Fireclay bricks: features, varieties and subtleties of use
When building a stove or fireplace in a house, the need to use materials resistant to fire comes to the fore. That is why most of the buyers make their choice in favor of fireclay bricks. This building material can withstand extremely high temperatures and direct long-term exposure to the flame. It is noteworthy that the chamotte is not deformed and does not crumble even with prolonged heating.
What it is?
Chamotte brick is characterized by a very uncomplicated composition, it is based on crushed dried chamotte powder, the concentration of which is 65-70%.This substance is made from simple white clay, which is subjected to cleaning and long-firing, due to which it exhibits pronounced refractory characteristics. Additionally, coke and graphite fillers and coarse-grained quartz grains are introduced into the raw materials. The original components are thoroughly mixed, then molded and sent for firing and molding.
It is the characteristics of the firing and determine the basic operational parameters of the material. The duration of baking material is of great importance. So, if the raw material is overexposed in a thermal furnace, then a vitreous film appears on its surface. It is quite durable and gives the material particular resistance to mechanical damage, but the refractoriness at the same time decreases.
If, on the contrary, the firing is insufficient, such material will be well absorbed and retain moisture inside, and therefore its strength will be very doubtful. The best brick for stoves and fireplaces can be obtained only if you stick to the "golden mean".
The production of fireclay bricks is regulated by current standards, while its size and weight can often vary significantly: from 2.5 to 6 kg, and the parameters are 230x111x65 mm, as well as 300x150x65 and 250x123x65 mm.In addition, the products differ in the density and porosity of the structure.
In fireclay construction material, made by existing technology, There are a number of operational features:
- the color of the product should be light yellow, rather, thatched with an admixture of brown inclusions;
- brick structure is only grainy;
- when you hit a brick, you hear a ringing like a metal one;
- the material is characterized by a higher degree of strength, therefore, with minor damage, the structure of the fireclay remains unchanged.
Professional builders and finishers highlight both the advantages and disadvantages of such a brick.
The benefits include the following options.
- The strict geometry of the parts, it is extremely important when using materials with a wedge-shaped bevel.
- Heat resistance. The internal structure of the brick does not affect the prolonged exposure to elevated temperatures, this material can withstand heat up to 1500 degrees or more. It should be noted that, in principle, heating of more than 1000 degrees from all types of bricks can withstand extremely chamotte.
- Low thermal conductivity.This characteristic, as well as the low density of individual varieties of material make such a brick the best option for the installation of chimneys and various pipes.
- Fortress. Fireclay materials have the ability to withstand even quite strong mechanical effects.
- Chemical resistance Chamotte products perfectly tolerate the effects of various acid-base solutions and resist many other chemical reagents.
However, nothing perfect has yet been invented, and the fireclay brick was no exception. There are negative aspects associated with its use.
- If the firing technology is observed incorrectly, then the dimensions of the products and their level of quality change significantly.
- Fireclay materials do not differ in low cost, so they can not be considered affordable for most of our compatriots.
- Not all mortars are suitable for masonry. Usually, a special compound called “mortar” is used, and it should be applied very carefully, so that the layer turns out to be very thin.
- Increased strength significantly limits the possibility of cutting material.Cutting it is possible only with a special diamond disc on the stone.
It should be noted that the existing negative sides do not reduce the popularity of the material and do not limit its use in the arrangement of fireplaces and domestic stoves.
Fireclay bricks are commonly used in industry, and are often used for the construction of different types of fuel chambers and technological boilers. It is in them that the coal is burned.
The material is also common in everyday life, here it has found its application for the construction of fireplace inserts, kitchen hearths and wood stoves. For chimneys, experts also recommend taking fire-resistant chamotte blocks, they can withstand not only hot air, but also adverse weather conditions.
There are a lot of rumors and myths about the features of the material. It is believed that when heated, it begins to emit harmful components and even radiation. Experts completely refute all these theories. Moreover, if the latter statement is still possible in principle in theory (if the brick is made from clay, mined in an area subjected to radiation contamination), then it is impossible to believe in the first one.Most likely, the reason for the appearance of such rumors is as follows: some types of fire-resistant materials and indeed when exposed to hot air begin to emit toxic substances. However, this does not apply to the chamotte block, since it was originally created as a material for household use.
Chamotte bricks differ for a number of reasons:
- by molding;
- by the appearance of the finished product;
- on porosity.
Depending on the variant of the formation of raw materials, there are several varieties of fireclay bricks:
- molded semi-dry method;
- thermoplastic extruded;
- hot pressed
According to the type of brick, there are shaped, shaped, wedge, as well as arched and trapezoidal types. The most popular is chamotte in the form of a rectangle, but when installing arched structures, it is better to use wedge material. Depending on the level of porosity, there are:
- high-density brick - with grit indicators not exceeding 3%;
- high-density - in this case, the granularity is differentiated from 3 to 10%;
- dense - with a porosity parameter from 10 to 16%;
- refractory compacted - with a parameter of porosity at the level of about 16-20%;
- medium dense - distinguished by grain size at the level of 20-30%;
- highly porous - in this case, the graininess index corresponds to 30-45%;
- lightweight - with increased grain parameters 45-85%;
- ultra lightweight - in this case, the grain exceeds 85%.
