Investigation on the temperature-strain rate coupled mechanical behavior and constitutive modeling of foamed concrete using a high-temperature viscoelastic SHPB technique

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This study aims to investigate the coupled effects of temperature and strain rate on the dynamic mechanical behavior of foamed concrete (FC) and to establish a reliable constitutive model for its stress-strain response. To achieve this, an improved high-temperature viscoelastic split Hopkinson pressure bar (HT-VSHPB) apparatus was developed, which enables dynamic compression tests on FC at temperatures up to 600°C. Using this method, the compressive responses of FC were systematically examined across a wide range of temperatures (25–600 °C) and strain rates (500/s-1300/s). The results show that the strength of FC decreases significantly with increasing temperature, while its strain rate sensitivity is greatly enhanced at elevated temperatures. This behavior is mainly attributed to the decomposition of hydration products, pore coarsening, fiber melting, and elevated pore gas pressure, which collectively amplify stress wave interactions and crack formation. Based on these findings, an enhanced constitutive model was proposed by incorporating strain rate and temperature terms together with a residual stress function, which accurately reproduces the stress peak and plateau behavior of FC under coupled high-temperature and dynamic loading conditions. The proposed methodology and model provide both experimental and theoretical insights into the performance of FC in extreme environments and are expected to offer valuable guidance for its design and application under more demanding service conditions.