An adhesion test method for spray-applied fire-resistive materials

Adhesion of spray-applied fire-resistive materials (SFRMs) to steel structures is critical in enabling a building to remain functional during a fire for a specific period of time for life safety and fire department access. Empirical tests such as ASTM E736 have been widely adopted by the industry in an effort to ensure sufficient bonding between SFRMs and steel structures. ASTM E736 assesses the adhesion of SFRMs by using tensile strength, a failure parameter that depends on the test geometry and has limited use for predicting failure in other geometries and conditions. These limitations have produced an urgent need for a scientifically based adhesion test method. In this paper, we propose a new test method that would provide more fundamental information that is independent of test geometry and has predictive capability. This paper utilizes a fracture energy-based failure criterion (GC ) to characterize the adhesion between SFRMs and steel. The theoretical basis of this test method is validated by experimental compliance tests. The dependence of GC on various test variables such as specimen width, substrate type, SFRM formulation, and test rate are examined. A comparison between this new test method, and the current widely used strength-based test method is also presented. Copyright 2010 John Wiley & Sons, Ltd.