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The Thermal Weakness of Steel
Steel is a non-combustible construction material, which differentiates it fundamentally from timber and other flammable building substances. Even so, high temperatures severely undermine its structural performance and mechanical stability. Both empirical research and real fire accident data demonstrate that steel undergoes significant strength deterioration and physical deformation once ambient heat reaches 450°C to 650°C. In intense fire scenarios, uninsulated steel components may fail to bear structural loads within merely 15 minutes.Such performance decline does not stem from burning. Instead, thermal softening alters the mechanical properties of steel, triggering structural instability and posing severe safety risks to buildings and occupants.To address this critical flaw, global building regulatory systems stipulate standardized minimum fire resistance requirements for steel structures. These specifications are formulated according to building functions and usage scenarios rather than being random provisions. Their core purpose is to sustain structural soundness during fire emergencies, allowing sufficient time for on-site evacuation and professional fire rescue operations.

Fire Protection of Steel Structures: Fundamental Principles and Practical Measures
Core fire protection strategies for steel structures centre on a single key objective: slowing down the heat absorption process of steel components to maintain their structural integrity and service performance throughout a fire event. A variety of practical fire prevention and protection techniques have been engineered for steel buildings, featuring unique functional attributes and targeted application scenarios to suit diverse construction demands.

Two Main Types of Fireproof Coatings: Intumescent Film & Cement-based Mortar Coatings
Intumescent fireproof coatings belong to the most widely applicable fireproof materials. Their construction mode is identical to common architectural paint. When encountering high heat, the coating layer expands rapidly and forms dense heat-insulating carbonized layers. This heat barrier can block heat conduction toward steel substrates, normally extending fire resistance duration for 1 to 2 hours depending on coating thickness and construction workmanship. Owing to their thin coating thickness and good decorative effect, they are perfect for exposed steel members with high aesthetic requirements. By contrast, cement-based fireproof coatings are made from inorganic mineral raw materials such as gypsum and vermiculite and adopt a distinct heat insulation mechanism. They do not expand when heated but rely on their low heat conductivity to isolate high temperature. This type of coating generally requires thick-layer construction and boasts superior durability. Therefore, it is mostly adopted in industrial workshops, equipment rooms and basements, where structural durability is prioritized over surface appearance.

Fireproof Panels and Cladding
When fireproof coating systems cannot be deployed or fail to deliver adequate thermal shielding, fire-resistant panels serve as a reliable substitute. Prefabricated slabs manufactured from calcium silicate, perlite and other mineral raw materials can be mounted directly onto steel structural components. They deliver stable fire insulation performance without being affected by ambient moisture, base material status or external mechanical loads. Capable of resisting heavy collision and surface abrasion, these panels work well for frequently accessed areas and locations prone to constant physical friction.

Concrete and Plaster Wrapping for Steel Fireproofing
Concrete and plaster cladding represents another mature passive fire protection technique, which wraps steel structural parts to build a physical barrier isolating metal substrates from fire flames. Concrete enclosure is usually reinforced with wire meshes; apart from outstanding fire endurance, it also enhances the overall mechanical strength of the building frame. Even so, the extra self-weight of such cladding and complicated construction procedures restrict its application in projects with tight load-bearing limits or narrow installation spaces.

Heat Insulation and Passive Fire Barrier Systems
For internal structures and non-load-bearing steel components, thermal insulation blankets and refractory barrier materials provide an economical and efficient fire protection solution for steel-structured buildings. Such protective systems work by reducing the rate of heat uptake of steel materials, making them highly applicable to mid-rise architectures and residential buildings where comprehensive heavy-duty fireproof treatment is impractical. In addition, passive fire protection methods, including concealing steel structural members behind fire-rated partition walls, can also meet standard fire resistance demands without the need for extra surface fireproof coatings.