## 2 Materials and Experimental Design
### Experimental Design  
The Marshall samples were produced with a bitumen percentage between 3.8% and 6.0% (by weight of mix), and in number equal to three for each bitumen content adopted. Table 3 summarizes the number of specimens produced for each combination of bitumen and aggregate; abbreviations coding the mixtures are also reported.  
Among the mechanical parameters of bituminous mixtures, the ITSM allows a rational performance-based characterization of the mixes to be performed [4; 55]. Therefore, the ITSM test (Figure 4) was executed on all BM samples using the standard testing conditions, defined by EN 12697-26 (temperature of 20 \({}^{\circ}\)C, target deformation fixed at 5 \(\upmu\)m, and rise time equal to 124 ms). Subsequently, considering that the Marshall parameters are still widely used in road pavement design [38; 39; 40; 41; 42; 43; 44; 45], MS and MF were evaluated for the bituminous mixtures produced, according to EN 12697-34. Finally, the specimens' volumetric characteristics have been determined applying EN 12697-8. The test results are reported in Table S1; such experimental data have been already discussed in previous papers [29; 50]. Table 4 shows some statistical information (minimum and maximum values along with the mean value and its standard deviation) about mechanical characteristics and volumetric property of the BMs.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Mixture** & \multirow{2}{*}{**Parameter**} & **Minimum** & **Maximum** & **Mean** & **Standard** \\
**ID** & & **Value** & **Value** & **Value** & **Deviation** \\ \hline \multirow{4}{*}{M1} & ITSM (MPa) & 3756 & 5554 & 4556.43 & 567.93 \\  & MS (kN) & 7.71 & 12.17 & 9.93 & 1.09 \\  & MF (mm) & 1.99 & 4.70 & 3.18 & 0.84 \\  & AV (\%) & 1.77 & 6.37 & 3.99 & 1.37 \\ \hline \multirow{4}{*}{M2} & ITSM (MPa) & 3628 & 5142 & 4345.50 & 486.50 \\  & MS (kN) & 8.74 & 14.00 & 11.35 & 1.73 \\  & MF (mm) & 2.00 & 4.20 & 3.20 & 0.57 \\  & AV (\%) & 2.20 & 6.29 & 4.18 & 1.23 \\ \hline \multirow{4}{*}{M3} & ITSM (MPa) & 3812 & 5942 & 4804.10 & 725.03 \\  & MS (kN) & 10.30 & 15.20 & 12.88 & 1.53 \\ \cline{1-1}  & MF (mm) & 2.00 & 5.00 & 3.35 & 0.95 \\ \cline{1-1}  & AV (\%) & 1.49 & 8.91 & 5.22 & 2.38 \\ \hline \multirow{4}{*}{M4} & ITSM (MPa) & 4035 & 6293 & 5076.17 & 759.06 \\  & MS (kN) & 11.60 & 16.43 & 13.62 & 1.42 \\ \cline{1-1}  & MF (mm) & 2.20 & 5.00 & 3.40 & 0.92 \\ \cline{1-1}  & AV (\%) & 1.33 & 8.36 & 5.05 & 2.18 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Statistical information about Marshall specimens.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Maximum** & **Aggregate** & **Bitumen** & **Production** & **Mixture** & **Specimens** \\
**Size (mm)** & **Type** & **Type** & **Site** & **ID** & **Specimens** \\ \hline
12.5 & Limestone & 50/70 & Laboratory & M1 & 30 \\
12.5 & Limestone & Modified & Laboratory & M2 & 30 \\
12.5 & Diabase & 50/70 & Laboratory & M3 & 30 \\
12.5 & Diabase & Modified & Laboratory & M4 & 30 \\
20 & Limestone & 50/70 & Laboratory & M5 & 39 \\
20 & Limestone & Modified & Laboratory & M6 & 30 \\
20 & Limestone & Modified & Plant & M7 & 41 \\
20 & Diabase & 50/70 & Laboratory & M8 & 30 \\
20 & Diabase & Modified & Laboratory & M9 & 30 \\
20 & Diabase & Modified & Plant & M10 & 30 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Number and codes of Marshall specimens.  
Figure 4: ITSM test setup.