## 2 Materials and Methods  
### Materials  
Mine tailings (MT) and well cuttings (WC) from the mining district of La Union (Spain) were used in this study (Figure 1) as a coarse aggregate. A porphyry aggregate (PA) was used as a benchmark for coarse aggregates of up to a 4 mm size. WC are produced during mine access shaft excavations with a generated volume in the order of 0.51 mm\({}^{3}\). As may be seen in Figure 1, individual fragments are flaky and show a homogeneous distribution of aggregate of between 50 and 150 mm. MT of the Cabezo Rajao mine, made up of waste rock left after mineral extraction, is currently about 3.01 mm\({}^{3}\)[10] in volume. These tailings are of heterogeneous morphology (Figure 1), ranging from sand grains to 300 mm blocks. The image of Figure 1, taken with a scanning electron microscope, shows an elevated porosity that may be of importance in the fabrication of bituminous mixes. The samples were taken at various points and altitudes in the waste dump. In order to reutilize these tailings, it was necessary to grind them with a laboratory crusher to reduce their size. Table 1 shows the oxides that are encountered in quantities of larger than 0.02%, according to chemical analysis. Coarse and fine aggregates were classified as materials retained on and passing through the 4 mm sieve, respectively. The coarse porphyry aggregate (PA) was used in fractions of 6/12 mm and 12/18 mm. The aggregate is typically used in this region in the fabrication of wearing courses. In all the mixtures studied, a fine aggregate limestone sand was used in a 0/4 mm fraction, along with a limestone mineral filler, produced by grinding the natural aggregate. Bitumen of 35/50-penetration grade was used for the mixtures, which is typically used in the region. Its properties are given in Table 2. \begin{table}
\begin{tabular}{c c c} \hline
**Component** & **WC** & **MT** \\ \hline Na\({}_{2}\)O & 0.89 & - \\ MgO & 1.18 & 1.18 \\ Al\({}_{2}\)O\({}_{3}\) & 18.67 & 1.71 \\ SiO\({}_{2}\) & 66.45 & 9.72 \\ P\({}_{2}\)O\({}_{5}\) & 0.16 & 0.44 \\ SO\({}_{3}\) & 0.16 & 23.51 \\ K\({}_{2}\)O & 2.44 & 0.04 \\ CaO & 0.04 & 1.36 \\ TiO\({}_{2}\) & 0.62 & 0.11 \\ MnO & 0.09 & 3.73 \\ Fe\({}_{2}\)O\({}_{3}\) & 9.14 & 36.02 \\ CuO & - & 0.05 \\ ZnO & 0.03 & 15.22 \\ Nb\({}_{2}\)O\({}_{5}\) & - & 0.36 \\ PbO & 0.05 & 1.12 \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of well cuttings (WC) and mine tailings (MT). Figure 1: Wellbore cuttings (WC) in the upper photos and mine tailings (MT) in the lower ones. Included are scanning electron microscope images. (**a**) WC deposits in the mine district of La Union; (**b**) scanning electron microscopy (SEM) micrograph of WC sample; (**c**) MT disposal; (**d**) SEM micrograph of MT sample. High-quality aggregates are required to make the wearing course. The level of quality is measured through parameters such as the Los Angeles abrasion loss (%), the flakiness index (%), and the polished stone value. Table 3 lists the principle physical and mechanical properties of the aggregates and the values of the limits established by the Spanish norm, PG-3 [31], for each of the aggregates used to make wearing courses. The flakiness index for WC limits its utilization to low-intensity road applications and weight categories of T32 or less according to Spanish norms (Traffic category T32 refers to the following interval of Annual Average Daily Heavy Traffic: 50 \(\leq\) AADTH < 99). MT has a mean Los Angeles abrasion loss coefficient that is greater than that of WC and PA, making its use limited to the T3 traffic level (50 \(\leq\) AADTH < 200). Both mining wastes (WC and MT) exhibit an accelerated polishing value that is adequate for wearing course use, being much higher than that of PA.  
As may be observed in Table 3, the properties of the MT and WC mine wastes comply with the limits required for aggregates in PG-3, the Spanish norm. There is no limitation on the density of the aggregates utilized in hot bituminous mixes.