## 5 Results and Discussion
### Effects of Mixtures Volumetric Change on the Rearrangement of Aggregates  
Asphalt mixture volumetrics in the Superpave mix design are the relationships between mass (aggregates and asphalt binder) and their volumes at 4% of the air voids. When the optimum asphalt content (obtaining 96%Gmm at Ndesign) is mixed with the aggregates for compaction, the asphalt binder forces the aggregates to slide and move to rearrange, and allows the aggregates to be moved into a denser condition. So, the same desired density can be expected at the same number of gyrations (applied with the same amount of compaction energy). Thus, the most important factor for compaction is the asphalt content that affects the internal friction due to the change in the frequency of aggregate contact by compaction when other factors are holding in the expression of the Mohr-Coulomb compaction theory. However, the viscosity, which is the cohesion in the theory, is one of factors that can affect the volumetrics. Temperature apparently influences the compaction resistance due to the change in viscosity. The viscosity corresponding to different temperatures can change the mixture volume due to asphalt binder absorption by aggregates. At a low temperature, compaction is resisted due to high viscosity, regardless of the aggregate contacts. However, at a high temperature, the viscosity helps the aggregate slide and move to the pore space; instead, it increases the internal friction to resist compaction. This can be proven by mixture volumetric analysis. In Superpave volumetric analysis, the VMA, volume of the voids filled with asphalt binder, consists of the volume of the effective asphalt binder (V\({}_{\text{eac}}\)) and air voids. The V\({}_{\text{eac}}\) can be calculated from volumetric analysis, as shown in Table 2. The V\({}_{\text{eac}}\) decreases for the PG64-28 mixtures when increasing the temperature from 115 \({}^{\circ}\)C to 140 \({}^{\circ}\)C. The volume differences in V\({}_{\text{eac}}\) for the PG58-28 mixtures are negligible at the temperatures between 110-140 \({}^{\circ}\)C. That is, the certain amount of asphalt for lubrication disappears and flows into the water-permeable voids that are distributed on the aggregate surface. Figure 11 shows the frictional behavior of aggregates corresponding to the volume change in the PG64-28 mixtures. Depending on the change in temperature, the absorbed asphalt binder (P\({}_{\text{ba}}\), wt% by aggregates) and V\({}_{\text{eac}}\) were calculated. For convenience, it was divided into two temperature sections, A (90 \({}^{\circ}\)C to 115 \({}^{\circ}\)C) and B (115 \({}^{\circ}\)C to 140 \({}^{\circ}\)C). In section A, the CFI, presenting the applied energy to achieve a desired density, is highest at 90 \({}^{\circ}\)C and decreases. Aggregates can be constrained by a highly viscous asphalt binder. P\({}_{\text{ba}}\) decreases, but V\({}_{\text{eac}}\) and \(\Delta\) increase. The increasing temperature shows a better rearrangement of the aggregate in terms of the volume change of the asphalt mixture. In contrast, the reduction in the viscosity of section B allows the initial cohesion of the asphalt binder to increase, but the majority of the aggregate in the mixture may strongly interact with each other. An increase of 0.35% in P\({}_{\text{ba}}\) causes a 0.4% reduction in V\({}_{\text{eac}}\). A reduction of lubricants can produce a larger contact surface area at the contact area, enabling the interfacial diffusion of the asphalt binder. This will give enhanced aggregate interfacial strength through increasing the temperature. The friction between the aggregates will increase and more compaction energy will be needed to achieve a desired  
Figure 10: Comparisons of the energy indices and the \(\Delta\) as function of temperature: (**a**) PG64-28 mixtures; (**b**) PG58-28 mixtures. density.