Steel loses approximately 50% of its load-bearing capacity when it reaches 1,000°F, or 537°C, posing serious risks during fire events. Reliable fireproofing material for structural steel is essential for protecting industrial buildings and facilities, ensuring fireproofing of steelwork for safety and safe evacuation.

Fireproofing Defined

Fireproofing is a protective measure that prevents structural materials, like steel, from reaching critical temperatures during a fire. By using sprayed fire-resistive material, or SFRM, and other protective layers, fireproofing enhances a building’s safety and stability during fire events.

Two Fireproofing Categories: Active vs. Passive

Fireproofing steel involves both active fire protection systems, which use sprinkler systems or extinguishers, and passive fireproofing solutions, which apply fireproofing materials directly to steel surfaces. These layers act as a barrier, reducing heat transmission and delaying structural failure.

Fire protection is also specified based on potential fire types:

• Cellulose Fires (wood-based): Slower to develop, reaching 2,000°F over four hours, seen in schools, hospitals, and residential buildings.
• Hydrocarbon Fires (fuel-based): Rapidly reach 2,000°F in five minutes, essential for industrial and petrochemical facilities.

Applications for Structural Steel Fireproofing

The purpose of fireproofing is to protect critical structural components in industrial settings, such as:

Structural Steel Fireproofing Code Requirements

Fireproofing code requirements vary by region, generally aligning with standards from organizations like International Code Council (ICC/IBC), National Fire Protection Association (NFPA) or NORSOK.

Fire-resistance ratings, typically expressed in hours, reflect how long fireproofing materials can withstand fire under specific conditions.

Testing for Fire-Resistance:

• ASTM E119 and UL263 for cellulose fires, where the temperature reaches 2,000F, or 1,093C, over four hours
• UL1709 for hydrocarbon fires, where temperatures reach 2,000F in five minutes and hold for the test duration.

Additional tests, such as Jet Fuel, Pool Fire, Blast, and Hose Stream testing, assess fireproofing resilience in specialized applications. Engineers and architects can refer to directories like Underwriter’s Laboratories to determine suitable ratings. Local building codes, model standards, and design specifications provide guidelines for project-specific requirements.

Traditional Structural Steel Fireproofing Methods

Spray-Applied Fire-Resistive Material (SFRM)

Spray-applied fire-resistive material (SFRM) is a commonly-used, cost-effective solution used for fireproofing steel beams and columns. Applied as either a wet or dry spray, cement fireproofing products like SFRM are designed to increase a structure’s resistance to high temperatures. Composed mainly of cement and gypsum, with mineral additives, SFRM can also offer limited acoustic and thermal insulation.

While effective, SFRM is not ideal for environments with high moisture or freeze-thaw cycles, as these conditions can degrade the material. Additionally, it provides minimal corrosion protection, making it essential to prepare surfaces thoroughly with blasting, priming, and reinforcement, especially in corrosive settings. Although SFRM is affordable, these preparatory steps can impact project costs.

Intumescent Coatings

Intumescent fire-resistive materials (IFRM) expand up to 100 times its original thickness, when exposed to heat, creating a thick barrier to protect steel. These lightweight coatings are popular for exposed steel surfaces, preserving design aesthetics without compromising fire protection.

However, IFRM are highly vulnerable to environmental conditions during application, which can affect performance, and they are more expensive than other fireproofing options, especially for higher fire ratings. While IFRM provides some corrosion protection, the application process, including surface preparation (blasting, primers, lath/attachments, etc), can be costly and time consuming.

Rigid Board Fireproofing

Rigid board fireproofing systems involve attaching fireproofing materials in board form to beams and columns, suitable for varied climates. Suitable for out-of-sequence construction, this method is effective in various climates, including areas prone to freezing.

Rigid boards, however, are slower and more expensive to install and do not offer corrosion protection, often requiring additional preparation like blasting, primers, or anti-corrosion paints, adding to project costs.

Flexible Blanket Systems

Flexible blanket systems combine fire, thermal, and acoustic insulation, providing lightweight protection without toxic smoke production. They are easy to install on complex shapes but lack customizable thicknesses and require additional fasteners.

These blankets offer no corrosion protection, so pre-installation steps like priming and blasting are often necessary. Limited manufacturers also mean fewer choices for this type of fireproofing.

Portland Concrete

Once widely used for fireproofing, Portland concrete remains a choice for large steel elements, such as columns. While it offers durability, it requires significant volume, has a high carbon footprint, and lacks design versatility.

Concrete fireproofing offers minimal corrosion resistance, so it typically requires additional protective measures, including primers or galvanizing, to maintain steel integrity.

Advances in Spray-On Fireproofing for Structural Steel

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