# A Detailed Review on Foam Concrete Composites: Ingredients, Properties, and Microstructure
## 2 Compositions of Foam Concrete
### Foam Agents  
One of the most important components of foam concrete is foam, and foaming agents are used to produce the foam [3]. Foaming agents affect the density, porosity, stability, and fluidity of foam concrete. Their main task is to introduce air bubbles into foam concrete. Foam can be produced in two different ways, as pre-foaming and mixed foaming methods. \begin{table}
\begin{tabular}{c c c} \hline \hline
**References** & **Aggregate Type** & **Effects on Foam Concrete** \\ \hline
[53] & Biomass aggregate & It increased strength both indoors and outdoors. \\ \hline
[29] & FA & Increased consistency and rheology were demonstrated with the addition of FA. There is a need for more foam for the desired plastic density. Especially after 28 days, its compressive strength was higher than sand concrete. \\ \hline
[54] & RHA & It increased its compressive strength. This situation is attributed to the pozzolanic property of rice husk ash. \\ \hline
[55] & EVP & The unit weight of the foam concrete was affected due to the water holding capacity of the EVP. It caused micro-cracks at high temperatures. It was reported that EVP is promising in terms of thermal conductivity and its soft structure may adversely affect the compressive strength. \\ \hline
[12] & RGP & Glass dust caused a decrease in the density of the foam concrete. It is recommended to use 20\% glass powder in terms of compressive strength. The reason for this was shown to be that more glass powder causes a decrease in compressive strength and increases the hydration temperature. In addition, glass powders with a particle size of less than 45 \(\mu\)m have a pozzolanic effect. Glass powder, which has a pozzolanic effect, has an improving effect on compressive strength. \\ \hline
[25] & RP & Increasing the amount of rubber powder decreased the workability. It increases the compressive strength and tensile strength, but the increase in its amount causes the compressive strength and tensile strength to decrease. \\ \hline
[18] & WMP & It reduced the collapse value. It contributed to the reduction of drying shrinkage and increased freeze–thaw resistance. It improved mechanical properties. \\ \hline
[56] & Quarry wastes & Quarry dust reduced flowability and it increased compressive strength and thermal conductivity. \\ \hline
[51] & RCA & The porous structure of recycling concrete wastes increased the porosity of the foam concrete. Therefore, water absorption increases, and ultrasound speed and thermal conductivity decrease. However, foam concrete containing up to 50\% recycling concrete wastes exhibited a compressive strength similar to control foam concrete. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Various types of aggregate. Foaming agents can be synthetic, glue resins, protein based, detergents, resin soap, saponin, and hydrolyzed protein. However, the most commonly used foaming agents are synthetic and protein-based ones [2; 3; 57]. Protein-based agents allow a stronger pore structure and more closed void space network. It creates a more stable air-void network. Synthetic agents, on the other hand, allow more expansion, so they have lower densities. Synthetic agents are more economical and easier to use than protein agents and also require less energy for storage [3; 4; 7; 57]. [PERSON] et al. [38] reported that a constant water/cement ratio resulted in more stable foam concrete samples than those obtained from protein ones. [PERSON] and [PERSON] [58] carried out the analysis of the foam produced using sodium lauryl sulfate (SLS) as surfactant. As a result, the foam produced with SLS could not keep the liquid in the foam, thus leading to a 40% reduction in density after 0 min. It also was reported that as the dilution amount of SLS increases, the drainage increases. In the study conducted by [PERSON] and [PERSON] [41], sodium bicarbonate (NAC) was used as a foaming agent. It was reported that dry density, compressive strength, burst tensile strength, thermal insulation, and water resistance decrease due to the increase in the amount of NAC.