The construction industry requires various diverse materials. Among the materials available, bricks are a fundamental component. The commonly used types of bricks are fly ash bricks and red bricks. Each type has distinct properties and advantages. Let’s look into their differences in detail.
Material Composition
Fly Ash Bricks:
The composition of fly ash bricks includes a by-product of burning coal (fly ash), which is then mixed with cement, water, and sand or gypsum, lime, water and sand to form fly ash bricks.
These materials are compressed at a very high pressure to produce fly ash bricks. They utilise industrial waste, which makes them eco-friendly.
Red Bricks:
Red bricks are produced by mixing natural clay with water and firing it in kilns. Typically, they are reddish brown, as the name says, which is due to the presence of iron content in the clay. It uses natural clay, which is a nonrenewable resource, therefore it is less eco-friendly.
Cost
Fly Ash Bricks:
Fly ash bricks are generally cheaper to produce when compared to red bricks as it utilises industrial waste material for manufacturing. The initial investment is low compared to traditional brick kilns. The smooth finish reduces the need for plastering, leading to lower maintenance costs.
Red Brick:
Red bricks are generally more expensive due to the traditional manufacturing process. The cost of raw materials used in this can be higher based on the location. The production process relies heavily on labour, which also drives up labour costs. Small-scale production of red bricks typically results in higher costs per unit.
Area Coverage
Fly Ash Bricks:
Fly ash bricks are uniform in shape and size, which reduces the need for plastering. They are also comparatively larger in size, thus reducing the number of bricks required to cover a unit area.
Red Brick:
Red bricks have varying shapes and sizes, requiring plastering. Their smaller size necessitates a larger quantity to cover a unit area. The construction speed is comparatively slower due to difficulties in handling and the need for plastering.
Surface Finish
Fly Ash Bricks:
Fly ash bricks have a smooth surface finish. The fly ash brick manufacturing process also ensures consistent and uniform texture. This provides an aesthetic and modern look to the building. All you need is any additional finishing for the construction based on your choice. Dimensionally, these fly ash bricks are precise, which ensures a uniform surface. This allows better bonding with mortar.
Red Brick:
Red bricks typically have a rough surface finish, which results in inconsistent texture. This is mainly due to the natural clay finish, which provides a traditional and rustic appearance. This leads to high water absorption and provides better mechanical bonding with mortar. Red bricks need extensive preparation before the painting process.
Insulation Properties
Fly Ash Bricks:
Fly ash bricks have lower thermal conductivity when compared to red bricks. This makes them conduct heat better, contributing to energy efficiency in the building. Their thermal conductivity can be 0.90–1.05 W/m2.
With better insulation properties, it is suitable for areas with extreme temperatures and has high fire insulation properties. The thermal mass of fly ash is less than the red bricks. Hence, it helps save energy in the building and reduces the overall life cycle costs.
Red Brick:
The red bricks have higher thermal conductivity compared to fly ash. They are less efficient and retain heat, which leads to temperature fluctuation. Heavy and denser characteristics of fly ash bricks provide good fire insulation properties.
These are less efficient due to higher thermal conductivity and are not appropriate for extreme weather conditions. The red bricks absorb high moisture and have inferior thermal insulation properties. This leads to higher life cycle costs, contributing less to energy savings in the building.
Environmental Impact
Fly Ash Bricks:
The fly ash brick utilises industrial waste, which reduces the landfill burden. Therefore, carbon emissions are lower due to reduced energy consumption. As it uses waste material, it is not likely to deplete natural resources.
Its manufacturing process also requires less water, thus helping in managing the fly ash waste from the power plants. These are not toxic and significantly cause lower environmental impact, encouraging innovation in construction techniques.
Red Brick:
Red bricks involve the moulding of clay and firing at high temperatures. This results in the need for high energy consumption due to the kiln firing. The use of natural clay leads to resource depletion with higher carbon emissions. This causes intense energy production with limited recyclability. They are non-toxic, but the production can release pollutants, which are less likely to qualify for green building certification.
Density
Fly Ash Bricks:
Fly ash bricks are generally lighter in density when compared to red bricks. This is due to the inclusion of fly ash, which is a lightweight material. They have a density of about 1200 to 1850 kg/m3. This reduced weight characteristic can be beneficial for high-rise buildings to reduce the overall load.
Red Brick:
Red bricks are denser and heavier when compared to fly ash bricks. The higher density results in greater weight, which increases the dead load on the structure. The density is about 1800 to 2000 kg/m3. The material used in its production creates high density due to the compact nature of clay. The heavier weight can be difficult to handle during construction, causing increased transportation costs.
Compressive Strength
Fly Ash Bricks:
Fly ash bricks have higher compressive strength, typically around 7.5 to 10 MPa. These also have higher tensile strength and are much more flexible in terms of usage. They are less prone to cracking and have higher flexural strength. They are resistant to chemicals and suitable for load-bearing structures.
Red Brick:
They have lower compressive strength, typically around 3.5 to 5 MPa. The red bricks have high workability and are more prone to cracking. It has lower tensile strength, but is heat resistant. The chemical resistance and flexural strength of these bricks are low.
Fire Resistance
Fly Ash Bricks:
Fly ash bricks have high fire resistance due to their noncombustible nature. It offers better thermal insulation.
Red Brick:
Red bricks also have good fire resistance due to the high firing temperature. They provide good thermal insulation.
Water absorption
Fly Ash Bricks:
Fly ash bricks typically have a lower water absorption rate, which is around 10 to 15%. The reduced water absorption also minimises the risk of efflorescence, which is the formation of white salt deposits on the brick surface. Thus, it lessens the risk of shrinkage and cracking during drying.
Red Brick:
Red bricks have a higher water absorption rate, which is typically around 20 to 25%. These are more porous due to the natural clay material leading to higher water absorption. This results in the risk of efflorescence causing high shrinkage and cracking.
Durability
Fly Ash Bricks:
Fly ash bricks perform well in harsh conditions and are highly durable. They provide high resistance to weathering effects and are prone to less cracking. It has a higher surface hardness.
Red Brick:
These are durable but can degrade over time, especially when left exposed without surface finishes. The red bricks are less resistant to weather adversities and have lower resistance to impact. It comes in variable quality due to traditional manufacturing and has lower surface hardness.
Conclusion
In conclusion, understanding the differences between these two types of bricks enables a user to make an informed decision on the choice of bricks. Each has different compositions, properties, advantages and disadvantages. Ultimately, the decision is based on specific requirements of the construction project.