- Technology for the production of natural, engobed and glazed tiles
- Technology for the production of cement-sand tiles
- Characteristics of natural and cement-sand tiles
- Which tile plate shape is preferable?
- In conclusion
In this article: the stages of the production of ceramic tiles; how are glazed and engobed tiles obtained; technology for the production of cement-sand tiles; comparative characteristics of ceramic and cement-sand tiles; average cost of natural tiles; dependence of the quality of a tile on its brand name.
There is no better roofing than one made of ceramic tiles, and this is an indisputable fact. However, the roofing market also offers homeowners sand-cement shingles similar in appearance to ceramic. To make the right choice, you need to understand the characteristics of these roofing coatings, determine what the difference is between them and how great it is. First of all, natural tiles – consider its production technology …
Technology for the production of natural, engobed and glazed tiles
Among the currently popular roofing materials, only baked clay tiles have been successfully used for several centuries. During this time, the technology for the production of tiles has practically not changed, except that manual labor was automated.
The raw material for ceramic tiles is high-quality pottery clay, which is mined near the tile production. After extraction from the quarry, the clay is conveyed to raw warehouses, where it is pretreated – aged for a certain time, then processed using a wheel mill, which breaks the clay mass into fragments, which are subjected to screening to eliminate impurities and grinding. Further, water and plasticizers are added to the powdered clay in specified proportions – a homogeneous plastic mass is obtained.
After mixing, the clay mass is compacted by means of screws and squeezed out through a flat die – a clay belt is fed to the conveyor, which is cut into plates of a given size. The second method of molding is pressing in a revolving press, in which, in order to obtain high-quality tiles, not metal, but gypsum molds are used..
The next stage is drying the molded clay plates in special chambers, under constant control of humidity and temperature. During uniform drying, excess moisture is removed from the future tiles, which avoids the formation of cracks and changes in shape due to uneven shrinkage.
Then the ceramic tiles are sent for firing. It is preliminarily subjected to engobing or glazing, but if the final color of the product should be red, then these types of processing are not performed. The tiles are natural red, i.e. not glazed or engobed, it is called natural, the color is given by the iron oxides contained in the clay. Engob is a white clay mixed with water, to which various mineral pigments are added, or colored clay. It is applied to the surface of the tiles and gives them a certain color that does not fade over time. In this case, the surfaces of engobed tiles will not crack during operation, because the starting material in both cases is clay, respectively, the coefficients of temperature contraction and expansion for tiles and engobe are identical.
Another method of painting tiles is glazing, i.e. its coating with a powdery material, after firing, gives the tiles a glassy surface with a characteristic shine. The color of glazed tiles depends on the metal ions included in the glaze. The advantages of glazed tiles are high protection against moisture penetration into the pores; after rain, the roof covered with such tiles looks like new – moisture washes away any dirt, returning the natural shine to the roofing.
In addition to imparting decorative properties to tiles, glazing and engobing provide a strong and dense layer on their surfaces, further reducing porosity. The fact is that when firing ceramic tiles, impurities present in the composition of pottery clay, even in small amounts, burn out, forming cavities of various volumes, which reduce the frost resistance and water resistance of this roofing material..
The tiles go through three stages of firing in tunnel kilns:
- heating up to 120 ° C, while physically bound moisture is eliminated from the raw plates, their material loses its plasticity;
- firing with a gradual rise in temperature to 1000 ° C. When the temperature reaches 450-600 ° C, the evaporation of chemically bound moisture occurs in the clay plates, the clay minerals are destroyed and the tile acquires its initial hardness. A further increase in temperature leads to the combustion of organic impurities, and the plasticity of ceramics is completely lost. The temperature reaches 800 ° C, as a result of its effect, the surface strength of ceramic plates increases. When the temperature in the furnace rises to 1000 ° C and higher, the low-melting minerals and compounds contained in the clay melt, enveloping and pulling the non-melting particles with the melt, which leads to shrinkage and compaction of ceramic tiles;
- gradual cooling of ceramic tiles, after which this roofing material acquires strength and water resistance.
After going through all the production stages, the finished natural tiles are rejected, marked and delivered to the finished product warehouses. The main criterion for the quality of ceramic tiles, in addition to the absence of the slightest visual defects, has remained unchanged for many centuries – when tapped with a metal object, it emits a clear and clear sound.
Technology for the production of cement-sand tiles
The inventor and the first manufacturer of cement-sand tiles was Adolf Kroger, the owner of a quarry in Bavaria – in the middle of the 18th century he developed a technology for manufacturing tiles by hand pressing. The stages of production of this roofing material are in many ways similar to the technology of creating natural tiles, the main difference is the absence of a firing stage in ovens, which significantly reduces the cost of production.
Like other concrete products, cement-sand tiles are created from four components – Portland cement, quartz sand, water and pigments, which are based on iron oxide. Dosed portions of sifted sand and pigment are sequentially put into the disperser mixer, after mixing them, Portland cement and, after a while, water are introduced. The moisture content of the mixture ready for molding is from 9.2 to 9.8%.
