# A Detailed Review on Foam Concrete Composites: Ingredients, Properties, and Microstructure
## 5 Mechanical Properties of Foam Concrete
### Flexural Strength  
The ratio between flexural strength and compressive strength of foam concrete is in the range of 0.25-0.35 [1]. When the sand-containing mixtures of foam concrete and the mixtures with FA are compared, higher values are observed in those containing sand. This is thanks to the improved shear capacity found between the sand particle and the paste phase [1]. Flexural strength increases with the increase in dry density. However, adding FA decreases the flexural strength. This is because FA contributes to strength in later ages [21].  
The use of fibers improves the flexural strength. It provides the transfer of tensile stresses with the bridging effect, thus increasing the strength. It must be of sufficient length, number, and size in order for the fibers to develop their tensile strength. With the fiber additive, the concrete becomes stronger and more ductile. The fiber improves flexural strength, toughness and improves post-cracking behavior [57]. [PERSON] et al. [59] increased the flexural strength by a minimum of 25% and a maximum of 400% by using PVA and polypropylene fiber. The use of basalt fibers has a positive effect on flexural strength. This is thanks to the high tensile strength of basalt fibers. The ability of basalt fiber is to resist the crushing of mortar samples, and this was observed to be positive for flexural strength [5]. The use of PVA fiber improved the flexural strength. Increasing fiber content decreased the strength but was reported to outperform the control sample [60]. It was stated that the  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**References**} & \multirow{2}{*}{**Cement and Additives**} & \multirow{2}{*}{**Aggregate**} & \multirow{2}{*}{**Superplasticizer**} & \multicolumn{2}{c}{**Foaming**} & \multirow{2}{*}{**w/c**} & \multirow{2}{*}{**Density (kg/m)**} & \multirow{2}{*}{**Compressive Strength (MPa)**} \\  & & & & & & & & \\ \hline
[46] & PC \(-\) GGBPS & - & ✓ & H\({}_{2}\)O\({}_{2}\) & - & 150–300 (dry) & 0.41–0.79 \\
[35] & PC & Inert powder \(-\) Sand & ✓ & Protein & 0.5–0.4 & 1600–1300 (fresh) & 5.5–243 \\
[29] & PC & FA \(-\) Sand & & – & 0.5 & 1000–1400 (fresh) & 3.9–73 \\
[85] & PC & Glass & ✓ & Protein & 0.55–0.45 & 1212–1579 & 5.28–10.26 \\
[8] & PC & Plastic & ✓ & Protein & 0.75–0.66 & 803–1250 & 1.35–0.66 \\
[72] & PC & - & & Protein & 0.4–0.60 & 0.1–6 \\
[40] & MPC & - & & H\({}_{2}\)O\({}_{2}\) & 0.6 & 300–1000 (dry) & 1.8–21.6 \\
[86] & PC \(-\) FA & Sand \(+\) GBS & & Protein & 0.55–0.91 & 975–1132 (bulk) & 1.10–1.62 \\
[48] & PC \(+\) FA + SF & & Synthetic & 0.3 & 873–1998 (dry) & 1.5–881 \\
[25] & PC \(+\) FA & & ✓ & 0.45 & 1800 & 5.70–17.15 (ave) \\
[26] & PC + FA & & ✓ & Protein & 0.33–0.36 & 970–1307 (dry) & 10.4 \\
[92] & PC & Sand \(+\) Rubber & ✓ & Synthetic & 0.38–0.5 & 1500–1660 & 6.4–18.3 \\
[93] & PC + GBS + GGBPS & River Sand & & Protein & - & 1425–1480 & 2.82–12.48 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Compressive strength values for different studies.  
use of 2% short polymer fiber used in conjunction with the glass type bi-directional grid reinforcement increased the bending strength. It was reported that after a certain amount of fiber (5%), the interaction and strength between the two reinforcement levels would also decrease significantly. Basalt grid and carbon grid foam concrete have an effect on increasing the average collapse load [45]. Water content is another important factor on the flexural and tensile strength of foam concrete. It was reported that excessive amounts of water decrease the flexural strength due to the decrease in the density of the mixture [57].