# Evaluation of _Jatropha curcas_ and Pistachio Shell Particles as Modifier for Asphalt Binder
## 3 Results and Discussion  
### Physical Properties  
Table 2 shows the physical properties of the asphalt binder modified with _Jatropha_ and pistachio shells. The softening point of all modified samples increased compared with that of the base asphalt; therefore, all modified asphalt blends are less susceptible to exhibit permanent deformations. The improvement in softening point makes the asphalt binder stiffer, which causes its straight-against mechanical damage to improve, and decreases susceptibility to permanent deformation [10; 17]. This behavior is an indicator of the improved performance of the modified binder relative to the pure asphalt. This behavior is similar to that reported previously when powder of waste crayfish shells is added to asphalt, increasing the softening point to 20% [21]. One of the basic rheological properties of asphalt binder is its viscosity, which can be regarded as a demonstrator of fluid resistance against shear. Another positive effect of the modification was detected as an increment of the rotational viscosity of the modified samples in the temperature range between 135 and 190 \({}^{\circ}\)C for modified asphalts compared with pure asphalt. The asphalt blends modified with _Jatropha_ seed shells registered the maximum rotational viscosity at a concentration of 6 wt.%. Interestingly, the viscosity of the samples containing 2% and 8% of _Jatropha_ shells was quite similar, which may be explained by the fatty acid content of the modifier that produces a softer asphalt at high concentrations of _Jatropha_; this behavior suggests the existence of a limit concentration of _Jatropha_ particles for obtaining the optimum viscosity. If the viscosity of the modified asphalt binder is too high, it causes the asphalt mixture to be too hard to compact during pavement construction; forming an eligible pavement surface would be difficult, leading to increased mixing and computation temperature, and higher construction costs. Mixtures with higher viscosity value would be harder to lay down and compact on the road [7]. The maximum viscosity of the asphalt mixtures modified with pistachio shells was observed for the 4 wt.% sample at 135 \({}^{\circ}\)C. The effect of varying the modifier content on the viscosity is less pronounced at 160 and 190 \({}^{\circ}\)C, which may reflect that the components of pistachio shells are not able to interact with the larger molecules of the asphalt. The softening points measured in the phase separation test show that the greatest difference between the top and bottom sections of the collapsible tube corresponds to the asphalt blend containing 8 wt.% _Jatropha_ shell. The other values are lower than 2.5 \({}^{\circ}\)C, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Softening Point R** & **Phase Separation** & **Rotational Viscosity** & **Rotational Viscosity** & **Rotational Viscosity** \\  & **and B (\({}^{\circ}\)C)** & **R and B (\({}^{\circ}\)C)** & **@135 \({}^{\circ}\)C, (cP)** & **@160 \({}^{\circ}\)C, (cP)** & **@190 \({}^{\circ}\)C, (cP)** \\ \hline Asphalt & 48.25 & 0 & 383.2 & 126.7 & 47.2 \\ J2 & 52.75 & 1.8 & 431.0 & 140.1 & 50.0 \\ J4 & 50.75 & 1.5 & 447.6 & 146.8 & 54.6 \\ J6 & 51.0 & 2.0 & 481.8 & 152.6 & 55.7 \\ J8 & 53.5 & 2.5 & 434.5 & 140.6 & 52.2 \\ P2 & 52.25 & 0 & 449.1 & 144.7 & 51.3 \\ P4 & 50.5 & 0.5 & 456.5 & 143.9 & 52.3 \\ P6 & 53.5 & 1.0 & 448.4 & 141.7 & 52.9 \\ P8 & 51.0 & 1.7 & 433.8 & 138.6 & 51.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Softening point, phase separation, and rotational viscosity results of pure asphalt and the _Jatropha_- and pistachio-modified asphalt mix. which reveals that both modifiers are efficient for avoiding phase separation.