## 1 Introduction  
The coefficient of thermal expansion (CTE) is a critical parameter that influences the overall service life of concrete pavements. Concrete properties are closely related to the CTE as the CTE reflects concrete's response to internal temperature variations, cracking, and ultimately deterioration. An increased CTE can cause temperature-related distress and thermal cracks in concrete after hardening and during early strength gain. Longitudinal, transverse, and corner cracks during curing are closely related to the development of distress in concrete caused by thermal deformation [1; 2; 3; 4]. In addition, the CTE has a significant influence on the temperature-related damage to concrete structures. Examples include joint openings and the reduction of sealant performance in jointed concrete pavement, crack development and propagation in continuously reinforced concrete pavements, and spalling [1; 5; 6; 7].  
Research efforts have been made to evaluate the CTE of concrete as an input parameter in the recent AASHTO (American Association of State Highway and Transportation Officials) design guide [8; 9; 10]. The CTE is directly influenced by the aggregate type and aggregate volume [6; 11; 12; 13], as well as internal moisture conditions [14; 15; 16] and cement paste [17]. The CTE has shown not to be significantly impacted by water-to-cement ratio [17] and concrete age [14; 18].  
Crushed stone results in higher strength than rounded gravel [19] because angular particles provide better interlocking and the rough surface texture develops a greater mechanical bond with the cement paste. The mineralogy of the aggregate can affect the chemical bonding during cement hydration. The weakest component of the cement paste matrix is widely considered to be interfacial transition zone (ITZ) for the normal strength concrete [20]. [PERSON] et al. [21] reported that the intrinsic strength of the coarse aggregate is not an important factor when the water-to-cement ratio is in the range of 0.5-0.7. Others suggested that rather than the strength of the aggregate, the strength of the cement-aggregate bond is usually the limiting factor in high-strength concrete [22].  
Only a few studies have examined the effect of fine aggregate in concrete. [PERSON] and [PERSON] [23] studied the effect of different types of crushed sand. The codes only include brief requirements for fine aggregate [24]. [PERSON] and [PERSON] [25] reported that the sand fineness modulus has a significant influence on the mechanical properties of concrete. Several studies reported that the presence of fine particles from stone dust with increased surface area contributes to cement hydration and ultimately affects the concrete strength [26; 27].  
In general, aggregates are approximately 60% to 75% of the concrete volume, therefore the types of aggregates play a critical role in determining the CTE of concrete since a variety of aggregates have different values of CTE. In addition, it would be obvious that the mechanical strength of a concrete structure can be affected by the thermal behavior and microstructure of the concrete [28]. Thus, it is essential to evaluate the effect of aggregate type and volume on the CTE and microstructure, especially ITZ region, of concrete. The objectives of this study are: (1) to investigate the correlation between different types of aggregate mineralogy (coarse aggregates (granite and dolomite) and fine aggregates (manufactured and natural sands)) and the performance of concrete specimens in association with the thermal expansion behavior (CTE) and compressive strength, (2) to evaluate the aggregates (surface texts and chemical compositions) and microstructure (micro-pores, micro-cracks and interfaces) of concrete specimens through petrographic examinations including scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses, and (3) to characterize the ITZ region between aggregate and paste matrix by performing the line scanning analyses (SEM and EDX).