Fireproofing is a specialized job. It’s not easy to fireproof a building structure and requires a thorough understanding of fire resistant building materials and the kind of design that makes the structure fire resistant.
What’s more, the location of the building determines the methodology used for fireproofing. Fireproofing Anchorage might have some points of differences with fireproofing a building in Washington.
One of the most preferred and commonly used fireproofing methods is spray painting a structure with fire resistant material. Other methods include:
• Gypsum plasters
• Cementitious plasters
• Fibrous plasters and
• Liquid convection cooling
We have covered all these five methods here to give you an understanding of how they work and in what circumstances they prove useful and more effective.
1. Sprayed Fireproofing
Spray fireproofing means spraying any substance in a way that covers a particular surface properly in order to provide it with fire resistance.
Spray applied fireproofing can be sprayed onto steel to insulate it from the heat of a fire, thus saving lives by providing enough time for people to get out of the building. The material can be cement based or fiber based since both materials have UL testing to ensure safety. Sprayed fireproofing can be used for various materials like wood, fabric, structural steel and more.
In the past, industry defined product classifications as “Cementitious Mixtures” or “Sprayed Fiber” materials. These product classifications have since been withdrawn to avoid complexities and combined to form a new single product classification called Spray-Applied Fire Resistive Material (SFRM).
The term “cementitious” often misleads people to believe the product contains cement, actually most commercial density fireproofing products called “cementitious” do not contain cement; ironically, most materials that are included in the “Sprayed Fiber” category actually do contain cement.
The specific characteristics of each material, the manner in which they are prepared and applied all affect the fire-resistive qualities of SFRM material. One of the most critical elements for a properly installed SFRM is its applied thickness. Sufficient insulation is available to mitigate the passage of heat from a fire to the structure being protected only if proper SFRM thickness is ensured.
The installed-SFRM must at least provide the level of thermal protection equivalent to that provided for the test assembly-during the standard test. There are various standards set and performance tests carried out for the fireproofing materials.
The industry has categorized SFRMs as either “Wet Spray” or “Dry Spray” materials so that the terms better describe the manner in which the material is mixed, conveyed and applied.
2. Gypsum Plasters
Gypsum plaster, or plaster of Paris, is produced by heating gypsum to about 300 °F (150 °C). When the dry plaster powder is mixed with water, it re-forms into gypsum. The unmodified plaster is not fully set for 72 hours even though the setting starts about 10 minutes after mixing, and is complete in about 45 minutes. If plaster or gypsum is heated above 392°F (200°C), an anhydrite is formed, which will also re-form as gypsum if mixed with water. A large gypsum deposit at Montmartre in Paris led “calcined gypsum” (roasted gypsum or gypsum plaster) to be commonly known as “plaster of Paris”.
For many decades, plasters have been in use for passive fire protection, as fireproofing products. The finished plaster slows the spread of the fire for as much as an hour or two because it releases water vapor when exposed to flame. It also provides some insulation to retard heat flow into structural steel elements that would otherwise lose their strength and collapse in a fire.
Early versions of these plasters actually used asbestos fibers, which by now have been outlawed in many countries.
Contemporary plasters fall into the following categories:
• Fibrous (including mineral wool and glass fiber).
• Cement mixtures either with mineral wool or with vermiculite.
• Gypsum plasters, leavened with polystyrene beads, as well as chemical expansion agents to decrease the density of the finished product.
There is a noticeable difference between interior and exterior fireproofing.
Interior products typically tend to be less substantial, with lower densities and lower cost and there is a lot more variety of choice. Exterior products have to withstand extreme fire and other environmental conditions and should be immune to dramatic weather changes. This is why exterior products are also more likely to be attractively tooled, whereas their interior cousins are usually merely sprayed in place.
Exterior fireproofing plasters are losing ground to more costly intumescent and endothermic products, simply on technical merit. Cementitious and gypsum based plasters tend to be endothermic.
Fireproofing plasters are closely related to fire stop mortars. Most fire stop mortars need to be sprayed extensively and tooled to perfection. This improves their fire resistance.
Heat resistant plaster is another building material used for coating walls and chimney breasts. If contractors think gypsum plaster might not stay on the wall due to high temperature, heat resistant plaster is used as an alternative. Heat resistant plaster should be used in cases where the wall is likely to exceed temperatures of 50°C.
3. Cementitious Plasters
Cementitious fireproofing is a wet mix plaster fireproofing substance, using a base of Portland cement or gypsum. Fireproofing steel for a fire resistance rating of 1 to 4 hours, for both restrained and unrestrained rating, is normally achieved by suing this type of coating.
Cementitious plasters are often referred to as Portland cement plasters. Portland cement plasters made with perlite aggregate instead of sand offer, many advantages. They are more fire resistant, better insulators, and weigh approximately 60% less than conventional cement and sand plasters.
Also, with the addition of fiber reinforcement, superior crack resistance is achieved. In addition, fiber reinforced perlite cement plaster panels can be safely and easily handled in the field. That’s a huge advantage in itself.
4. Fibrous Plasters
Fibrous plaster is Gypsum plaster reinforced or backed with sisal or canvas. Fibrous plasters, containing either mineral wool or ceramic fibers tend to simply entrain more air, thus displacing heavy fibers.
On-site cost reduction efforts can further enhance such displacement of solids through at times purposely contravening the requirements of the certification listing. This resulted in architects’ specifying the use of on-site testing of proper densities to ensure the products installed meet the certification listings employed for each installed configuration; that’s because excessively light inorganic fireproofing does not provide adequate protection and is thus in clear violation of the listings.
Materials used for covering items to provide increased fire-resistance include proprietary boards and sheets, made of gypsum, calcium silicate, vermiculite, perlite, mechanically bonded composite boards made of punched sheet-metal and cellulose reinforced concrete.
5. Liquid Convection Cooling
Liquid convection cooling in hollow structural members is an alternative method to keep building steel below its softening temperature. This will keep the temperature under control and prevent fire occurrences.
The 5 techniques discussed here are the most widely used worldwide. They have evolved and the usage of materials has changed over time to better handle the fireproofing needs of the clients and buildings thus making fireproofing methods better and safer.