Based on their physical and mechanical properties, clay bricks are classified into_____classes.
🧱 Understanding the Classification of Bricks
Clay bricks are graded to help engineers and builders select the appropriate quality for a specific application. A high-quality brick for an exposed structural wall has different requirements than a brick used for an internal, plastered partition. The classification is primarily based on key physical and mechanical properties like compressive strength, water absorption, hardness, and overall appearance.
🔬 Detailed Analysis of the Classification
D. four
This is the correct answer. Based on their properties, burnt clay bricks are traditionally classified into four categories. This allows for a graded selection based on the structural importance and environmental exposure of the masonry work. The classes are: First Class, Second Class, Third Class, and Fourth Class.
A. two, B. one, C. six
These are incorrect. The standard classification system for common burnt clay bricks does not use two, one, or six categories. The four-class system is widely adopted and referenced in engineering practices and standards.
📊 Summary: Brick Classifications and Properties
| Class | Min. Compressive Strength | Max. Water Absorption | Typical Use |
|---|---|---|---|
| First Class | 10 N/mm² | 12-15% | Exposed face work, important structures, flooring. |
| Second Class | 7 N/mm² | 16-20% | All kinds of hidden masonry work, interior walls. |
| Third Class | 3.5 N/mm² | ~25% | Temporary and unimportant structures. |
| Fourth Class | Very Low (Crushed) | N/A | Used as aggregate (ballast) in foundations, floors, roads. |
Note: The property values can have slight variations based on different codes and local standards, but the general hierarchy remains the same. The values in the table are based on the provided source material.
💡 Study Tips
- The Magic Number: Remember that common building bricks are sorted into four main classes.
- Quality Hierarchy: The classification is a direct indicator of quality: 1st Class is the best, and 4th Class is unsuitable for masonry.
- Inverse Relationship: As the class number goes up (1st to 3rd), the quality, strength, and cost go down, while the water absorption rate goes up.
- Associate Use with Class: 1st (Facing), 2nd (Filling/Plastered), 3rd (Temporary), 4th (Aggregate/Ballast).