# Evaluation of _Jatropha curcas_ and Pistachio Shell Particles as Modifier for Asphalt Binder
## 3 Results and Discussion
### Rheology  
The evolution of \(\mid\)G*\(\mid\)/sin \(\delta\) as a function of the temperature of the asphalt blends containing _Jatropha_ particles is shown in Figure 3. The complex modulus \(\mid\)G*\(\mid\) is related  
Figure 1: Fluorescence microscopy of asphalt binder with _Jatropha_ _curcas_ shell particles:(**a**) 2, (**b**) 4, (**c**) 6, and (**d**) 8. Figure 2: Fluorescence microscopy images of asphalt mix with pistachio shell particles: (**a**) P2, (**b**) P4, (**c**) P6, and (**d**) P8. to the rigidity of the asphalt samples, and the \(\mid\)G*\(\mid\)/sin \(\delta\) parameter is associated with the binder's rutting or permanent deformation resistance. The failure temperatures of the asphalt blends modified by _Jatropha_ seed shells are 79.6 \({}^{\circ}\)C (J2), 75.3 \({}^{\circ}\)C (J4), 75.9 \({}^{\circ}\)C (J6), and 75.1 \({}^{\circ}\)C (J8), while the failure temperature of the unmodified asphalt is 74.3 \({}^{\circ}\)C. The failure temperature, also known as T\({}_{\rm SHRP}\), is the temperature where \(\mid\)G*\(\mid\)/sin \(\delta\) = 1 kPa. All the modified asphalt curves in Figure 3 are located above the reference asphalt curve, which implies that adding _Jatropha_ seed shells as an asphalt modifier improves its rheological properties [6]. Furthermore, Figure 3 also evidences that the asphalt sample modified by 2 wt.% _Jatropha_ particles has significantly improved its rheological behavior relative to the pure asphalt throughout the complete domain of examined temperatures. However, the behavior of the rheological parameter plotted in Figure 3 approaches that of the base asphalt when the proportion of _Jatropha_ modifier grows in the asphalt blends, which suggests that the shell components act as the lighter fraction of the asphalt when they are present in significant proportions. Additionally, the saturation of the highly concentrated samples may prevent the interactions between the lignin and the polar groups of the asphalt; therefore, the 2 wt.% content appears to be the critical point where the \(\mid\)G*\(\mid\)/sin \(\delta\) parameter reaches its maximum value. Figure 4 shows the parameter \(\mid\)G*\(\mid\)/sin \(\delta\) as a function of the temperature of the asphalt modified by pistachio shells. The failure temperatures of the pistachio-modified asphalt blends are 75.5 \({}^{\circ}\)C (P2), 80.9 \({}^{\circ}\)C (P4), 74.9 \({}^{\circ}\)C (P6), and 80.4 \({}^{\circ}\)C (P8), which are also higher than the corresponding failure temperature of the unmodified asphalt, and reveal that pistachio shell particles enhance the mechanical resistance of the asphalt binder. The highest values of \(\mid\)G*\(\mid\)/sin \(\delta\) in this experiment correspond to a concentration of 4 wt.% of the modifier, which has already been attributed to the interaction between the lignin of the shells and the polar groups of the asphalt binder. The P4 failure temperature (Figure 4) is close to that of J2 (Figure 3), which is coherent with the fact that the lignin in pistachio shells is not as abundant as it is in _Jatropha_ seed shells; therefore, a relatively greater amount of pistachio modifier produces almost the same rheological response as a lower concentration of _Jatropha_ particles. The sample modified with 6 wt.% of pistachio shells presents a rheological behavior similar to that of the base asphalt, but a concentration of 8 wt.% increases the \(\mid\)G*\(\mid\)/sin \(\delta\) values to a level close to that of the P4 sample. This behavior may be a consequence of the pistachio shell's stiffness, which results in forming strong modifier aggregates, like those revealed by the fluorescence microscopy  
Figure 3: Isochronal plots of \(\mid\)G*\(\mid\)/sin \(\delta\) vs. temperature of asphalt binder modified by _Jatropha_ _curas_ seed shell particles. analysis (Figure 2d), whichact not only as a filler but also as a reinforcement agent of the modified binder.