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Bricks are amongst the oldest of building materials. The brick's popularity as an ideal building material has not diminished over the years as they are relatively inexpensive to manufacture, very durable, and requires minimal maintenance.
Conventionally, bricks are made of kiln-baked mixtures of clay. In ancient times, mud was used to make bricks and simply dried in the sun. The oldest known bricks date back to 7,500 BC. Presently, concrete, sand and lime, and glass with clay are being used to make bricks.
The color and hardness of the brick is determined by the raw materials used and the baking temperature. Most bricklaying is done manually, hence the brick size is maintained at a size comfortable to fit in the hand. Bricks are held together by mortar. Bricks are arranged in numerous patterns called bonds to enhance the overall strength. Ideally, the compressive strength of a common brick should be 50 kg/cm2, and the water absorption capacity should not be more than 20% by weight.
Types of Bricks
The different types of bricks are listed below:
- Common brick is red. It is sometimes used as a backup brick based on the quality.
- Face brick is used in front of the common backup brick. Face brick is available in many colors and has a uniform surface appearance. It is more durable and is graded based on how it endures freezing temperatures and moisture.
- Calcium silicate bricks are often produced in places where clay is not easily available.
- Glazed bricks are primarily used to build walls in buildings such as hospitals, and laboratories where easy cleaning and maintenance are a prerequisite.
- Refractory bricks or engineering bricks are made from fireclays. This type of clay contains high levels of alumina or silica, or non-clay minerals such as silicon carbide, bauxite, zircon, or dolomite. As refractory bricks are heat resistant, they are often used in furnaces, kilns, and fireplaces.
- Concrete bricks are made of concrete and sand aggregate using a simple machine and following a basic assembly line method. A conveyor belt adds the mixture to the machine, which pours a specific amount of mixture into a mold. The mold is shaken thoroughly to remove bubbles. The mold is removed and the wet brick is left on a plywood sheet. A small elevator is used to arrange the palettes, and a forklift operator transports them to the brickyard for drying.
Features of Brick
The following are the key features of brick:
- High compressive strength and durability
- Possesses the natural and pleasant colors of burnt clay
- Natural sound and thermal insulator and less expensive than other building materials
- Features good porosity due to its fine capillaries. This ensures that moisture is released during the day and re-absorbed during the night, thus maintaining the humidity and temperature in a house or building.
- Resistant to atmospheric action and high temperatures
- Excellent acoustic performance and good fire resistance
- Compact size, colors, textures, and shapes are possible enabling infinite design options
- Good wear resistance due to strong ceramic bonds formed by heat impact at high temperatures
Manufacturing Process of Brick
The primary component for brick manufacture is clay, which is mined either from open-pits or underground mines. The primary crushing of the procured clay mixture is performed by large rollers to break it into smaller chunks. It is then sent to the manufacturing unit where the clay mixture is further pulverized and screened for impurities.
The most common brick manufacturing method is the stiff-mud process. The clay is placed in a pug mill where it is mixed with water at a ratio of 12-15% by weight, kneaded to remove trapped air, and then transferred to an auger machine. The auger extrudes the wet clay via a die to form a continuous rectangle-shaped column. The column is cut using steel wires into the required lengths. The newly made bricks are placed on drying racks for a few days and then fired in a kiln.
Another method called the soft-mud process is used when the mined clay is naturally very wet. The clay is mixed, extruded, and placed in lubricated molds. Drying takes longer in this process but the firing procedure is the same as the previous method.
The third method is the dry-press process, which is often used to make refractory bricks. The clay has minimal water, about 10% by weight, and is put under a hydraulic or mechanical press while in molds. The bricks are then dried and fired.
When the newly made brick is still damp and moldable, textures, patterns, or functional grooves can be pressed into the brick. Special glazes can also be coated for decorative and functional purposes.
Handmade bricks are usually costlier than machine-made bricks.
Applications of Bricks
The construction industry is the major consumer of bricks. Bricks can be used to construct numerous structures and other elements of the built environment such as arches, fireplaces, pavements, dams, bridges, tunnels, and walls.
Bricks also find use in the metallurgy and glass industries, which require bricks as lining material of furnaces.
Environmental Impacts of Brick
Brick is one of the most environmentally friendly and efficient building materials currently available. Although construction and demolition (C&D) waste tends to accumulate in many places and accounts for about 24% of materials in landfills, it is no longer a huge problem as old, broken, and used bricks are now sought after materials. Several countries enforce recycling of C&D waste by law.
Today, antique bricks command a higher price than a new brick, which is advantageous as it reduces large-scale wastage.
As well as being reused, bricks can be recycled. When homes, buildings, roadways, bridges, and other brick constructions are demolished, the resultant rubble can be collected and crushed and turned into new aggregate materials. These materials can be used by the same company or sold to other companies.
Brick is recycled by first crushing the material with a primary jaw crusher then further reducing the crushed material with cone crushers. Then the material must be screened and, where required, blended through the pugmill to obtain several recycled products. Unused bricks, as well as bricks that do not pass the manufacturers’ standards, can also be recycled using the same crushing process to form brick chips.
Applications of Recycled Brick
Recycled bricks have as much use as the virgin material. The key uses are as follows:
- Recycled or reused bricks can be used in historical restoration projects
- Recycled bricks can be sold as aggregate, drainage media, and general fill
- Landscaping and decorative purposes around the garden
- To preserve water in homes by placing a recycled brick in the cistern to displace water. The brick takes up volume, thereby reducing the amount of water used to flush the toilet each time.
- Recycled bricks are ideal for a brick barbecue or fire pit
Sources and Further Reading
This article was updated on 7th February, 2020.