Study on dynamic mechanical properties of high-temperature concrete with different cooling methods

Concrete materials are widely used in the construction of infrastructure and defense facilities. In order to study the dynamic mechanical properties of high-temperature concrete with different cooling methods, the dynamic mechanical properties of C30 cylindrical concrete samples at different temperatures with different cooling methods were tested by $\varnothing$74 mm split Hopkinson pressure bar (SHPB), and their mechanical properties under the combined influence of heat, water and force were obtained, while the effects of cooling methods, temperature and loading velocity on the average strain rate were studied, with the focus on the analysis of the dynamic stress-strain curve of high-temperature concrete with different cooling methods, as well as the effects of cooling methods, temperature and loading velocity on its crushing morphology, dynamic compressive strength, elastic modulus, peak strain and a range of dynamic effects. The main findings are as following. In the static mechanical tests, the peak points of the concrete stress-strain curve are shifted down and to the right with the two cooling methods. The average strain rate of concrete specimens is more obviously affected by temperature during water-cooling, and the loading velocity is approximately varying linearly with the average strain rate under different cooling methods. When the temperature reaches 400 °C or above, the color of the sample changes significantly, and cracking, at the same temperature, the water-cooled sample is darker than the air-cooled color, more fine cracks appear, and the aggregate morphological damage is more serious. The dynamic stress-strain curves of concrete under different temperatures and cooling methods maintain their basic shape, and the dynamic compressive strength of concrete with different cooling methods is proportional to the loading velocity and inversely proportional to the heating temperature. The damage coefficient of elastic modulus of concrete under various loading velocity and temperatures when cooled by water is lower than that under air cooling. The peak strain of high-temperature concrete is directly proportional to the heating temperature and inversely proportional to the loading velocity, and the peak strain under water cooling is higher than that under air cooling. The dynamic increase factor (DIF) of concrete is proportional to temperature and loading velocity, and the higher the temperature, the more obvious the strain rate effect of concrete. When the temperature is 200 °C, the energy consumption coefficient of concrete rebounds.