PREDICTION OF THE THERMAL SPALLING RISK OF CONCRETE STRUCTURES EXPOSED TO HIGH TEMPERATURES

A very characteristic mode of concrete damage at high temperature, especially for the materials characterized by a low intrinsic permeability, like for example HPC or UHPC, is so called thermal spalling. In this paper the results of simulations performed with a mathematical model, which considers concrete as multiphase porous material, are applied to define some spalling indexes based on various collapse mechanisms. A validation of the quantities proposed, carried out by means of a comparison with some experimental test results, is presented. Moreover, the results of a simulation dealing with a structural element exposed to a parametric fire, including a cooling phase, usually not considered in analyses, is described and discussed.