Bricks are a fundamental building material in construction, renowned for their durability, low cost, and versatility. Their usage dates back to ancient times and continues to be prevalent in modern construction. Based on material composition and manufacturing processes, bricks are classified into various types, each serving specific functions and applications. This article delves into the different types of bricks used in masonry construction, highlighting their properties, suitability, and identification techniques.
Broad Classification of Bricks
Bricks can be broadly categorized into two main types: Sun-Dried or Unburnt Bricks and Burnt Bricks.
Sun-Dried or Unburnt Bricks
Sun-dried bricks, often referred to as unburnt bricks, are characterized by their low durability and strength. These bricks are primarily used in temporary structures due to their inability to withstand adverse weather conditions. The manufacturing process involves three key steps: preparing the clay, molding it into shape, and drying it under sunlight. As a result of this process, sun-dried bricks exhibit low water and fire resistance, making them unsuitable for permanent constructions.
Burnt Bricks
Burnt bricks are generally of higher quality compared to their sun-dried counterparts and are classified into four distinct categories based on their characteristics:
- First Class Bricks: These are considered the best quality bricks. They are molded using a table-molding process and are burnt in large kilns. Their standardized shape, sharp edges, and smooth surfaces make them highly durable, suitable for permanent structures. However, due to their superior properties, they are more expensive than other classes.
- Second Class Bricks: These bricks are of moderate quality, molded through a ground-molding process and burnt in kilns. While they lack the smooth surfaces and sharp edges of first-class bricks, they still provide satisfactory strength and durability. Structures built with second-class bricks usually require smooth plastering to enhance appearance.
- Third Class Bricks: Classified as poor quality, third-class bricks are ground-molded and burnt in clamps. Their surfaces are rough, and edges are uneven, making them more suitable for temporary structures. They are not recommended for use in areas with heavy rainfall due to their low durability.
- Fourth Class Bricks: These are of very poor quality, often over-burnt, which makes them brittle and weak. Rather than being used as bricks in construction, fourth-class bricks are typically crushed and repurposed as aggregates in concrete production.
Types of Bricks by Material Composition
Fly Ash Bricks
Fly ash bricks are made using fly ash, a byproduct of coal combustion, mixed with water. These bricks have several advantages over traditional clay bricks, including better freeze-thaw resistance and lower weight. High in calcium oxide, they are also referred to as self-cementing bricks. Fly ash bricks are lightweight, reducing the overall weight of structures, and exhibit properties such as high fire insulation, uniform size, and lower water penetration. They do not require soaking before use in masonry construction, making them convenient for builders.
Concrete Bricks
Concrete bricks are manufactured from a mixture of cement, sand, coarse aggregates, and water. One of their significant advantages is that they can be produced on-site, allowing for flexibility in size and color during the production process. Concrete bricks reduce the amount of mortar needed for construction and are commonly used in masonry, framed buildings, facades, and fences, providing an excellent aesthetic presence.
Engineering Bricks
Engineering bricks are known for their high compressive strength and durability, making them ideal for specialized applications. These bricks are used where strength, frost resistance, acid resistance, and low porosity are essential, such as in basements that are susceptible to chemical attacks and water infiltration.
Sand Lime or Calcium Silicate Bricks
Sand lime bricks, also known as calcium silicate bricks, are made from a mixture of sand and lime. They are often used for ornamental works in buildings and various masonry applications. Their smooth finish and uniform size contribute to their popularity in construction.
Identification of Brick Quality at Construction Sites
To ensure the quality of construction materials, identifying good quality bricks at the construction site is crucial. Several indicators can help assess brick quality:
- Bright, uniform color
- Well-burned, smooth surfaces, and sharp edges
- Low thermal conductivity and soundproofing properties
- Water absorption not exceeding 20% by weight
- Producing a ringing sound when struck together
- Homogeneous structure with no cracks or defects
- Resilience to dropping from a height of 1 meter without breaking
- No scratches left when scratched with a fingernail
- Absence of white deposits after soaking in water for 24 hours
Key Properties of Bricks
Bricks possess several essential properties that make them suitable for construction:
Hardness
The hardness of a brick refers to its resistance to abrasion. A good quality brick should be able to withstand wear and tear without being damaged, ensuring the longevity of the brick structure.
Compressive Strength
Compressive strength indicates the load a brick can carry per unit area. According to the Bureau of Indian Standards (BIS), the minimum compressive strength of bricks should be 3.5 N/mm². The strength of bricks can diminish when soaked in water, impacting their structural integrity.
Water Absorption
Bricks generally absorb water, but there are limits based on their class. The water absorption percentages by weight for different classes of bricks are as follows:
- Heavy-duty bricks: 5%
- First class: 20%
- Second class: 22%
- Third class: 25%
Applications of Different Types of Bricks
Bricks serve various purposes in the construction industry:
- Good Quality Bricks (1st and 2nd class): Used in the construction of buildings, tunnels, and other permanent structures.
- 3rd Class and Unburnt Bricks: Appropriate for temporary structures.
- 4th Class Bricks: Used as aggregates in concrete.
- Architectural Applications: Employed for aesthetic purposes to enhance the visual appeal of structures.
Conclusion
Understanding the different types of bricks and their properties is essential for making informed decisions in masonry construction. From sun-dried and burnt bricks to modern fly ash and concrete options, each type has its unique advantages and applications. Identifying the quality of bricks at the construction site is crucial to ensure durability and structural integrity. As the construction industry continues to evolve, the role of bricks remains fundamental, serving as a reliable and versatile building material.