# A Detailed Review on Foam Concrete Composites: Ingredients, Properties, and Microstructure
## 1 Introduction  
Foam concrete is a type of concrete that is produced by locking air voids in the mortar with the help of a suitable foaming agent and is classified as lightweight concrete. It has low self-weight, minimum aggregate consumption (no coarse aggregate is used), high fluidity, controlled low strength and thermal insulation [1]. The properties of foam concrete are affected by the production method and the materials used. Unlike other porous lightweight concrete, prefabricated foams with foaming agents are added to fresh cement paste and mortar. The air pores brought by the foams constitute 10-90% by volume of the hardened body. This porous structure forms the basis of the mechanical properties, thermal conductivity, acoustic and durability properties of foam concrete [2]. One of the advantages of foam concrete is its weight reduction (up to 80%) compared to conventional concrete [3]. The air bubbles are evenly distributed in the foam concrete body. The pore structure may be affected during the mixing, transportation and placement of fresh concrete, so it should have fixed walls. Air bubbles range in size from approximately 0.1 to 1 mm [4]. The density of foam concrete is mainly affected by the amount of foam and varies between 400 and 1600 kg/m\({}^{3}\). It can be used for structural, partitioning, insulation and filling applications with excellent acoustic/thermal insulation, high fire resistance, lower raw material costs, easier pumping and finally no compaction, vibration or leveling [1,3]. It emerges as an economical and innovative contribution to the production of lightweight building blocks, partition wall systems, panels, walls, blocks, road fill and roof insulation. It is effectively deployed in countries such as Turkey, Germany, England, Thailand and thePhilippines. It is preferred for the production of foam concretes, bridge fill, insulated wall panels and floor insulation [5]. Researchers show interest in high energy-saving materials in terms of energy savings. In this respect, foam concrete, which is a lightweight, porous material with a high strength-to-weight ratio, stands out. It is widely used in modern buildings. It also offers advantages, such as transportation, cost and production [6]. The Romans made a concrete mixture (made of lime, water, small gravel and coarse sand) into which they mixed animal blood. They discovered that the added animal blood produced air bubbles, making the mixture more useful and durable. It is thought that a similar technology was used by the Egyptians 5000 years ago [7]. The first skate on foam concrete was bought by [PERSON] in 1923. Wall panels and floor boards were used in commercial and residential buildings by the Soviet Union in the 1930s. In 1950, aerated concretes produced for carrier elements prepared using coal slag were put on the market. For foam concrete, the first scientific research was conducted by Valore in 1954. Hydrolyzed protein agents that improve the stability of air cells were introduced to the market at the end of the 1950s. By the end of the 1970s it was used in oil well cementing projects and excavation projects [1,7,8]. Some properties of foam concrete are given in Table 1.  
Today, understanding the properties of foam concrete is of interest to researchers, and many studies focusing on different properties of foam concrete are being conducted. The properties of foam concrete vary depending on many factors. Factors such as foam type, cement type, mineral additives, aggregate type, and the properties of the air spaces created directly affect the strength, fresh and hardened properties of foam concrete.