Glass curtain wall fire protection treatment

First, if a glass curtain wall is poorly constructed or has an inadequate fire protection design, a fire can easily spread both horizontally and vertically. A glass curtain wall generally consists of two components: walls and windows. Ordinary glass is prone to shattering at high temperatures. Without effective fire-proofing measures in both the horizontal and vertical directions, fire and smoke can spread from the exterior and interior surfaces of the curtain wall to adjacent floors.

Second, shattering and falling glass in a fire can affect firefighting glass. Curtain walls are typically constructed of glass, aluminum alloy frames, or shaped steel frames. Steel melts at temperatures reaching 6,000 degrees Celsius, while aluminum alloy melts at 2,500 to 3,300 degrees Celsius. This makes glass easily shattered and shatter in fire. Furthermore, glass is inherently prone to shattering in high-temperature environments, complicating safe evacuation and firefighting. Finally, thick smoke is difficult to dissipate, hindering safe evacuation and firefighting. Considering the structural stability and airtightness of the walls, glass curtain walls often lack shoulder windows. Even if shoulder windows are included, they are typically very small to ensure the safety of the window frames. Furthermore, the window openings are top-hung, with a maximum angle of 45 degrees to the wall. This not only reduces the ventilation area, but also places the windows above the curtain wall, leaving no windows below for ventilation. This results in external pressure exceeding internal pressure, making it difficult to exhaust dense smoke in the event of a fire.

Furthermore, the high position of the windows on the wall often makes them difficult to reach, making them difficult to open in an emergency, posing a serious safety hazard. Based on the above analysis, glass curtain walls lack effective natural smoke exhaust. In the event of a fire, dense smoke will inevitably accumulate indoors, making it difficult to exhaust promptly and effectively, hindering safe evacuation and firefighting.

1. Fireproofing of Steel
Typically, steel frames can withstand only 15 minutes of high temperatures, significantly lower than the fire resistance requirements of glass curtain walls. Therefore, fireproofing of the wall steel frame is essential. Generally, there are two main methods for fireproofing steel frames.
(1) Fire-retardant coating
The main purpose is to apply the coating to the surface of the steel frame. It can be used to insulate and prevent fire, protect the integrity of the steel frame function, and improve the material's high-temperature resistance. This coating is also called steel frame fire retardant coating. According to the thickness of the coating, the coating can be divided into three types, namely thick layer, thin layer, and ultra-thin layer. For example, the thickness of the thick layer coating is usually between 8 mm and 50 mm. The coating surface is granular and relatively sparse, with poor heat conductivity. The high temperature resistance time is between half an hour and three hours. Because the thick layer coating is thick and the dry density is not high, it cannot withstand too much pressure from the building. In addition, the heat conductivity is not strong, which can effectively insulate and prevent fire. This coating is suitable for some building walls that are enclosed, isolated, and shielded building walls after the construction project is completed. The fire retardant 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) Encapsulation fire protection treatment
This method mainly uses heat-insulating and fire-proof materials to encapsulate the steel frame to prevent high temperature damage to the steel frame. Specifically, the encapsulation fire protection method primarily includes the following measures:
① Steel frame enclosure treatment: Use fire-resistant ceilings and isolation walls to surround and protect the steel frame, protecting it from high temperatures.
② Fire-resistant material encapsulation of the steel frame surface: Fire-resistant sheet materials such as gypsum board, calcium silicate board, and vermiculite board can be bonded and fixed to the steel frame. Generally, a 25mm thick vermiculite board can increase the steel frame's maximum heat resistance time to 90 minutes.
③ Spraying inorganic thermal insulation and fire-retardant coatings on the steel frame surface: Main coatings include vermiculite powder, gypsum, glass fiber, mineral wool fiber, cement mortar, and perlite powder. For example, applying 50-type metal mesh mortar to the steel frame surface for protection with a coating thickness of 25mm can increase the steel frame's maximum heat resistance time to 48 minutes. If the coating thickness is 50mm, the maximum heat resistance time can reach 81 minutes.

General glass will break when exposed to high temperatures, making it extremely fireproof and far from meeting the fire isolation requirements of glass curtain walls. Therefore, standard glass must undergo fireproofing treatment to improve its high-temperature resistance.

Common fireproof glass types include the following:
1. Wired Fireproof Glass
This type of glass consists of a metal mesh composite material added to the organic or inorganic adhesive layer between two layers of glass. The addition of the wire mesh significantly enhances the overall strength and compressive strength of the glass. It also allows for the attachment of fire alarms and heat sensors to the glass for fire prevention. Wired fireproof glass is primarily made of inorganic glass. The organic adhesive layer is polyvinyl chloride or polyvinyl butyral, and the inorganic adhesive is primarily composed of water and metal salts, including phosphates, aluminates, and silicates. Stainless steel is used as the wire. However, this type of glass has the disadvantage of being less transparent.

2. Composite Fire-Resistant Glass
Because wired fire-resistant glass has low light transmittance, using special materials significantly increases costs, making its price unattainable. Transparent laminated composite fire-resistant glass is now more common on the market. This type of glass typically consists of at least two layers of standard glass, bonded together with a transparent fire-resistant adhesive that expands with heat. Regarding composite fire-resistant glass, the primary focus is on the transparent fire-resistant adhesive used to bond the glass, as the quality of the fire-resistant adhesive directly determines the performance of the fire-resistant glass.
3. High-Strength Fire-Resistant Glass
This is essentially a single-piece cesium potassium fire-resistant glass. Utilizing the latest technology, it is now widely used in production. Its advantages include high strength, excellent compressive resistance, and effective thermal insulation and fire protection. It is currently primarily used for curtain walls, doors, and windows in fire-resistant building exteriors. High-strength fire-resistant glass is made from float glass that has undergone chemical and physical treatments. It can withstand temperatures of 1000 degrees Celsius without breaking for 84 to 183 minutes, effectively controlling the spread of fire and smoke, providing ample time for safe evacuation and ensuring smooth fire rescue operations.

Because fires in glass curtain walls can easily spread vertically and horizontally, hindering evacuation and firefighting, fireproofing glass curtain walls is particularly important. First, the steel structure of the glass curtain wall is fireproofed using a fire-retardant coating and encapsulation method. High-performance fire-resistant glass, such as wired fire-resistant glass and laminated composite fire-resistant glass, is then selected. Of course, during the construction process, details such as the construction company's qualifications and the installation of fire-resistant materials must also be carefully considered.