## 2 Materials and Methods
### Materials
#### 2.1.4. Bitumen Emulsion  
The binder is one of the main elements in bituminous mixtures. In order to minimize the environmental effects of the conformation of bituminous mixtures, bitumen emulsion is used as a binder in this research. The use of this type of binder has a main advantage over others, which is that it is formed at room temperature, since it is not necessary to raise the temperature of the bituminous mixture to high temperatures to obtain the mixture.  
The bitumen emulsion is mainly composed of water and bitumen. Both elements are immiscible, so it is necessary to carry out a process in which they are homogeneously mixed and an emulsifier is added to prevent the separation of the aforementioned elements. The nature of this emulsifier is essential, since it must react with the aggregate of the  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Test** & **Standard** & **Value/Unit** \\ \hline Particle density & UNE-EN 1097-7 [30] & 2.62 \(\pm\) 0.07 t/m\({}^{3}\) \\ Bulk density & UNE-EN 1097-3 [31] & 0.70 \(\pm\) 0.01 t/m\({}^{3}\) \\ Plasticity index & UNE-EN ISO 17892-12 [32] & 4.1 \(\pm\) 0.1\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Physical properties of limestone filler.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Ophite Filler** & \\ \hline
**Test** & **Standard** & **Value/Unit** \\ \hline Particle density & UNE-EN 1097-7 [30] & 2.71 \(\pm\) 0.07 t/m\({}^{3}\) \\ Bulk density & UNE-EN 1097-3 [31] & 0.65 \(\pm\) 0.02 t/m\({}^{3}\) \\ Plasticity index & UNE-EN ISO 17892-12 [32] & 2.2 \(\pm\) 0.1\% \\ \hline \hline \multicolumn{3}{c}{**Ophite aggregate**} \\ \hline
**Test** & **Standard** & **Value/Unit** \\ \hline Resistance to fragentation & UNE-EN 1097-2 [33] & 14 \(\pm\) 1\% \\ Resistance to freezing and thawing & UNE-EN 1367-1 [34] & 0.865 \(\pm\) 0.022\% \\ Polished stone value & UNE-EN 1097-8 [35] & 57 \(\pm\) 2 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Physical and mechanical properties of ophite aggregate and fillers.  
bituminous mixture producing the breaking of the emulsion. When the emulsion breaks, the bitumen envelops the aggregate, and the water is free to evaporate by natural processes. Therefore, the chemical nature of the emulsifier and the emulsion must be compatible with the aggregate for this process to occur. In this case, and due to the fact that the main element is the ophite aggregate, the emulsion selected is of a cationic nature. This type of emulsion reacts adequately with the composition of the ophite aggregate.  
At the same time, the emulsion must have an adequate breaking time, otherwise the mixing and spreading times on the infrastructure would be unacceptable. Emulsions are classified according to their breaking time as fast, medium, and slow. This factor is mainly conditioned by the percentage of fine aggregate and filler. Specifically, and due to the fact that the bituminous mixture developed in this research has a discontinuous grading in which the percentage of fine aggregate and filler is reduced, an emulsion with medium breaking time was used. If, on the other hand, the percentage of fines is high, an emulsion with a slow breaking time should be used to allow an adequate mixing time for coating all the aggregates. In short, the emulsion chosen is a medium cationic emulsion, designated according to European standards as C60 BF3 MBA. However, the compatibility of this emulsion with the aggregates will be studied in the methodology.  
Table 3 shows the general characteristics of the C60 BF3 MBA emulsion.