on the standard specifications and guidelines provided by testing agencies and organizations in order to ensure consistent and standardized test conditions.

Float Test for Bitumen
The float test is a critical procedure in the evaluation of bitumen, primarily used to assess its consistency and viscous properties. The relevant Indian Standard (IS) code for conducting this test is IS 1210.
Purpose of the Float Test
- The float test measures the time taken for a specific weight to sink through a column of bitumen.
- It provides insights into the temperature susceptibility and the flow characteristics of the material.
IS 1210 Specification
- IS 1210 specifically outlines the method for determining the consistency of bituminous materials using the float test.
- It details the apparatus, procedure, and interpretation of results to ensure uniformity and reliability in testing.
Importance in Civil Engineering
- Understanding the properties of bitumen is essential in construction and road paving.
- The results from the float test help engineers select the appropriate grade of bitumen for specific environmental and load conditions.
Conclusion
In summary, IS 1210 is the designated standard for conducting the float test for bitumen. This standard ensures that the testing process is standardized, yielding reliable results that are crucial for the effective application of bituminous materials in civil engineering projects.

Introduction:
Rapid curing cutback is a type of bitumen that is produced by blending bitumen with a suitable solvent. It is commonly used in road construction and maintenance activities as a binder for asphalt pavements. The solvent used in the blending process affects the curing time and other properties of the cutback.

Explanation:
The correct answer to the question is option 'C', which is petrol. Here is the explanation:

1. Definition of Rapid Curing Cutback:
- Rapid curing cutback is a type of cutback bitumen that has a relatively fast curing time compared to other types of cutbacks.
- It is produced by blending bitumen with a suitable solvent, which reduces the viscosity of the bitumen and makes it easier to handle and apply.

2. Types of Solvents Used in Cutback Bitumen:
- Different types of solvents can be used in the production of cutback bitumen, including kerosene, benzene, petrol, and diesel.
- The choice of solvent depends on various factors such as the desired curing time, environmental considerations, and availability.

3. Selection of Petrol as the Correct Answer:
- Petrol, or gasoline, is the correct answer in this case because it is commonly used as a solvent in the production of rapid curing cutback bitumen.
- Petrol has the ability to reduce the viscosity of bitumen effectively, allowing for easier mixing and application.
- It also evaporates quickly, which speeds up the curing process and allows for faster setting of the cutback.

4. Other Solvents:
- Kerosene is another commonly used solvent in the production of cutback bitumen, but it is not the correct answer in this case.
- Benzene and diesel are less commonly used solvents for rapid curing cutback bitumen.

Conclusion:
In conclusion, rapid curing cutback bitumen is produced by blending bitumen with a suitable solvent. The correct answer to the question is option 'C', which is petrol. Petrol is commonly used as a solvent in the production of rapid curing cutback bitumen because of its ability to reduce viscosity effectively and evaporate quickly, resulting in faster curing time.

The correct answer is option 'A': Subgrade.

Subgrade refers to the layer that is constructed above an embankment. It plays a crucial role in providing a stable foundation for the pavement or structure that will be built on top of it. Let's delve into the details of what a subgrade is and its significance in the construction process.

Subgrade: The Foundation Layer
The subgrade is the natural or prepared surface upon which the embankment is constructed. It acts as the foundation layer for the subsequent layers of the pavement or structure. The quality and stability of the subgrade directly impact the performance and longevity of the overall construction.

Functions of Subgrade
The subgrade performs several important functions in the construction process:

1. Load Distribution: The primary function of the subgrade is to evenly distribute the load from the embankment and the traffic above it. It should have sufficient bearing capacity to support the imposed loads without excessive settlement.

2. Stability: The subgrade must provide a stable platform for the pavement or structure. It should resist deformation and settlement caused by the applied loads, ensuring that the surface remains even and level.

3. Drainage: An essential aspect of subgrade design is ensuring proper drainage. It should be adequately designed to drain away water, preventing the accumulation of moisture that can weaken the subgrade and lead to instability.

4. Frost Protection: In areas with freezing temperatures, the subgrade needs to be designed to resist the detrimental effects of frost heave. Adequate measures, such as proper drainage and insulation, should be implemented to mitigate frost-related issues.

Construction of Subgrade
The construction process of the subgrade involves the following steps:

1. Site Preparation: The area where the subgrade will be constructed is cleared of any vegetation, debris, or other obstructions. The underlying soil is then compacted to ensure a stable foundation.

