Brick
- This page is about bricks used for construction. For other uses of the word "brick" please see Brick (disambiguation).
A brick is a ceramic block made of kiln-fired material, usually clay or ground shale. Clay bricks are formed in a mould (the soft mud method), or more frequently in commercial mass production by extruding clay through a die and then wire-cutting them to the desired size (the stiff mud process). Brick made from dampened clay must be formed in molds with a great deal of pressure, usually applied by a hydraulic press. These bricks are known as hydraulic-pressed bricks, and have a dense surface which makes them highly resistant to weathering, and thus suitable for facing work. The shaped clay is then dried and fired to achieve the final, desired strength. In modern brickworks, this is usually done in a continuously fired kiln, in which the bricks move slowly through the kiln on conveyors, rails, or kiln cars to achieve consistent physical characteristics for all bricks. Bricks are also known in the building trades as compressed earth blocks or CEBs.
History
In the Near East and India, bricks have been in use for more than five thousand years. The Tigris-Euphrates plain lacks rocks and trees. Sumerian structures were thus built of plano-convex mudbricks, not fixed with mortar or with cement. As plano-convex bricks (being rounded) are somewhat unstable in behaviour, Sumerian bricklayers would lay a row of bricks perpendicular to the rest every few rows. They would fill the gaps with bitumen, straw, marsh reeds, and weeds.
The Ancient Egyptians and the Indus Valley Civilization also used mudbrick extensively, as can be seen in the ruins of Buhen, Mohenjo-daro and Harappa, for example. In the Indus Valley Civilization particularly, all bricks corresponded to sizes in a perfect ratio of 4:2:1, and made use of the decimal system. The ratio for brick dimensions 4:2:1 is even today considered optimal for effective bonding.
The Romans made use of fired bricks, and the Roman legions, which operated mobile kilns, introduced bricks to many parts of the empire. Roman bricks are often stamped with the mark of the legion that supervised its production. The use of bricks in Southern and Western Germany, for example, can be traced back to traditions already described by the Roman architect Vitruvius.
In the 12th century, bricks from Northern Italy were re-introduced to Northern Germany, where an independent tradition evolved. It culminated in the so-called brick Gothic, a reduced style of Gothic architecture that flourished in Northern Europe, especially in the regions around the Baltic Sea which are without natural rock resources. Brick Gothic buildings, which are built almost exclusively of bricks, are to be found in Denmark, Germany, Poland and Russia. However, bricks were long considered an inferior substitute for natural rock.
During the Renaissance and the Baroque, visible brick walls were unpopular and the brickwork was often covered with plaster. It was only during the mid-18th century that visible brick walls regained some degree of popularity, as illustrated by the Dutch Quarter of Potsdam, for example.
The transport in bulk of building materials such as bricks over long distances was rare before the age of canals, railways, good roads and large, reliable heavy goods vehicles. Before this time bricks were generally made as close as possible to their point of intended use (it has been estimated that in England in the eighteenth century carrying bricks by horse and cart for ten miles over the poor roads then existing could more than double their price). Bricks were made using locally-available materials in regions that lacked stone and other materials suitable for building close at hand, including for example much of south-eastern England, large parts of the American south-west and The Netherlands---all places lacking stone but possessing the essential requisites for brick making: suitable clays and fuel for firing.
Construction and types
Bricks can be mainly divided into three main categories which include 1) clay bricks, (2) concrete blocks and (3) calcium silicate bricks. The standard dimensions of clay and calcium silicate bricks are the same; the standard dimensions are 230 x 110 x 76 mm. The standard dimension for a concrete block modular is 390 x 190 x 190 mm.
Hard-burned brick should be used for face work exposed to the weather, and soft brick for filling, foundations, and the like. The mainstay standard US brick measures approximately 8 x 4 x 2.25 inches (203 x 102 x 57 millimeters), and has a crushing strength of between 1000 and 15000 lbf/in² (7 to 105 megapascals) depending on quality. The modern standard UK brick size is 215 x 102.5 x 65 millimetres.
A highly impervious and ornamental surface may be laid on brick either by salt glazing, in which salt is added during the burning process, or by the use of a "slip," which is a glaze material into which the bricks are dipped. Subsequent reheating in the kiln fuses the slip into a glazed surface integral with the brick base.
Proportions
Regardless of size, bricks are usually manufactured with the depth equal to half the length (assuming that the brick is laid horizontally), in a 1:2:4 ratio. This allows for several convenient layouts which must necessarily interweave the bricks in any structure, often both at the corners and within the wall depth in order to ensure the greatest possible durability of the structure.
Use
Bricks are typically used for building and pavement. In the USA, brick pavement was found incapable of withstanding heavy traffic, but it is coming back into use as a method of traffic calming or as a decorative surface in pedestrian precincts.
Bricks are also used in the metallurgy and glass industries for lining furnaces. They have various uses, especially refractory bricks such as silica, magnesia, chamotte and neutral (chromomagnesite) refractory bricks. This type of brick must have a series of properties such as good thermal shock resistance, refractoriness under load, high melting point, satisfactory porosity (which can influence several other properties), all of which are high-temperature properties. There is a large refractory brick industry, especially in the United Kingdom, Japan and the U.S.A..
See also
