Types of Bricks in Masonry Construction – Properties & Uses
Bricks have been a fundamental construction material for centuries, owing to their affordability and durability. In masonry construction, various types of bricks are utilized, each possessing unique properties and serving specific purposes. Understanding the characteristics and uses of different brick types is crucial for selecting the most suitable option for construction projects.
This article delves into the classification, properties, and applications of bricks, shedding light on their significance in the realm of construction.
A. Types of Bricks used in Masonry Construction:
Bricks are broadly classified into two categories based on the manufacturing process: sun-dried or unburnt bricks and burnt bricks.
1. Sun-Dried or Unburnt Clay Bricks:
Sun-dried or unburnt bricks, although less durable, find utility in temporary structures. These bricks undergo three main steps: clay preparation, molding, and drying. After molding, they are exposed to sunlight for drying, resulting in reduced strength, water resistance, and fire resistance. Consequently, unburnt bricks are not suitable for permanent structures.
2. Burnt Clay Bricks:
Burnt clay bricks, on the other hand, offer superior quality, albeit with some variations. They are further classified into four types:
a. First Class Bricks:
First-class bricks are considered the highest quality among the different classes. They are molded using table-molding techniques and fired in large kilns. As a result, these bricks exhibit standard shape, sharp edges, and smooth surfaces. They possess remarkable durability and strength, making them suitable for permanent structures. However, due to their superior properties, first-class bricks are relatively more expensive.
b. Second Class Bricks:
Second-class bricks are of moderate quality and are molded through ground-molding processes. Similar to first-class bricks, they are fired in kilns. However, the ground-molding technique leads to less smooth surfaces and irregular shapes due to ground unevenness. Although second-class bricks offer satisfactory strength and durability, they require smooth plastering for improved aesthetics.
c. Third Class Bricks:
Third-class bricks are poor quality bricks primarily employed in temporary structures. These ground-molded bricks are burnt in clamps, resulting in rough surfaces and uneven edges. They are not suitable for areas with heavy rainfall and are used akin to unburnt bricks.
d. Fourth Class Bricks:
Fourth-class bricks are of very low quality and are not employed as standalone construction units. Instead, they are crushed and utilized as aggregates in concrete manufacturing. Overburning makes these bricks brittle and prone to breakage, rendering them unsuitable for construction purposes.
3. Fly Ash Bricks:
Fly ash bricks, produced using fly ash and water, exhibit superior properties compared to clay bricks. These self-cementing bricks have high concentrations of calcium oxide, aiding in cement production. Fly ash bricks are lightweight, reducing the overall weight of structures. Their advantages over clay bricks include high fire insulation, strength, uniform sizes for better joints and plaster, reduced water penetration, and no requirement for soaking before use in masonry construction.
4. Concrete Bricks:
Concrete bricks are manufactured using a mixture of cement, sand, coarse aggregates, and water. Their production can be tailored to desired sizes. Concrete bricks offer several advantages over clay bricks, such as on-site manufacturing, reduced mortar requirements, the possibility of different pigmented colors, and excellent aesthetic appeal. They find application in masonry and framed buildings, facades, fences, and other architectural elements.
5. Engineering Bricks:
Engineering bricks possess high compressive strength, making them ideal for specialized applications that demand strength, frost resistance, acid resistance, and low porosity. These bricks are commonly employed in basements prone to chemical or water attacks, as well as for damp proof courses.
6. Sand Lime or Calcium Silicate Bricks:
Sand lime bricks, also known as calcium silicate bricks, are manufactured using sand and lime. They find diverse applications in construction, including ornamental works in buildings and masonry projects. Calcium silicate bricks offer unique properties suitable for various construction needs.
B. Identification of Brick Quality at Construction Site:
Ensuring the use of good-quality bricks is essential for constructing robust structures. The following criteria aid in identifying superior bricks at construction sites:
1. Bright and Uniform Color:
Good-quality bricks exhibit a bright and uniform color throughout.
2. Well-Burned with Smooth Surfaces and Sharp Edges:
Superior bricks are well-burned, resulting in smooth surfaces and sharp edges, indicating high manufacturing standards.
3. Low Thermal Conductivity and Soundproofing:
Bricks with low thermal conductivity provide better insulation and soundproofing properties.
4. Water Absorption:
Bricks should not absorb more than 20% of their weight when submerged in water.
5. Ringing Sound:
When struck together, good-quality bricks produce a clear ringing sound.
6. Homogeneous and Uniform Structure:
The structure of bricks should be consistent and uniform without any irregularities.
7. Drop Test:
Bricks should withstand a drop from a height of 1 meter without breaking.
8. Scratch Test:
No scratch marks should be left on the brick when scraped with a fingernail.
9. Absence of White Deposits:
After soaking the brick in water for 24 hours, there should be no white deposits on its surface.
C. Properties of Bricks:
Bricks possess several important properties that contribute to their significance in construction:
i. Hardness:
Bricks should exhibit resistance to abrasion, enabling them to maintain their structural integrity over time.
ii. Compressive Strength:
Compressive strength refers to the load a brick can withstand per unit area. According to the Bureau of Indian Standards (BIS), the minimum compressive strength of a brick should be 3.5 N/mm².
iii. Absorption:
Absorption denotes the brick’s capacity to absorb water. Bricks with optimal absorption characteristics offer better durability and resistance to water-related damage.
D. Uses of Different Types of Bricks:
Bricks find extensive applications in the construction industry, serving various purposes:
1. Good Quality Bricks (1st and 2nd Class):
High-quality bricks are utilized in the construction of buildings, tunnels, pitching works, and other permanent structures.
2. 3rd Class and Unburnt Bricks:
Lower-quality bricks, such as 3rd class bricks and unburnt bricks, are suitable for temporary structures.
3. 4th Class Bricks:
Fourth-class bricks, due to their poor quality, are crushed and utilized as aggregates in concrete production.
4. Architectural Applications:
Bricks are also employed for architectural purposes, providing an aesthetic appearance to structures, enhancing their visual appeal.
Understanding the various types of bricks, their properties, and suitable applications is crucial for effective construction practices. From the durability of first-class bricks to the versatility of fly ash and concrete bricks, each type offers unique advantages.
By identifying high-quality bricks and utilizing them appropriately, construction professionals can ensure the integrity and longevity of their structures while achieving the desired aesthetic appeal.