## 3 Results and Discussion
### Volumetric Analysis by Gyratory Compactor
Such considerations can be important for a better comprehension of the compaction process and can be useful for the piloted design of optimized processes. In our opinion, the physical origin of the higher efficiency in compaction when aged bitumens are employed must be searched for in the rheology involved in the transport properties of these materials. The higher viscosity possessed by RTFOT-aged bitumens--both with filler and without it--compared to the corresponding neat bitumens allows a higher momentum transfer during shear through intermolecular interactions. This turns up in a better energy and momentum propagation within the sample under compaction in the gyratory press and therefore a more efficient process, turn by turn. The stronger intermolecular interactions present in RTFOT-aged samples cause also a higher activation energy, which is the energy barrier at the molecular level that must be overcome by the gyratory press for the flow to occur. Interestingly, it can be noticed that the ratio between the activation energies for the neat bitumen/filler and RTFOT-aged bitumen/filler (which are usually indicated as the basic mixtures undergoing compaction with the mineral aggregates so that the rheological properties are usually referred to these [63; 64]), is 97.3/83 = 1.17 \(\pm\) 0.03 which is recurrently within the range of experimental uncertainty as the same number was arrived at previously. Coherently, the quantities derived from the shear resistance values (CFI and TFI, see Appendix A for their derivation) also follow this behavior. In fact, the ratio of the CFI values is 24,930 kN m\({}^{-2}\) / 21,540 kN m\({}^{-2}\) = 1.16 whereas the ratio of TFIs, (involving the integral up to Nmax) is 65,370 kN m\({}^{-2}\) / 70,590 kN m\({}^{-2}\) = 0.93. All these ratios are reported in Table 6 for a schematic panorama. Of course, more samples need to be investigated to validate our hypothesis and more studies-both experimental and theoretical are needed to better define the correlation between workability in the gyratory press and rheological properties. Finally, the indirect tensile stress (ITS) values of the asphalt with neat bitumen are lower than those ones registered for the mix with bitumen RTFOT as reported in Table 7. In particular, Table 7 shows the increase in ITS and CTI resistance accompanied by a decrease in compressive deformability from neat vs. aged bitumen, highlighting the increase in viscosity of the bitumen due to aging by RTFOT, as expected. Note that ITS test is a measure of bitumen adhesion to mineral aggregate and the internal bitumen cohesion. It is determined by both mechanical factors (the degree of moistening and dust of the aggregate, the micro-texture of the aggregate, the granulation of the mineral mix) and the physicochemical-chemical nature of aggregate (acidic, alkaline, in-between) as well as the physicochemical properties of the bitumen, such as viscosity and adhesion [65; 66]. This investigation can be a good starting point for deriving a proper model. This would have great importance for optimizing the conditions in asphalt concretes preparation and related processes, with enormous benefits in terms of energy saving and environmental concerns.