Dynamic mechanical response, energy absorption capacity, and constitutive modeling of polypropylene fiber-reinforced foamed concrete under high temperature

This study utilized a modified split Hopkinson pressure bar apparatus to subject polypropylene fiber-reinforced foamed concrete (PPFRFC) to substantial deformation loading at high temperatures and strain rates. Based on experimental results, the study systematically investigated the coupled effects of temperature and strain rate on the dynamic mechanical behavior of PPFRFC across a broad range of strain rates (0.001 s−1 to 1300 s−1) and temperatures (25 °C–600 °C). The findings revealed that elevated temperatures significantly affected various mechanical parameters including peak stress, plateau stress, elastic modulus, densification strain, dynamic increase factor (DIF), and energy absorption. Notably, with increasing temperature, the strain rate amplified the peak stress, plateau stress, and energy absorption, whereas its influence on the elastic modulus diminished. Microstructural examination revealed the absence of notable cracks in the pore walls after high-temperatures exposure. However, degradation of the cement matrix results in a loose skeleton structure within the pore walls, leading to a considerable reduction in material strength. Finally, a constitutive model was developed, considering the coupling effects of temperature and strain rate. This model accurately describes the mechanical response of the PPFRFC across various stages, including the elastic, plateau, and densification stages, as well as the stress drop behavior in the transition stage. Moreover, it effectively reflects the influence of strain rate and temperature coupling effects on the material's mechanical properties.