Bricks are an indispensable part of both commercial and residential construction. They are popularly known for their excellent strength, workability, and fire-resistant properties. It is commonly made of clay or fly ash. Bricks are commonly used in many construction works by applying mortar on them and arranging them in a desired shape.
The properties and durability of the brick depend on the materials or resources used in it. Based on the quality, they are categorised into four different types, including first-class bricks, second-class bricks, fourth-class bricks. and third-class bricks
The manufacturing process of each type is different. However, fourth-class bricks are among the least ideal choices. In this article, you will discuss their properties, characteristics, and quality standards.
What are Fourth Class Bricks?
Fourth-class bricks are either overburnt or underburnt. They are characterised by very low quality and are not suitable for construction. They may cause distortions, cracks, or any other costly defects in the structure. Overburnt bricks are dark in colour with irregular shapes and are easily breakable. They are crushed and used as aggregates for PCC works in roads, foundations, floors, etc.
Characteristics of Fourth Class Bricks
Generally, fourth-class bricks are very low-quality bricks that are unsuitable for any construction works. They can be characterised by the following:
- They are either overburnt or underburnt, possessing a weak and brittle structure.
- These bricks can cause distortions, visible cracks, and other imperfections that can result in poor structural integrity.
- They have a low porosity and absorption, while they are quite strong in compressive strength, which is typically above 150 g/cm². But still, this strength is lower than the high-quality bricks.
- They are available in the form of lumps and seem irregular in shape and size.
- Due to their high water absorption capacity, they lead to issues like reduced durability and efflorescence.
Properties of Fourth Class Bricks
Here are properties associated with fourth-class bricks:
- Fourth-class bricks are rough and misshapen due to uneven burning.
- Compared to high-quality bricks, they have very low density and strength.
- Their compressive strength is significantly low, which makes it unsuitable for load-bearing applications.
- Due to their poor durability, fourth-class bricks are subjected to weathering and erosion within a short period of time.
- As mentioned earlier, they have very little porosity, allowing water to enter the cracks and cause severe damage.
- Fourth-class bricks possess low fire resistance capacity and can easily catch fire.
- It has lower thermal insulation properties and is less energy efficient.
Advantages of Fourth Class Bricks
Fourth class bricks don’t have adequate strength to use directly in the construction, but they can be used as an aggregate in foundations, floors, and road construction.
Cost-Effective: Fourth-class bricks are brittle and can break easily. So, it is available at a cheaper price when compared to higher-quality bricks. It can be a preferable option for certain non-structural applications.
Used as an Aggregate: The bricks are crushed and repurposed as aggregates in concrete. It can be efficient in road construction and foundations. Repurposing can reduce wastage and conserve natural resources.
Non-Structural Applications: Overburnt or underburnt bricks are easily susceptible to damage, and they can’t be used in regular construction works. However, they can be crushed and mixed with concrete to use it for non-load-bearing applications like leveling ground, filling gaps, or foundations for minor structures.
Disadvantages of Fourth Class Bricks
Of course, fourth-class bricks are a cost-effective option but contain certain significant disadvantages, including:
- Overburnt or underburnt bricks are not suitable for construction, leading to significant variations in the quality and strength of the structure.
- They are unsuitable for carrying heavy loads and weight.
- High water absorption weakens the structure and leads to various issues, such as reduced durability, mold growth, and affects the aesthetic appeal of the overall building.
- They are available in irregular shapes and sizes, which makes it difficult to arrange and obtain the desired result.
- Highly prone to damage from freeze-thaw cycles, weathering, and erosion.
Quality Standards for Fourth Class Bricks
Before coming to usage, bricks need to meet certain quality standards defined by organisations like the Bureau of Indian Standards (BIS). It focuses on various aspects, including size, shape, colour, texture, water absorption, and compressive strength.
Unfortunately, fourth-class bricks often fail to meet these standards, making them unsuitable for regular construction purposes. They may be suggested for non-load-bearing applications, temporary structures, and other minimal foundations where cost is a primary concern. However, it is essential to ensure that their usage should be based on specific project requirements and conditions.
Manufacturing Process of Fourth Class Bricks
The manufacturing process of fourth class bricks is is similar to that of high-quality bricks. However, due to suboptimal burning conditions and less stringent quality control, they are unsuitable for use in construction work. Here’s a general manufacturing process of bricks:
Clay Extraction & Preparation: In general, clay is extracted from quarries or pits and then mixed with water to form a workable clay mixture.
Molding: The clay mixture is molded into brick shape either by hand or mechanically.
Drying: To drain out the excess moisture content, the molded bricks are kept for sun drying or artificially in drying chambers.
Burning: Burning is a crucial step, which determines the actual quality of a brick. When the process is less controlled, leading to overburnt or underburnt, we name them as fourth class bricks.
Cooling and Sorting: Cooling is the final process, once the bricks are sufficiently burned. However, the fourth class bricks don’t meet the qualities of high-standard bricks, and it may cause cracks or other defects in the construction.
How to Identify Fourth Class Bricks
Fourth-class bricks can be easily identified with the following ways:
- They are dark in colour and irregular in shape.
- Such bricks are easily brittle and breakable.
- They are not water resistant.
- Fourth class bricks have distortions, cracks, and other defects, which are easily visible and notable.
Final Wordings
When it comes to construction work, only high-quality bricks are considered high-priority. This is to ensure the strength, durability, and workability of the structure. However, when reusing the fourth-class bricks, we can reduce wastage and save resources. In this blog, you may have understood where low-quality bricks can be used efficiently.