What is the minimum allowable bond strength of SFRM on the primer when qualifying a primer for use beneath SFRM?

The minimum allowable bond strength of Spray Fire-Resistive Material (SFRM) on the primer is crucial in ensuring that the fireproofing material adheres properly to the surface, providing the necessary fire resistance. Upon qualifying a primer for use beneath SFRM, it is essential to meet specific standards to ensure that the primer can support the applied load of the fireproofing material effectively.

A bond strength of 400 psf is established as the minimum acceptable value in industry standards. This high standard is necessary to ensure that under the conditions of exposure to fire and potential thermal expansion, the bond between the SFRM and the primer remains intact, thereby maintaining the fire-protective properties of the SFRM application. Sufficient bond strength helps prevent delamination or failure of the fireproofing system.

When examining the other choices, they fall below the established minimum standard, making them insufficient for reliable applications. Thus, understanding that the correct bond strength is 400 psf helps highlight the importance of verifying the adhesion properties of the primer used to ensure the overall effectiveness of the fire-resistive strategy in building safety.