# Bitumen and Bitumen Modification: A Review on Latest Advances
## 5 Concluding Remarks  
This paper summarizes the findings obtained from an extensive literature review focused on the basic aspects related to different types of bitumens, processing technologies and polymers, chemical and nanocomposite-modified bitumen characterizations' pros and cons, as well as identifying corresponding areas of study for future perspectives. The comprehensive review implies that the relative abundance of the bitumen SARA fractions results in significant differences in bitumen chemical composition and further mechanical properties. It is evident that different types of processing of crude oil result in bitumens with different chemical compositions. This also has a great influence on the compatibility with any polymer through polymer modification. The author believes that the widespread use of the PmB technologies within the road pavement industry is advisable considering the genuine shortcomings of neat bitumens and the heavy-duty pavements of current transportation networks. The review conducted on the different kinds of PmBs can be concluded as the follows:  
* While plastomer-modified bitumens are suitable for improving the permanent deformation resistance of the bituminous compounds and asphalt concrete mixtures over high stresses, the absence of elasticity at low temperature limited the application of these bitumins. * The field recorded data, as well as experimental works, showed that plastomer-modified bitumens, such as polyethylene and polypropylene, are the most common plastomers resulting in compatibility problems. This is due to their non-polar chemical nature. * Despite the thermal and aging stability of plastomer-modified bitumens due to the absence of double bonds, the main problem resides in the stability of the blend (polymer + bitumen) during storage and difficulties to disperse them homogenously in the bitumen matrix. * Thermoplastic elastomer copolymers, owing to their elastic component, are usually more effective than plastomers for bitumen modification in pavement applications. The modification ranges from low-modified containing 3% polymer to a high level with polymer content of 7%. * Bitumen modification via styrene butadiene styrene (SBS) as the most commonly used elastomer has numerous benefits, including the improved thermal susceptibility, increased softening point, and slight decrease of penetration value at 25 \({}^{\circ}\)C. In addition, it has been observed that SBS can moderate the increase of stiffness due to oxidation processes. * Bitumens modified with thermosetting polymers show a high elasticity and no viscous behavior. Asphalt mixtures produced with thermosetting polymer-modified bitumen have excellent adhesive ability, excellent resistance to deformation, excellent fatigue performance, and high stiffness modulus. Even though the PmBs with thermosetting plastics have relatively high adhesion to the mineral particles and high strength they are not common for paving applications. This is because the technological properties of PmB are almost immediately deteriorated by these polymers due to their hardening properties; secondly, the rigidity of the PmB is increased at low temperatures, which results in increased thermal sensitivity; thirdly, the use of TP complicates the system and raises its price; and, finally, the effectiveness of thermosetting plastics usually appears due to their large quantities in bitumen (more than 10 wt%)
* Natural rubber latex has potential for improving bitumen binder performance by enhancing the thermal sensitivity, flexibility, stability, and stripping. In addition, its inherent elastomeric properties proved its high potential in improving long-term pavement performance of asphalt concrete by increasing rutting resistance, fatigue life, etc. Natural rubber also decreases the optimum binder content in asphalt concretes, increasing its density and stability. However, natural rubber is a highly valuable biomaterial compared to other biopolymers, hence natural rubber has been commercialized into synthetic rubber.