The viscoelastic property of bitumen is measured using dynamic shear rheometer (DSR). However, elastic property refers to the bitumen ability to recover after deformation, while the viscous property indicates the inability of binder to recover after removing load (Pszczola et al., 2018). DSR aims to determine the performance of bitumen at high, intermediate, and low temperatures through identifying the complex shear modulus (G*) and phase angle (δ). In other words, DSR test measures the resistance of binder to rutting and fatigue. However, G* refers to the rutting resistance of binder, while δ indicates the elastic behavior of bitumen. The increase in G* implies the better resistance to rutting, while the decrease in the δvalue implies the better elastic behavior of binder. In other words, higher G* and lower δ refers to the desirable performance of bitumen. However, the rutting factor of G*/sinδ is used to assess the rutting resistance of bitumen sample (Zeng et al., 2022; Gu et al., 2019; Liu et al., 2022). According to Superpave specifications, the value of rutting factor must be at least 1 kPa for unaged binder, while the rutting factor of short-term aged (RTFO) bitumen should be higher than 2.20 kPa.On the other hand, the factor of G*sinδ refers to the resistance of bitumen to fatigue cracking. The lower the factor of G*sinδ, the better the resistance to fatigue. According to Superpave specifications, the value of G*sinδ for long-term (PAV) aged binder should be less than 5,000 kPa. Additionally, the value of G*sin for long-term (PAV) aged binder at low temperature must be less than 5,000 kPa (Jia et al., 2005).

The decrease in the surrounding temperature leads to shrinkage of bitumen, which, in turn, generates stresses leading to thermal cracks due to inability of bitumen to relax stresses. However, the tests of bending beam rheometer (BBR) and direct tension tester (DTT) are used to measure the stiffness and relaxation properties at low temperatures. In the test of BBR, the bitumen specimen is submerged in a cold liquid bath, followed by subjecting the center of the sample to a specific load. Thereafter, the generated deflection by the load is identified. However, the stiffness and relaxation of bitumen is measured by the test of DTT through subjecting the sample to a constant rate of elongation, followed by the determination of sample stress and strain at failure (Jia et al., 2005).

The blend of polymers maybe miscible (homogeneous) or immiscible (heterogeneous). The main factors that affect miscibility of polymer blend are temperature, polarity, molecular weight, pressure, interfacial tension, and composition of polymer. The higher the temperature of blend, the better the miscibility of polymer blend, while the difference in polarity of polymers refers to the immiscibility of blend. This is because polar materials are attractive to polar materials and polar solvent, while the non-polar materials are attractive to the non-polar materials and non-polar solvent. In other words, there is no attraction between the polar materials and non-polar materials. Additionally, the increase in the weight of molecular significantly decrease the miscibility of blend. The high interfacial tension between the components of polymers leads to immiscibility/separation phase in the blend of polymer. Furthermore, the blend of polymer can be classified into miscible polymer blend, partially miscible blend (compatible blend), and immiscible polymer blend (Robeson, 2014; Ajitha and Thomas, 2020a; Shanks, 2020). However, the thermodynamic parameter of Gibbs free energy is used to evaluate the separation phase of polymer blend. Gibbs free energy (ΔGm) is calculated through the difference between enthalpy (ΔHm) and entropy (TΔSm) of mixing (ΔGm = ΔHm- TΔSm). Polymer blend is considered miscible if the Gibbs free energy is negative, while the positive value of Gibbs free energy implies the immiscibility of polymer blend. In other words, the negative Gibbs free energy indicates the superior interaction between the components of polymers in the blend.

