## 1 Introduction  
Sand, defined as natural gravel deposit or crushed rock, is a non-renewable resource [1]. Sand is often used in concrete or mortar as fine aggregate and plays a significant role in building construction. However, high demand from the development of construction has required excessive sand over the years. The exploitable yield of river sand has exceeded 10 billion tons for the last decade [2], which causes threats to the environment. Therefore, it is crucial to identify alternative materials to reduce the dependency of non-renewable sand. Thus, locally available desert sand was used in this study. Chinese National Standard BJG19-65 [3] classifies fineness modulus of sand below 1.5 as superfine. The fineness modulus of desert sand, which ranges between 0.194 and 1.009 [4; 5; 6; 7], was not frequently considered in concrete production due to its low workability. Previous studies indicated the possible application of desert sand in concrete [1; 4; 5; 6]. The workability of desert sand concrete (DSC) increased with the enhancement of desert sand replacement ratio (DSRR) up to 50% since the spheres shape of desert sand moved easier compared to angular or awkward shapes of particles [1; 5]. The sand/cement ratio also had a significant effect on the workability of DSC. The desert sand filled the internal gap of concrete as the sand/cement ratio was below 1.14, which did not decrease the workability of DSC [4; 6]. However, the workability reduced when the sand/cement ratio was over 1.14, because of the excess layer of water absorbed on the surface of desert sand. Thus, desert sand had a great workability under proper or suitable conditions. Besides that, many studies have been carried out to investigate mechanical behaviors of DSC and mortar containing desert sand [1; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15]. Conclusions differed with each other since region of desert sand or experimental conditions were different. The compressive strength and tensile strength of drying shrinkage cracking of concrete increased firstly, and then decreased with the enhancement of desert sand [7]. The increases of both strength values were because the compaction increased with the enhancement of DSRR. At the same time, the decreases of both strength values were because the round particles of desert sand decreased the cohesive force between coarse aggregate and grouts. Besides, both strength values had a maximum value when the DSRR was 20%. Meanwhile, the mechanical behaviors of concrete containing Mu Us desert sand (China) after elevated temperature (tensile splitting strength, axial compressive strength and elastic modulus) had the same trend with the enhancement of DSRR and reached the optimal value with DSRR of 40% [8; 9]. However, the compressive strength, tensile strength, and static modulus of DSC gradually decreased with the increase of desert sand (Oman) [1]. This was because the increase on the surface of fine aggregate required more mortar to coat and the mortar of coating coarse aggregate decreased. Meanwhile, the maximum value of decrease of strength values was less than 15%. The 20% desert sand (Algeria) and 20% crushed sand, 60% desert sand (Tunisia), and 40% crushed sand could provide a great compressive strength for self-compacting concrete and concrete for pavement applications [10; 11], respectively. The highest compressive strength of concrete containing Mu Us desert sand decreased by only 3% compared to that of plain concrete [12]. Besides, the optimal value of the water/cement ratio was 0.4. According to these above studies, it was feasible that desert sand was employed in concrete as fine aggregate. The improvement of feasibility may be due to different experimental conditions. The current research mainly focused on the static mechanical behavior of DSC and mortar containing desert sand exposed to different temperatures. However, buildings may also subject to crash or impact loading during the period of service.