According to national standards, in addition to meeting fire resistance requirements, the combustion performance of fire-resistant coatings is divided into Class I and Class II. Under the specified experimental conditions, the flame resistance time of the first level fireproof coating is not less than 20 minutes, and the heat resistance time of the second level fireproof coating is not less than 10 minutes. Users should pay attention to distinguishing between them when making choices, to avoid companies passing off inferior products as good and failing to achieve fire protection effects.

The on-site construction of tunnel fireproof coating should be based on the manufacturer's product packaging instructions, and generally does not require dilution with water. The coating should be applied in two or more times, with a coating amount of not less than 500 grams per square meter. When the fireproof coating is diluted with water or the coating amount is insufficient, it will have a significant impact on its fireproof performance. The fire department should strengthen supervision of the construction site to prevent construction companies from cutting corners.

Qualified fire-resistant coatings will undergo significant foaming and expansion when exposed to strong flames such as blowouts, resulting in surface aggregation and protrusions that will not cause burning damage within a few minutes. On the other hand, counterfeit and inferior fire-resistant coatings will not foam at all and will result in a large amount of scattering and debris. Wooden substrates will also quickly experience burning and damage.

In practical use, in order to ensure the fire resistance and other performance of fireproof coatings, transparent topcoats are generally required. The dosage of fireproof coating is generally 350-500 grams per square meter, and the dosage of topcoat is generally 50 grams per square meter.

The application of tunnel fireproof coatings has gradually expanded with the development of industry towards large-scale and buildings towards clustering and high-rise, as well as the continuous development of science and technology. In the past, emphasis was placed on preventing combustion in warehouses, ships, and other places. Nowadays, fireproof coatings are gradually adapting to higher requirements, able to withstand higher temperatures and extend longer periods of time, while maintaining the bottom layer temperature within a lower range. However, as a new type of paint, fire-resistant coatings also have some drawbacks, such as high cost and suboptimal physical properties of certain varieties of fire-resistant paints. At present, the variety of fireproof coatings is still increasing, and we believe that the market prospects are broad.

The use of concrete in building structures is very common. Among them, prestressed reinforced concrete has better crack resistance, stiffness, shear resistance, and deformation stability than ordinary reinforced concrete, is lighter in weight, and can save concrete and steel. However, the fire resistance performance of prestressed reinforced concrete hollow floor slabs, which are widely used, is poor. The reason is that when the temperature of the prestressed steel reaches 200 ℃, the yield point begins to decrease, and by 300 ℃, the prestress almost disappears, and creep accelerates, resulting in a rapid decrease in the strength and stiffness of the prestressed slab. As a result, the deflection change in the slab accelerates, and cracks appear below the slab. Prestressed steel bars are directly subjected to high temperatures, resulting in a further decrease in their stiffness and strength. The performance of concrete also changes at high temperatures, and the direction of thermal expansion of concrete under the slab is consistent with the direction of tension, which promotes changes in deflection in the slab. At 300 ℃, the strength of concrete begins to decrease. At 500 ℃, the strength decreases by about half, and at 800 ℃, the strength is almost lost. In building fires, these types of floor slabs break and collapse within about 0.5 hours. Due to the poor fire resistance of prestressed concrete hollow slabs, in order to improve the fire resistance limit of prestressed floor slabs, fireproof coating is sprayed on the reinforcement side of prestressed concrete floor slabs. When encountering fire, the coating effectively blocks flames and heat, reduces the speed of heat transfer to the concrete and its internal prestressed steel bars, delays their heating time, thereby improving the fire resistance limit of prestressed floor slabs and achieving the purpose of fire protection.

The necessity of fire protection for steel structures has been widely applied in the construction industry in recent years. Although steel is a non combustible material, it is highly thermally conductive and will quickly lose its strength and deform under high temperatures. A large number of steel structure fire cases and research results indicate that the fire resistance performance of steel structures is inferior to other structures. The mechanical strength of steel is a function of temperature and generally decreases with increasing temperature. When the temperature reaches the critical temperature value of steel (usually 540 ℃), its yield stress is only 40% of the yield stress at room temperature, resulting in a sharp decrease in bearing capacity. The temperature at the fire scene is mostly between 800-1200, and within 15 minutes of the fire, the temperature can reach over 700 ℃. Bare steel components lose their load-bearing capacity in just over ten minutes due to reaching their fire resistance limit, and the steel structure inevitably undergoes deformation, leading to partial or complete collapse and damage of the building. Therefore, it is extremely necessary to provide fire protection for steel structures. There are many protective measures, and in practice, steel structure fireproof coatings are widely used for fire protection. Liaoning Tunnel Fireproof Coating