Thick-type steel structure fire-retardant paint refers to coatings with a thickness greater than7 mm, less than or equal to 45 mm, granular surface, low density, low thermal conductivity, fire-resistant steel structure coating with a耐火limit exceeding 3 hours.

Due to the inorganic composition of thick fire-resistant coatings, they offer stable fire protection and long-lasting performance. However, the larger particle size of the coating components results in an uneven finish, affecting the overall aesthetics of the building. Consequently, they are predominantly used in concealed structural applications. During fires, these coatings utilize the granular surface of the material, its lower density, and low thermal conductivity, or the material's heat absorption properties, to delay the temperature rise of steel, thereby protecting it.

This type of fire-resistant coating is made with suitable inorganic binder.(like water glass, silicate, aluminum phosphate salts, refractory cement, etc.), mixed with inorganic lightweight insulating aggregates (such as expanded perlite, expanded vermiculite, sea spalling, fly ash, etc.), fire-retardant additives, chemicals, reinforcing materials (such as aluminum silicate fibers, rock wool, ceramic fibers, glass fibers, etc.), and fillers, etc., offering the advantage of lower cost.

Construction often employs spraying, suitable for fire-resistant requirements of2-hour or more concealed steel structures for indoor and outdoor use, high-rise full steel structures, and multi-story factory steel structures. For example: The fire resistance limit of columns in high-rise civil buildings and columns supporting multiple floors in general industrial and civil buildings should all reach 3 hours, and the thick-type fire-resistant paint should be used for protection.

RoomThick-walled steel structural frame

Fireproof coating application process

1. Purpose and Application Scope

To ensure the construction quality meets the fire prevention design requirements.

　　Suitable for our company's roomThick-type steel structure fire-resistant coating application

2. Construction Requirements

2.1 Structural steel fire-resistant spraying protection should be carried out by a professionally trained and qualified construction team. Safety technology and labor protection requirements during construction shall be in compliance with the current national regulations.

2.2 After the steel structure is installed and the connecting hoisting rods, walkways, pipe racks, and other related components are fully installed and inspected and approved, fire-resistant coating work can then be carried out.

2.3 Prior to construction, the surface of the steel structure should be de-rusted, and anti-rust treatment should be determined according to the usage requirements. The de-rusting and anti-rust treatment should comply with the relevant provisions in the current "Code for Construction and Acceptance of Steel Structure Engineering."

2.4 All debris on the surface of the steel structure should be cleaned thoroughly, and the gaps at the joints should be filled and sealed with fire-resistant paint or other fire-resistant materials before construction.

2.5 The fire-resistant coating for construction should be applied before indoor decoration and under conditions where it will not be damaged by subsequent work. During application, areas and objects that do not require fire protection should be shielded and protected. The newly coated surface should be protected from contamination by dirty liquids and mechanical impacts.

3. Steel component base material surface treatment

3.1 The surface to be coated should be free of oil stains and loose dust. The steel structure surface should be rusted according to requirements (rust removal grade not lower than St2) before applying two coats of anti-rust primer.

3.2 For areas where the rustproof layer has been damaged, a touch-up coat should be applied and allowed to dry before proceeding with the construction.

4. Construction Environment

4.1 During the application process and before the coating dries and cures, the ambient temperature should be between 4℃ and 20℃ for an ideal environment. For thick-type fire-resistant coatings on indoor or outdoor steel structures, the ambient temperature must not be below 4℃ during application and within the first 24 hours after application; otherwise, the fire-resistant coating may suffer frost damage before curing. However, after curing and drying, the coating can withstand frost damage. When the ambient temperature is above 20℃, to prevent excessive water loss, the fire-resistant coating should be maintained, using the same method as for cement mortar coating. It is not advisable to work when the wind speed exceeds 5m/s, or during rain or when condensation forms on the surface of the components.

5. Construction Tools: Low-speed mortar mixer, air compressor with automatic pressure increase to maintain 0.4Mpa, air volume not less than 0.17M2/min, spray gun with nozzle diameter of 8-10mm, wall trowels, material buckets, tap water (clean drinking water), and other relevant tools.

6. Mixed

6.1 Use a low-speed mortar mixer for the fire-resistant coating to prevent over-grinding of light aggregates, which may affect the quality of the coating. The mixing time should be between 5 to 10 minutes. Materials should be used immediately after mixing; do not mix too much at once. The mixed slurry should be used within one hour at room temperature. Do not use slurry that has been contaminated or stored for more than one hour after mixing, as it may lead to reduced bonding strength and other adverse effects. (Note: Do not use fire-resistant coatings that are unpacked or have lumps.)

7. Construction Techniques

7.1 Construction Requirements

a. Apply each coat with a thickness of <10mm, but if a thickness of 10mm is required, it must be applied in two coats.

b. The interval between two applications is 24 hours, with the environmental temperature below 20°C. Adjustments can be made accordingly for varying temperatures.

c. Once mixed, the slurry should be used within 1 hour at room temperature; avoid prolonged storage as it may negatively affect the bonding strength.

d. For structural steel fire-resistant coating and钉backing mesh requirements: when applying fire-resistant coating on I-beams, H-beams, or rectangular steel with horizontal and vertical spacings exceeding 300mm, mesh reinforcement is required prior to coating application. Options include steel mesh or metal mesh, which can be fixed using welded steel rods as weld nails or thermally bonded insulation nails.

e-Netting Method: First, measure the circumference of the structure that requires e-netting, then add 1-2 times the diameter length. Cut the netting, place it over the coating through the thermal insulation nails, twist and flatten the joints with galvanized wire. Proceed to the next construction process.

8. Construction Method

8.1 Spraying: When spraying once, the surface of the steel structure should be treated with a spot pattern, without requiring complete coverage of the coated surface but rather presenting a peppering finish; after the first coat is fully dried, proceed with the next spraying, aiming for a thickness of 5~6mm per coat.

8.2 Troweling: Similar to the traditional cement mortar troweling method, it requires an even and consistent thickness, firmly compacted and dried to avoid defects such as honeycomb and hollows. The thickness of one layer should be 5~6mm, and each subsequent layer should be 7~10mm, until the desired design thickness is achieved.

8.3 After the plane reinforcement insulation nails for steel beams and pillars are securely fastened, start applying fire-resistant coating. Once it dries at room temperature, hang the mesh, bend the insulation nails, and then secure the wire mesh with 0.6-1.0mm galvanized iron wire (mesh size: 20mm x 20mm, wire thickness: 0.5-1mm). Proceed to the next stage of construction.

8.4 During the application of outdoor heavy-duty steel structural fire-resistant coating, the coating should be applied to the design thickness at the beam-to-column and beam-to-beam joints according to their geometric shapes. Special attention should be given to joints and blind spots: the coating must be applied evenly and densely without any hollowing.

5. Inspection

5.1 Fire-resistant coating thickness measurement, within the upper and lower limits of the design requirement value.

5.2 Surface Quality

5.2.1 The surface should be flat, with no visible indentations or protrusions.

5.2.2 Cracks should generally not be present, but up to 1-3 cracks per square meter are permitted, with a width of ≤1mm.

5.3 There should be no missed coatings on critical areas, such as component interfaces and corner areas.

5.4 If there are no special requirements for steel section components, the outer shape should basically remain consistent with the material after the fire-resistant coating work is completed.

Special requirements: After the application of the fire-resistant coating is completed, the exterior should essentially match the material.