Importance of Bricks in Construction
Bricks have been a fundamental building material for centuries, playing a pivotal role in construction due to their strength, durability, and availability. Their cost-effectiveness and ease of production make them a preferred choice for builders worldwide. Bricks can be manufactured in various shapes and sizes, catering to diverse architectural needs and allowing for creative and functional designs.
Necessity of Good Quality Bricks
The integrity of a masonry structure heavily depends on the quality of bricks used. Inferior bricks can compromise safety, leading to structural failures and increased maintenance costs. Therefore, it’s crucial to ensure that bricks meet specific quality standards. Adhering to guidelines set by national and international standards—such as the Indian Standards (IS 1077, IS 2180), the American Society for Testing and Materials (ASTM C62, ASTM C216), and the Canadian Standards Association (CSA A288)—ensures that bricks possess the necessary qualities for safe and durable construction.
Specifications for Good Quality Bricks
Based on the standards set by ASTM, IS, and CSA, good quality bricks should meet the following specifications:
1. Compressive Strength of Bricks
The compressive strength of a brick is a critical measure of its ability to withstand loads without crushing. According to ASTM C62, the minimum required compressive strength varies based on exposure conditions:
- Severe Weathering: Average of 5 bricks should have a minimum strength of 20.7 MPa, with individual bricks not less than 17.2 MPa.
- Moderate Weathering: Average strength should be at least 17.2 MPa, with individual bricks not less than 15.2 MPa.
- Normal Weathering: Average strength should be 10.3 MPa, with individual bricks not less than 8.6 MPa.
Similarly, the Indian Standard IS:3495 (Part-1) specifies that bricks used in all types of works should not have a crushing strength less than 7.356 MPa unless otherwise specified.
Table 1: Minimum Compressive Strength of Bricks
| Grade of Bricks | Minimum Compressive Strength (MPa) |
|---|---|
| Average of 5 Bricks | |
| Severe Weather | 20.7 |
| Moderate Weather | 17.2 |
| Normal Weather | 10.3 |
Explanation: The compressive strength test involves applying a load to the brick until it fails. This test determines the brick’s ability to withstand structural loads.
2. Shape of Bricks
Bricks are shaped through molding, pressing, or extrusion, using either hand or machine methods. Standard bricks are rectangular solids, but custom shapes are also produced for specific construction needs.
Good quality bricks should have:
- Regular and Uniform Size: Ensuring consistency in construction.
- Sharp, Straight, and Right-Angled Edges: Facilitating proper alignment and bonding.
- Smooth Rectangular Faces with Parallel Sides: Providing an even surface for mortar application.
Explanation: Accurate brick shapes contribute to the structural integrity and aesthetic appeal of masonry work.
3. Brick Construction Materials
Bricks should be made from suitable soils and kiln-burnt to achieve optimal strength and durability. According to ASTM standards, bricks may be constructed from clay, shale, fire clay, or mixtures thereof. Proper firing is essential:
- Well-Burnt Bricks: Exhibit uniform color and strength.
- Under-Burnt Bricks: Have lower strength and may contain residual moisture.
- Over-Burnt Bricks: May be distorted and brittle.
Using appropriately fired bricks ensures consistency in performance and longevity.
4. Brick Size
Consistency in brick size is crucial for uniform construction. The Indian Standard specifies:
- Conventional Bricks: 225 mm x 110 mm x 75 mm.
- Modular Bricks: 190 mm x 90 mm x 90 mm or 190 mm x 90 mm x 40 mm.
Permissible tolerances in size are:
- Length: ±3.0 mm
- Breadth: ±1.5 mm
- Depth: ±1.5 mm
According to ASTM C62, the size of solid bricks is specified by the purchaser, with maximum permissible variations outlined in Table 2.
Table 2: Variations in Dimensions of Solid Bricks
| Specified Dimension (mm) | Maximum Permissible Variation (mm) |
|---|---|
| Up to 76 | ±2.4 |
| Over 76 to 102 | ±3.2 |
| Over 102 to 152 | ±4.8 |
| Over 152 to 203 | ±6.4 |
| Over 203 to 305 | ±7.9 |
| Over 305 to 406 | ±9.5 |
Explanation: Standardizing brick sizes ensures compatibility and uniformity in construction, reducing waste and improving efficiency.
5. Brick Color
The color of a brick is an indicator of its quality and firing process. Good quality bricks should have a uniform color, typically deep cherry red or copper. This uniformity signifies:
- Proper Firing: Indicates consistent kiln temperatures and durations.
- Quality Materials: Reflects the purity and consistency of raw materials used.
Explanation: A consistent brick color enhances the aesthetic appeal of masonry work and indicates good manufacturing practices.
6. Brick Appearance
Upon fracture, bricks should display:
- Fine-Grained, Uniform, Homogeneous, and Dense Texture: Signifying high-quality material and manufacturing processes.
- Freedom from Defects: Such as lumps of lime, laminations, cracks, air holes, and soluble salts that cause efflorescence.
Bricks should not be under-burnt, as this can affect their strength and durability.
Explanation: The internal structure of a brick impacts its performance; a uniform texture without defects ensures reliability.
7. Water Absorption
Excessive water absorption can weaken bricks and lead to structural issues. Standards specify limits:
- Indian Standard IS:3495 (Part-2): Water absorption should not exceed 15% of the dry weight after 24 hours of immersion.
- ASTM C62 (Table 4): Specifies maximum water absorption percentages for different weathering grades.
Table 4: Maximum Water Absorption of Bricks
| Grade of Bricks | Maximum Water Absorption (%) |
|---|---|
| Average of 5 Bricks | |
| Severe Weather | 17 |
| Moderate Weather | 22 |
| Normal Weather | No limit |
Explanation: Controlling water absorption ensures the brick’s durability, especially in freeze-thaw conditions.
8. Brick Cracks
Cracks can compromise the structural integrity of bricks. Good quality bricks should be:
- Free from Cracks and Flaws: Ensuring strength and durability.
- Free from Nodules of Free Lime: Preventing future expansion and cracking.
According to ASTM C62, cracks should not exceed the brick’s least dimension in length.
9. Brick Soundness
Brick soundness tests assess the internal integrity of the brick:
- Sound Test: Striking the brick with a mallet should produce a clear, metallic ringing sound.
- Drop Test: A saturated brick dropped from a height of 600 mm onto its flat face should not break.
These tests help identify defects that are not visible externally.
10. Efflorescence
Efflorescence is the formation of white salt deposits on the brick surface, which can affect appearance and indicate potential durability issues.
- Indian Standard IS:3495 (Part-3): Efflorescence should not cover more than 10% of the brick’s exposed area.
- ASTM Standards: Testing for efflorescence is optional unless specified by the purchaser.
Explanation: Controlling efflorescence enhances the brickwork’s aesthetic and reduces potential deterioration.
Conclusion
Good quality bricks are essential for constructing safe, durable, and aesthetically pleasing structures. Adhering to established standards ensures that bricks possess the necessary properties to perform effectively under various conditions. By selecting bricks that meet these quality specifications, builders can enhance the longevity of their constructions, reduce maintenance costs, and ensure the safety of occupants.
Understanding and applying these quality parameters is crucial for architects, engineers, builders, and anyone involved in the construction industry. Consistent quality control and adherence to standards not only uphold the integrity of individual projects but also contribute to the overall advancement of construction practices.