Temperature effect on the thermal-physical properties of fire-protective mineral wool cladding of steel structures under the conditions of fire resistance tests

Abstract

The value of the thermal conductivity coefficient depending on the temperature of the samples of steel rod fragments with fire-retardant cladding has been deter mined in the present research. The thermal conductivity coefficient of mineral wool fire-retardant cladding was determined; special patterns of its depen dence on temperature were revealed. This is explained by the thermal decomposi tion with the release of thermal energy of inclusions between the fibers of min eral wool and its fibers at a temperature of 750 °C. The apparent minimum of the thermal conductivity factor for fire-retar dant mineral wool cladding with a thick ness of more than 50 mm is observed at a temperature of about 100 °C. This hap pens due to the fact that at this tempera ture the free moisture contained between the fibers of the mineral wool evaporates. Generalized temperature dependence of the thermal conductivity coefficient of mineral wool fire-retardant cladding has also been derived, in a tabular form. It can be used for calculating the tempera ture in steel structures with such fire pro tection. The thickness range for applica tion is up to 80 mm for the specific heat capacity of 1,000 J/(kg °C) and a density of 200 kg/m3. It is shown how the obtained depen dence can be used for predicting heat ing in steel structures with fire-retardant mineral wool cladding. The relative error between the calculated and experimen tal data was calculated. The Cochrane, Student, and Fischer criteria for the results of temperature calculation in steel structures with fire-retardant mineral wool cladding between the calculated and experimental data accept values that do not exceed the tabular quantities. This means that the results of the calculation using the obtained temperature depen dence of the thermal conductivity coeffi cient are adequate