# Concrete Silos: Failures, Design Issues and Repair/Strengthening Methods
## 2 Failure of Reinforced Concrete Silos
### Materials for Reinforcing Concrete
A further increase did not translate to an improvement in tensile strength. The values in Table 3 show that there is a linear relationship between mechanical properties and chemical composition. Even though the replacement of steel reinforcements with alternative materials with high tensile strength is viable from a theoretical and economic perspective, steel is the material of choice in concrete reinforcements [31; 32; 33]. The preference for steel is informed by the availability of raw materials and cost. Steel is both cheap and readily available [28], and new methods have been developed to mitigate the risk of corrosion, including non-destructive methods, passivation techniques, and embedding fiber-optic point sensors within the concrete structure. The complexity of steel reinforcements underscores the need to develop affordable and alternative materials that can be produced via facile and scalable routes. Additionally, it is necessary to ensure that both tensile strength and thermal coefficients are optimized in FRP materials in concrete structures. From an abstract perspective, the development of new materials might be a practical short-term solution due to market-related factors. However, \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Consistency Test (Slump Test)**} \\ \hline
0 & 3 & 10.33 a & 0.47 \\
3.0 & 3 & 9.50 a & 0.41 \\
4.5 & 3 & 7.16 b & 0.24 \\
6.0 & 3 & 6.33 b & 0.47 \\  & \(\text{f}_{\text{c medium}}\)—28 days (MPa) & & \\ \hline \hline \multicolumn{3}{c}{**Axial Compression Test on Cylindrical Specimens**} \\ \hline
0 & 4 & 5.45 c & 0.12 \\
3.0 & 4 & 14.86 a & 0.73 \\
4.5 & 4 & 12.94 b & 0.65 \\
6.0 & 4 & 2.69 d & 0.14 \\ \hline \multicolumn{3}{c}{**Tensile Test in Bending on Prismatic Specimens**} \\ \hline
0 & 4 & 5.78 b & 0.00 \\
3.0 & 4 & 8.30 a & 1.11 \\
4.5 & 4 & 8.15 a & 0.42 \\
6.0 & 4 & 5.33 b & 0.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Strength grade of different concrete used for concrete silo construction [29]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{3}{c}{**Physical Properties**} & \multicolumn{3}{c}{**Chemical Properties**} \\ \hline Specific Weight & 2.98 gr/cm\({}^{3}\) & Ignition Loss & 1.20\% \\ Specific Surface (Blaine) & 3135 cm\({}^{2}\)/gr & SiO\({}_{2}\) & 19.80\% \\ Volume Expansion & 3 mm & Al2O\({}_{3}\) & 5.71\% \\ Initial Set & 160 min. & Fe2O\({}_{3}\) & 3.14\% \\ Final Set & 235 min. & CaO & 63.23\% \\
2-day Compressive Strength & 25.0 MPa & MgO & 2.43\% \\
7-day Compressive Strength & 34.4 MPa & SO\({}_{3}\) & 2.85\% \\
28-day Compressive Strength & 49.1 MPa & Cl & 0.006\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Composition of different concrete used for concrete silo construction [30]. the thermal expansion co-efficient related factors could be resolved by the proposals listed in the EN 1991-1-5 silo design codes. The recommendations propose the following:  
* The design and material selection process should take into account the climate-induced thermal effects (such as solar radiation and air temperature), which impact temperature distribution and silo operating conditions. * The engineers should define the uniform temperature component in line with the ambient air temperature (operating temperature). * Solar gain-based stepped temperature component should be estimated at 15 \({}^{\circ}\)C unless otherwise stated. * The differences between the inside fillings and the ambient air are considered as the difference between the inner and the outer surfaces, after accommodating the impact of insulation. * The temperature-related estimates and assumptions should be based on hot summer days (to accurately determine the effect of solar gains), and an empty silo. Impact of Silo Materials on Quality of Stored Grains and Reverse Effects  
Beyond impacting the material properties and the failure risk, the type of material used in the construction of the silo predicts the quality of grain (risk of aflat growth, protein content, moisture accumulation/loss, crude fiber content, and oil content).