The quality and value of the cladding directly depend on the symmetry and uniformity of its individual components, i.e. individual tiles in relation to the quality of the surface and its dimensions. That is why, any dimensional differences and asymmetries of the tiles, deviations of the surface from flatness, which violate the harmony of the cladding and worsen its appearance, will be considered defects. The quality of the surface is determined by the presence of the following defects: gaps, cracks, lack of glaze, unevenness, depressions, pits, damage to the vitrified surface, specks and stains, body defects, decorative defects, darkening, chipped edges and corners.
The appearance characteristics, as well as the dimensional characteristics, are checked randomly on the tiles before they are packaged. Control is carried out visually by specially trained personnel (MANUAL SORTING) or by machine (AUTOMATIC SORTING).
The difference in size and dimensional deviations are expressed as a percentage of the working size of the tile.
The method for controlling size and appearance characteristics is described in EN ISO 10545-2. To control the appearance, a minimum of 30 samples of tiles are selected, which must form a surface area of at least 1 m². The appearance of the tiles is checked visually (with the naked eye) at an illumination of 300 lux from a distance of 1 m from the observer’s eyes. According to the standard, preparation of the sample surface and visual assessment of the surface are carried out by different persons. Surface quality is expressed as a percentage of the number of tiles without defects.
If defective tiles do not exceed 5%, then the batch is assigned FIRST GRADE, and if they exceed 5%, then the batch is assigned SECOND GRADE.
The following type characteristics are important: length of the sides and thickness, straightness of the sides, orthogonality, flatness of the surface.
Information on this issue is presented in the article Dimensional and type characteristics .
Bending strength is an important mechanical property of ceramic tiles, according to which its quality is controlled. In this case, the resistance of the material is measured in relation to the maximum specific load, with constantly increasing pressure on the surface. Flexural strength is measured in Newtons per square millimeter (N/mm2). In order to fully appreciate the significance of this tile property and correctly apply the test results, you must first check your own understanding of this issue. Please indicate the correct conclusions in your opinion:
The bending strength is determined by an equation that includes such variables as: breaking force, distance between support rods, width of the tested sample and the smallest thickness of the tested samples along the fracture line.
Bending strength is an indicator that does not require additional calculations. It is measured in KG (maximum load leading to destruction of the sample), per surface area (in mm2) to which the force was applied.
Flexural strength is a characteristic that determines the load-bearing capacity of a tile. In addition to the density of the material, it is also affected by the linear dimensions of the tile: length, width and thickness. So, for example, if one tile is twice as thick as another, and they are made of the same material, then its bending strength will be twice as high.
In the applied aspect, the tensile strength of the tile, measured in accordance with the standards, is somewhat overestimated relative to the real load-bearing capacity of the tile as part of a multilayer structure, i.e. after installation. This is due to an increase in the area under pressure.
The tensile strength of the tile, measured in accordance with the standards, in fact, as a rule, is inferior to the real load-bearing capacity of the tile as part of a multilayer structure, i.e. after installation.
Flexural strength is a property of the material, not the tile. This indicator is used to measure the internal cohesive properties of the material that form the tile, rather than to measure a specific mechanical characteristic of the tile itself. In other words, if we take two tiles from the same material, but of different shapes and sizes, for example, one tile is twice as thick as the other, their bending strength will be the same, although the tensile strength will be different. Thus, the characteristics of the tiles differ, despite the fact that they have the same flexural strength.
Material on this issue is presented in the article Flexural strength .
Water absorption is a parameter that determines the porosity of ceramic tiles. It is measured by the amount of water that ceramic tiles absorb under certain laboratory conditions, and is expressed as a percentage of the dry weight of the tiles.
Mark the true statements.
According to EN ISO 10545-3, the penetration of water into the open pores of samples is determined exclusively using the water saturation method in a vacuum. The boiling method, as a test that does not allow determining open porosity and bulk density, is considered obsolete.
According to EN ISO 10545-3, the penetration of water into the open pores of samples is determined using two methods: boiling and water saturation in a vacuum. When boiling, water saturation occurs only in easily filled open pores; with the vacuum method, almost all open pores are filled.
According to the EN 14411 standard, ceramic tiles and slabs are divided into three main groups based on water absorption. Where the third group corresponds to the lowest water absorption rates.
