Dynamic mechanical properties of concrete with freeze-thaw damage under different low-temperature conditions

The mechanical properties of hydraulic concrete structures in cold regions are affected by low temperature and freeze-thaw cycles, and their mechanical properties differ greatly compared with those of the room temperature state. Especially for concrete structures with being susceptible to dynamic loads such as earthquakes and collisions, the mechanism involved the effect of low temperature on the dynamic mechanical properties of concrete with freeze-thaw damage is still not clear. The design of different low-temperature environment containing different freeze-thaw damage of concrete dynamic load tests are conducted to reveal the change patterns of dynamic mechanical properties of concrete with initial freeze-thaw damage in the low temperature range of 0 degrees C similar to -30 degrees C. The results show that low-temperature conditions can improve the concrete compactness, and weaken the enhancement effect of high strain rate loading conditions on the concrete strength, which will reduce rate sensitivity of the mechanical properties. Meanwhile, the effect of low temperature can improve the brittleness and compressive strength of concrete and make up for part of the strength loss caused by freeze-thaw damage, and containing different freeze-thaw damage in the mechanical properties of the concrete gap with the reduction of the temperature gradually narrows. Quadratic function relationship exists between temperature and compressive strength together with other mechanical parameters, and the minimum value of R-2 is 0.9721. The stress-strain relationship curve of concrete under low-temperature condition is narrowed, and the brittleness of concrete increases; the damage process becomes more intense, the integrity of concrete is high after the damage, and the number of cracks on the fracture surface decreases significantly.