Which test is used to measure bond strength between fireproofing and the substrate?

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Bond strength between fireproofing and its substrate is measured with a pull-off adhesion test. This test attaches a small dolly to the fireproofing surface and pulls it directly away from the substrate to determine the force needed to detach it. The resulting value directly reflects how well the fireproofing bonds to the surface and helps identify whether the coating will stay put under service conditions. It also shows the failure mode—whether the bond to the substrate failed or the fireproofing itself failed—which guides repairs or reapplication. Other tests measure different properties: viscosity checks how the coating flows during application, a surface hardness test gauges the hardness of the surface or coating, and a tensile strength test evaluates the material’s own strength, not its adhesion to the substrate. Therefore, the pull-off adhesion test is the appropriate method for assessing bond strength.