Bricks are one of the oldest types 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 require less maintenance.
Conventionally, bricks are made of kiln-baked mixtures of clay. In the ancient times, mud was used to make bricks, and simply dried in the sun. The oldest known bricks date back to 7500 BC. Presently, concrete, sand and lime, and glass along 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. Mostly 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 so as 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 basically red in color. It is sometimes used as a backup brick based on the quality.
- Face brick is used on top of 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 its ability to endure 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, laboratories, and dairies where easy cleaning and maintenance are a prerequisite.
- Refractory 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 fireclays 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, following which a forklift operator transports them to the brickyard for drying.
- CORDI-Géopolymère has developed a new brick using their LTGS brick technology, which is patented (80 20386) in France and filed on September 23, 1980. The LTGS brick is inexpensive as it primarily uses lateritic clay earth, which is abundantly available, and hence can be easily adopted by developing countries with mass population. Lateritic clay earth is mixed with a simple geopolymer binder, shaped to form a brick and heated in a furnace at 85°C (185°F).
Features of Brick
The following are the key features of brick:
- High compressive strength and durable
- 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 has to be mined either from open pits or underground mines. Primary crushing of the procured clay mixture is performed by large rollers so as 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 12-15% by weight, kneaded so as 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 the bricks takes longer in this process. 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 things 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 available in the market. Although construction and demolition (C&D) waste tend to accumulate in many places and account for about 24% of trash in landfills, it is no longer a huge problem as old, broken, and used brick are sought after materials these days as they are just as virgin materials. Several countries enforce recycling of C&D waste by law.
Today, antique bricks actually command a higher price than a new brick, which becomes an advantage as it reduces large-scale wastage.
Bricks can be recycled. When homes, buildings, roadways, bridges, and other brick constructions are demolished, the resultant rubble can be collected and crushed to be transformed 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 reduce the crushed material with cone crushers. Then the material must be screened and wherever 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 old 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. Studies reveal that about 500 gallons of water can be saved each year per toilet with just one brick!
- Recycled bricks are ideal for a brick barbecue or fire pit