Model Answer
0 min readIntroduction
Rocks form the foundation of most civil engineering projects, and understanding their properties is crucial for safe and durable construction. Granite, sandstone, and Deccan Trap basalt are widely used in India due to their availability and varying characteristics. Granite, an intrusive igneous rock, is known for its strength and aesthetic appeal. Sandstone, a sedimentary rock, is relatively easier to work with but less durable. Deccan Trap basalt, an extrusive igneous rock, covers a large portion of the Indian peninsula and possesses unique properties stemming from its volcanic origin. This answer will detail the engineering properties of each rock type, highlighting their strengths and weaknesses in construction contexts.
Granite
Granite is a coarse-grained, intrusive igneous rock composed primarily of quartz, feldspar, and mica. Its formation deep underground results in a dense, crystalline structure.
- Strength: High compressive strength (140-250 MPa), making it suitable for load-bearing structures.
- Durability: Excellent resistance to weathering and abrasion due to its mineral composition and density.
- Permeability: Very low permeability, making it resistant to water penetration.
- Workability: Relatively difficult to work with due to its hardness; requires specialized tools for cutting and shaping.
- Weathering Resistance: Highly resistant to chemical weathering, though susceptible to thermal expansion and contraction.
Sandstone
Sandstone is a sedimentary rock formed from cemented sand grains, primarily composed of quartz. Its properties vary depending on the type of cement (silica, calcite, iron oxide).
- Strength: Moderate compressive strength (60-180 MPa), lower than granite.
- Durability: Moderate durability; susceptible to weathering, especially if the cement is weak (e.g., calcite).
- Permeability: Moderate permeability, depending on grain size and cementation.
- Workability: Relatively easy to work with; can be cut, shaped, and polished easily.
- Weathering Resistance: Variable; prone to erosion and disintegration, particularly in acidic environments.
Deccan Trap Basalt
Deccan Trap basalt is a dark-colored, fine-grained extrusive igneous rock formed from volcanic lava flows. It covers a large area of western and central India.
- Strength: Moderate to high compressive strength (70-200 MPa), depending on the degree of vesicularity (presence of gas bubbles).
- Durability: Good durability, but can be susceptible to weathering along joints and fractures.
- Permeability: Low to moderate permeability; vesicularity can increase permeability.
- Workability: Moderate workability; can be cut and dressed, but requires robust tools.
- Weathering Resistance: Generally good, but susceptible to chemical weathering in certain environments.
Comparative Table of Engineering Properties
| Property | Granite | Sandstone | Deccan Trap Basalt |
|---|---|---|---|
| Compressive Strength (MPa) | 140-250 | 60-180 | 70-200 |
| Durability | Excellent | Moderate | Good |
| Permeability | Very Low | Moderate | Low to Moderate |
| Workability | Difficult | Easy | Moderate |
| Weathering Resistance | High | Variable | Good |
Engineering Applications: Granite is commonly used for high-end construction, monuments, and paving due to its strength and aesthetic appeal. Sandstone is used for facing stones, paving, and decorative elements where lower strength is acceptable. Deccan Trap basalt is extensively used in road construction, railway ballast, and as aggregate in concrete due to its abundance and reasonable strength.
Conclusion
In conclusion, granite, sandstone, and Deccan Trap basalt each possess distinct engineering properties that dictate their suitability for different construction applications. Granite excels in high-strength, durable applications, while sandstone offers ease of workability for decorative purposes. Deccan Trap basalt provides a cost-effective and readily available material for large-scale infrastructure projects. A thorough understanding of these properties is essential for selecting the appropriate rock type to ensure the longevity and safety of any construction endeavor. Future research should focus on enhancing the durability of sandstone and optimizing the use of basalt in sustainable construction practices.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.