Everyone who is involved in construction, or just thinking of getting started, is faced with new concepts. For example, the fire resistance limit of structures determines the fire safety of a building. Let's take a look at some of the most commonly used building materials and how they meet this requirement.
Stone buildings have a high natural fire resistance. This is determined by their natural thermophysical properties and the massiveness of the material itself. In case of fire, such structures are able to withstand heating up to 900 degrees, while their strength does not decrease and there are no signs of destruction. Therefore, in many cases, stone buildings do not require additional thermal protection.
Reinforced concrete and concrete structures have relatively low thermal conductivity and resist fire well. But nowadays they are made thin-walled, do not have a monolithic connection. Therefore, their safe functions in case of fire can only be performed for one hour, in some cases even less. The fire resistance limit of such structures depends on their cross section of the material and the size of the product itself. taken into accountthe diameter of the reinforcement used, the quality of the concrete, the brand of filler from the magnitude of the load on this structure, the layout of the supports and the percentage of moisture in the concrete. Concrete has the greatest fire resistance, the moisture content of which approaches 3.5%.
However, when moistened more than 1200 kg / m3, it can explode even with little exposure to fire. This can lead to a fairly rapid destruction of the structure. The fire resistance limit of slabs that have beams of the same structural parameters will be higher than that of beams. In case of fire, the slab is heated from one side, while the beam is exposed to fire from three. In the case of supporting the plate on the counter, the fire resistance limit will be significantly higher than when installed on both sides. Solid section slabs made from normal concrete with a 10mm cover and using A-III grade rebar have a fire resistance rating of one hour.
The fire resistance of building structures made of concrete can be improved by making a plate based on mineral fibers, perlite and vermiculite, plaster and plaster.
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Structures made of metal, aluminum alloys and cast iron are much easier to install than reinforced concrete materials, although they are equivalent in their bearing capacity. However, the metal has a high thermal conductivity and a low critical temperature, so the fire resistance limithas no more than 15 minutes. It increases in structures of this type due to the use of fire protection. The most common way to protect a metal structure from fire is to use fireproof building materials as a facing material, as well as plastering. For example, if you veneer a steel structure in half a brick, the fire resistance limit will reach five hours. When plastering the column using a metal mesh, the fire resistance will increase to 45 minutes. By increasing the layer of plaster up to 5 cm, you can increase the fire resistance up to two hours. Also, to increase the resistance to heating temperature, asbestos-cement, expanded clay, mineral-fiber and gypsum boards are used. The use of these materials makes it possible to achieve an increase in the fire resistance of the material up to two hours and more.