The lower the degree of water absorption, the more resistant the tile will be to intense mechanical and hydrothermal influences.
A low water absorption coefficient indicates that the structure of the tile is porous, and a high coefficient indicates that the structure of the material is more dense.
Material on this issue is presented in the article Water absorption .
Frost resistance - the ability of ceramic tiles to withstand freezing in a humid environment and at temperatures below 0 degrees Celsius. The freezing mechanism is divided into two stages. The first stage is the penetration of water from the environment into the pores of the tile. The second stage is the hardening (freezing) of water inside the pores. As is known, the transition of water from a liquid to a solid state is accompanied by an increase in volume, since the density of ice is less than the density of water. Thus, when water freezes inside the pores, the tile is subjected to mechanical stress, which can lead to cracks or chipping of part of the material.
The frost resistance property of ceramic tiles is not guaranteed in extremely low temperature zones (below -40 °C). This is due to the test conditions of EN ISO 10545-12:1997, as they are carried out at temperatures between +5°C and -5°C. In this regard, manufacturers mark materials suitable for use in such an environment with a special EXTRA°C sign, which in turn indicates testing in the temperature range from -50 °C to +100 °C.
Based on the mechanisms described above, the frost resistance of a material is determined by the possibility of water penetration into the material, in other words, the degree of water absorption. Thus, if a material does not absorb water, it is frost-resistant, but if it does, it is not.
Frost resistance also prevents ice from forming on the face of the tile. This is due to the fact that water, without getting inside the material through the pores of the top layer, seems to “roll off” from the surface.
According to EN ISO 10545-12:1997, tests confirming frost resistance properties are not carried out as such. A material is considered frost-resistant if it falls into group 1 of materials according to the degree of water absorption (<3%).
Based on the mechanisms described above, the frost resistance of a material is determined by two parameters: 1) The presence and number of pores that allow water to penetrate into the material; 2) The shape and size of the pores, the volume of voids of which, allows you to distribute the loads of the changing state of water. It follows from this that frost resistance is directly related to water absorption: the lower the water absorption, the greater the likelihood that the material is frost-resistant. However, there are also highly porous materials (with a high rate of water absorption) that are characterized by frost resistance. Frost resistance in this case is due to the shape and size of the pores, allowing moisture to penetrate into the material without destroying it as a result of hydrothermal loads.
According to EN ISO 10545-12:1997, tests confirming frost resistance properties are carried out as follows: ceramic tiles or slabs, after being saturated with water, are subjected to alternate temperatures of +5 ° C and minus 5 ° C. They are then completely frozen for at least 100 freeze-thaw cycles. After 100 freeze/thaw cycles, the faces and edges of ceramic tiles or slabs are examined for damage.
Material on this issue is presented in the article Frost resistance .
Thermal resistance is the ability of ceramic tiles to withstand without damage the stress caused by dimensional deformations due to sudden changes in temperature, especially if such changes are repeated frequently. Which statements do you think are correct?
If we compare the thermal resistance testing methods of the EN ISO 10545-9 standard and GOST 27180-2001, we can conclude that the test requirements of the EN ISO 10545-9 standard are somewhat stricter than the requirements of GOST 27180-2001.
“Resistance to thermal shock” is a property characteristic only of refractory materials, the scope of which is the metallurgical, glass, chemical industries, as well as all other industries where work takes place using blast furnaces, shaft and rotary furnaces.
Thermal resistance is the ability of a material to resist the transfer of energy (heat exchange) from more heated parts of the body to less heated bodies, carried out by chaotically moving body particles (atoms, molecules, electrons, etc.).
Thermal resistance is an important physical property of ceramic tiles. Let's imagine, for example, the tiled surface of a kitchen countertop on which a hot pan is placed. The surface of the tile heats up sharply and, as a result, expands, and the lower layers become colder and less expanded as they move away from it. In this state of thermal inhomogeneity, the tile, which does not have the property of heat resistance, could be deformed and, being an inherently rigid material, could crack.
The test method described in GOST 27180-2001 is as follows: samples are subjected to 10 rapid cycles of temperature changes from 15 °C to 145 °C. The maximum temperature is achieved by placing the samples in an oven for at least 20 minutes, the minimum by completely immersing them in water at a temperature of 15°C. At the end of 10 cycles, samples are inspected for visible defects.
Material on this issue is presented in the article Thermal resistance .
