Archive for the ‘Bricks’ Category

Bricks manufacturing

December 30, 2010 1 comment

A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar.


The oldest discovered bricks, originally made from shaped mud and dating to 7500 B.C., were found in in the upper Tigris region and in southeast Anatolia close to Diyarbakir. Other more recent findings, dated between 7,000 and 6,395 B.C., come from Jericho and Catal Hüyük. The first sun-dried bricks were made in Mesopotamia (what is now Iraq), in the ancient city of Ur in about 4000 BC, although the arch used for drying the bricks was not actually found.
Other examples of civilizations who used mud brick include the ancient Egyptians and the Indus Valley Civilization, where it was used exclusively. In particular, it is evident from the ruins of Buhen, Mohenjo-daro and Harappa.

The trend of building upwards for offices that emerged towards the beginning of the 19th century displaced brick in favor of cast and wrought iron and later steel and concrete. Some early ‘skyscrapers’ were made in masonry, and demonstrated the limitations of the material – for example, the Monadnock Building in Chicago (opened in 1896) is masonry and just seventeen stories high; the ground walls are almost 6 feet (1.8 m) thick, clearly building any higher would lead to excessive loss of internal floor space on the lower floors. Brick was revived for high structures in the 1950s following work by the Swiss Federal Institute of Technology[disambiguation needed] and the Building Research Establishment in Watford, UK. This method produced eighteen-story structures with bearing walls no thicker than a single brick (150–225 mm). This potential has not been fully developed because of the ease and speed in building with other materials; in the late-20th century brick was confined to low- or medium-rise structures or as a thin decorative cladding over concrete-and-steel buildings or for internal non-load-bearing walls.

Methods of  manufacture

Bricks may be made from clay, shale, soft slate, calcium silicate, concrete, or shaped from quarried stone.
Clay is the most common material, with modern clay bricks formed in one of three processes – soft mud, dry press, or extruded.

Normally, brick contains the following ingredients:

  1. Silica (sand) – 50% to 60% by weight
  2. Alumina (clay) – 20% to 30% by weight
  3. Lime – 2 to 5% by weight
  4. Iron oxide – 5 to 6% (not greater than 7%) by weight
  5. Magnesia – less than 1% by weight
  • Clay Bricks

The soft mud method is the most common, as it is the most economical. It starts with the raw clay, preferably in a mix with 25-30% sand to reduce shrinkage. The clay is first ground and mixed with water to the desired consistency. The clay is then pressed into steel moulds with a hydraulic press. The shaped clay is then fired (“burned”) at 900-1000 °C to achieve strength.

Clay Bricks

  • Rail kilns

In modern brickworks, this is usually done in a continuously fired tunnel kiln, in which the bricks move slowly through the kiln on conveyors, rails, or kiln cars to achieve consistency for all bricks. The bricks often have added lime, ash, and organic matter to speed the burning.

Brick likn in india

  • Bull’s Trench Kilns

In India, brick making is typically a manual process. The most common type of brick kiln in use there are Bull’s Trench Kiln (BTK), based on a design developed by British engineer W. Bull in the late nineteenth century.

An oval or circular trench, 6–9 meters wide, 2-2.5 meters deep, and 100–150 meters in circumference, is dug. A tall exhaust chimney is constructed in the centre. Half or more of the trench is filled with “green” (unfired) bricks which are stacked in an open lattice pattern to allow airflow. The lattice is capped with a roofing layer of finished brick.

In operation, new green bricks, along with roofing bricks, are stacked at one end of the brick pile; cooled finished bricks are removed from the other end for transport. In the middle the brick workers create a firing zone by dropping fuel (coal, [wood], oil, debris, etc.) through access holes in the roof above the trench.


Bull's trench kiln Process

  • Dry pressed bricks

The dry press method is similar to Clay brick but starts with a much thicker clay mix, so it forms more accurate, sharper-edged bricks. The greater force in pressing and the longer burn make this method more expensive.

  • Calcium silicate bricks (Fly ash Bricks)

The raw materials for calcium silicate bricks include lime mixed with quartz, crushed flint or crushed siliceous rock together with mineral colourants. The materials are mixed and left until the lime is completely hydrated, the mixture is then pressed into moulds and cured in an autoclave for two or three hours to speed the chemical hardening. The finished bricks are very accurate and uniform, although the sharp arrises need careful handling to avoid damage to brick (and brick-layer). The bricks can be made in a variety of colours, white is common but pastel shades can be achieved.
It is very common in Sweden, especially in houses built or renovated in the ’70s. Here it is referred to as “Mexitegel” (en: Mexi[can] Bricks).
In India these are known as Fly ash bricks, manufactured using the Falg process.

Optimal dimensions, characteristics, and strength

For efficient handling and laying bricks must be small enough and light enough to be picked up by the bricklayer using one hand (leaving the other hand free for the trowel). Bricks are usually laid flat and as a result the effective limit on the width of a brick is set by the distance which can conveniently be spanned between the thumb and fingers of one hand, normally about four inches (about 100 mm). In most cases, the length of a brick is about twice its width, about eight inches (about 200 mm) or slightly more. This allows bricks to be laid bonded in a structure to increase its stability and strength (for an example of this, see the illustration of bricks laid in English bond, at the head of this article). The wall is built using alternating courses of stretchers, bricks laid longways and headers, bricks laid crossways. The headers tie the wall together over its width.

A hastily-made wall of rough bricks without using cement or even mud in an Indian town. Only plainest type of bricks are used in India. Such constructions are often risky
A bigger brick makes for a thicker (and thus more insulating) wall. Historically, this meant that bigger bricks were necessary in colder climates (see for instance the slightly larger size of the Russian brick in table below), while a smaller brick was adequate, and more economical, in warmer regions. A notable illustration of this correlation is the Green Gate in Gdansk; built in 1571 of imported Dutch brick, too small for the colder climate of Gdansk, it was notorious for being a chilly and drafty residence. Nowadays this is no longer an issue, as modern walls typically incorporate specialized insulation materials.
The correct brick for a job can be picked from a choice of colour, surface texture, density, weight, absorption and pore structure, thermal characteristics, thermal and moisture movement, and fire resistance.


Bricks are 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. For example, in the early 1900s, most of the streets in the city of Grand Rapids, Michigan were paved with brick. Today, there are only about 20 blocks of brick paved streets remaining (totalling less than 0.5 percent of all the streets in the city limits).

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 good thermal shock resistance, refractoriness under load, high melting point, and satisfactory porosity. There is a large refractory brick industry, especially in the United Kingdom, Japan and the United States.
In the United Kingdom, bricks have been used in construction for centuries. Until recently, almost all houses were built almost entirely from bricks. Although many houses in the UK are now built using a mixture of concrete blocks and other materials, many houses are skinned with a layer of bricks on the outside for aesthetic appeal.

Categories: Bricks