Discuss the fire protection treatment of glass curtain wall

First of all, if the construction of the glass curtain wall is unreasonable or there is a problem with the fire protection design, once a fire occurs, it is easy to spread horizontally and vertically at the same time. Generally speaking, the glass curtain wall consists of two parts, the wall and the window, because ordinary glass is easy to break at high temperatures. If effective fire prevention and isolation measures are lacking in the horizontal and vertical directions, in the event of a fire, fire and smoke will spread from the outer wall and inner surface of the curtain wall to the next floor. Secondly, after the glass is broken and dropped in case of fire, it will affect the fire-extinguishing glass. Usually the curtain wall material is mainly glass, aluminum alloy frame or shaped steel frame. When the temperature reaches 6000 degrees, the section steel will melt; and the aluminum alloy will melt when the temperature reaches 2500 degrees to 3300 degrees, so in the fire environment, the glass can easily break and fall. In addition, in a high temperature environment, the glass itself has the characteristics of breaking, which increases the difficulty of safe evacuation and fire fighting. Finally, the thick smoke is not easy to discharge, which hinders safe evacuation and fire fighting. Taking into account the stability of the wall structure and the closeness, the glass curtain wall often does not have shoulder windows. Even if the shoulder windows are opened, in order to ensure the safety of the window frame, the windows are basically very small. At the same time, the window opening is overhanging, and the angle between it and the wall is up to 45 degrees, which not only reduces the area of the air vents, but also the windows.It is mostly opened above the curtain wall, and there are no windows for ventilation under the wall, which makes the external pressure greater than the internal pressure. In the event of a fire, the thick smoke is difficult to discharge. In addition, the location of the wall windows is too high, it is often difficult to reach, and it cannot be opened in time in critical situations, which brings serious safety risks. According to the analysis of the above reasons, the glass curtain wall does not have a good natural smoke exhaust function. In the event of a fire, the thick smoke will inevitably gather indoors in large quantities, and it is difficult to discharge it in a timely and effective manner, thus hindering safe evacuation and fire fighting. 

 　　2 Fire protection treatment of glass curtain wall materials

 　　2.1 Fire protection treatment of steel

 　　Usually, the limit time for steel frames to withstand high temperatures is only 15 minutes, and there is still a big gap between the fire resistance limit requirements of glass curtain walls, so the wall steel frames must be treated for fire protection. Generally speaking, there are two main methods for fire protection treatment of steel frames. 

 　　2.1.1 Coating of fireproof coatings

 　　Mainly, the coating is applied to the surface of the steel frame, which can be used for heat insulation and fire prevention, to protect the complete function of the steel frame, and to improve the high temperature resistance of the material. This kind of coating is also called steel frame fireproof coating. Depending on the thickness of the coating, the coating can be divided into three types, namely thick layer, thin layer and ultra-thin layer. For example, thick-layer coatings are usually between 8 mm and 50 mm in thickness, the surface of the coating is granular, relatively sparse, and the heat conduction capacity is poor. The high temperature tolerance time is from half an hour to three hours. Due to the large thickness of the thick-layer coating, the dry density is not high, and it cannot withstand too much pressure on the building, and the heat conductivity is not good.Strong, can effectively heat and prevent fire. This kind of coating is suitable for the walls of some buildings that are enclosed, isolated and shaded after the completion of the construction project. The fireproof coating does not have high aesthetic requirements, but it must withstand high temperatures for more than one and a half hours, such as super-high-rise all-steel frames. 

 　　2.1.2 Fire protection treatment by encapsulation method

 　　This method is mainly to encapsulate the steel frame with heat-insulating and fire-retardant materials to prevent high temperature damage to the steel frame. Specifically, the encapsulation fire protection treatment method mainly includes the following measures: (1) Steel frame enclosure treatment: the use of fireproof ceiling and isolation wall to surround and protect the steel frame to prevent the steel frame from being exposed to high temperature; (2) fireproof materials encapsulate the surface of the steel frame: sheets of fireproof materials can be used, such asGypsum board, calcium silicate board and vermiculite board are pasted and fixed on the steel frame. Generally speaking, 25 mm vermiculite slabs can increase the high temperature tolerance limit time of the steel frame to 90 minutes; (3) Spray inorganic thermal insulation and fireproof coatings on the surface of the steel frame: The main coatings include vermiculite powder, gypsum, glass fiber, mineral wool fiber, cement mortar, perlite powder, etc. For example, apply type 50 metal mesh mortar to the surface of the steel frame for protection. The coating thickness is 25 mm, and the steel frame can withstand high temperature for up to 48 minutes. If the coating thickness is 50 mm, the limit time for the steel frame to withstand high temperature can reach 81 minutes. 

 　　3 Fire protection treatment of glass

 　　Generally, glass will break when it encounters high temperature, and its fire resistance is extremely poor. There is a big gap between the fire protection and isolation requirements of the glass curtain wall. Therefore, the general material glass must be treated with fire protection to enhance the high temperature resistance of the glass. Usually fireproof glass mainly includes the following types：

 　　3.1 Laminated fireproof glass

 　　This kind of glass mainly adds metal wire mesh composite materials to the organic adhesive layer or inorganic adhesive layer between the two layers of glass. Due to the addition of metal wire mesh to the glass, the overall strength and compression resistance are greatly improved. At the same time, fire alarms and heat sensors can be connected to the glass to prevent fires. The material of fireproof glass with wire is mainly inorganic glass, the organic adhesive layer is polyvinyl chloride glue or polyvinyl butyral glue, and the inorganic adhesive composition is mainly water and metal salts, including phosphate, aluminate, silicate, etc., stainless steel material is used as the metal wire. One disadvantage of this kind of glass is that it is not very translucent. 

 　　3.2 Composite fireproof glass

 　　Because of the poor light transmittance of wire-sandwiched fireproof glass, if the glass uses special materials, the cost will be greatly increased, and the expensive price is difficult to be accepted. Now the more common on the market is transparent laminated composite fireproof glass. This kind of glass is usually composed of at least two layers of general glass superimposed, and the glass layers are bonded with a transparent fireproof adhesive, and this adhesive will be expanded by heat. Regarding composite fireproof glass, people are mainly concerned about the transparent fireproof adhesive for bonding glass. This is because the quality level of fireproof adhesive directly determines the performance of fireproof glass. 

 　　3.3 High-strength fireproof glass

 　　In fact, this is a monolithic cesium-potassium fireproof glass. This glass adopts the latest technology and has been widely put into production. Its advantages are high strength, good compression resistance, and effective heat insulation and fire prevention. Most of them are now mainly used for glass curtain walls and door and window materials on the exterior walls of fire-proof buildings. High-strength fireproof glass is made of float glass that has been chemically and physically treated. It can remain non-breaking for 84 minutes to 183 minutes in a high temperature environment of 1000 degrees. It plays a good role in controlling the fire situation and the spread of thick smoke, and provides sufficient time for safe evacuation to ensure the smooth progress of fire rescue. 

 　　4 Conclusion

 　　Since fires on the glass curtain wall are easy to spread vertically and horizontally, affecting personnel evacuation and fire fighting, the fire prevention treatment of the glass curtain wall is particularly important. First, the steel structure of the glass curtain wall is fireproof by coating fireproof coating and encapsulation method, and then high-performance fireproof glass such as sandwich fireproof glass and laminated composite fireproof glass are selected. Of course, in the specific construction process, the details of the qualification of the construction unit and the installation of fireproof materials must also be fully considered.