## 3 Test Results and Discussion
### Energy Dissipation Analysis  
The energy consumed by the specimen is a comprehensive reflection of the two mechanisms of strength and ductility. The energy dissipation performance of concrete is mainly affected by the external impact energy and internal initial damage state. The external impact energy causes the initiation, development, penetration, and destruction of concrete cracks, which consume a lot of energy. The initial defects formed in the processes of preparation and maintenance of the specimen affect the ability of the specimen to resist the impact load, and then affect the macro-energy performance of the specimen.  
The process of the dynamic splitting and failure of the specimens was essentially a process of energy transfer and conversion. Ignoring the energy loss between the rods, the bullet impacted the input bar under high pressure and converted kinetic energy into incident energy, which was transferred in the form of stress waves and finally converted into reflected energy, transmitted energy, and dissipated energy. The formula for calculating the energy carried by the stress wave propagation process in an SHPB test is as follows:  
\[W_{\text{I}}=AEC_{0}\int e_{\text{I}}^{2}(t)\text{d}t \tag{1}\]  
\[W_{\text{R}}=AEC_{0}\int e_{\text{R}}^{2}(t)\text{d}t \tag{2}\]  
\[W_{\text{T}}=AEC_{0}\int e_{\text{T}}^{2}(t)\text{d}t \tag{3}\]  
where \(W_{\text{I}}\) is the incident wave energy, \(W_{\text{R}}\) is the reflected wave energy, and \(W_{\text{T}}\) is the transmitted wave energy. \(\epsilon_{\text{I}}(t)\), \(\epsilon_{\text{R}}(t)\), and \(\epsilon_{\text{T}}(t)\) are the incident strain, reflected strain, and transmitted strain at time \(t\), respectively. \(C_{0}\) is the wave velocity in the bar, \(A\) is the cross-sectional area of the press bar, and \(E\) is the elastic modulus of the material. Ignoring the energy loss between the bar and the specimen when the stress wave propagates, the dissipated energy of the specimen (\(W_{\text{s}}\)) is calculated as follows:  
\[W_{\text{s}}=W_{\text{I}}-W_{\text{R}}-W_{\text{T}} \tag{4}\]  
According to the above formula, the variation law of the dissipated energy of the concrete specimens treated at different temperatures in the dynamic compression test and dynamic splitting test is shown in Figure 11. With the increase in the temperature, the energy absorption value of the samples in the two groups of tests gradually decreased, showing a strong temperature effect. At a high temperature, the cohesiveness and viscoelasticity of the test specimens decreased due to various thermal damages caused by the high temperature, such as the decomposition of gelling products and the weakening of the interface adhesion in the transition zone. The energy absorbed by the specimen for crack  
Figure 10: Dynamic compressive strength at different temperature.  
initiation development increased, and the energy dissipation increased. However, as the temperature increased, the strength of the specimen decreased continuously, the absorbed energy became less under the same impact load, and the absorbed energy required for the specimen to achieve failure decreased. Therefore, in the dynamic splitting test and dynamic compression test, the dissipated energy of the specimens decreased with an increase in temperature.