Frost resistance is 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 (rain, snow and ice in the case of external cladding; accumulation of water in freezers) 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 of the tile, the tile is subjected to mechanical stress, which can lead to cracks or chipping of part of the material. Consequently, freezing of non-frost-resistant ceramic tiles can lead to the formation of gaps and the tiles breaking off. As a rule, triangular parts break off.
Based on the mechanisms described above, the frost resistance of a material is determined by two parameters: the presence and number of pores, the possibility of water penetration into the material; the shape and size of the pores, depending on the filling of the available space, the volume of voids, determine the degree of load.
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, since in this case it is difficult for water to penetrate through the material. It should be noted, however, that there are highly porous materials characterized by a high degree of frost resistance. For example, bricks, the water absorption of which is 10-15%. The frost resistance of these materials depends on the shape and size of the pores.
So, frost-resistant tiles are necessary for covering surfaces that are exposed to a humid environment and low temperatures. However, this is not enough to avoid frost damage unless the rest of the structure is frost-resistant.
The test method for determining the frost resistance of ceramic tiles and slabs in contact with water at subzero temperatures is given in the EN ISO 10545-12:1997 , IDT standard. Ceramic tiles or slabs, after being saturated with water, are subjected to alternating temperatures of +5 °C and minus 5 °C. Ceramic tiles or slabs are completely frozen for at least 100 freeze-thaw cycles.
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Detection of damage to facial surfaces and edges
After 100 freeze/thaw cycles, the front surfaces and edges of ceramic tiles or slabs are examined. The examination is carried out with the naked eye or with glasses when they are constantly worn at a distance of 25 to 30 cm at a lighting intensity of 300 lux. To speed up the submission of a report, when damage is detected relatively early, a random check is allowed. All damage detected on the front surface and on the edges of ceramic tiles or slabs is recorded.
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