Fireproofing materials for steel structures

Methods of fire protection for steel structures: In addition to carrying out basic fire-resistant design, it is necessary to consider feasible fire protection measures and integrate the two closely. The fundamental principle of fire protection for steel structures is to use fire-resistant, insulating, or heat-absorbing materials to block flames and heat, thereby slowing down the rate at which the temperature of the steel structure rises and delaying the time it takes for its surface to reach the critical temperature. The main methods are as follows: 1) Encapsulation method: Fire-resistant and lightweight panels such as gypsum boards, calcium silicate boards, and perlite boards are used, and these panels are enclosed and fixed to the steel components using adhesives or connecting elements (such as steel nails). Concrete can also be poured to make fire-resistant bricks. 2) Shielding method: This involves enclosing the steel components within walls or ceilings made of fire-resistant materials. This protection method is commonly used in steel structure roof systems. 3) Water cooling method: Hollow steel columns (or steel beams) are connected to form a network, which is filled with an aqueous solution containing antifreeze and rust inhibitors. Due to the temperature difference during a fire, this solution circulates and carries away the heat ； An automatic sprinkler system can also be installed; a sprinkler supply network is set up on the top of the steel structure, and it activates automatically in case of a fire, creating a dense, continuous stream of water over the surface of the steel components to provide fire protection. 4) Spraying method: The fire-resistant coating is applied to the surface of steel structural members by spraying or manual application. This is the commonly used method at present; it is easy to construct, lightweight, and not restricted by the geometric shape of steel components, offering good economic efficiency and practicality. The fire protection methods for steel structures do not rely on just one of the methods mentioned above, but rather involve a combination of multiple approaches. Modern steel structures, especially those in high-rise or super-high-rise buildings, often have several fire protection layers; typically, the sprinkler system serves as the first line of defense, while encapsulation and spraying methods constitute the second and third lines of defense, respectively. 2.2 Fire-resistant coatings for steel structures Fire-resistant coatings are the most common and convenient method for providing fire protection to steel structures. It is a functional coating that, in addition to the protective and decorative properties of ordinary coatings, also has the special function of fire resistance. In our country, they are generally divided into two categories: thick-coating type (Class H) and thin-coating type (Class B). A comparison of their properties and functions is shown in Tables 1 and 2 below [3]. Table 1 Comparison of properties between thin-coated and thick-coated fireproof coatings. Type, Thickness (mm), Properties, Fire resistance limit (hours), Characteristics: Thin-coated type (Class B): 2–7; Organic intumescent phase-based fire protection; 0.5–1.5. It has strong decorative qualities, high adhesion, good vibration and warpage resistance, and is easy to apply. Thick-coating type (Class H): 8–20; inorganic intumescent permanent fire protection: 0.5–3.0. Offers strong protection, low thermal conductivity, high effectiveness, is non-toxic, but its application is relatively complex. Table 2 Comparison of functions between thin-coated and thick-coated fireproof coatings. Type, Scope of application, Application method, Coating type: Thin-coated type (Class B): Steel structures with decorative requirements that require a fire resistance limit of less than 1.5 hours. Exposed grid structures, lightweight roof trusses, stadiums. Layered spraying, brushing, rolling application; no curing required. LB SG-1 SB-2 SS-1 Heavy-coating type (Class H): for steel structures, concealed structures, important structures, and structures in humid environments with a fire resistance limit of over 1.5 hours. Fully steel-framed high-rise buildings, steel-framed multi-story factory buildings, steel structures in the presence of hydrocarbon fires, etc. Applied manually in layers or by mechanical spraying; requires curing. The LG STI-A JG276 SG-2ST-86 SB-1 models – it is worth noting that for outdoor steel structures, fire-resistant coatings suitable for use in outdoor environments must be selected. When choosing such coatings, the following points should also be taken into account: (1) Do not use coatings whose technical properties are only suitable for indoor use in outdoor applications. (2) Do not readily use finish-type fireproof coatings for protecting steel structures. (3) Toxic paints cannot be used

SH 3137-2003 Technical Code for Fire Protection of Steel Structures in Petrochemical Industries http://bbs.hcbbs.com/thread-19288-1-1.html GB14907-2002 Fire-Resistant Coatings for Steel Structures http://bbs.hcbbs.com/viewthread.php?tid=239802&extra=page%3D1&frombbs=1

Fire-resistant coatings for steel structures are divided into three types: 1. Thin-coat fire-resistant coatings for steel structures, also known as intumescent decorative coatings or intumescent mortars; the thickness of such coatings is generally 2–10 mm, and their fire resistance duration can range from 0.5 to 2 hours. 2. Ultra-thin steel structure expansion fireproof coating, also known as steel structure fire paint, has a coating thickness of generally 1–4 mm, with a fire resistance duration of up to 0.5–1.5 hours. 3. Thick-coated fire-resistant coatings for steel structures: the coating thickness is generally 8–50 mm, with a fire resistance duration of 1.5–4 hours. Firstly, fire-resistant coatings for steel structures must come with **fire resistance test reports and physical and chemical property test reports issued by testing institutions, as well as a production license granted by the fire supervision authorities, before they can be used. Secondly, the fireproof coating selected must come with a certificate of conformity from the manufacturer, and it should include the name of the coating, its technical specifications, manufacturing batch number, shelf life, and instructions for use. During construction, the following aspects should be taken into account: dust and oil on the surface of the steel structure before spraying. Miscellaneous items should be removed completely. Apply the primer coating using a gravity-fed spray gun with a nozzle diameter of 4–6 mm; the air compressor should have a capacity of 0.6–0.9 m3/min, and the air pressure should be 0.4–0.6 MPa. When applying the topcoat, change the nozzle diameter to 1–2 mm and adjust the air pressure to 0.4 MPa. The fire-resistant coating for steel structures, once delivered to the construction site, must be mixed using a portable electric mixer to ensure uniformity before it can be sprayed. Coatings in two-component packaging should be mixed on-site according to the proportions specified in the instructions, and used immediately after mixing. The mixed and prepared paint should have an appropriate consistency, so that it does not flow or sag after spraying. The primer should generally be applied 2 to 3 times, with an interval of 4 to 24 hours between applications; for the first application, it is sufficient to cover 70% of the surface of the base. The thickness per pass should not exceed 2.5 mm. Based on experience, applying a coating 1 mm thick requires approximately 1.2 to 1.5 kg/m2 of wet paint. When spraying, hold the gun firmly; keep the nozzle perpendicular to or at a 70-degree angle to the steel surface, and maintain a distance of 40–60 cm between the nozzle outlet and the surface to be sprayed. The surface coating is usually applied 1 to 2 times; if the first application is done by spraying from top to bottom, the second application should be done by spraying from bottom to top. Ensure the entire base coat is covered. The application rate on the surface is generally 0.5~1.0 kg/m2. The acceptance shall be carried out in accordance with the requirements specified in the \"Code for Acceptance of Construction Quality of Steel Structure Engineering\" GB50205-2001 regarding the application of fireproof coatings on steel structures.

There is also a standard atlas, 06SG501: Fire protection design for steel structures in civil buildings, which can be used as a reference.

The fire-resistant coating should be selected based on the fire resistance requirement of the steel structure – thin coatings provide a shorter fire resistance duration, while thick coatings offer a longer one!

Thicker materials have a longer fire resistance time.