This paper analyzes the relationship between the rates of change of elastic strain energy, the strength during the concrete failure process, and proposes that the increased dynamic strength of concrete was caused by the hysteresis effect of energy release—according to the basic principle of energy conversion. Dynamic Brazilian disc tests were carried out on concrete specimens, with diameter of 100 mm, by using the split Hopkinson pressure bar. Test results were obtained through using a gas gun, with an impact pressure of 0.15 MPa, 0.20 MPa and 0.25 MPa, respectively. The dynamic failure process of concrete is then reproduced by numerical calculation methods. Finally, the energy characteristics during the concrete failure process at different strain rates are studied, and the enhancement mechanism of the dynamic strength of concrete is verified. The results showed that the dynamic tensile strength of concrete increased by 9.79% when the strain rate increased by 61% from 60.25 s⁻¹; and when the strain rate increased by 92.8% from 60.25 s⁻¹, the dynamic tensile strength of the concrete rose by 46.28%. The rates of change of both input energy and dissipated energy meet at the peak stress of the material. The increases in rates of change for the two kinds of energy were not synchronized, so excess input energy could be stored as concrete strength increased. As a result, the extra energy stored after peak stress led to a higher degree of concrete fragmentation and greater kinetic energy of the fragment. These results offer research directions for improving the dynamic strength of concrete.

In this study, the portable power loading device and medical Marconi M8000 spiral CT scanner are used to conduct the uniaxial compression CT scanning test of the concrete. The concrete porosity, hardened cement rate, and aggregate rate are defined, and the variation law of the concrete is analyzed in the uniaxial compression CT test. The proposed method is considered to utilize the value of each CT number, to realize the quantitative partition of the various components of concrete, and to quantitatively evaluate the damage evolution law of the concrete and strain localization during stress. It is shown that damage at the middle section increased from inside to the outside in the uniaxial compression CT test of the concrete.

The dynamic characteristics of concrete are the key point of the dam seismic safety design. In order to study the dynamic characteristics of concrete, a CT scan test of concrete under dynamic load was carried out; CT scan images of the concrete loading process were obtained. Based on the definition of integrity, integrity area, and intercepted sections in the quantitative zoning theory, the concrete CT images were divided into the hole or crack area (), hardened cement stone area (), and aggregate area (). And the determination method of partition threshold is studied. Then, based on the CT resolution unit, a concrete numerical calculation model of structural random is established, and the numerical simulation experiment of concrete under uniaxial dynamic load is carried out. The results show that the concrete numerical calculation model of structural random is very close to the actual mesostructure of concrete, and the interface thickness between aggregate and hardened cement is very close to the actual interface thickness (which is 40~50 μm). Under the action of dynamic load, the damage of the sample is mainly concentrated in the upper part of the sample, and the damage is easy to occur at the initial defect place, and the damage occurs at multiple points at the same time. The damage crack is relatively straight, the phenomenon of the crack passing through the aggregate is obvious, and the crack expands along the fastest path of energy release.