Study on dynamic mechanical properties and damage evolution model of C80 concrete

In order to accurately assess the response of a structure when subjected to impact or vibration loading, there is an urgent need to carry out studies on the dynamic mechanical properties of high-strength concrete. Impact tests on C80 concrete with different combinations of stress wavelengths and strain rates were conducted using a 75 mm SHPB test system and compared with dynamic impact tests on C35 plain concrete. The following conclusions can be obtained: Under the action of multiple impacts, the cumulative damage of C80 concrete and the number of impacts show the form of "rapid rise - smooth development-rapid rise." The dynamic strength of C80 concrete is positively correlated with the peak strain and strain rate, and the increase of stress wavelength and impact velocity raises the overall development trend of peak strain. As the impact velocity increases, the cumulative damage increases significantly while the number of repeated impacts gradually decreases. The established C80 concrete cumulative damage evolution model can calculate the physical significance of the model parameters and simultaneously reflect the impact velocity and impact number. Additionally, it confirms the model's logic and accuracy of the physical parameters, which might serve as a particular benchmark for related studies. Comparative analysis shows C35 exhibits greater deformability than C80 at equivalent strain rates (80 s^-1). The growth in peak strain for C35 surpasses that of C80 as strain rates escalate from 50 s^-1 to 80 s^-1, with C35's strain-rate curve showing a steeper slope. Microstructural analysis attributes C80's restrained deformation to its denser matrix, which enhances strength retention but limits crack propagation. These findings provide critical insights for material selection in protective structures.