Separately, it is necessary to dwell on this variant of fireclay bricks, as quite popular lightweight products. These bricks are usually used instead of insulation. They consist of special oily clay, as well as peat, shavings or sawdust, and some other organic components. In the process of heat treatment, they completely burn out, leaving instead of themselves pores of various sizes. As a result of this technology, a porous material with high energy efficiency is obtained.
Lightweight bricks are made entirely of organic matter, therefore, are considered environmentally safe, they do not emit harmful and toxic substances, and therefore are suitable for use in residential areas. By the way, a special structure does not affect the material's heat resistance: a lightweight brick can even withstandExtremely high exposure up to 1800 ° C.
As for the form, such bricks are wedge-shaped or rectangular. In order for the material to fully retain all of its original operational features in full, it must be distinguished by a strict geometry with smooth corners and edges.
Lightweight bricks are usually used to form a heat insulation layer when equipping electric furnaces, as well as evaporating installations and heaters. Quite often it is purchased for facing heat exchange boilers and steam lines. At the same time, such protection can significantly reduce heat loss (by 25-75%) and thereby reduce the size of thermal devices. Experts note that if we take fireclay materials for lining furnaces, the heating and cooling period will decrease by 5 times, while all heating costs will be reduced by 10-15% in continuously operating furnaces and by 45% in those that work from time to time .
All fireclay products in Russia are subject to mandatory labeling, which is applied to one of the sides of the brick. Manufacturers usually make it up from several letters and numbers, with the total number of characters varying from 5 to 47. Signs in the marking mean the chemical and physical characteristics of the material. You can usually see the following notation.
- ША / ШБ / ШАК - under this designation are common purpose bricks that have extremely high strength parameters and are able to withstand heating up to 1700 ° C. Such brands are very popular among developers, because they have an optimal price / quality ratio.
- ШВ / ШУС is a marking for industrial chamotte. It is characterized by high heat capacity, therefore, it is optimal when arranging gas passages of heat generators, as well as for facing fencing of convective mines.
- HQ - such materials are used in the construction of industrial process equipment for the manufacture of coke.
- SL is a brick that is characterized by a high degree of porosity. It is most often used for the lining of industrial furnaces and can retain its operational properties with prolonged exposure to high temperatures (up to 1300 ° C).
- SCU - is a fire-resistant end blocks, which are widely used for the manufacture of rotating parts of industrial furnaces.
- PB - is a common chamotte, which is commonly used in everyday life.
- PV - includes the products which found the application at installation of flues and an internal part of house fireplaces.
The numbers indicate the dimensions of bricks in strict accordance with current regulations and standards. For example, under the ShB-8 marking, a brick with dimensions of 250x124x65 mm is covered, and the ShA-5 is a product with the parameters of 230x114x65 mm.
How to choose?
Chamotte brick is quite expensive, so you need to take its purchase seriously. If you buy low-quality material, then you risk simply losing all your money. If you find yourself in a building store with a good reputation, this does not guarantee at all that you will be offered the perfect product without external defects, so when choosing, pay attention to all the important details.
- The basic indicator of product quality is its color, it must necessarily be straw yellow. If you have lighter, almost white blocks in front of you, most likely you see a brick that is not burned in a furnace, which absorbs moisture well and is susceptible to destruction from the inside. And the heat in it is accumulated much worse, which means that the functionality will be a big question.
- The brick should have a fairly smooth finish and perfect shape. Many believe that these requirements are dictated by the aesthetic component of the project, but this is far from the case. The fact is that when arranging a fireplace or stove, the inner surface should be smooth, any relief resulting from the preservation of mortar residues or the expansion of bricks leads to the creation of barriers to the flow of heated gas. If the defect is not eliminated, then an uneven distribution of heat begins, as a result, the level of thrust will be insufficient, and the heat transfer will drop dramatically.
- Kiln has a very strong joining of fireclay bricks, a small number of seams and a tight seal. If the material used has cracks, chips and other defects, it is impossible to provide a reliable grip. In this regard, buying bricks, be sure to choose them from one batch. Otherwise, you risk getting a completely non-uniform material, which may have the most deplorable effect on the operational features of your future thermal element.
How to put?
The technology of construction of stoves and fireplaces of fireclay bricks at home consists of 2 stages:
- preparatory work;
- directly laying.
At the stage of preparation for work, the marking of all future corners and walls, as well as the production of the necessary adhesion mortar and preliminary dry laying are performed. For permanent masonry bricks use a special composition, you can buy it ready-made in the store, and you can prepare yourself. You will need refractory powdered clay, high-quality chamotte sand, as well as process water.
First you need to grind the clay, then sift all the sand and add water to the resulting clay-sand mixture with constant stirring. The finished composition is left for two to three days, stirring occasionally. Clay and sand are taken in a 1: 2 ratio, some builders recommend adding salt or 3% liquid glass to the composition at the rate of 100 g per 10 liters of water.
Fire-resistant bricks are first cut and then fastened so that each successive row completely overlaps the seams between all the blocks of the preceding row. This technology determines the strength of the whole structure, and also contributes to the normal redistribution of the load.
When carrying out the installation of their own hands, pay special attention to the jointing.If it is made incorrectly, that is, the seam is too deep, or not fully sealed, rain and snow drops begin to fall inside (this applies to street constructions), and when cold weather sets in, the masonry cracks. The fireplace, cracked at the seams, cannot perform all its functions in full, and its heat capacity is significantly reduced.
For information on how to properly put fireclay bricks with your own hands, see the following video.