Which SFRM testing method incorporates polystyrene beads?

The displacement method is the correct answer as it specifically involves the use of polystyrene beads as a component in the testing process. This method is designed to assess the density and structural integrity of spray-applied fire-resistant materials (SFRM). In this context, polystyrene beads serve as a lightweight aggregate, helping to create a measurable volume displacement when mixed with the fireproofing material. This allows for the determination of the fireproofing's properties, particularly behavior under load and its effectiveness in fire protection.

While the other testing methods listed—compression, tensile, and shear—focus on evaluating the material's performance under various stresses and loads, they do not utilize polystyrene beads. Their primary objectives are to analyze how the material reacts to force or stress rather than measuring density or displacement with the help of specific additives like polystyrene. Thus, the displacement method stands out for its unique incorporation of these beads in the testing protocol.