## 2 Supplementary Cemertitious Material (SCM)
### Limestone-Calcined Clay Cement (LC\({}^{3}\))  
Among various SCMs available for substituting Portland cement clinker, the features of a ternary blend identified as LC\({}^{3}\) is evaluated broadly in terms of its benefits over OPC [45; 52; 59; 60]. Calcination at temperatures between 600 and 800 \({}^{\circ}\)C results in the pozzolanic activity of kaolinite [50]. Limestone and kaolinite clay are present in the earth crust abundantly, and much lower heating temperature compared to Portland cement clinker is required to produce calcined clay. Only 0.3 tons of CO\({}_{2}\) may be emitted for producing 1 ton of calcined clay [45; 61], which is much less than the production of the same mass of OPC [62] (which is typically 1 ton of CO\({}_{2}\)). There are many types of clay with different mineral composition depending on the region. Usually, most of clay types have about 40% kaolinite content or higher, which means they are suitable for calcination to produce highly reactive pozzolan. There are three common methods for calcination including rotary kilns, flash calcination and fluidized bed [56; 63; 64]. Therefore, LC\({}^{3}\) mixes have considerable variations in performance and color, based on the material source as well as calcination and use method. It is noteworthy that by substitution of clinker with limestone in LC\({}^{3}\) blends, both cost and the environmental impacts are reduced [45]. Optimal mechanical characteristics and enhancement in durability tests are observed with the replacement of 50% of clinker [45; 52]. The viability of any technology depends on four key elements, including economic viability, technical feasibility, easy accessibility of raw materials and low \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Chemical** \\ **Composition and** \\ **Physical Properties** \\ \end{tabular} } & **Ordinary** & \multirow{2}{*}{**SF**} & \multirow{2}{*}{**FA**} & \multirow{2}{*}{**Limestone**} & \multirow{2}{*}{**Metakaolin**} & **Calcined Clay** \\  & **Portland** & & & & & **Kaolinite** \\  & **Cement** & & & & & **Content** \\ \hline SiO\({}_{2}\) (\%) & 19.2-21.63 & 90–95 & 46.44-50.96 & 0.1–0.8 & 51.8–57.37 & 44.9 \\ Al\({}_{2}\)O\({}_{3}\) (\%) & 4.18-4.27 & 0.25-1.2 & 25.88-38.01 & 0.3 & 38.63–42.4 & 32.3 \\ Fe\({}_{2}\)O\({}_{3}\) (\%) & 3.32–3.45 & 0.15–1.3 & 3.12–8.25 & 0.3 & 0.77–4.15 & 15.4 \\ TiO\({}_{2}\) (\%) & — & — & 1.36 & — & 1.07 & 2.4 \\ CaO (\%) & 63.25–64.93 & 0.36–1.5 & 2.15–7.5 & 55–58 & 0.03–0.071 & 1.3 \\ MgO(\%) & 1.61–2.77 & 0.47–2 & 0.23–2.60 & 1.8–0.2 & 0.07 & 0.8 \\ Na\({}_{2}\)O (\%) & 0.09 & 0.13–0.5 & 0.33–1.26 & 0.01–0.1 & 0.39 & 0.4 \\ MnO (\%) & — & 0.02–0.07 & — & — & — & 0.1 \\ K\({}_{2}\)O (\%) & 0.78 & 0.2–0.84 & 0.88–2.65 & 0.01 & 0.218–0.49 & 0.2 \\ SO\({}_{3}\) (\%) & 2.02–3.35 & 0.69 & 0.65–0.69 & 0.05 & 0.105–0.15 & 0.1 \\ P\({}_{2}\)O\({}_{5}\) (\%) & 0.09 & 0.04–0.17 & 0.06–0.35 & & 0.61 & 0.4 \\ \hline Loss of ignition (\%) & 1.24–2.49 & 2.29–3 & 2.79–3.2 & 42.6–43.4 & 1.04 & 1.7 \\ \hline Specific gravity & 3.2 & 1.9–2.15 & 2.14 & — & 2.59 & — \\ (g/cm\({}^{3}\)) & & & & & & \\ \hline Specific surface & \multirow{2}{*}{3280–9000} & \multirow{2}{*}{2730} & \multirow{2}{*}{3640} & \multirow{2}{*}{18,000} & \multirow{2}{*}{—} & \multirow{2}{*}{45,700} \\  & & & & & & \\ (cm\({}^{2}\)/g) & & & & & & \\ \hline Bulk density & — & 300–660 & — & — & — & — \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Typical composition and properties of ordinary Portland cement (OPC), SF, FA, limestone, metakaolin and calcined clay [6; 13; 35; 36; 37; 38; 39; 40; 41]. capital investment. The developed LC\({}^{3}\) technology meets all the mentioned criteria [45]. One of the challenges with using limestone and calcined clay as SCM is the reduction in workability compared to the OPC binder. This issue could be managed by using the appropriate dosage of superplasticizer (SP) and also viscosity-modifying admixture (VMA) [56; 64].