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.

This study investigates the impact of high temperatures on the mechanical properties of fire-protected versus unprotected S235 cold-formed steel (CFS) specimens with variable thicknesses. Through axial tensile tests, we assessed how intumescent coatings influence the behavior of steel under fire-like conditions. The results reveal that as temperatures increase, the mechanical strength of unprotected steel diminishes significantly, especially at temperatures beyond 400 °C. However, at temperatures between 500 and 900 °C, coated specimens demonstrate considerably enhanced strength compared to their uncoated counterparts. The coating effectively reduces the steel’s temperature exposure by approximately 200 °C, crucially preserving its integrity at critical temperatures. The thickness of the steel also plays a role, with thicker specimens maintaining higher ultimate strength up to a threshold temperature. The study culminates in a predictive analytical model that estimates the ultimate strength of coated and uncoated steel based on temperature and specimen thickness. These insights contribute substantially to the design of safer, more fire-resistant steel structures.

In this study, it is aimed to investigate the properties of the most commonly used metal and alloy steel materials, which are used in our country and in the world as engineering materials, under the influence of fire of the rebar in the concrete. Inspection standard TS 708:2010 S420 quality 8 mm diameter ribbed construction iron bars for 90 minutes in resistant furnace, atmospheric environment at 600 °C, 800 °C and 1000 °C concrete inside and outside the concrete at the specified temperature fire simulation, the process was allowed to cool in air. With the protective environment created by reinforced concrete, the temperature directly affecting steel bars located outside the concrete under the same conditions, The variable properties of the sample, which are inside the concrete and outside the concrete, were evaluated comparatively. Surface images of the specimens prepared in metallography were taken at different magnifications. The tensile strength of rebar bars did not change significantly according to the environment, but the samples in the concrete showed a more ductile tendency than the samples outside the concrete. The hardness values of the steel bars in the concrete and the steel bars other than the concrete decreased as the temperature increased and this decrease was higher in the samples in the concrete.