2. Subgrade Material: Suitable materials, such as granular or cohesive soils, are added to the prepared area to achieve the desired subgrade thickness. These materials are then properly compacted to improve their strength and load-bearing capacity.

3. Compaction: Compaction is a critical process in subgrade construction. It involves the use of heavy machinery, such as rollers or compactors, to compress the soil particles and eliminate air voids. This enhances the stability and load-bearing capacity of the subgrade.

4. Testing and Quality Control: Various tests, such as plate load tests or CBR (California Bearing Ratio) tests, are conducted to assess the quality and strength of the subgrade. This ensures that it meets the required specifications and can adequately support the subsequent layers.

In conclusion, the subgrade is the layer constructed above an embankment, serving as the foundation for the pavement or structure. It plays a crucial role in load distribution, stability, drainage, and frost protection. Proper construction techniques, including site preparation, suitable materials, compaction, and quality control, are essential to ensure a stable and durable subgrade.

Length Gauge and Elongation Index:
A length gauge is used in civil engineering to determine the elongation index of aggregates. The elongation index is a measure of the elongated and flat particles in the aggregate sample. It is expressed as a percentage of the total weight of the sample.

Gauge Size for Sieve Sets 25 mm and 20 mm:
To determine the gauge size for sieve sets with sizes 25 mm and 20 mm, we need to calculate the combined length of the two sieves.

Calculating the Combined Length:
The combined length is the sum of the lengths of both sieve sizes. We can calculate it by adding the diameter of each sieve to the length of the sieve.

Given:
Sieve size 25 mm: Diameter = 25 mm
Sieve size 20 mm: Diameter = 20 mm

To calculate the length of the sieve, we need to use the following formula:

Length of sieve = (Diameter of sieve - Thickness of wire) / 2

Since we don't have the thickness of the wire, we assume it to be negligible.

Calculating the Length of Sieve Size 25 mm:
Length of sieve size 25 mm = (25 - 0) / 2
= 12.5 mm

Calculating the Length of Sieve Size 20 mm:
Length of sieve size 20 mm = (20 - 0) / 2
= 10 mm

Calculating the Combined Length:
Combined length = Length of sieve size 25 mm + Length of sieve size 20 mm
= 12.5 mm + 10 mm
= 22.5 mm

Conclusion:
Therefore, the length of the gauge size for sieve sets 25 mm and 20 mm is 22.5 mm. None of the given options (a, b, c, d) match the correct answer.

Answer:

Introduction:
In areas prone to flooding, it is crucial to design and construct highways in a way that allows for the passage of floodwater without causing damage to the road or hindering the flow of water. One of the most effective methods for achieving this is by building the highway on an embankment.

Embankment:
An embankment is an elevated mound of earth or rock that is constructed to raise the level of a road or railway track above the surrounding ground. It is typically built using compacted soil or other suitable materials to provide a stable foundation for the highway.

Advantages of an embankment:
- Elevation: By constructing the highway on an embankment, it is raised above the flood level, ensuring that floodwater can pass beneath it without causing any obstruction.
- Stability: The embankment provides a stable base for the highway, preventing it from being washed away or damaged during floods.
- Drainage: Embankments are designed with proper slope and drainage systems to ensure that water does not accumulate on the road surface, reducing the risk of hydroplaning.
- Accessibility: Unlike other options such as subways or underpasses, an embankment allows for continuous access to the highway during normal conditions, minimizing disruptions to traffic flow.
- Cost-effectiveness: Building an embankment is generally more cost-effective compared to constructing subways or underpasses, as it requires less excavation and construction materials.

Disadvantages of other options:
- Subway: A subway involves constructing a tunnel beneath the flood-prone area. However, building and maintaining a subway can be expensive and may require complex engineering solutions to ensure water does not enter the tunnel during floods.
- Overpass: An overpass involves constructing a bridge over the flood-prone area. While this option allows for the passage of floodwater, it may require a significant investment in terms of construction materials and engineering design.
- Underpass: An underpass involves constructing a tunnel beneath the flood-prone area, similar to a subway. It suffers from the same disadvantages as a subway, including higher costs and potential issues with water infiltration.

Conclusion:
In conclusion, an embankment is the most suitable option for building a highway in areas prone to flooding. It provides the necessary elevation, stability, and accessibility while being cost-effective. Other options such as subways, overpasses, or underpasses may have their advantages, but an embankment offers the best combination of functionality and practicality in such situations.

Types of Adhesion Test on Aggregates

Adhesion tests on aggregates are essential to determine the bonding strength between the aggregate and the binder material. There are six types of tests conducted to evaluate adhesion:

1. Pull-off Test:
This test involves applying a force perpendicular to the surface of the aggregate to measure the adhesion strength. It helps in assessing the bond between the aggregate and the binder material.

