## 4 Results
### Aggregate Characterization
While calcium silicate (Ca\({}_{2}\)SiO\({}_{4}\)) within BOF slags can impart some hydraulic properties, the presence of other inert phases and free lime, along with magnesium, makes BOF slags challenging to use as aggregates due to their tendency to undergo volume instability. However, the carbonation of BOF slags can lead to the transformation of calcium silicate and free lime into calcite, addressing the issue of volumetric instability. Figure 12: (a) XRD pattern of one typical fresh BOFS; (b) XRD pattern of one typical stockpiled BOFS. Figure 13: Sieved BOFS with different particle sizes (stockpiled BOFS). The carbonation reaction that led to the aged products happened due to Equations (1)-(3):  
\[\text{Ca}_{2}\text{SiO}_{4}+\text{CO}_{2}+\text{H}_{2}\text{O}-\text{CaCO}_{3}+ \text{SiO}_{2}+\text{H}_{2}\text{O} \tag{3}\]  
Tables 2 and 3 present data on the moisture content, absorption capacity, and specific gravity of both coarse and fine BOFS. Regarding the coarse BOFS, it was observed that the stockpiled BOFS exhibited a higher overall moisture content and specific gravity when compared to fresh BOFS, but it showed a lower capacity to absorb water. It is essential to highlight that the stockpiled BOFS had undergone a weathering process, resulting in the presence of more aged products, including intense hydration and carbonation products, as well as a higher in situ moisture content. Additionally, the fresh coarse BOFS was more porous than stockpiled BOFS, leading to its higher water absorption capacity. In contrast, when examining fine BOFS, it is evident that the stockpiled BOFS had a lower total moisture content and specific gravity, but it exhibited a higher water absorption capacity compared to the fresh BOFS. This difference can be attributed to the fact that the products generated through the weathering (aging) process had a higher specific surface area, were lightweight, and included substances like portlandite and calcite. Both the fine fresh and stockpiled BOFS, however, possessed a higher specific gravity than the river sand. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Material** & **Soundness Test (\%)** & **Freeze and** & **Moisture Content (\%)** & **Specific Gravity** & **Specific Gravity** & **Specific Gravity** & **Absorption** \\ \hline
2 nd Batch & & & & & & & \\ Fresh BOF & 3.01 & 1.49 & 3.07 & 3.28 & 3.33 & 3.45 & 1.51 \\ \hline
2 nd Batch & & & & & & & \\ Stockp. BOF & 0.63 & 1.46 & 4.02 & 3.50 & 3.54 & 3.65 & 1.14 \\ \hline
1 st Batch & & & & & & & \\ Fresh BOF & 1.36 & 4.52 & 2.68 & 2.83 & 2.95 & 3.23 & 4.43 \\ \hline
1 st Batch & & & & & & & \\ Stockp. BOF & 1.37 & 5.25 & 3.94 & 3.14 & 3.2 & 3.32 & 1.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Moisture content, absorption capacity, and specific gravity of coarse BOF slags. Figure 14: Weatherped BOFS with different particle sizes (stockpiled BOFS). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Material** & **Soundness Test (\%)** & **Freeze and** & **Moisture Content (\%)** & **Specific Gravity** & **Specific Gravity** & **Specific Gravity** & **Absorption** (\%)** \\ \hline
2 nd Batch & & & & & & & \\ Fresh BOF & 3.03 & 2.97 & 3.07 & 3.26 & 3.42 & 3.87 & 4.82 \\ \hline
2 nd Batch & & & & & & & \\ Stockp. BOF & 4.14 & 4.25 & 4.02 & 3.16 & 3.32 & 3.78 & 5.17 \\ \hline
1 st Batch & & & & & & & \\ Fresh BOF & 1.46 & 3.40 & 2.68 & 3.36 & 3.47 & 3.77 & 3.24 \\ \hline
1 st Batch & & & & & & & \\ Stockp. BOF & 1.65 & 11.62 & 3.94 & 3.02 & 3.11 & 3.34 & 3.17 \\ \hline River sand & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Moisture content, absorption capacity, and specific gravity of fine BOF slags and sand. The tables above also provide data on the soundness properties, including sulfate and freeze-thaw resistance. According to ASTM C 88, an aggregate is considered to have good sulfate resistance if it exhibits less than an 18% total loss before and after exposure to sodium sulfate (Na\({}_{2}\)SO\({}_{4}\)).