The Importance of Temporary Heat When Patching Damaged Fireproofing

Most SFRM applications require temporary heat and there are very real reasons why you don’t want any freezing within the SFRM. Most importantly, freezing can impede adhesion in a variety of ways, and cold temperatures have a deleterious effect on the necessary and critical chemical reaction going on within the SFRM. Any violation of the material manufacturer’s heating requirements most likely will lead to a pre-mature failure of the passive fire protection system.

When damaged SFRM needs to be patched, particularly with a cementitious SFRM material, the same concerns persist.  Patch materials are typically mixed with water; combined with cold temperatures, freezing can happen. How?  The industry rule is the steel must be heated to 40oF  – 24 hours prior to, during, and 24 hours after the patch.  Particularly in northern climates, the steel can cool to 20oF or less. When you apply a wet patch material to the steel, the very first layer (molecules) will instantaneously freeze. Upon the steel warming, it will provide little or no adhesion.  If the underside of the patch is smooth as a baby’s behind, that is a telltale sign of surface freezing.

The reverse situation also needs to be considered. You apply the material during the warm day, but temperatures drop significantly at night. Freezing will begin on the cold side and over time will penetrate the fireproofing to a partial depth or even the full depth of the applied SFRM thickness.  This will lead to delamination and failed cohesion of the fireproofing.  The applied fireproofing and patch should have a clean, crisp, durable texture to it; if it looks grey and “punky” that is an indication of SFRM freezing.

However applied, the cementitious material must develop a chemical reaction within it to hold the water molecules in place until released – likely in the event of a fire.  This is the essentiality of fireproofing, slowing down the transfer of heat thereby protecting the steel for a defined period of time.

So what’s the solution? Use temporary heat!  The size and scope of environmental conditions at the time of patching should be taken into account as part and parcel of any patching protocol.