# Analysis of the Aggregate Effect on the Compressive Strength of Concrete Using Dune Sand
## 1 Introduction  
Among its components, the aggregate accounts for approximately 60-70% of the total volume of concrete; thus, it has a significant impact on concrete properties. In general, concrete aggregate can be classified as fine aggregate (FA) or coarse aggregate (CA). The workability and mechanical properties of concrete vary depending on the physical properties and mix proportions of the different aggregates. In some regions, three or more types of aggregates are used because of the quality characteristics of the aggregates produced in those regions. As the number of aggregates used in a concrete mix increases, the influences of each aggregate on the properties of the concrete become increasingly complicated. Therefore, to optimize the basic properties of concrete, including workability and strength, significant attention needs to be paid to the proportions of aggregates used in the concrete mix. In the Middle East and North Africa, crushed sand (CS) and dune sand (DS) have been used as FAs for concrete. However, the CS produced in these regions does not meet the standard particle size requirement for a FA because it is composed of relatively large particles with angular shapes. Unlike CS, DS is composed of relatively small particles with spherical shapes [1]. Due to these properties, if only CS is used for concrete production, the workability of the resulting concrete is considerably low, which makes it quite difficult to perform pumping and compaction when the concrete is used in construction. However, mixing these two types of FAs could effectively improve the workability of concrete because each FA could compensate for the drawbacks of the other. [PERSON] et al. [2] performed basic experiments on DS mortar and concrete and reported that 28-32% was the appropriate proportion of CA in a DS mix to ensure concrete workability. [PERSON] et al. [3] reported that when DS and CS were used together as FAs, theslump of the resulting concrete increased until a DS replacement ratio of 50% was attained; thereafter, the slump decreased as the DS replacement ratio increased. [PERSON] et al. [4] conducted research on high-flow sand concrete composed of DS and river sand (RS). They reported that the fluidity of the resulting concrete improved by up to 10% when DS (with a fineness modulus, FM = 1) was replaced by RS (FM = 3.03), wherein the RS particles met the standard particle size requirement for a FA. [PERSON] and [PERSON] [5] examined the differences in the basic properties of mortar based on different mix proportions of DS and CS sourced from four regions of Egypt, and found that the slump increased as the DS replacement ratio increased up to 70%. [PERSON] et al. [6] studied the mechanical properties of sand concrete composed of RS, DS, CS, or RDS (i.e., RS + DS, 1.7:1) and observed that the performance of the concrete could be improved by improving the particle size distribution through the addition of DS. As discussed above, although improvements in the workability of concrete have been reported when a certain proportion of a FA with a large FM, such as CS, is added with DS, different results have been obtained in terms of the compressive strength properties of the resulting concrete. [PERSON] et al. [3] reported that the compressive strength of concrete decreased as the DS replacement ratio increased. [PERSON] et al. [7] examined the properties of sand concrete composed of DS and CS and reported that the compressive and flexural strengths of this sand concrete were lower than those of sand concrete composed of only CS. [PERSON] and [PERSON] [5] observed that the compressive strength of sand concrete slowly decreased as the DS replacement ratio increased up to 70%; however, it rapidly decreased thereafter. In contrast, [PERSON] et al. [8] reported that the compressive strength of concrete increased until a DS replacement ratio of 15% was attained; however, it slowly decreased thereafter. In addition, [PERSON] et al.