Experimental investigation of the post-fire dynamic mechanical properties of concrete exposed to fire

The mechanical properties of concrete structures can be affected in high-temperature environments, such as extreme situations like fires. Studying these changes can help ensure the safety of structures in extreme environments. In this work, a large-diameter (74 mm) split Hopkinson pressure bar combined with high-temperature treatment and high strain rate impact was used to test the dynamic mechanical properties of concrete specimens exposed to different temperatures (100°C, 200°C, 400°C and 600°C). A damage evolution equation considering temperature and strain rate was established, and the impact mechanisms of high temperature on the aggregate–cement interface and the aggregate itself were assessed through analysis of failure modes, crack development and fragment size. The results showed that, for an exposure temperature below 400°C, the concrete performance did not decrease significantly. However, above 400°C, the dynamic strength and elastic modulus decreased significantly, crack development was intensified and the failure mode showed fundamental changes. Comparison with experimental data showed that the developed damage evolution equation can effectively simulate the impact resistance of concrete materials under different temperature and strain rate conditions.