# Concrete Silos: Failures, Design Issues and Repair/Strengthening Methods
## 2 Failure of Reinforced Concrete Silos
### Materials for Reinforcing Concrete  
Considering that thermal ratcheting in silos was influenced by the thermal conductivity of the materials, a primary question is whether modifications in the composition of the reinforced concrete would help to mitigate the impact of thermal ratcheting and compensate for the design code limitations. From the researcher's point of view, the coefficient of thermal expansion, and thermal ratcheting by extension in reinforced concrete can be tailored through the use of different reinforcing materials. The observation is based on the wide variability of the coefficients of thermal expansion in steel, concrete, glass fiber reinforced polymers (GFRP), Amarid Fibre reinforced polymers (AFRP), basalt fiber reinforced polymers (BFRP), and carbon fiber reinforced polymers in Table 1[25]. Based on the evaluation of the data, it can be deduced that replacing steel reinforcements in the concrete with Amarid Fiber-reinforced polymers and basalt fiber reinforced polymers (BFRP) would help to reduce the coefficient of thermal expansion and thermal ratcheting; this is because the coefficient of thermal expansion for steel was fivefold higher relative to the BFRP and the AFRP. The alternative materials are also suitable from a material strength standpoint because the tensile strength of steel is lower relative to the new materials; steel, concrete, glass fiber reinforced polymers (GFRP), Amarid Fibre reinforced polymers (AFRP), basalt fiber reinforced polymers (BFRP), and carbon fiber reinforced polymers (CFRP). The material solutions which address the risk of thermal ratcheting in silos do not involve a tradeoff with the mechanical strength of the structure; the tensile strength of steel is lower relative to the alternative reinforcement materials [25]. The need to replace steel (tensile strength (TS) = 599) with glass fiber reinforced polymers (GFRP) (tensile strength (TS) = 883), \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type of Concrete** & \begin{tabular}{c} **Thermal Expansion** \\ **Coefficient (I\({}^{\prime}\)C)** \\ **(Longitudinal)** \\ \end{tabular} & \begin{tabular}{c} **Thermal Expansion** \\ **Coefficient (I\({}^{\prime}\)C)** \\ **(Transverse)** \\ \end{tabular} & \
\begin{tabular}{c} **Values in the** \\ **Literature (I\({}^{\prime}\)C)** \\ **(Longitudinal)** \\ \end{tabular} &
\begin{tabular}{c} **Values in the** \\ **Literature (I\({}^{\prime}\)C)** \\ **(Transverse)** \\ \end{tabular} \\ \hline Steel & \(11.3\times 10^{-6}\) & \(11.3\times 10^{-6}\) & \(11.7\times 10^{-6}\) & \(11.7\times 10^{-6}\) \\ GFRP & \(4.43\times 10^{-6}\) & \(22.5\times 10^{-6}\) & \(6.10\times 10^{-6}\) & \(21\)–\(23\times 10^{-6}\) \\ CFRP & \(1.05\times 10^{-6}\) & \(93\times 10^{-6}\) & \((-9)(0)\times 10^{-6}\) & \(74\)–\(104\times 10^{-6}\) \\ AFRP & \(-5.2\times 10^{-6}\) & \(51\times 10^{-6}\) & \((-6)\times 10^{-6}\) & \(60\)–\(80\times 10^{-6}\) \\ BFRP & \(1.92\times 10^{-6}\) & \(17.1\times 10^{-6}\) & \(4\times 10^{-6}\) & \(18\)–\(26\times 10^{-6}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Coefficients for thermal expansion for selected materials used in concrete reinforcement [25]. Amarid Fibre reinforced polymers (AFRP) (tensile strength (TS) = 1224), basalt fiber reinforced polymers (BFRP) (tensile strength (TS) = 1021), and carbon fiber reinforced polymers (CFRP) (tensile strength (TS) = 1304) [25] is also informed by the economic implications of corrosion on the construction industry. In addition to GFRP, BFRP, AFRP, and CFRP, other materials have been proven effective in reinforcing concrete silo structures such as bamboo [27]. The direct cost of corrosion-induced damage to concrete reinforced structures in the US exceeds USD 22 billion [28]. The data presented in Table 2 show the various composition and strength grade of different concrete used for concrete silo construction; it is evident that fiber reinforcement had an upper limit. Optimal tensile strength was observed after increasing the fiber concentration to 3.0-4.5.