# Effect of Dune Sand on Drying Shrinkage Cracking of Fly Ash Concrete
## 1 Introduction  
It is essential for concrete structures to continue to perform their intended functions during their expected service lives. It follows that concrete must be able to withstand the processes of deterioration to which it can be expected to be exposed [1]. That is, it is necessary to make concrete durable, and an appropriate concrete mix for the specific environment to which the concrete structure is exposed should be determined [2; 3; 4]. Many countries on the Arabian Peninsula have continuously invested in the development of infrastructure. In particular, they have invested the most significantly in the construction of petrochemical and power plants, and global contractors have been conducting many related projects. These structures are mainly located along the coast of the Arabian Peninsula, and the groundwater and subsoils in coastal areas are likely to be contaminated with various salts that are aggressive to concrete [5]. Therefore, corrosion induced by both chlorides from sea water and chemical attacks should be considered when designing concrete for durable coastal structures. Various international and regional codes provide guidelines for durable concrete mix design. Among them are the BS (EN) codes and the ACI codes, which are widely used internationally. On the Arabian Peninsula, specifications based on the BS codes are applied in most projects. According to the BS codes, the maximum water/cement ratio, minimum cement content, and minimum compressive strength are limited for the design of durable concrete structures in special environments. In particular, to address the chemical attack of underground structures, the type of cement is limited to prevent the concrete from deteriorating. Instead of ordinary Portland cement (OPC), it is recommended to use sulfate-resisting Portland cement or a combination with a large amount of fly ash or ground-granulated blast-furnace slag. In addition, the climatic and material conditions should be considered in order to ensure the consistent quality of the structural concrete on the Arabian Peninsula. First, the Arabian Peninsula lies in hot and dry desert climate zones. This area has a higher risk of concrete cracking caused by increased plastic and drying shrinkage. As a raw material for concrete, dune sand (DS) is used as fine aggregate (FA) for concrete in this area. DS has a spherical grain shape and a smooth surface, and it can help improve the grading of crushed sand (CS). However, most of the particles in DS are smaller than 0.6 mm. Thus, the excessive use of DS may reduce workability by increasing viscosity [6]. Many studies have been conducted on the characteristics of concrete that used DS as an aggregate, and most of them have been focused on strength and workability [7; 8; 9; 10; 11; 12]. However, as previously mentioned, a high risk of cracking is evident on the Arabian Peninsula due to drying shrinkage. Therefore, it is necessary to examine the characteristics of drying shrinkage cracking of concrete in this area. As previously mentioned, sulfate-resisting Portland cement or a combination with fly ash or ground-granulated blast-furnace slag should be used as a binder for structures in coastal areas on the Arabian Peninsula. In order to review the drying shrinkage cracking characteristics of concrete for structures in this area, an experimental study considering binders other than OPC is required. Some researchers have studied the characteristics of geopolymers made with fly ash or ground-granulated blast-furnace slag as a binder and DS [13; 14]. The properties of blended cement mixtures incorporating ground DS and ground-granulated blast-furnace slag have also been studied [15; 16]. However, the material conditions and shrinkage cracking properties of concrete for coastal structures on the Arabian Peninsula were not considered in these investigations.