Currently, the most common method of protecting steel structures is to coat their surfaces with The fire-retardant coating on steel structures serves as a fire-resistant and heat-insulating protective layer in the event of a fire, effectively improving the fire resistance limit of steel components and meeting the requirements of current national regulations. As a means of fire protection, coating steel structures with fire retardant coatings not only has high fire protection efficiency, but is also very convenient to use. The construction is not restricted by the geometry of the steel structure, and generally does not require auxiliary facilities, so it has wide applicability. According to the fire protection mechanism, it can be divided into two categories: insulating fire retardant coatings and intumescent steel structure fire retardant coatings.
The main application of fire retardant coating for expanded steel structures The mechanism of action is that the coating rapidly foams and expands after being heated, thereby forming a honeycomb-shaped oxygen-insulating and heat-insulating carbonized foam layer. The thermal conductivity of this foam layer is very low, which can significantly reduce the heat conduction to the steel to effectively protect the steel structure and improve its performance. Fire resistance limit, generally speaking, expanded steel structure fire retardant coating is based on natural or synthetic high molecular polymer, supplemented by foaming agent, assistant foaming agent, carbon source and other ingredients to form an expansion system, and then combined with various colors Fillers and additives are made into a mixture. It forms an ordinary coating at room temperature, and expands and carbonizes to provide fire protection in case of fire.
Selection and construction of fire retardant coatings for steel structures:
Steel structureFire retardant coating in construction The practical application involves many aspects of problems, and the selection of coating varieties, product quality and construction quality all need to be paid attention to.
1. Selection principle: In view of the steel structure’s use in construction The parts used in the building are different, and the load-bearing forms and strengths are different, so the requirements for their fire resistance are also different. In addition, according to the characteristics of the building and the differences in fire hazards and hazards, the fire resistance requirements for the components are also different. Therefore, The scientific and reasonable selection of fire retardant coatings to protect steel structures is crucial to the fire safety of buildings. Product quality and construction quality should be ensured as a prerequisite. It is not advisable to overemphasize reducing the cost, otherwise it will be difficult to ensure the product quality and coating thickness of the coating. Ultimately, Affects the fire protection of steel structures.
Generally follow the following principles: First, the steel structure fire retardant coating must be selected Have a qualified inspection report issued by a national testing center and have product type approval. Do not use decorative fire retardant coatings on steel structures because it is difficult to meet the fire resistance requirements of steel structures;
Secondly, fire retardant coatings that meet performance requirements should be selected based on the type characteristics, fire resistance level, and use environment of the steel structure. For indoor exposed steel structures, light roof steel structures, and parts with decorative requirements, when the required fire resistance limit is </ When the span is less than 1.5 hours, indoor intumescent steel structure fire retardant coating can be used; when the fire resistance limit is more than 2.0 hours, it should be filled. For special coatings that can ensure fire resistance when the coating is thin, according to the actual conditions of the project, after After certification, it is not recommended to use intumescent steel structure fire retardant coatings for indoor hidden parts, high-rise all-steel structures and multi-story factory building steel structures. Outdoor steel structure fire retardant coatings should be used for open-air steel structures. Technical performance cannot be compromised. We are only satisfied with indoor fire retardant coatings for outdoor use; finally, we should not over-promote super flashy steel structure fire retardant coatings. We cannot think that the thinner the coating, the better. From a fire protection mechanism, it uses the expansion and foaming of the coating. Fire protection only requires more stringent requirements for the control of raw materials and rationalization of formulas, and the difficulty of processing is also increased accordingly. Since it mainly relies on the physical and chemical reactions of organic components, any factors that affect expansion will ultimately affect the fire protection performance, among which Some components are sensitive to temperature. If exposed to the air for a long time, they will inevitably precipitate and decompose, leading to aging and failure problems such as cracking and peeling of the coating. They will eventually lose expansion and affect the fire protection performance.
2. Construction technology: steel structure fire retardant coating as An important means of fire prevention, the quality of its coating performance is not only related to the quality of the coating product, but also closely related to the operation of the coating construction technology. Only good coating products without corresponding construction technology will ultimately fail. It will cause powdering, cracking and peeling of the fire retardant coating, so the construction technology should be strictly operated to ensure the performance of the coating.
Construction has the following factors:
First of all, the personnel, the coating construction personnel are not trained and qualified Construction shall not be carried out to ensure the quality of the project. Secondly, before the steel structure is coated with fire-retardant paint, the surface must be cleaned to ensure that there is no oil, water and other contaminants, and anti-rust paint must be applied without chemical reaction between the anti-rust paint and the fire-retardant paint.
Also, the ambient temperature during construction has a great influence on fire-retardant coatings. For most fire-retardant coatings, during the construction process and before the coating is dried, the ambient temperature should be maintained at 5~40 degrees Celsius, and the relative humidity should not be More than 90%, the ventilation condition of the site is good. It is not suitable to operate when the wind speed is high, on rainy days or when there is condensation on the surface of the components. The newly constructed coating should be protected from rain, exposure, pollution and mechanical damage. If it is damaged, it needs to be repaired. In order to ensure the fire resistance limit, any kind of fire retardant coating has certain thickness requirements. Excessive pursuit of a thin coating, It is not advisable to use a small amount. Any part of the load-bearing steel components should be painted with fire-retardant coating, and the protective layer on all sides should have the same thickness. Therefore, the construction should be carried out strictly according to the construction process, and no safety should be left for the building. Hidden danger.
After completion, the coating should be maintained and managed to eliminate weaknesses During each step, defective parts should be repaired as appropriate to ensure the effectiveness of the coating, but it cannot be done once and for all. It is believed that as long as the steel structure fire retardant coating is used, the structural stability of the building can be guaranteed.
At present, intumescent steel structure fire retardant coatings have been successfully used in steel structures in various industrial and civil buildings Fire protection, although its research and application in my country started late, it is very active and rapid, and is developing in the direction of ultra-thin, low pollution, high performance, good decoration and other multi-functional directions.
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