What is the allowable test cap diameter range when testing SFRM bond strength?

The allowable test cap diameter range for testing Spray-Applied Fire-Resistive Material (SFRM) bond strength is indeed between 2 to 3-1/4 inches. This specification is crucial because it ensures that the area over which the bond strength is measured is large enough to obtain a representative sample of the fireproofing material's adherence to the substrate. If the test cap is too small, it may not effectively capture the bond strength characteristics of the SFRM, leading to unreliable results. A test cap within this specified range facilitates a consistent and standardized testing method, which is essential for evaluating the material’s performance under fire conditions. Other specified ranges would either not provide sufficient testing area or would exceed practical limits for evaluating bond strength effectively.