# Experimental Investigation on Shear Behavior of Dune Sand Reinforced Concrete Deep Beams
## 1 Introduction  
With the growth in the scale of infrastructure construction, the demand for river sand is continuing to increase. The lack of fresh water resources in several desert areas has led to a severe scarcity of river sand and consequently increased construction and transportation costs [1, 2, 3]. The use of dune sand (DS), which is abundant in those areas [4], as a fine aggregate to replace some of the river sand in the production of structural elements may be promising. Sand could reduce the volume change of cementitious materials caused by environmental effects to a certain extent, and plays a skeletal role in the concrete. There are many studies on the replacement of river sand by recycled aggregate for concrete production [5, 6], such as recycled plastic aggregates [7], metal lathe waste [8, 9], waste glass [10], and rubber tree seed shells [11]. DS is a very fine aggregate with a mineral composition dominated by quartz, and it is therefore unsuitable as a construction aggregate when used alone [12]. However, mixing it with natural sand improves the gradation and gives the concrete a certain bearing capacity in dry or waterlogged conditions [13, 14, 15]. Therefore, a number of scholars around the world have conducted a lot of research on the feasibility of using DS instead of river sand in the production of concrete. These studies have mainly focused on the engineering properties [16, 17, 18], the mechanical properties [17, 19, 20, 21], durability [22, 23], and workability [24, 25, 26] of DSC. Most of the available studies show that the replacement of river sand by DS as fine aggregate has a positive effect on the performance of concrete. Therefore, some researches on the effect of DS on structural member performance have been carried out. [PERSON] et al. [27] conducted an experimental study on the mechanical properties of DS concrete-filled steel tubular stub columns and beams. Results showed that the failure pattern of the DS concrete-filled steel tubular stub specimens with a DS replacement rate of 10% were similar to those of normal members. The damage mode and mechanism of DSRC beam-column joints were investigated by [PERSON] et al. [28]. The results of the experiment revealed that when the DS replacement ratio was 20%, the ductility of the specimens increased to some extent. [PERSON] et al. [29] also performed shear strength tests on DSRC beams from the Gurbantunggut Desert to assess the feasibility of partially replacing river sand with DS in RC beams. The results of flexural strength tests conducted on beams by [PERSON] [30] showed that cementitious mortar based on DS could be used for improving the flexural strength and stiffness, as well as the ductility of RC beams. The shear transfer mechanism of RC deep beams is relatively complicated and no longer in compliance with the classical plane sectional theory. Numerous studies on the influence of key parameters on the shear performance of CRC beams have been carried out. [PERSON] [31] proposed an optimal strut-and-tie model (STM) by using evolutionary structural optimization and conducted an experiment on eight RC deep beams based on this model. The results showed that the optimal STM could retard the crack expansion and reduce the amount of steel. The experimental results of [PERSON] et al. [32] showed that the shear strength of deep beams increased with decreasing shear span-to-depth ratio. [PERSON] et al. [33] found that the increase in reinforcement area limited the tensile strength of the compression strut, and thus improved the compressive strength of the compression strut, which improved the shear strength of the deep beam. [PERSON] et al. [34] pointed out that the shear strength of RC deep beams can be improved to some extent by reducing the size effect through proper configuration of loading and supporting areas. [PERSON] and [PERSON] [35] found that the diagonal crack width of RC deep beams can be reduced to a certain extent by increasing the number of web reinforcements. [PERSON] et al.