## 3 Mechanical Behaviors
### Dynamic Compressive Strength and Dynamic Increase Factor (DIF) at Room Temperature
#### 3.1.1 Influence of Strain Rate  
The relation between strain rate and dynamic compressive strength of DSC at room temperature is presented in Figure 3. It can be clearly characterized in Table 5 and Figure 3 that strain rate had a strong effect on the dynamic compressive strength of DSC at room temperature. The dynamic compressive strength increased with the enhancement of strain rate at room temperature, which was in line with previous studies [34]. This phenomenon can be analyzed as follow: As a result of generation of new cracks and propagation of cracks, concrete specimens gradually appeared damage in the compressive process. The generation and propagation of cracks required consuming energy and the energy consumed for generation of cracks was far more than the propagation. The quantity of cracks increased with the enhancement of strain rate in the compressive process, which indicated that the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Strain Rate (s\({}^{-1}\))**} & \multicolumn{5}{c}{**Compressive Strength Results of DSC at Room Temperature (MPa)**} \\ \cline{2-7}  & **M1** & **M2** & **M3** & **M4** & **M5** & **M6** \\ \hline \multirow{3}{*}{\(1.45\times 10^{-6}\)} & 53.3 & 57.1 & 54.1 & 48.6 & 54.7 & 49.5 \\  & 54.5 & 51.8 & 56.9 & 55.0 & 51.8 & 53.1 \\  & 54.0 & 57.5 & 57.2 & 56.8 & 52.0 & 50.4 \\ \hline average value & 53.9 & 55.5 & 56.1 & 53.5 & 52.8 & 51.0 \\ \hline \multirow{3}{*}{\(1.45\times 10^{-5}\)} & 55.1 & 59.1 & 59.3 & 56.3 & 55.1 & 54.1 \\  & 58.4 & 57.6 & 61.3 & 56.6 & 55.0 & 55.1 \\  & 53.7 & 58.2 & 57.4 & 56.4 & 57.5 & 56.7 \\ \hline average value & 55.7 & 58.3 & 59.3 & 56.4 & 55.9 & 55.3 \\ \hline \multirow{3}{*}{\(1.45\times 10^{-4}\)} & 63.0 & 64.1 & 63.1 & 63.9 & 59.9 & 59.0 \\  & 57.4 & 58.2 & 66.6 & 55.5 & 60.2 & 57.9 \\ \cline{1-1}  & 58.9 & 65.0 & 63.8 & 64.6 & 60.2 & 57.5 \\ \hline average value & 59.8 & 62.4 & 64.5 & 61.3 & 60.1 & 58.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Quasi-static and dynamic compressive strength results of DSC at room temperature. Figure 2: The heating process of desert sand concrete (DSC) specimen. After the dynamic compressive test, the typical failure features of DSC M1 andM6 at different strain rates are shown in Figure 5. As displayed in Figure 5, DSC specimens created a failure shape with an hourglass-like profile in the dynamic compressive test with different strain rates. The production of an hourglass-like profile was due to the friction of the specimen up and down with steel plates in the compressive test. The DSC specimen gradually expanded with the increase of loading in the compressive test. However, the friction between specimens and steel plates up and down constrained the process of expansion. The effect of expansion decreased with the distance away from steel plates. Thus, the middle position of the DSC specimen, which was the minimum effect of friction, had severe damage [17]. The size of the hourglass-like profile became generally decreased with the strain rate, which indicated that the effect of expansion gradually increased with the strain rate. Moreover, it also can be found from Figure 5 that the size of the hourglass-like profile was gradually decreased with the increase of DSRR. This phenomenon was because the desert sand was characterized by small particles and less-angular appearance [45]. The less-angular appearance of desert sand indicated that desert sand easily rolled down after the compressive process. The rolling of desert sand produced fragments. As the enhancement of DSRR, the rolling amount of desert sand and fragments increased. On the other hand, the damage of DSC specimen was more severe with the increase of strain rate as shown in Figure 5. This phenomenon can be analyzed as follows: When the dynamic compressive strength of DSC specimen was tested at low strain rate, a small quantity of micro-cracks appeared and had adequate time to stretch until the failure of the specimen. Meanwhile, the interaction of micro-cracks was weak towards each other.