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

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.

Ductility of Bitumen
Ductility is a crucial property of bitumen, especially in civil engineering applications, as it reflects the material's ability to deform under tensile stress without breaking.
Measurement of Ductility
The ductility of bitumen is primarily measured in terms of:

• Distance: Ductility is quantified by the distance that a standard sample of bitumen can be stretched before it breaks. Typically, this is measured using a ductility testing apparatus, where a sample is pulled apart at a specified rate.

Significance of Ductility

• Performance in Pavements: High ductility indicates that the bitumen can accommodate the deformations caused by temperature changes and traffic loads, making it suitable for road construction.
• Resistance to Cracking: Ductile bitumen can resist cracking, especially in colder climates where thermal stresses can lead to pavement failure.

Other Factors
While distance is the primary measurement for ductility, other parameters can influence the performance of bitumen:

• Temperature: The ductility of bitumen can vary with temperature, requiring analysis at different thermal conditions.
• Bitumen Grade: Different grades of bitumen will exhibit varied ductility, impacting their use in specific applications.

In conclusion, ductility is a vital property for evaluating bitumen's performance in construction, with distance as the key measurement metric to determine its ability to endure stress without failure.

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.

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.

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

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.

Standard California Bearing Ratio Test
The California Bearing Ratio (CBR) test is a penetration test used to evaluate the strength of subgrade soil. It is commonly used in geotechnical engineering to assess the quality and load-bearing capacity of soil for road and pavement construction.

Expansion Ratio
The expansion ratio is a measure of the increase in volume or height of the soil specimen during the CBR test. It is calculated by dividing the difference between the initial and final dial gauge readings by the initial dial gauge reading, and then multiplying by 100 to express it as a percentage.

Given Information
- Sample height (H) = 125 mm
- Difference between initial and final dial gauge readings (∆h) = 0.125 mm

Calculation
The expansion ratio (ER) can be calculated using the formula:

ER = (∆h / H) * 100

Substituting the given values:

ER = (0.125 / 125) * 100
ER = 0.001 * 100
ER = 0.1

Therefore, the expansion ratio of the soil sample is 0.1 or 10%.

Interpretation
The expansion ratio of 0.1 indicates that the soil specimen expanded by 10% of its initial height during the CBR test. This expansion is typically caused by the compaction of the soil under the applied load.

Conclusion
The correct answer is option C) 0.1. The expansion ratio of the soil, calculated using the formula (∆h / H) * 100, is 0.1 or 10%.

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.