Effects of thermal properties on temperature field of UHPC structures under fire conditions

Ultra-high-performance concrete (UHPC) is increasingly used for bold structures worldwide due to its exceptional mechanical properties, but its fire performance is not well known. Standards and literature provide limited information and data on the thermal-physical properties of some UHPC mixes exposed to high temperatures. This study aims to partially fill this gap. The thermal parameters of UHPC were determined experimentally and then compared with another UHPC mix proposed in the literature and also with those defined in EN 1992–1.2 for normal strength concrete (NSC). To understand the thermal diffusivity (i.e., the thermal field) of UHPC and NSC structures, a FEM -based numerical application was performed using Abaqus software, assuming the thermal-physical data of UHPC and NSC. Cross sections with the experimentally determined UHPC properties showed quite similar behavior to NSC. However, using the UHPC data proposed in the literature, the thermal diffusion in the cross-section appeared to be much more severe. The thermal-physical properties of UHPC can vary greatly depending on the mix design, with UHPC cross-sections exhibiting a maximum 110% greater thermal field than those simulated with NSC properties.