## 1 Introduction  
Foamed concrete can be considered to be a cellular material containing many pores, with their distribution, shape, and size being significant factors controlling the material characteristics of the concrete [1]. It has high flowability and high thermal insulation properties [2; 3]. Foamed concrete is used as a promising construction material in several fields, due to its reduced energy consumption, low cost, high thermal insulation, and energy saving characteristics [4; 5]. It has low self-weight, a low cement content, and low aggregate usage [6]. Foamed concrete can be produced with different densities, ranging from 400 to 1600 kg/m\({}^{3}\)[1; 7]. Due to its numerous advantages, foamed concrete can be applied in many civil engineering areas, such as filling insulation, lightweight blocks, thermal and acoustic insulation, trench reinstatement, and soil stabilization [6; 8]. Pore size distribution and pore volume and shape strongly affect the microstructure and characteristics of foamed concrete [9; 10]. [PERSON] et al. [11; 12] examined the influence of pore size, distribution, and shape on the properties of foamed concrete with different densities with the help of X-ray micro-computed tomography (micro-CT) imaging. They reported that as the density increases, the size of the pores becomes smaller. Moreover, the density of the solid part of the foamed concrete influences pore size and shape because of the ability of the solid structure to hold the pores inside the concrete specimen. With increasing the foamed concrete density, the microstructure becomes more compact and denser [12]. As such, the physical and mechanical properties of foamed concrete can be adjusted by controlling its density. Foamed concrete contains many pores, which enhances thermal insulation. However, this also has a negative effect on compressive strength and stiffness, which are both significantly decreased [13; 14; 15]. In addition to pore shape and size, foam stability has a considerable effect on the properties of foamed concrete. Several parameters influence the stability of foamed concrete, including the amount of foam added and the water content in the cement paste [16]. The basic materials for foamed concrete are cement, water, and foam. Sometimes fine sand, fly ash, superplasticizer, fibers, or silica fume are used as well [17]. [PERSON] et al. used directional composite grid reinforcement to improve the mechanical properties of foamed concrete [18]. For a given dry density, foamed concrete prepared using fly ash as a filler has better mechanical properties than the equivalent sand-based foamed concrete [19]. Foaming agents are commonly synthetic, with their content and type having a considerable influence on the properties of both fresh and hardened foamed concrete [20]. The quality of the foam is of great importance in the production of foamed concrete, because it influences the stability of the foamed concrete in the fresh state and significantly affects its stiffness and strength in the hardened state [21]. In foamed concrete mixtures, strength is strongly influenced by the type and dosage of foaming agent, as well as by the water:solid ratio [6]. [PERSON] et al. demonstrated that there is a strong relationship between the water:solid ratio and the type of foaming agent used, with both factors influencing the final characteristics of foamed concretes [22]. The stability of the concrete mix depends mainly on the water:solid ratio, as well as on the foam quantity and quality. These parameters also have considerable influence on the consistency of foamed concrete [23]. One of the main disadvantages of foamed concrete is the high drying shrinkage that takes place at early ages [24; 25]. Due to the absence of coarse aggregates in the foamed concrete, its drying shrinkage is about 4-10 times higher than that of traditional concrete [6]. The incorporation of supplementary materials can reduce both drying shrinkage and hydration heat [26].