## 2 Materials and Methods  
### Material Properties and Mix Proportion Design  
The specimens were cast with P\(\cdot\)O 42.5 cement, grade II fly ash natural sand with a particle size of less than 1.18 mm, Kumtag desert sand, and PE fiber. The chemical composition of the desert sand used in the study is listed in Table 1. Sand water absorption tests were carried out according to the operational specifications [46]. The average water absorption of desert sand was 1.1% and that of natural sand was 0.75%. The main water absorption test results of sand are shown in Table 2.  
Particle grading tests were carried out on the sand according to the specifications, and the results showed that the natural sand particles belonged to grading zone III, with fineness modulus Mx = 1.87 and particle grading between 2.3 mm\(\sim\)1.5 mm, which indicates fine sand. The desert sand grain gradation zone belonged to the overfine sand zone, with fineness modulus Mx = 0.60, which indicates powder sand. The main sieving results of sand are shown in Table 3. The PE fiber was acquired from Shandong Laiwu Telfi Company in China. The PE fiber composite material had a surface density of 0.97 g/cm\({}^{3}\) and a single fiber diameter of 24 \(\upmu\)m. The tensile strength, modulus of elasticity, and elongation of the PE fiber were 3000 MPa, 120 GPa, and 5%, respectively. The main mechanical property parameters of PE fiber are shown in Table 4.  
In order to study the section bonding properties of desert sand, the mix was divided into 2 groups. The best PE\(-\)ECC ratio was chosen based on the results of the authors' previous research [47; 48]. The first group was a natural sand group, which was used as a control group of desert sand. The second group was the desert sand experiment group, in which 30% natural sand was replaced and the volume content of PE fiber was 2%. The specific mix proportions are shown in Table 5.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Composition** & **SiO\({}_{2}\)** & **FeO** & **Fe\({}_{2}\)O\({}_{3}\)** & **AL\({}_{2}\)O\({}_{3}\)** & **MgO** & **K\({}_{2}\)O** & **CaO** & **Na\({}_{2}\)O** \\ \hline Content/wt\% & 82.66 & 0.80 & 1.05 & 8.72 & 1.51 & 0.12 & 2.00 & 0.07 \\ \hline \end{tabular}
\end{table}
Table 1: Chemical composition of desert sand.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline  & **Particle Size** & **4.75 mm** & **2.36 mm** & **1.18 mm** & **600 \(\upmu\)m** & **300 \(\upmu\)m** & **150 \(\upmu\)m** & **75 \(\upmu\)m** \\ \hline \multirow{3}{*}{Natural Sand} & Sieve margin/g & 0 & 0 & 0 & 140.45 & 209.45 & 95.75 & 30.74 \\  & Subtotal sieve residual/\% & 0 & 0 & 0 & 28.09 & 41.89 & 19.15 & 6.15 \\  & Cumulative sieve balance/\% & 0 & 0 & 0 & 28.09 & 69.98 & 89.13 & 100 \\  & Sieve margin/g & 0 & 0 & 0 & 17.3 & 45.11 & 156.55 & 272.13 \\ \hline \multirow{2}{*}{Desert Sand} & Subtotal sieve residual/\% & 0 & 0 & 0 & 3.46 & 9.02 & 31.31 & 54.43 \\  & Cumulative sieve balance/\% & 0 & 0 & 0 & 3.46 & 12.66 & 43.97 & 100 \\ \hline \end{tabular}
\end{table}
Table 3: Sieving results of sand.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Density** & **Tensile** & **Elastic** & **Ultimate** & & & \\ **/g/cm\({}^{3}\))** & **Strength** & **Modulus** & **Elongation** & **Length** & **Diameter** \\  & **/MPa** & **/GPa** & **/GPa** & **/\%** & **/mm** & **/\(\upmu\)m** \\ \hline
0.97 & 3000 & 120 & 5 & 12 & 24 \\ \hline \end{tabular}
\end{table}
Table 4: PE fiber performance parameters.