Residual physio-mechanical properties and degradation analysis of foamed concrete exposed to elevated temperatures

High-strength and thermally resistant foamed concrete is increasingly demanded in low- to mid-rise energy-efficient buildings, serving as insulating material as well as part of the structural systems in lightweight load-bearing applications. Existing studies characterized foamed concrete strength below 600 °C and thermal/durability properties above 600 °C but inadequately addressed mechanical degradation beyond this threshold. Following the standard procedures for post-fire assessment of buildings, the foamed concrete with densities of 625 and 750 kg/m3 were investigated after exposure to temperatures ranging from ambient to 800 °C, with an emphasis on the residual mechanical properties and macroscopic morphology. The experimental results indicate that fire exposure temperature is the dominant factor affecting the morphological evolution and mechanical degradation, whereas density has a limited influence on the post-fire appearance in low-density mixes. The uniaxial compressive strength, splitting tensile strength, and elastic modulus exhibit similar degradation trends with increasing temperature. Degradation functions are proposed for the stress-strain relations and the compressive and splitting tensile strength for post-fire evaluation. Additionally, the underlying chemical degradation mechanisms responsible for the strength loss is revealed through thermogravimetric and differential scanning calorimetry analyses. These results provide a valuable basis for the structural application and fire safety assessment of high-performance foamed concrete.