The approximation of concrete thermophysical properties for solving a nonlinear heat conduction problem under fire conditions

This article is devoted to approximating thermophysical properties of concrete when solving a nonlinear heat conduction problem. The study is relevant to engineers in the context of assessing the fire resistance of concrete building structures and improving their safety during fire conditions. Various types of concrete, ranging from lightweight to heavy, and their behaviour under high-temperature heating were considered. Special attention was given to the influence of porosity, aggregate composition, and moisture content of concrete on the thermophysical characteristics of the material. New approximation formulas for the thermophysical properties of concrete as a function of density and temperature were obtained. The results were confirmed by comparison with existing models and regulations. The obtained results can be used to improve existing engineering approaches and develop new standards.