What is brick made from and how?
There are many advantages that make brick one of the most popular building materials. In addition to standard sizes and simple shapes, this artificial stone can boast of strength, durability and beauty, which is why it has been used for a very long time and almost everywhere.
The technologies by which they make bricks are worthy of attention, as a combination of processes that make it possible to obtain material with all the characteristics needed by the customer.
Composition depending on the type
Among all types of bricks, two of the most popular are ceramic and silicate, also referred to as red and white, respectively.
They are distinguished by the following features.
- The main component of ceramic brick produced by roasting is clay.This material has an aesthetic appearance, extinguishes noise and perfectly stores heat indoors.
- The composition of silica brick, manufactured under the action of high pressure and steam, provides for the presence of sand and lime. Compliance with the technology allows to obtain durable and inexpensive products that endure temperature and humidity drops.
It is also necessary to allocate a refractory brick, made of fireclay with the addition of coke or graphite - components that significantly increase its strength.
Another actual variety is facing, the production of which involves the use of cement, limestone and the pigment ingredient. Such a brick, manufactured by pressing technology, has not only an aesthetic appearance, but also an impressive operational resource.
Given the greatest significance of the red and white varieties, they should be considered in more detail - which will be done later.
The main ingredient of this type of brick is ordinary clay. It is a mineral mass that:
- becomes plastic when water is added to it;
- keeps the form in the process of drying;
- hardens as a result of firing, finding comparable to the natural stone strength.
Special attention is given to the origin of the clay used. Depending on the depth, it may have different properties - both suitable for the production of bricks and not meeting the established requirements.
If you select the component that most often forms the basis of clay, then this kaolinite is one of the aqueous silicates of aluminum. Also in the composition of the raw materials used may include montmorillonite, illite, quartz and other minor ingredients.
In addition to clay, ceramic brick consists of other components, which are additives. They are used to impart certain properties of the manufactured products, and major among them are the following.
- Scares - ash, sand, slag. Promotes better mass formation and less shrinkage.
- Burnout - sawdust, powdered coal or peat. Increase the porosity of the material, which naturally reduces its density.
- Dyeing - As a rule, metal oxides. Give the product the desired color or shade.
In addition, it is worth mentioning the iron ores and sandstone, the use of which allows you to effectively regulate the firing temperature.
Plasticizers can also be used - additives that minimize the chance of cracking of the ceramic material. The specific amount of each of the listed ingredients is determined by the customer’s requirements and / or the manufacturer’s policy.
The production of white brick involves the use of three mandatory components, a list of which is as follows.
- Sand. It may have both natural and artificial origin. It is desirable that the grains used are homogeneous and have a size of from 0.1 to 5 mm. No less important are the features of the surface of grains of sand (in the presence of sharp angles, they provide better grip). Prerequisite is to pre-clean the material from foreign inclusions.
The recommended proportion of sand in the composition of silicate brick is from 85 to 90%.
- Lime. To obtain this component, raw materials are used, which are characterized by a high content of calcium carbonate (90% or more) - primarily limestone and chalk.Before roasting at a temperature of about 1150 ° C, the prepared rock is crushed to a size not exceeding 10 cm. Upon completion of the above procedures, lime is introduced into the composition of silicate brick (the optimal value is 7%).
- Water. This ingredient is needed to solve two main problems - slaking lime and giving plasticity to the molded mass. It is applied at all stages of the manufacture of silicate bricks.
Often the production of the described products involves the use of additional components necessary to give the product the desired characteristics.
- Chemical compounds. An example is titanium dioxide, due to which silicate bricks remain white for as long as possible.
- Components that increase frost resistance. Most often, to solve this problem, products of industrial processing are used, which allow to reduce the thermal conductivity of the material by 10-12%.
- Colorants. Used in situations where the manufacturer needs to give the products a specific shade or tone.
It is worth mentioning and expanded clay sand - an additive that can simultaneously solve two problems at once.In addition to a noticeable increase in thermal efficiency of silicate products, it gives them a beautiful coffee color, thanks to which they look more solid.
