Everyone who is engaged in construction, or just thinking to get started, is faced with new concepts. For example, the fire resistance of structures determines the fire safety of the structure. Let's look at some of the most commonly used materials in construction 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 a relatively low thermal conductivity, they resist fire well. But in our time they are made thin-walled, do not have a monolithic connection. Therefore, their safe functions in case of fire can only be performed within one hour, in some cases even less. The fire resistance of such structures depends on their material cross section and the size of the product itself. The diameter of the reinforcement used, the quality of
concrete, the type of aggregate of the load on this structure, the location of the supports and the percentage of moisture of the concrete are taken into account. The greatest fire resistance is concrete, whose moisture is approaching 3.5%.
However, if moistened with 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 of slabs that have the same structural parameters with beams will be higher than that of beams. In a fire, heating of the stove occurs on one side, while the beam is exposed to fire from three. In the case of supporting the slab on the counter, the fire resistance will be significantly higher than when installed on both sides. Slabs with a solid section, made of ordinary concrete and using a protective layer of 10 mm, in which A-III class reinforcement is used, have a fire resistance limit of one hour.
The fire resistance of building structures made of concrete can be increased by making slabs 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 capacities. However, the metal has a high thermal conductivity and a low
critical temperature; therefore, the fire resistance limit is 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 exposure to fire is to use non-combustible building materials as a facing material, as well as plastering. For example, if a
steel structure is faced in half a brick, the fire resistance limit will reach five hours. When plastering a column using a metal mesh, fire resistance will increase to 45 minutes. By increasing the plaster layer to 5 cm, fire resistance can be increased up to two hours. Also, to increase resistance to the temperature of heating, asbestos-cement, expanded clay, mineral-fiber and gypsum boards are used. The use of these materials allows to increase the fire resistance of the material up to two hours or more.