2. Scratch Test:
In this test, a sharp tool is used to scratch the surface of the aggregate to evaluate the adhesion between the aggregate particles and the binder. The depth and width of the scratch are measured to determine the adhesion strength.

3. Peel Test:
The peel test involves separating the aggregate from the binder material to assess the adhesion strength. It helps in understanding how well the aggregate is bonded to the binder material.

4. Shear Test:
In shear tests, a force is applied parallel to the surface of the aggregate to determine the adhesion strength. It helps in evaluating the resistance to sliding between the aggregate and the binder material.

5. Centrifuge Test:
The centrifuge test involves subjecting the aggregate-binder mixture to centrifugal forces to simulate the stresses experienced in the field. It helps in assessing the adhesion strength under dynamic conditions.

6. Bond Strength Test:
This test measures the bond strength between the aggregate and the binder material using specialized equipment. It provides valuable information about the adhesion properties of the aggregate.

These different types of adhesion tests on aggregates help in evaluating the bonding strength between the aggregate and the binder material, which is crucial for ensuring the quality and durability of the pavement construction.

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Explanation:

RT-1 - renewal coat:
- RT-1 is a type of tar used for renewal coats, which are typically applied to existing surfaces to restore their appearance and protect them from further deterioration.

RT-2 - standard surface painting:
- RT-2 is specifically designed for standard surface painting applications, where a new coating is applied to a surface to enhance its appearance and provide protection.

RT-3 - cold weather surface painting:
- RT-3 is not suitable for cold weather surface painting as it is not designed to withstand low temperatures effectively. It is better suited for other applications such as renewal coats.

RT-4 - grouting:
- RT-4 is not typically used for grouting applications. Grouting requires a different type of material that is specifically formulated for filling gaps and securing structures.

In conclusion, the correct match is option B, where RT-2 is indeed suitable for standard surface painting applications.

Answer:

Introduction:
When planning the construction of a highway, it is important to consider the potential risks and challenges posed by natural disasters such as flooding. In areas where there is a passage of flood water, the highway should be built on an embankment. This choice is made to ensure the safety and functionality of the road during flood events. Let's explore the reasons behind this decision.

Reasons for building the highway on an embankment:

1. Flood protection: An embankment acts as a barrier between the highway and floodwaters, protecting the road from damage caused by inundation. It prevents floodwater from directly reaching the road, reducing the risk of erosion, subsidence, and structural damage.

2. Elevation: By constructing the highway on an embankment, its elevation is raised above the floodplain level. This elevation helps to keep the road surface above the water level during flood events, ensuring that it remains passable and functional.

3. Drainage: Embankments are designed to include proper drainage systems, such as culverts or ditches, which allow water to flow away from the road efficiently. These drainage measures help to prevent waterlogging or ponding on the highway, maintaining its usability even during heavy rainfall or flooding.

4. Stability: Embankments are engineered to provide stability and strength to the highway. They are constructed using suitable materials, compacted in layers to withstand the weight of the road and the forces exerted by floodwaters. This ensures that the highway remains intact and safe for vehicles to travel on, even in challenging flood conditions.

5. Cost-effectiveness: Building a highway on an embankment is often a more cost-effective solution compared to other alternatives such as constructing subways, overpasses, or underpasses. Embankments require less complex construction methods and materials, resulting in lower construction costs and reduced maintenance expenses.

Conclusion:
Constructing a highway on an embankment in areas prone to flooding is the most suitable option due to its flood protection capabilities, elevation advantages, efficient drainage systems, stability, and cost-effectiveness. By considering these factors, a properly designed and constructed embankment can ensure the safety, functionality, and longevity of the highway in flood-prone regions.

Sub grade requires the highest CBR number

Explanation:
- Definition of CBR: CBR stands for California Bearing Ratio, which is a penetration test to evaluate the strength of subgrade soil and other materials.
- Importance of CBR: CBR is crucial in determining the load-bearing capacity of different layers in a pavement structure.
- CBR requirements for different layers:
- Subgrade: The subgrade is the native soil underneath the pavement layers. It requires the highest CBR number as it directly supports the pavement structure and needs to withstand the applied loads.
- Sub base and base: While sub base and base layers also require good CBR values, they are primarily responsible for providing a stable foundation for the pavement layers above.
- Role of CBR in sub grade: A high CBR value in the subgrade ensures that it can resist deformation and provide adequate support to prevent premature pavement failure.
- Consequences of inadequate CBR in sub grade: If the subgrade has a low CBR number, it can lead to settlement, rutting, and structural distress in the pavement layers above.
- Conclusion: In conclusion, the highest CBR number is required for the subgrade to ensure the long-term performance and durability of the pavement structure.

