## 2 Materials and Methods
### Production  
For this study, the aggregate plant where the mudstone aggregates were sourced out is Seondo Industry Co., Ltd., situated in Gongju City, Republic of Korea. In this aggregate plant, the mudstone aggregates are reduced to the desired size using a combination of three processes: crushing using the jaw crusher, crushing by the cone crusher, and refining using the vertical shaft impactor (VSI). The process of mudstone aggregates is shown in Figure 2.  
The jaw crusher is a compression-type crusher used predominantly for the primary crushing of rocks and ores. In operation, rocks are fed into the crusher, where they are compressed between a fixed jaw and a moving jaw, resulting in impact and compressive forces that fracture the material. The crushed material then descends through the discharge opening by gravity and the force of the crusher. jaw crushers are capable of handling large rocks exceeding 1000 mm in size, with an average reduction ratio--defined as the ratio of feed size to product size--ranging from 4 to 6.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Material** & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **CaO** & **MgO** & **Na\({}_{2}\)O** & **K\({}_{2}\)O** & **TiO\({}_{2}\)** & **MnO** \\ \hline Mudstone & 66.5\% & 13.2\% & 4.12\% & 3.37\% & 1.9\% & 3.16\% & 2.63\% & 0.64\% & 0.06\% \\ Granite & 71.8\% & 14.3\% & 4.1\% & 3.71\% & 1.85\% & 1.65\% & 1.22\% & 0.72\% & 0.31\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Percentage of the composition of mudstone and granite.  
Figure 2: Process of mudstone aggregate production. (**a**) Jaw crusher. (**b**) Cone crusher. (**c**) Vertical shaft impactor.  
After reducing the size of the mudstone aggregates using jaw crusher, the resulting aggregates are then fed to the cone crusher. The cone crusher operates by compressing material between a gyrating mantle and a concave surface. The material is fed into the crusher, where it undergoes gradual size reduction due to the eccentric movement of the mantle, which creates a narrowing gap for compression and shearing forces to break down the material. This process ensures a consistent product size, which can be adjusted via the closed side setting (CSS) for optimal performance.  
Lastly, after obtaining a more consistent size of the mudstone aggregates, the aggregates are refined using the VSI. The VSI refines aggregates and improves their shape by using high-speed impact forces. Material is fed into the center of the rotor, which spins at high speeds, using centrifugal force to accelerate the material outward. This high-speed material is then directed to collide with anvils or a rock bed surrounding the rotor, causing the material to break upon impact. This process of high-velocity collisions ensures the material is finely crushed and helps produce aggregates with improved shape and particle consistency, making VSI an essential tool for creating high-quality construction materials.  
Gradation  
In this study, two sizes of coarse aggregates are replaced by mudstone aggregates, 13 mm and 10 mm, to produce the colored asphalt mixture. In accordance with the Korean standard for the use of single-particle size aggregates in the production and construction of asphalt mixtures, the 13 mm and 10 mm mudstone aggregates are sieved to satisfy the required gradation for each particle size. Table 2 summarizes the required percentage gradation of each single-particle size aggregate, and Figure 3 shows the gradation of the mudstone coarse aggregates. Additionally, samples of each particle size of the mudstone coarse aggregates are shown in Figure 4 for visualization.