Reformative Effects of Intumescent Coating on the Structural Characteristics of Cold-Formed Steel

Intumescent fire-resistive coatings are a more recent type of passive fireproofing thin film that swells many times its initial applied thickness, generating an insulating char that functions as a thermal barrier between the fire and structural steel. It keeps the heat of steel members from reaching critical levels and aids in the structural integrity during a fire. They are architects and designers' favorite choice for passive fire protection of load-bearing steel frame structures because of their aesthetic look, versatility, rapidity of application, and ease of inspection and maintenance. In this study, axial tensile, thermal conductivity, and hardness tests have been performed on S235 cold-formed steel specimens that were exposed to increasing temperature periods. The mechanical behavior of coated and uncoated specimens was investigated over the modulus of elasticity, yield strength/strain, and ultimate strength/strain values for all temperatures. As a result of the research, gradually increasing changes were observed in the mechanical properties of coated and uncoated specimens at increasing temperature levels, compared to each other. However, performance increment on the coated specimens was limited in terms of strength and strain characteristics than expected. Two essential reasons for this conclusion are that the specimens were exposed to heat for a long time after reaching the target temperature and also that the wall thickness of the specimens was thinner with respect to the usual application method of the protective coating. In order to examine the structural properties of the test specimens after elevated temperature effects, thermal conductivity measurement was also performed. Temperature difference between coated and uncoated surfaces provided a benefit in the range of 29-56% due to the coating. Lastly, microstructure imaging techniques demonstrated grain coarsening and no crack development with the increase in temperature.

Research on Thermal Response Behavior of the Intumescent Coating at High Temperature: An Experimental and Numerical Study

Intumescent coating is able to provide effective fire protection with both practicality and aesthetics. In this study, expansion performance and thermal physical property experiments are firstly carried out to obtain the basic parameters at different temperatures. Then, the thermal response model of the concrete-filled steel tubular (CFST) structure under the protection of intumescent coating in a fire is established. Finally, based on the experimental data and thermal response model, the effects of initial thickness, expansion rate, intra-pore emissivity and reaction heat on the structure temperature are discussed in detail. The results of this study can provide guidance on intumescent coating formulation design, as well as fire protection design.

Combined Heat Transfer Mechanisms in the Porous Char Layer Formed from the Intumescent Coatings under Fire

This study examines the combined heat transfer by thermal conduction, natural convection and surface radiation in the porous char layer that is formed from the intumescent coating under fire. The results show that some factors, such as the Rayleigh number, conductivity ratio, emissivity, radiation–conduction number, void fraction and heating mode have a certain effect on the total heat transfer. In addition, the natural convection of the air in the cavity always inhibits surface radiation among the solid walls and thermal conduction, and the character of the total heat transfer is the competition result of the three heat transfer mechanisms.