An experimental study of the behavior of intumescent coatings under localized fires

Abstract

This paper presents an experimental study of the behavior of intumescent coatings exposed to localized fires. The main objective is to assess the extent to which thermal properties of intumescent coatings obtained under uniform heating can be applied for localized fire exposures. The experiments used two types of specimens representing protected steel beams and columns. Localized pool fires were placed underneath horizontal specimens or beside vertical specimens. Solvent-based and waterborne intumescent coatings were applied to the specimens. Measurements were made of temperatures of the steel specimens and the adjacent gas phase, as was coating expanded thicknesses at several locations. Depending on their location relative to fires, the intumescent coatings were variably unreacted, melted, partially expanded, or fully expanded (corresponding to steel temperatures of about less than 100 °C, 100–300 °C, 300–400 °C, and above 400 °C, respectively). The appearances and expansion ratios for various regions of coatings under localized fires were consistent with those under uniform heating from previously obtained furnace test results. Steel temperatures of the specimens were calculated using thermal conductivities of coatings derived from furnace tests, and were found to agree reasonably with the experimental results, thus indicating that it may be feasible to apply thermal conductivities derived from furnace tests to predict steel temperatures under localized heating scenarios.