%0 Journal Article
%T In situ thermal
%A Fumiaki Takahashi
%A James S TĦŻien
%A Jiyuan Kang
%J Journal of Fire Sciences
%@ 1530-8049
%D 2018
%R 10.1177/0734904118794955
%X Thermal insulating performance and char-layer properties have been studied for water-based intumescent coatings for structural steel fire protection using a new laboratory-scale mass-loss cone apparatus. A specimen (100 ĦÁ 100 mm mild steel plate; the initial coating thickness: 0.3¨C2.0£żmm) is placed horizontally and exposed to a constant incident radiant heat flux (25, 50, or 75£żkW/m2). The apparent thermal conductivity of the expanding char layer is determined in situ based on real-time measurements of the temperature distribution in the char layer and the heat flux transmitted through the char layer. Three-dimensional morphological observations of the expanded char layer are made using a computed tomographic¨Cbased analytical method. The vertical variation of the porosity of the expanded char layer is measured. The measured heat-blocking efficiency is correlated strongly with the incident heat flux, which increases the expanded char-layer thickness, and porosity for sufficiently large initial coating thicknesses (>0.76£żmm). For a thin coating (0.30£żmm), violent off-gassing disrupts the intumescing processes to form a consistent char layer after abrupt exposure to higher incident heat fluxes, thus resulting in lower heat-blocking efficiency. Therefore, the product application thickness must exceed a proper threshold value to ensure an adequate thermal insulation performance
%K Passive fire protection
%K char layer
%K porosity
%K computed tomography
%K heat-blocking efficiency
%U https://journals.sagepub.com/doi/full/10.1177/0734904118794955