Depending on the type of bricks made, their production has its own characteristics. This is due to the specifics of the ingredients used, requiring the use of various technological processes.
There are two main methods of producing ceramic bricks - semi-dry molding and plastic. The latter, which is more popular, involves the step-by-step solution of the following tasks.
- Preparation of the main component - clay. It is allowed to include additives in the mixture - no more than 1/3 of its total amount. In this case, the fraction of the main ingredient should not exceed 1.2 mm.
- Move the prepared mass for further molding.
- The division of the total array into sizes.
- Drying ceramic bricks.
- Perforation of products (relevant in situations where products need to be hollow).
- Burning. This type of treatment involves a smooth change in temperature in the furnace (first upward, and then vice versa).Following this rule allows you to avoid the appearance of cracks on the bricks due to sharp temperature changes.
As for the production of ceramic bricks by semi-dry molding, it implies the following procedure:
- preparation of raw materials and its grinding;
- drying and re-crushing;
- slight moistening with steam;
- removal of the last traces of moisture from pottery.
It is reasonable to mention the production of red brick in the home: in this way it is quite possible to make a full-bodied "raw" variety of this material.
To solve this problem it is necessary:
- make a ball out of a homogeneous piece of clay, pre-moistened with water;
- carefully examine the sample after 4 days - for the presence of uneven shrinkage and cracks;
- subject to the absence of visible defects, the ball must be dropped to the ground;
- if the sample does not pass the strength test, its composition should be strengthened with appropriate additives.
Upon completion of all preparatory procedures, the mixture should be distributed in forms made of wood.Finished ceramic products will remain dry in the shade, after which they can be used for the construction of light one-story buildings.
To make the surface more durable, it is desirable to cover them with paint or high-quality cement mortar.
One of the main features of the manufacture of silicate bricks is the complexity that does not allow to solve this problem at home. In particular, this is due to the impressive list of necessary equipment - conveyors and conveyors, crushers and metering devices, mixers and autoclaves, cranes and loaders.
The main methods of production of the products in question are two - drum and silage.
The technology of making silica brick involves the following steps:
- inspection and preparation of the main components - sand and lime (the first is separated from large inclusions, and the second is crushed);
- mixing the components, followed by settling in the bunker;
- grinding the mixture and adding water to it;
- lime slaking carried out in a drum or silo (determined by the chosen production method);
- removing moisture from the sand;
- press molding;
- steam treatment in an autoclave (recommended temperature - 180-190 ° С, pressure - 10 atmospheres).
At the final stage, the temperature and pressure are gradually reduced. Upon completion of all the procedures foreseen by the technology, the finished silicate bricks are packed and sent to the customer.
Types of firing
Separate consideration is deserved by the process of heat treatment of ceramic bricks, called firing. It represents the final stage of production of these products and provides for the presence of 3 stages - heating, roasting and cooling itself.
- The bricks are heated to 120 ° C to remove residual water.
- To eliminate inclusions of organic origin and the last traces of moisture, the temperature is increased to 600 ° C and then to 950 ° C, which gives products additional strength.
- Upon completion of hardening, the bricks are cooled, gradually reducing the temperature.
Subject to compliance with the technology, a product with a uniform structure and an orange-red shade will be obtained.
I would also like to mention two types of devices used to solve the problem described above.
- Tunnel. It is a long sealed furnace consisting of 3 chambers, inside which are laid rails for transporting ceramic bricks. In the first chamber, the products are dried, in the second - firing using burners, and in the third - cooling.
- Annular. The design of this furnace assumes the presence of a large number of individual sections, having their own heat source and placed in the form of a ring. Its peculiarity is that the bricks go through all the stages of firing, without leaving the limits of one chamber. Thus, the adjacent compartment provides initial heating, calcination is carried out due to its own heat source, and the product cools down under the influence of the next section.
Thus, knowledge of the brick production technology makes it possible to obtain a strong, aesthetic and wear-resistant material from brittle and ductile raw materials, which are initially of no value to the builder.
The intricacies of modern brick production are described in detail in the video below.