Classification of types of bricks

Bricks can be classified in different ways.

Such as: classification in terms of color, dimensions, gender, etc

Classification of bricks by gender

Brick is divided into two categories based on its type:

Pressed bricks:

The reason for the name of this type of brick is that at the beginning of the production of this type of brick, its clay was beaten by hand and the corners of the mold were filled with special mud by manual pressure of the clay workers. The dimensions of pressed brick are 5x10x20 or 5.5x11x22 cm. Pressed brick is suitable for all construction works such as knotty, arch, bearing walls and porcelain blade.

Machine bricks:

Machine-made brick or perforated brick, which has 8 or 10 holes with a diameter of 1.5 to 2 cm on its larger surface, and is known as eight- or ten-hole machine-made bricks in the Iranian market.

According to the standard number 7 of the Iranian Institute of Standards and Industrial Research, these holes must go through the entire thickness of the brick, and the total cross-sectional area of the holes should not be more than 25% of the larger surface of the brick, and the distance of the holes from the edge of the brick, as well as the distance of the holes from each other in each dimension of the brick, should not be less than 30% of the length of the same dimension. The reason for the existence of these holes is that during the wall construction, the mortar penetrates vertically into the brick and makes the wall stronger.

This type of brick is used in the construction of bearing walls because it can be reinforced with rebar through the holes in the surface of the brick. A reinforced brick wall is built to withstand the force of an earthquake. The material of this type of bricks is very brittle and brittle compared to pressed bricks, and its suction properties are less than pressed bricks.

These bricks cannot be axed due to their brittleness, and they are not used in percussion arch because they do not have great suction properties and cannot adhere well to mortar. The dimensions of this type of brick are 5.5 x 11 x 22 cm. The sides of this type of brick are rounder and have smoother surfaces than pressed bricks.

Alumina brick:

It is called a wide range of refractory bricks that contain 45 to 99 aluminum oxide (Al2O3).

refractory bricks

Firebrick is actually a type of porcelain that is prepared from various types of fireclay. Porcelain is a quality ceramic that has a finer and denser structure than pottery. The firing temperature of firebrick is about 1500 degrees Celsius. The types of refractory bricks and their applications are as follows:

Aluminum refractory brick:

These bricks contain a high percentage of aluminum (Al2O3). They are prepared from a mixture of kaolin, bauxite and corundum, which has more than 70% alumina. The firing temperature of these bricks is about 1200 to 1800 degrees Celsius. This type of brick is used to cover the inner walls of steel melting furnaces. Due to the resistance of these bricks against alkaline substances, they are also used as lining of the inner walls of cement and glass furnaces.

Silica refractory brick:

Most of these bricks are made of siliceous soil known as quartzite. Quartzite contains 95% SiO2 and a small amount of Al2O3, Fe2O3, Ti2O, K2O and Na2O. These bricks were used in the past to cover the inner walls of steel production furnaces; But due to its high thermal conductivity and impermeability against gases, nowadays it is mostly used to cover the inner walls of glass pulp production furnaces in glass factories, gas-burning coke furnaces, and ceramic production furnaces.

Special refractory bricks:

These bricks are a special type of refractory bricks that have special applications in the industry. These bricks are made of transition metal compounds. The most common bricks of this group are:
Chromium Oxide – Corundum Refractory Brick:
These bricks have 5 to 10 percent chromium oxide I and II and 90 to 95 percent aluminum oxide (Al2O3) and are resistant to alkaline substances. This type of brick is used to build the inner part of the iron smelting blast furnace.

Zirconium refractory brick:

This brick is made from natural zirconium sulfate by adding a small amount of alumina to quartz. It is most widely used in making aluminum melting furnaces, molten glass tank furnaces, and furnaces with high temperatures.
By melting zirconium sulfate with lime, its impurity is separated along with calcium silicate and pure Zr2O (zirconium oxide) is obtained.

Zr2O has a high thermal resistance, which is why it is used in the construction of metal melting plants in steel smelting industries and in atomic reactors as a neutron reflector.

Chrome oxide refractory brick:

This type of brick contains 95% Cr2O3. Synthetic Cr2O3 is used for its preparation. This type of brick is used in the production of glass paste melting furnaces in the glass industry.

Alkaline refractory brick:

These bricks include silicon oxide (SiO2) and magnesium oxide (MgO). To prepare magnesium oxide, natural magnesium carbonate (magnesite) or dolomite is heated at a temperature between 550 and 1800 degrees Celsius.
These bricks are used to cover the inner walls of steel furnaces, rotary furnaces in cement factories, and in the upper parts of glass melting furnaces and non-ferrous metal industries.

Welding brick:

This brick is baked with soil that does not become pasty in the heat of more than a thousand degrees and it is kept in the furnace until the grains of the soil sweat a little and stick together and the brick becomes one piece. This brick should not be kneaded in the heat of the oven, and the difference in the degree of sweating and kneading of the soil of the welded brick should be large. In order for the brick to sweat less, it is given a flux, which is mostly iron oxide. Iron oxide, apart from being fusible, turns the color of the welded brick baked at 1000 to 1200 degrees from red to black.

The beige color of the hot brick is due to the lack of iron oxide and the abundance of lime and bases. This brick must be hard, not broken, not brittle, not cracked, resistant to impact and not full, wear less, be rough, and the worn place should remain rough, its broken surface should not be glassy, it should be grainy. and be full, stable against frost and chemical substances. The compressive deflection of welding brick should not be less than 35N/mm2. Construction welded brick should not absorb more than 6% and carpet brick more than 4% of its weight. The specific weight of welding brick should be more than 1.9. The welded brick that is used for carpeting the pavement and the sidewalk must have high impact resistance. Abrade very little, be rough and remain rough after wear. Welded brick is also used to cover the walls of tunnels and manholes.

Glazed brick:

This type of glazed brick is made like normal brick. The only difference is that it is covered with tile glaze and is only used in building facades. The smooth and polished texture of this brick prevents water from penetrating into the brick; Therefore, it is more resistant to chemicals. If the glaze has a different coefficient of expansion and contraction than brick, its surface will crack and its appearance will be disproportionate and unpleasant. Glazed bricks are used to beautify the facade of the building and increase its resistance to erosion and weathering.

Classification of types of bricks in terms of color:

If brick is used in the display, the color of the brick becomes important. There are pale yellow bricks called white bricks and bright yellow bricks called Golbahi bricks, as well as bright red or garlic red bricks in the market for use in Namachini.

Around the years 1320 to 1340, a type of Ablaq brick in red and yellow colors called Bahmani brick was sold in the market, which was prepared by the brick kiln of the same name.

The thickness of the bricks used in the facade may be 3 to 4 or 5 cm, but the other two dimensions of these bricks are like 10×20 pressed or machine bricks.

The reason for the color of these bricks is related to the way the bricks are laid in the kiln and how to fire them and control the surfaces that are in direct contact with the fire, or it is related to the metal oxides that are present in the raw materials of the bricks. such as various iron oxides. For the preparation of primary materials, as well as the steps of claying and drying of colored bricks, more precision and cost are used.