## 4 Conclusions  
In this study, Graphene Nano-Platelets (GNPs) were added to asphalt to modify its properties. Various tests were carried out to study rheology, moisture susceptibility, temperature susceptibility, bond strength, and skid resistance of the GNP-doped asphalt in comparison to conventional asphalt. Based on the results of the performance testing, the following conclusions have been drawn:  
* In comparison to other nanomaterials, Graphene Nano-Platelets are easy to disperse. Unlike GNPs, other nanoparticles (i.e., CBNPs and CNTs) either require high shear mixing or solvent-based dispersion. The usage of smaller percentages of GNPs produces more pronounced results than with other nanoparticles [31]. GNPs save the cost of solvent and high shear mixing, making it possible for pavement engineers to use GNPs for asphalt modification on a larger scale. * As per the results of conventional testing, GNPs have the potential to reduce the penetration value of asphalt binder by up to 48% and increase its softening point by up to 19%. The enhancement in these properties can be attributed to the small size and large surface area of GNPs, which aids in stronger bonding. The lower softening point values of the locally produced non-modified binders make them susceptible to rutting during the summers. Upon the addition of 4% of GNPs, the softening point increases to 57 \({}^{\circ}\)C, which is desirable due to the high temperature in Pakistan. * According to the result of the storage stability test, GNP-modified asphalt binder is stable and can be stored for longer periods without the settling down of the nanoparticles. This makes it suitable for use in the pavement industry. * Upon the addition of 4% of GNPs, PG 70 is achieved, which caters to the environmental conditions of Pakistan [13]. * The study of the rheology of the binder shows a significant increase in the stiffness properties of the GNP-modified binder. A maximum increase in the complex shear modulus and a decrease in the phase angle is recorded when 4% of GNPs are added to the binder. The Superpave rutting factor also increases for the GNP-doped asphalt binder, suggesting a better performance at a high temperature. The elastic nature of the GNPs contributes to this improvement. * The optimum binder content (OBC) increases with an increase in the content of the GNPs. This trend shows that the initial cost of GNP-modified asphalt would be slightly more than conventional asphalt. But, by observing the modified asphalt performance in the results, we can conclude that doping asphalt with GNPs would reduce the life cycle cost of the pavements. This is due to the fact that pavements in Pakistan fail prematurely. A highway section designed for 20 years sometimes fails within the first two to three years of service because of excessive deformations during summers. GNP-doped asphalt pavements would require far less frequent maintenance or reconstruction cycles, thus positively affecting the life cycle costs. * The addition of GNPs significantly reduces the temperature susceptibility and increases the resistance to permanent deformation. GNP-modified asphalt shows around a 35% reduction in the rut depth at a high temperature. At 55 \({}^{\circ}\)C, the wheel-tracking slope (WTS) decreased from 0.58 to 0.35 when 4% of GNPs were added to the asphalt binder. This reduction in the WTS is also suggestive of high resistance to permanent deformation. * GNPs act as supporting material in asphalt and give it strength, similar to a steel reinforcement in concrete. This leads to an increase in the dynamic modulus of the asphalt. The dynamic modulus of GNP-modified asphalt is around 21% higher than that of non-modified asphalt, which represents a greater resistance to permanent deformation. * GNPs significantly reduce the moisture susceptibility of asphalt. The addition of 2% and 4% of GNPs to the binder increases the percentage of bitumen coverage from 15% to 60% and 70%, respectively.