Abstract:

In order to predict the temperature field of SFRC structures under fire, the apparent density, porosity, thermal conductivity,thermal diffusivity and specific heat capacity of SFRC after elevated temperature were studied. The mechanism of thermal conductivity decline was analyzed by numerical simulation in meso scale. The research indicated that the apparent density, thermal conductivity, specific heat capacity and thermal diffusivity of SFRC decrease with the rise of heating temperature,while the porosity increases in 1%~3%due to heating and the thermal cracking. On the basis of mesoscopic finite element analysis, the crack thermal resistance effect of thermal cracks generated during heating is one of the important reasons for the decrease of thermal diffusivity of mortar and concrete with the increase of temperature. When the heating temperature reaches 300 ℃, the thermal diffusivity of SFRC has an inflection point beyond which the thermal conductivity shows an upward trend. For the same heating temperature, the thermal conductivity andthermal diffusivity show an upward trend with the increase of steel fiber content.

Key words: high performance concrete, steel fiber, elevated temperature, thermal properties, crack thermal resistance