Bricks consist of fired ceramic, clay, or cement materials that are cut into specific shapes, such as a rectangle, and used for building walls or furnaces or for paving surfaces. Bricks vary in material makeup, size, and shape and include products for specific applications, such as firebricks or refractory bricks, acid bricks for flooring, and bricks for masonry applications.
Bricks are manufactured using raw materials such as clay, concrete, calcium silicate, or shale mixed with a specific amount of water. They are shaped or extruded and then kiln-dried to hardness. A relatively new type of brick composed of fly ash, a by-product of burning coal, came on the scene in 2007. Fly ash bricks are just as strong as traditional clay bricks, but they may contain small amounts of pollutants such as heavy metals.
Bricks vary by the ratio of raw material to water and how they are formed. For example, the stiff mud process uses 12%-15% water and extrudes the formed bricks through a die. The soft mud process uses 20%-30% water and forms bricks in molds. The dry press process uses less water than the previous two, only 10%, and forms the bricks in molds under high pressure. All types of bricks are dried in furnaces or kilns to ensure proper characteristics such as durability, hardness, and weather resistance. The material-to-water ratio, forming process, temperature, and time in the furnace all depend upon how the finished bricks will be used.
- Red bricks are used to build walls in structural masonry or in load bearing applications.
- Firebricks, or refractory bricks, are made with clays that are mined deeper down and have fewer impurities. They resist heat and are useful in furnace applications.
- Acid bricks are used to build industrial flooring, and, therefore, must be dense and durable. Acid bricks are made using high-quality shale that is dried at high temperatures for a long period of time to ensure uniform density.
Constructing walls or paving floors with bricks involves the use of a mortar to bond the bricks together. Mortar is typically composed of Portland cement, masonry cement, lime, and other aggregates. The mixture depends upon how coarse or fine the mortar needs to be for the application. The bricks are stacked together with a layer of mortar in between each brick, bonding it to the surrounding bricks. The patterns used to build walls or other structures or to pave floors varies according to the application. Some of the common patterns include the Flemish or Dutch bond, in which shorter bricks called headers are alternated with longer bricks called stretchers. This type of pattern is often used for load bearing walls. Other variations of this alternating pattern include the English bond, Rat-trap bond, Monk bond, and header bond. Patterns for paving surfaces include Basket bond and Herringbone bond. Some more complex patterns are selected for aesthetic reasons, while simple patterns are used for brick surfaces that will be covered with plaster or stucco.
Bricks are an environmentally friendly building material, since they are manufactured using abundant raw materials, they are durable, long-lived, and efficient at maintaining a constant temperature, and they are completely recyclable at the end of their life.
Oula Lehtinen / CC BY-SA 3.0