long term is in doubt [5]. LC\({}^{3}\) primarily consists of two alternative materials: calcined kaolinite clay and limestone [3; 6]. Therefore, studying the suitability of South African clay for LC\({}^{3}\) production is important. Calcined clays, particularly when combined with limestone, have promising potential for expanding the use of SCMs in cement and concrete as a partial substitute for clinker [7]. The use of industrial waste, such as fly ash and granulated blast furnace slag, is commonplace in cement production but is generally limited in replacing clinker in Portland cement (PC). LC\({}^{3}\) has been shown to reduce clinker up to 50% (50% ground Portland clinker, 30% ground calcined clay, 15% ground limestone, and 5% ground gypsum) [7]. Other component proportions are also possible, but cement prepared according to the above composition achieves mechanical properties similar to ordinary Portland cement (OPC) at 28 days of curing at most, provided that the clay contains at least 40% kaolin [7; 9]. The kaolinite content of calcinated clay is directly proportional to the performance of the LC\({}^{3}\)[6; 10], including better pore refinement, hydration, strength, and durability. Deposits of kaolinite clay in South Africa are abundant, as shown in Table 1. With these deposits, an LC\({}^{3}\) project can potentially lead to a standard and mainstream general-use cement in South Africa for better environmental sustainability and cost-efficiency. CO\({}_{2}\) emission can be potentially reduced by 40%/tonne, cost reduced by 33%/tonne, and embodied energy reduced by 22%, implying cleaner production and sustainability if a production plant is situated close to huge clay deposits [11; 12; 13]. The pozzolanic mineral of interest in clay is the kaolinite content, but it also contains other passive phase crystals such as quartz, carbonates, and metal oxides. Generally, the structural composition of kaolinite is one tetrahedral layer of (Si\({}_{2}\)O\({}_{5}\))\({}^{2-}\) and one octahedral layer of (Al\({}_{2}\)(OH)\({}_{4}\))\({}^{2+}\), with each layer forming each face of the sheet. During calcination, the mineral loses its crystallinity and reduces to active silica and alumina (metakaoin), known for their reactivity as SCM. The metakaoin is formed during the calcination of raw clay as a transition phase that retains the lamellar structure of kaolinite while reducing the sheet and tubular dimensions [4]. Due to varying geological and weathering conditions in different regions of the world, clay soil can have varying crystallinity, resulting in various mineral \begin{table}
\begin{tabular}{c c c} \hline \hline
**Country** & **Deposit** & **Estimated Amount** \\  & **Location** & **Estimated Amount** \\ \hline South Africa & Hopefield—Western Cape & 50 million tonnes \\  & Grahamstown—Eastern Cape & 60 million tonnes \\  & Bronkhorstspruit—Gauteng & \textgreater{}35 million tonnes \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Selected kaolinite clay deposits in South Africa [5]. Figure 1: Estimated availability of possible SCMs vs. cement production [8]. structures. The kaolinite content varies based on the mode of formation of the kaolin, the source rocks, and the climatic conditions prevailing during its formation, ranging from 17% to 95% [4]. Based on geological formation, the potential of South African clays for LC\({}^{3}\) is evaluated. One method to determine the kaolinite content of clay is thermogravimetric analysis (TGA). From the TGA, the mass loss between room temperature and 200 \({}^{\circ}\)C is neglectable due to dehydration. An endothermic peak from 400 \({}^{\circ}\)C to 600 \({}^{\circ}\)C shows the dehydroxylation of kaolinite and the formation of metakaolin [5,14]. The proportion of kaolinite may be calculated using the mass change throughout this temperature range and the known molecular weights of kaolinite and water. This principle was used to determine the kaolinite content of the clay samples for this study.