# Enhanced Eco-Friendly Concrete Nano-Change with Eggshell Powder  
[PERSON]  
1 Department of Engineering Geology, Bases, and Foundations, Don State Technical University, 344003 Rostov-on-Don, Russia; au-generalmail.ru (E.M.S. ); [EMAIL_ADDRESS] (S.A.S.) 2 Department of Transport Systems, Don State Technical University, 344003 Rostov-on-Don, Russia 2  
[PERSON]  
1 Department of Engineering Geology, Bases, and Foundations, Don State Technical University, 344003 Rostov-on-Don, Russia; au-generalmail.ru (E.M.S.) 2 Department of Transport Systems, Don State Technical University, 344003 Rostov-on-Don, Russia 2  
[PERSON]  
2 Department of Technology Engineering and the Departments in the Construction Industry, Don State Technical University, 344003 Rostov-on-Don, Russia; [EMAIL_ADDRESS] 2  
[PERSON]  
3 Department of Management of  
for their intended purpose, a large amount of waste accumulates in the form of eggshell. Thus, this problem exists and needs a non-trivial, original solution. Eggshells are high in calcium, mostly composed of several layers of calcium carbonate, which is one of the four main ingredients for cement production. The main cement compounds are dicalcium silicate (C\({}_{2}\)S), tricalcium silicate (C\({}_{3}\)S), tricalcium aluminate (C\({}_{3}\)A), and tetracalcium aluminoferite (C\({}_{4}\)AF). Thus, the eggshell can be used as a replacement for part of the cement. The use of eggshell powder (CaCO\({}_{3}\)) as a partial replacement for cement improves compressive strength by stabilizing ettringite and monocarbonate [1]. As a rule, the main enterprises that produce eggshells in large quantities are bakeries, restaurants, and bakery factories. Before using the eggshell instead of the binder component, the raw shell goes through a certain preparation process. The standard stages of eggshell preparation to obtain an additive are its washing, ultrasonic cleaning, and drying in an electric oven at a temperature of 120 \({}^{\circ}\)C for 24 h [2; 3; 4]. For example, the preparation of nanosized CaO in most cases is carried out by calcination (formula (1)) [2; 3]:  
\[\text{CaCO}_{3}\ \xrightarrow{900\ ^{\circ}\text{C for 2 h}}\ \ \ \ \text{CaO}+\text{CO}_{2} \tag{1}\]  
Ignition at a temperature of 900 \({}^{\circ}\)C for 3 h makes it possible to completely burn out all organic material and convert a significant proportion of CaCO\({}_{3}\) into CaO [4]. As for the chemical composition of the eggshell, it mainly consists of CaCO\({}_{3}\) (approximately 94% of the total weight), organic matter (approximately 4%), calcium phosphate (approximately 1%), and magnesium carbonate (approximately 1%) [1]. Table 2 presents the chemical compositions of eggshell powder obtained from the results of some studies [5; 6; 7; 8; 9]. Table 2 shows that the main component of eggshell powder is CaO, the content of which ranges from 50% to 98%. Silicon oxide is present, but in a much smaller amount. The strength characteristics of concrete directly depend on the amount of eggshell powder used as an additive or replacement for part of the cement (Table 2). \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Source** & **SiO\({}_{2}\)** & **CaO** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **Na\({}_{2}\)O** & **Cl** & **K\({}_{2}\)O** & **SO\({}_{3}\)** & **MgO** & **P\({}_{2}\)O\({}_{5}\)** & **SrO** & **LOI** \\ \hline
[5] & 0.09 & 50.7 & 0.03 & 0.02 & 0.19 & 0.219 & - & 0.57 & 0.01 & 0.24 & 0.13 & - \\
[6] & 0.13 & 50.09 & 0.03 & 0.03 & 0.16 & - & - & 0.61 & 0.02 & - & - & - \\
[7] & 0.24 & 93.2 & 0.23 & - & 0.13 & - & 0.07 & 0.2 & 0.85 & 0.47 & 0.28 & - \\
[8] & 0.05 & 98.0 & 0.05 & 0.02 & - & - & 0.11 & 0.49 & 1.12 & 0.1 & - & - \\
[9] & 0.1 & 53.6 & 1.55 & 0.62 & - & - & 0.01 & 1.57 & - & - & - & 40.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of eggshell powder.