The dispersed mixture is transported by a belt conveyor to the hopper of the extruder-molding machine, passes through the die and follows in the form of a continuous belt to the knives that cut it into tiles (half and ordinary tiles) or to the press that forms curved shapes (hip and initial backbone tiles ). Painting is next – a conveyor belt delivers the molded wet tile to the painting booth, where a layer of acrylic paint is applied to the outer surface of the tile.
The next stage is the preliminary curing of the tiles in a drying chamber, where they are kept for 24 hours at a temperature of 60 ° C. After a day, the tiles are sent for re-painting and drying, then marked, stacked on racks and sent to the warehouse, which contains 28 days for curing.
Characteristics of natural and cement-sand tiles
It is well known that ceramic tiles have the highest characteristics in terms of service life – 100 years of operation are not at all extreme for it, provided that the coating is restored in small areas (literally two or three tiles) after each winter season. Consider other positive characteristics:
- environmentally friendly material, i.e. does not emit any chemicals and is odorless;
- fire resistance;
- heat and frost resistance;
- is not a store of static electricity;
- resistant to chemical and biological effects, ultraviolet radiation;
- does not require painting during the entire service life;
- good sound and heat insulation of the attic in any bad weather, ideal for the attic;
- almost complete absence of windage, due to the significant weight of the tile plates.
It should be noted that the listed advantages of ceramic tiles largely depend on adherence to production technology and professionalism when laying on the roof. For example, a large number of pores in the structure of a natural tile seriously reduces its performance, because moisture penetrates them.
Negative characteristics of natural tiles:
- relatively high cost – from 1100 rubles. per m2;
- considerable weight m2 – reaches 65 kg, i.e. a reinforced rafter crate is required (while the total load on the walls and foundation of the building practically does not increase);
- requires a steep roof slope, from 22 ° and above. A smaller slope angle will cause snow to accumulate and form an ice crust underneath, destroying the tile floor;
- fragile material;
- can be split and partially knocked off the roof to the ground during hail.
The characteristics of sand-cement tiles will be considered in comparison to ceramic tiles. Their service lives are almost the same – about 100 years, provided that cracked tiles are replaced in time after each winter. The positive and negative characteristics of cement-sand and ceramic tiles are also similar, except that cement-sand tiles will cost the homeowner cheaper – about 500 rubles. per m2.
If we compare the weight of ceramic and cement-sand tiles, the latter weighs about a third less. One point should be noted – in production conditions, cement-sand tile gains 70% strength, a full set of strength occurs already during operation, with precipitation. In addition, tiles on a cement-sand base, like any concrete product, have a larger number of internal pores than ceramic – they are overlapped from the outside by several layers of paint. Pore-minimization technology is one of the most guarded trade secrets of major manufacturers of sand and Portland cement tiles..
Which tile plate shape is preferable?
Among the variety of tile shapes, three of them are especially popular – flat (“beaver tail”), in the form of a gutter (“Tatar”, “antique”, “monk-nun”) and wave form (“baking sheet”, “Dutch”).
A roof covering made of flat or grooved tiles has one common drawback – gaps, which cannot be completely eliminated and through which oblique rain and snow penetrate under the roof. Roof structures formed by tiles of such shapes are usually protected from moisture seepage with lime or lime-cement mortar, but this measure seriously interferes with the natural ventilation of the roof structure and increases the total weight of the roof.
“Dutch” wave tiles have no disadvantages of flat and grooved, because each of its plates has grooves (locks) on the back side and does not need additional fixing to the solution. During the installation of such a tile, the tiles are joined together by a “lock” connection – as a result, such a coating completely isolates the roofing structure from moisture penetration. At the same time, three-millimeter sinus channels are preserved in the interlocks, through which air exchange occurs.
If there are no questions with the choice of ceramic tiles and this, of course, will be the German brands “Braas”, “Creaton”, “Erlus”, “Jacobi”, “Meyer-Holsen” and others, produced for more than half a century and are out of competition in this segment of the Russian building materials market, then in relation to cement-sand tiles, there is a temptation to save money, because at low equipment costs, it can be produced at small production facilities, and there are such manufacturers. And here it would be appropriate to note that the quality and service life of Braas, Benders and Baltic Tile brands produced in Russia by the largest German and Swedish manufacturers will differ for the better from their domestic counterparts produced under little-known brands. In addition, small manufacturers produce and sell roofing materials in limited configuration, while branded manufacturers offer all the necessary roofing accessories without any restrictions and in high quality..
Based on a comparative analysis of production technologies and operational characteristics of natural tiles – ceramic and cement-sand – we come to the conclusion that, despite the differences in raw materials and stages of creation, both types of tiles have similar characteristics and will serve as a roof covering for more than a dozen years. , subject to quality performance.