## 3 Results and Discussions
### Characterization of Raw Materials  
As mentioned above, the characterization of the chemical composition and the physical or mechanical properties of the waste is essential for its correct use within the final material. Usually, this type of materials have a series of particularities, that even not being negative, if they must be taken into account for the conformation of a final material of quality. Firstly, the discarded cellulose fibers from the papermaking industry were analyzed. These cellulose fibers, as indicated, are the additive used in the different families of bituminous mixtures to absorb a greater percentage of bitumen. They must therefore have a suitable chemical composition. To determine the chemical composition, the elemental analysis test was carried out, detecting the presence of carbon, nitrogen, hydrogen, and sulfur, because it is an organic material. The results of the elemental analysis test are detailed in Table 3.  
As can be seen, the elemental analysis test reflects the composition of an organic material. The percentage of carbon and hydrogen demonstrate such a composition. On the other hand, the low nitrogen and sulfur values reflect the material's suitability for use in bituminous mixtures, since otherwise these pollutant elements could damage the bituminous mixture and produce polluting leachate. It should be noted that the sum of the elements analyzed does not correspond to 100%. This is due to the fact that the fibers have been washed with sodium hydroxide, so this chemical element has been retained in the matrix of the fibers without prejudice to the final material. In turn, the cellulose fibers must be distributed homogeneously in the conformed bituminous mixtures to avoid the production of bleeding. In addition, they must be of an appropriate size for the correct formation of a music capable of resisting the traction loads of traffic. Therefore, the scanning electron microscope test was carried out to the aim to evaluate the size of the fibers. The images taken from this test are detailed in Figure 2.  
Figure 2 shows a millimeter size of cellulose fiber. This fiber size is ideal for use in bituminous mixtures, as larger sizes would make the mixing process more difficult. At the same time, it can be seen that there are no agglomerations of cellulose fibers that could be detrimental to the correct homogenization in bituminous mixtures. If this were not the case, bitumen bleeding and heterogeneities in the properties of the mixtures conformed \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Nitrogen, \%** & **Carbon, \%** & **Hydrogen, \%** & **Sulfur, \%** \\ \hline Fibers & 0.447 \(\pm\) 0.008 & 44.489 \(\pm\) 0.325 & 5.884 \(\pm\) 0.178 & 0.000 \(\pm\) 0.000 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Elemental analysis of cellulose fibers discarded by the Papermaking Industry. Figure 2: Image of the cellulose fibers of the Paper Industry obtained with the Scanning Electron Microscope in the secondary option. could be produced. Therefore, the suitability of the fibers for the correct absorption of a higher percentage of bitumen into the bituminous mixtures was demonstrated through the above-mentioned tests. After evaluating the cellulose fibers, the chemical composition of the ladle furnace slag was determined. To do this, the elemental analysis test was first carried out, reflecting the results shown in Table 4.  
The elemental analysis test showed the absence of harmful and polluting elements such as nitrogen and sulfur, and therefore their suitability for use in bituminous mixtures was confirmed. In turn, the percentage of carbon and hydrogen of the ladle furnace slag seems to correspond with high probability to the carbonation and hydration of different chemical compounds, not being a harmful fact but to be taken into account. Given the mainly inorganic composition of the ladle furnace slag, the elemental composition was determined by means of the X-ray fluorescence test.