Types of Clay Bricks

Types of Clay Bricks

Bricks are one of the oldest and most popular building materials. They are widely used in construction because they are affordable, durable, and easy to handle. Clay bricks are commonly used for building exterior and interior walls, partitions, piers, footings, and other load-bearing structures.

A brick is a rectangular building material that can be easily handled with one hand. It can be made of burnt clay, a mixture of sand and lime, or Portland cement concrete. Clay bricks are commonly used due to their affordability and widespread availability.

The dimensions of a brick are interrelated as follows:

• The length of a brick is twice its width plus the thickness of the mortar.
• The height of a brick is equal to its width.

A standard brick, also known as a modular brick, should have dimensions of 19 cm length, 9 cm width, and 9 cm height, or 19 cm length, 9 cm width, and 4 cm height. However, when used in masonry, the brick with mortar becomes 20 cm length, 10 cm width, and 10 cm height.

In most parts of the country, field bricks are still commonly used, which have dimensions of 9 inches length, 4.5 inches width, and 3 inches height. These field bricks weigh around 3.0 kg. They typically have an indent called a frog, which is 1-2 cm deep and serves as a key for holding the mortar. Bricks with a height of 9 cm have a frog, while 4 cm high bricks and extruded bricks do not have a frog. The size of the frog should be 10 cm length, 4 cm width, and 1 cm depth. The presence of the frog allows for proper mortar adhesion, so bricks with frogs are laid with the frogs facing upwards.

Types of Clay Bricks

1 CLASSIFICATION OF BRICKS

1.1 On Field Practice

Clay bricks are categorized into different classes, such as first class, second class, third class, and fourth class, based on their physical and mechanical characteristics.

1.1.1 First Class Bricks

Here are the characteristics of high-quality clay bricks:

1. Thorough Burning: The bricks undergo thorough burning, resulting in a deep red, cherry, or copper color.
2. Smooth Surface and Rectangular Shape: The bricks have a smooth and rectangular surface, with parallel, sharp, and straight edges, as well as square corners.
3. Flaw and Stone-Free: The bricks do not have any flaws, cracks, or stones, ensuring their structural integrity.
4. Uniform Texture: The bricks exhibit a consistent and uniform texture throughout.
5. Scratch Resistance: When scratched with a fingernail, the bricks do not leave any impression or mark.
6. Absence of Lime Lumps: The fractured surface of the brick shows no lumps or deposits of lime.
7. Metallic Sound: When striking two bricks together, they produce a metallic or ringing sound, indicating their density and solid composition.
8. Controlled Water Absorption: The bricks absorb controlled amounts of water, ranging from 12% to 15% of their dry weight after being immersed in cold water for 24 hours.
9. The brick should have a minimum crushing strength of 10 N/mm². However, it’s important to note that this requirement may vary depending on different government organizations across the country.
10. Uses: First class bricks are highly recommended for applications such as pointing, exposed face work in masonry structures, flooring, and reinforced brickwork. Their superior quality makes them suitable for these specific purposes.

1.1.2 Second Class Bricks

Second class bricks have similar requirements to first class bricks, with the following exceptions:

1. Permissible small cracks and distortions are allowed.
2. Slightly higher water absorption of approximately 16-20% of its dry weight is permitted.
3. The minimum crushing strength should be at least 7.0 N/mm².

Uses: Second class bricks are suitable for both important and unimportant concealed masonry works, as well as for centering in reinforced brick and reinforced cement concrete (RCC) structures. These bricks are recommended for such applications due to their properties and quality standards.

1.1.3 Third class bricks

Third class bricks are classified as underburnt. They possess a soft texture and light color, resulting in a dull sound when struck together. These bricks have a water absorption rate of approximately 25% of their dry weight.

Uses: Third class bricks are primarily employed for constructing temporary structures. Due to their underburnt nature and characteristics, they are suitable for temporary applications where long-term durability is not a requirement.

1.1.4 Fourth class bricks

Fourth class bricks are characterized by being overburnt and having severe distortions in shape and size. Additionally, they tend to be brittle in nature.

Uses: These bricks are primarily utilized as ballast material for foundations, floors in lime concrete, and road metal. The broken or crushed pieces of fourth class bricks serve as a suitable aggregate for these applications.

1.2 On Strength

The Bureau of Indian Standards (BIS) has classified the bricks based on their compressive strength, as shown in the table.

1. Bricks with a compressive strength exceeding 40.0 N/mm2 are categorized as heavy-duty bricks. These bricks are utilized in the construction of heavy-duty structures like bridges, industrial building foundations, and multi-story buildings. They have a limited water absorption rate of 5%.
2. Each specified class of bricks is further divided into subclasses A and B, based on tolerances and shape. Subclass-A bricks are required to have smooth rectangular faces, sharp corners, and a uniform color. On the other hand, subclass-B bricks may exhibit slightly distorted shapes and rounded edges.

1.3 On The Basis of Uses

1.3.1 Common Bricks

Common Bricks are versatile units manufactured economically without specific emphasis on appearance. They can vary significantly in terms of strength and durability and are commonly employed for filling, backing, and non-aesthetic wall construction.

1.3.2 Facing Bricks

Facing Bricks are primarily crafted to achieve an appealing visual aspect, whether through color, texture, or both. These bricks exhibit durability even under harsh exposure conditions and are utilized on the facades of buildings where an attractive appearance is desired.

1.3.3 Engineering Bricks

Engineering Bricks possess remarkable strength, impermeability, smoothness, and are meticulously molded. They adhere to defined standards of absorption and strength. These bricks are utilized in all load-bearing structures where robustness is of utmost importance.