## 2 Materials and Methods  
### Materials  
To produce the aggregates, waste from the cities of Ares and Currais Novos in Rio Grande do Norte, Brazil, were used. These wastes were the by-products of sugar and alcohol activities in the case of sugarcane bagasse ash (SBA) and mining in the case of scheelite mining residue (SMR). The aggregates used in this study were selected based on previous research by [PERSON] et al. [25] and [PERSON] et al. [26]. The selection was made based on the characteristics and results presented by the authors, considering the technical feasibility and accessibility for larger-scale production. Figure 1 illustrates the waste materials used. Three types of calcined lightweight aggregates were produced for the study: two using sugarcane bagasse ash at two percentages, SBA50 and SBA90, and one aggregate sintered with scheelite mining residue and rice husk ash, SMR37. All aggregate formulations used red clay from the regional ceramic industry, originating from the municipality of Assu in Rio Grande do Norte, Brazil, along with water for mixture homogenization. Table 1 presents the proportions of the constituent materials for each aggregate and the sintering temperatures. To produce SBA50 and SBA90 aggregates, the sugarcane biomass residue was processed by drying in an oven at 110 \(\pm\) 5 \({}^{\circ}\)C for 24 h, grinding in a Willey knife mill (model SL-31) at 1750 rpm, using 2 kg of SBA for 0.20 h, and sieving to obtain fractions no larger than 0.30 mm, as per [PERSON] et al. [25]. To produce SMR37, the scheelite residue was processed similarly to the SBA, with the difference being the use of a three-phase ball mill and sieving with an opening of 0.15 mm, according to the methodology used by [PERSON] et al. [26]. A schematic illustration of the procedure used to prepare aggregates from waste is described in Figure 2.  
The constituent materials of each aggregate were mixed dry, then placed in a mortar mixer with water. The mixture was subsequently pelletized, limiting the aggregate diameter to approximately 9.5 mm. After air-drying and oven-drying, with each process lasting 24 h, the raw aggregates were sent for sintering in a muffle furnace (Figure 3). In this sintering stage, the aggregates were subjected to temperatures of 1175 \({}^{\circ}\)C and 1150 \({}^{\circ}\)C for SBA and SMR aggregates, respectively, for 15 min, with heating rates of 10 \({}^{\circ}\)C/min and 8 \({}^{\circ}\)C/min. Approximately 45 dm\({}^{3}\) of each sintered aggregate was produced. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Aggregate** & **Constituents** & **Temperature** \\ \hline SBA50 & 50\% sugarcane biomass residue (SBA) + 50\% red clay + 56\% water & 1175 \({}^{\circ}\)C \\ SBA90 & 90\% sugarcane biomass residue (SBA) + 10\% red clay + 77\% water & 1175 \({}^{\circ}\)C \\ SMR37 & 37\% scheelite residue (SMR) + 29\% rice husk ash + 34\% red clay + 30\% water & 1150 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition of aggregate mixtures (% in mass). Figure 1: Waste materials from the sugar, alcohol activities, and the scheelite residue used. After sintering, the produced lightweight aggregates were characterized in terms of expansion index, bulk density, unit weight, 24 h water absorption, and crushing strength. Table 2 presents the characteristics of the aggregates developed in this study. After the production and characterization of the lightweight aggregates, the production of self-compacting lightweight concrete (SCLC) used the materials described in Table 3.