Exploring the fire treatment of glass curtain wall

1 Fire characteristics of glass curtain walls

First of all, if the construction of glass curtain walls is unreasonable or if there are problems with the design of fire protection, once a fire breaks out, it will easily spread in both horizontal and vertical directions. Generally referred to as glass curtain wall includes the wall and window parts, because the ordinary glass is easy to crack in high temperature, if there is no effective fire and isolation measures in the horizontal and vertical direction, in case of fire, fire and smoke will follow the wall from the outside wall of the curtain wall. And the inner table spreads to the next floor. Second, the glass will have an impact on the fire extinguishing glass when it breaks down after a fire. Usually the curtain wall material is mainly glass, aluminum alloy frame or modeling steel frame. When the temperature reaches 6000 degrees, the steel will melt; and the aluminum alloy will melt when the temperature reaches 2500 degrees to 3300 degrees, so that in a fire environment, the glass is easily broken and dropped. In addition, in the high temperature environment, the glass itself has the characteristics of rupture, which increases the difficulty of safe evacuation and fire fighting. Finally, smoke is not easily expelled, hindering safe evacuation and fire fighting. Considering the stable and closed wall structure, glass curtain walls often do not have shoulders and windows. Even if the shoulders and windows are opened, in order to ensure the safety of the window frames, the windows are basically small. At the same time, the window openings are suspended upwards, and the angle between the walls is up to 45 degrees, this not only reduces the vent area, but also the window is more open on the curtain wall, and there is no window ventilation under the wall, so that the external pressure is greater than the internal pressure, in case of fire, the smoke is difficult to discharge. In addition, the position of the wall window is too high, which is often difficult to reach, and cannot be opened in time in a critical situation, thus posing a serious safety hazard. According to the above reasons, the glass curtain wall does not have a good natural smoke exhaust function. In the event of a fire, smoke will inevitably accumulate in large quantities indoors, making it difficult to discharge in a timely and effective manner, thereby impeding safe evacuation and fire fighting.

2 Fire treatment of glass curtain wall materials

2.1 Fire protection of steel

Generally, the steel frame has a limit time of only 15 minutes at high temperature, and there is still a big gap between the requirements of the fireproof limit of the glass curtain wall. Therefore, the wall steel frame must be fireproofed. In general, there are two main methods for fire protection of steel frames.

2.1.1 Coating of fireproof coatings

It is mainly applied to the surface of the steel frame, which can be used to insulate fire and heat, protect the integrity of the steel frame, and improve the high temperature resistance of the material. This kind of coating is also called steel frame fireproof coating. According to the different coating thickness, the coating can be divided into three types, namely thick layer, thin layer and ultrathin layer. Thick coatings, for example, usually have a thickness of between 8 mm and 50 mm. The coating surface is granular. It is sparse and has poor thermal conductivity. The high temperature withstand time is from half an hour to three hours. Due to the large coating thickness of thick coatings, the dry density is not. High, can not afford the building too much pressure, and the thermal conductivity is not strong, can effectively insulation and fire. This kind of coating is suitable for building walls after the completion of construction work. Some fire protection coatings do not have high aesthetic requirements, but must withstand high temperatures for more than an hour and a half. All steel frames, etc.

2.1.2 Envelopment Fire Prevention

This method mainly uses the heat-insulating fireproof material to encapsulate the steel frame to prevent the steel frame from being damaged by high temperature. Specifically, the encapsulation fire treatment method mainly includes the following measures: (1) Steel frame enclosing treatment: the fire protection ceiling and the isolation wall are used to surround the protection steel frame to prevent the steel frame from contacting the high temperature; (2) the fireproof material encapsulating steel Frame surface: It can be made of fireproof material, such as gypsum board, calcium silicate board and slate board. In general, a 25mm flake board can increase the high temperature withstand time limit of the steel frame to 90 minutes; (3) Spray the inorganic heat-insulating fireproof coating on the surface of the steel frame: The main coatings include vermiculite powder, gypsum, fiberglass, and mineral wool. Fiber, cement mortar, perlite powder, etc. The surface of the steel frame is coated with a 50-type metal mesh mortar for protection. The coating thickness is 25 mm, and the steel frame can withstand 48 minutes at high temperatures. If the coating thickness is 50 mm, the steel frame can withstand a maximum temperature limit of 81 minutes.

3 Fireproofing of glass

General glass will rupture when it encounters high temperature, the fireproofing ability is very poor, and there is a big gap between fireproof and glass curtain wall insulation. Therefore, the general material glass must be fireproofed to enhance the high temperature resistance of the glass. Generally, fireproof glass mainly includes the following types:

3.1 wire fire protection glass

This type of glass is mainly used to add a wire mesh composite material to an organic glue layer between two layers of glass or an inorganic adhesive layer. Thanks to the addition of a wire mesh to the glass, the overall strength and pressure resistance are greatly enhanced, and fire alarms and heat sensors can be attached to the glass to prevent fire. The material of the wire fireproof glass is mainly inorganic glass, the organic glue layer is polyvinyl chloride glue or polyvinyl butyral glue, and the inorganic adhesive components are mainly water and metal salts, including phosphate, aluminate, silicate, etc. A stainless steel material is used as the wire. One disadvantage of this type of glass is that it is not light transmissive.

3.2 Composite fireproof glass

Because of the poor light transmittance of fire-resistant glass, if the glass is made of special materials, it will greatly increase the cost, and the expensive price is difficult to be accepted. Nowadays, transparent laminated fire-retardant glass is more common on the market. This type of glass is usually composed of a stack of at least two layers of normal glass. The glass layers are bonded together with a transparent fireproof adhesive and the glue expands thermally. With respect to composite fireproof glass, people are mainly concerned with transparent flame-retardant adhesives bonded to glass. This is because the quality level of fireproof adhesives directly determines the performance of fireproof glass.

3.3 High-strength fire-resistant glass

In fact, this is a monolithic antimony-potassium fireproof glass. This kind of glass adopts the latest technology and has been widely put into use. Its advantages are high strength, good pressure resistance, and can effectively insulate and fire. Now most It is mainly used for glass curtain wall and door and window materials for fireproof building exterior walls. High-strength fire-resistant glass is made of float glass by chemical and physical treatment. It can maintain a constant temperature of 1000 degrees Celsius for 84 minutes to 183 minutes. It plays a very good role in controlling the spread of fire and smoke. It is safe for evacuation. Provide sufficient time to ensure that fire rescues proceed smoothly.

4 Conclusion

Since the fire of the glass curtain wall is easy to spread in the vertical and horizontal directions, affecting personnel evacuation and fire fighting, the fire treatment of the glass curtain wall is particularly important. Firstly, the fireproof coating and encapsulation method are applied to fire-proof the steel structure of the glass curtain wall, and then high-performance fireproof glass such as wire-fired glass and laminated composite fireproof glass is selected. Of course, details such as the qualification of the construction unit and the installation of fireproof materials in the specific construction process should also be fully considered.