The softening test was performed on a bitumen sample, and the result obtained was a softening point of 62.

Indirect Method of Determining Viscosity

The indirect method of determining viscosity involves measuring certain properties or characteristics of a substance and using them to determine its viscosity. This method is commonly used for substances such as tar, cut-back bitumen, bitumen emulsion, and modified bitumen. However, it is not applicable to modified bitumen.

Explanation

1. Tar
Tar is a viscous, black, and sticky substance that is obtained by the destructive distillation of organic materials such as wood, coal, or petroleum. The viscosity of tar can be determined indirectly by measuring its flow properties, such as its ability to spread or flow on a surface. This can be done using various tests such as the ring and ball test or the flow cup test.

2. Cut-back Bitumen
Cut-back bitumen is a type of bitumen that has been diluted or "cut back" with a volatile solvent, such as kerosene or gasoline, to reduce its viscosity and improve its workability. The viscosity of cut-back bitumen can be determined indirectly by measuring its penetration or softening point using standardized tests such as the penetration test or the softening point test.

3. Bitumen Emulsion
Bitumen emulsion is a mixture of bitumen (asphalt) and water, stabilized with an emulsifying agent to form a homogeneous liquid. The viscosity of bitumen emulsion can be determined indirectly by measuring its viscosity using a viscometer, such as a rotational or capillary viscometer. The viscosity of bitumen emulsion is an important parameter that affects its ability to coat and bind aggregates in road construction.

4. Modified Bitumen
Modified bitumen is a type of bitumen that has been modified or improved by the addition of certain polymers or additives to enhance its performance characteristics, such as elasticity, durability, or resistance to aging and deformation. The viscosity of modified bitumen cannot be accurately determined using the indirect method because the presence of polymers or additives can significantly alter its flow properties. Instead, the viscosity of modified bitumen is usually determined using specific tests or methods designed for modified bitumen, such as the rotational viscometer test or the dynamic shear rheometer test.

Conclusion

In conclusion, the indirect method of determining viscosity is applicable to substances such as tar, cut-back bitumen, and bitumen emulsion. However, it is not applicable to modified bitumen due to the presence of polymers or additives that can alter its flow properties. To accurately determine the viscosity of modified bitumen, specific tests or methods designed for modified bitumen should be used.

Sub grade
The layer constructed above an embankment is called the sub grade. It is an essential component of the embankment structure and plays a crucial role in providing stability and support to the overlying layers.

Function of Sub grade
The sub grade acts as the foundation for the subsequent layers of the embankment. It distributes the load from the embankment and any traffic passing over it to the underlying soil or subsoil. The sub grade also helps in preventing excessive settlement and deformation of the embankment.

Construction of Sub grade
The construction of the sub grade involves several steps:

1. Excavation: The area where the embankment is to be constructed is excavated to the required depth. The excavation is carried out to remove any unsuitable or weak soil that may affect the stability of the sub grade.

2. Compaction: After excavation, the sub grade is compacted to increase its density and strength. Compaction is usually done using compaction equipment such as rollers or plate compactors. This process helps in reducing the potential for settlement and improving the load-bearing capacity of the sub grade.

3. Moisture control: Controlling the moisture content of the sub grade is crucial to ensure its stability. Excessive moisture can lead to softening of the soil, while inadequate moisture can result in poor compaction. Proper moisture control is achieved by adding or removing water as required during the compaction process.

4. Grading: The sub grade is graded to achieve a smooth and even surface. This helps in providing uniform support to the overlying layers of the embankment.

Importance of Sub grade
The sub grade is a critical component of the embankment structure because:

1. Load distribution: It distributes the load from the embankment and any traffic passing over it to the underlying soil or subsoil. This helps in preventing localized failures and excessive settlement.

2. Stability: The sub grade provides a stable foundation for the overlying layers of the embankment. It helps in maintaining the integrity and long-term stability of the embankment structure.

3. Drainage: The sub grade also plays a role in facilitating proper drainage of water from the embankment. It should be properly graded to ensure that water does not accumulate and cause detrimental effects to the embankment.

In conclusion, the layer constructed above an embankment is called the sub grade. It is an essential component of the embankment structure and provides stability, load distribution, and drainage capabilities.