# Mechanical Properties of Desert Sand-Based Fiber Reinforced Concrete (DS-FRC)
## 2 Experimental Program  
### Mix Proportions and Material Properties  
In this experiment, ordinary Portland cement (P.O 42.5 R), river sand with a particle size under 1180 \(\upmu\)m, fly ash I, undisturbed Mu Us desert sand with a fineness modulus of 0.721, polyvinyl alcohol fiber (PVA) made in Japan, superplasticizer and fresh water were the main ingredients used to prepare DS-FRC. Chemical compositions of raw materials and properties of PVA fiber are revealed in Tables 1 and 2. Besides, the particle size distribution of raw materials and the appearance of river sand and desert sand are showed in Figure 1a-c. It can be observed (see Table 1) that the content of silica in the sand used in this study was lower than that of other researches. In terms of river sand and desert sand, the silica contents were only 45.2% and 74.2%, respectively. Besides, the content of calcium in the fly ash was also low, which may have had a certain impact on the mechanical properties of DS-FRC. PVA fiber with a diameter of 40 \(\upmu\)m and a length of 12 mm was used in this experiment (see Table 2). As clearly illustrated in Figure 1a, the particle distributions of cement and fly ash were comparable with smaller particle size, which will facilitate fiber dispersion. The particle size of desert sand, with a size under 450 \(\upmu\)m, was approximately 2.5 times lower than that of the sieved river sand. The median particle sizes of cement, fly ash, desert sand and river sand were 10.82 \(\upmu\)m, 9.68 \(\upmu\)m, 130.11 \(\upmu\)m, and 235.6 \(\upmu\)m, respectively. As in [29], the strain hardening property of cementitious composites will be activated only when the particle sizes of aggregates are under 300 \(\upmu\)m. However, it is \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Description** & **Al2O3** & **Na2O** & **CaO** & **SiO2** & **P2O3** & **SO3** & **Fe2O3** & **K2O** & **TiO2** & **Cl** & **MgO** \\ \hline
**Cement** & 5.05 & 0.73 & 60.24 & 21.22 & / & 2.67 & 3.26 & 0.50 & / & / & 0.97 \\
**Fly ash** & 23.6 & 13.2 & 6.12 & 38.5 & 1.06 & 2.13 & 7.49 & 1.84 & / & 0.26 & 3.66 \\
**River sand** & 11.8 & 16.0 & 6.87 & 45.2 & 1.01 & 0.58 & 6.33 & 4.65 & 0.86 & 0.33 & / \\
**Desert sand** & 12.3 & / & 4.83 & 74.2 & 0.80 & 0.50 & 3.69 & 2.62 & 0.49 & 0.41 & / \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition analysis of the raw material. Figure 1: Particle size distributions of raw materials and appearances of two sands: (**a**) particle distribution; (**b**) river sand; (**c**) desert sand. worth noting that the particle size of sand used in this experiment was far greater than that recommended by [PERSON], and desert sand exhibits relatively poor particle gradation, which may limit the ductility property of DS-FRC. Additionally, the appearance colors of two sands (see Figure 1b,c) were significantly different due to the differences of material compositions, which was consistent with the results of Table 1. As for the desert sand, its color was slightly reddish while the river sand was gray. It was also observed that desert sand and river sand had less-angular appearances which are anticipated to promote fiber slippage and dispersion and facilitate to the strain hardening development of DS-FRC. The reasonable optimization of raw materials, such as fly ash or fine sand, is the driving force for achieving the successful strain-hardening and multiple-cracks properties of high ductility cementitious composites. Therefore, in this study, ten mixtures were designed to further study the effect of W/B, S/B and DSRR (replacing the equivalent weight of river sand) on uniaxial tensile/compression properties of FRC. The control group without desert sand has been included in previous research [47], so there is no discussion about it. Moreover, the mechanical properties of DS-FRC without superplasticizer were compared to that with superplasticizer.