# Effect of Different Gradings of Lightweight Aggregates on the Properties of Concrete
## 1 Introduction  
Concrete is a representative building material and has a very important role in the construction field. Since the control of energy consumption has become a worldwide issue, many efforts have been performed to enhance energy efficiency in the field of building and concrete materials. Among the various types of concrete for special applications, lightweight concrete has been widely used due to its advantageous characteristics, such as lower density and higher insulation effect than those of conventional concrete [1; 2]. According to EN 206, lightweight concrete is a material with density lower than 2000 kg/m\({}^{3}\), and it contains natural or synthetic lightweight aggregates (lightweight aggregate concrete) or foam agent (foamed concrete) to reduce the weight of material; this material can be used for both structural and nonstructural purposes, i.e., insulation and concrete block [3; 4]. To produce lightweight aggregate concrete, several types of materials have been used as lightweight aggregates. [PERSON] et al. [5] used sawdust and water treated sludge as lightweight aggregates and confirmed its effect to reduce the environmental impact. [PERSON] et al. [6] utilized raw rice hush for lightweight concrete and demonstrated that the material can be used as a filling material to improve the mechanical performance of concrete. [PERSON] et al. [7] used hollow nanospheres from fly ash as lightweight aggregates for the material and confirmed its effect on the improvement of tensile strength. [PERSON] et al. [8] used a recycled municipal solid waste incinerator (MSWI) fly ash as lightweight aggregates and showed that the material can effectively be utilized as lightweightaggregates with average performance. [PERSON] et al. [9] used ferrochromium slag to improve the performance of lightweight concrete and confirmed that the material endowed a dense microstructure and high bond strength of the interfacial transition zone. [PERSON] and [PERSON] [10] produced lightweight concrete with volcanic scoria aggregates, and the obtained material showed better mechanical behavior at high temperatures than conventional concrete. [PERSON] et al. [11] used recycled polyolefins waste and demonstrated that this material can be used as a sustainable practice in lightweight concrete manufacturing. [PERSON] et al. [12] utilized nanosilica for lightweight concrete and showed its impact on the workability of self-compacting lightweight concrete. [PERSON] et al. [13] evaluated the performance of the material with silica fume for 91 days and confirmed its advanced durability against chemical deterioration. In addition, artificial lightweight aggregates, such as Poraver(r) (Postbauer-Heng, Germany), Leca(r) (Randers SV, Denmark), and Liaver(r) (Ilmenau, Germany), are also utilized for lightweight aggregate concrete due to their low densities and advanced properties [14]. In general, lightweight aggregates occupy more than 50% of the volume of concrete, and the total volume of the lightweight aggregates is a significant factor to determine the properties of lightweight concrete. For example, the density of lightweight concrete, which is a factor that strongly affects both mechanical and thermal properties, varies between 800 and 1500 kg/m\({}^{3}\) depending on the volume of lightweight aggregates [15], and when the specimen contains a large volume of lightweight aggregates, the density and thermal conductivity decrease, while the stiffness and compressive strength also tend to decrease [16]. In addition, the physical properties of lightweight concrete, such as density, and mechanical and thermal properties, are affected significantly by the characteristics of lightweight aggregates [17]. Therefore, a proper use of the lightweight aggregates should be carefully considered to produce lightweight concrete with acceptable performance for both mechanical and thermal responses.