PERFORMANCE OF FIRE PROTECTING MATERIALS FOR STRUCTURAL STEEL

Abstract

Steel as a material of Civil Engineering construction is very extensively used. It is used both in conjunction with some other materials such as cement-concrete in the shape of reinforcing bars as well as independently in the shape of various structural forms (I, Channel, Ti Angle sections). Its independent use in the construction of industrial sheds, bridges and high-rise buildings (70-storey and above) has shown definite advantages interms of good strength-to-weight ratio, small cross sectional area, resistance to vibrations and overall cost. However, at high temp. (above 350°C), steel appears to undergo certain changes in its properties which are quite detrimental to its use in situations such as fire. Properties like strength, modulus of elasticity and creep yet substantially altered turning many advantages into disadvantages. Steel itself is noncombustible but is a good conductor of heat. It, therefore, becomes essential to protect steel structural sections from agencies such as fire causing rise of temperature in them. Reinforcing steel bars have a natural protecting material in the form of cement concrete around them. It is only for naked structural steel sections that protection against fire is needed. In the present study, certain heat insulating materials have been investigated for their effectiveness with regard to the rise of temperature and dimensional stability when subjected to intensive fire protecting materials studied here in are gypsum, gypsum-vermiculite mix, cement-vermiculite mix, cement-concrete and fire resistant paint. Experiments have been designed and carried out with a view to studying the relative performance of these materials in providing a temperature shield to the steel plate. Relevant conclusions arrived at are presented in the dissertation.