Cementitious Fireproofing (Medium Density 22-30 pcf)

Spray-applied fire resistive materials (SFRMs) are cementitious fireproofing materials made primarily of gypsum and/or Portland cement. They are designed to protect structural steel and help a building keep its shape in the event of a fire, allowing building occupants to escape. Depending on the application they can be specified as normal (15-18 pcf), medium (22-30 pcf), or high density (≥40 pcf). These densities refer to the product in its cured state. Normal density SFRM products use gypsum as a binder, while high density products typically use Portland cement or other pozzolanic materials as a binder. This Common Product covers medium density products that use a mix of Portland cement and gypsum as a binder, and that can be used in buildings greater than 420 feet tall. 

Medium density cementitious fireproofing is used to protect structural steel and concrete, floor/ceiling, and roof/ceiling assemblies. It can be used in both conditioned and unconditioned interior locations that are exposed to abrasion and moisture. Typical locations where it may be specified are stairwells, parking garages, mechanical and electrical rooms, and elevator shafts. In North America these products are tested in accordance with ASTM E119 and ANSI/UL 263 (or CAN/ULC-S101 in Canada) to verify that they meet required fire resistance ratings; the products reviewed for this Common Product typically had fire resistance ratings of up to four hours. 

The product is supplied as a dry powder that is mixed with potable water in heavy-duty mortar mixers prior to application. It is then pumped through hoses to pressurized nozzles where it is spray applied to the substrate. Optionally, a set accelerator composed of aluminum sulfate powder can be mixed with water and injected at the nozzle to reduce the set time. This acidic set accelerator can also act as a foaming agent by reacting with basic materials, like calcium carbonate, to release carbon dioxide. Air entraining agents may also be added, though these were not identified as common. Some surfaces, such as painted substrates, require a bonding agent to be applied before the fireproofing product is applied. These bonding agents may add additional hazards not considered by this Common Product.