Moreover, the miscible blend shows negative Gibbs free energy, single-phase morphology, and single glass transition, while the compatible blend shows negative Gibbs free energy, single/two-phase morphology, and single/two glass transition. Otherwise, the immiscible blend displays positive Gibbs free energy, two-phase morphology, and two-glass transition. Furthermore, the degree of miscibility of polymer blend can be identified through the diagram of phase. Figure 2 shows the phase diagram of polymer blend. It can be seen in the figure that there are three regions, which are stable/miscible region, unstable/immiscible region, and metastable region. The miscible region is located between the two binodal, while the immiscible region is surrounded by the curve of spinodal. Otherwise, the region area between the curve of binodal and spinodal refers to the metastable region. However, the binodal separation phase occurs when the temperature of miscible polymer blend brought to the temperature of immiscible/unstable region. The phase of binodal separation produces a fine two-phase. The separation phase of spinodal occurs when the miscible blend at the stable region is forced to the immiscible/unstable region. This separation phase generates an interconnected structures in both minor and major phases (Utracki and Wilkie, 2002; Sarath et al., 2014; Shanks, 2020). However, incompatibility/separation of polymer-modified bitumen is occurred by the same mechanism of separation phase/immiscibility of polymer blend, in which the occurrence of incompatibility and uneven poorly structure/spherical droplets between polymer and bitumen is attributed to the difference in polarity, high interfacial tension, and different in density between the components of blend. Therefore, the addition of compatibilizer to polymer-modified bitumen is required to improve homogeneity between polymer and bitumen. However, the occurrence of separation due to difference in densities of blend components is slightly different from the separation phase that occurs at the interface of the blend due to the differences in polarity, high interfacial tension, and temperature. However, the change in densities results in a significant change in the physical properties and rheological properties of polymer-modified bitumen. This is because the addition of polymer/nanomaterials with low density as compared to that of bitumen will float, while the introduction of polymer/nanomaterials with a density higher than the density of bitumen will sink. The sinking/floating of bitumen modifiers depends on the diameter and viscosity of polymer-modified blend. According to the principles of the Stokes’ law, the higher the viscosity of blend, the lower the sinking/floating (velocity of separation) of bitumen modifiers, while the lower the diameter of nanomaterials/droplet of blend, the lower the velocity of separation. The velocity of separation is identified through the equation below (Munera and Ossa, 2014; Porto et al., 2019; Behnood and Gharehveran, 2019; Brûlé, 1996). V = 2 * g * r 2 * d 1 − d 2 9 * μ (1)

Where V is velocity of separation, g is the acceleration of gravity, r is the radius of droplet, d1is the density of minor phase (nanomaterials/polymer), d2is the density of major phase (bitumen), and μ is the viscosity of the major phase (bitumen). The negative value of velocity indicates that the minor phase will float, while the positive value implies that the minor phase will sink. Furthermore, it should be indicated that this formula is used to describe the sepration due to difference in density and not the separation at the interface of blend. The separation at the interface of blend is evaluated using of morphology and glass transition temperature.

Understandably, the separation between water and oil is occurred by the difference in density, in which oil floats due to its low density as compared to density of water. In addition, separation phase/immiscibility at interface is attributed to the difference in polarity, in which water is polar and oil is non-polar, thus there are no attraction between molecules. Furthermore, the difference in polarity leads to the increase of interfacial tension, which, in turn, leads to the immiscibility between water and oil (separation phase at interface). The sepration phase at interface leads to uneven poorly structure/spherical droplets. Thus, the addition of emulsifier/surfactant is required to stabilize the blend of water and oil through coating droplets and eliminate forming of coalescing. In other words, the blend of water and oil becomes miscible by the addition of emulsifier/surfactant, this is because the molecules of emulsifier has one end attracted to water (polar) and one end attracted to oil (non-polar). Therefore, the addition of emulsifier reduces the interfacial tension and links between molecules of water and oil, which, in turn, improve morphology at interface and separation due to the difference in densities (Lu et al., 1999; Pérez-Lepe et al., 2006; Pérez-Lepe et al., 2006; Xue et al., 2014; Padaki et al., 2015; Gupta et al., 2017; Pérez-Lepe et al., 2007).

Most polymers are susceptible to degradation over time when exposed to heat, light, and oxygen. These conditions make a significant change in the physical and mechanical properties of polymers. However, the mechanism of polymers degradation can be divided into initiation, propagation, and termination. In the initiation mechanism, when the polymer is exposed to heat and light, the oxidative degradation is started by forming radical chains/free radical (R) through the hydrogen abstraction (He et al., 2021; Visan et al., 2021). The reactions of initiation are shown below. R H   → R * + H *

The propagation mechanism refers to the form of peroxy radical (ROO*) by the reaction between free radical (R) and Oxygen (O₂), which then produce new radical to react with more chains and obtain more base radicals. The reactions are described as follow: R * + O 2 →   R O O * R O O H   → R O * + O H * R O * + R H   → R * + R O H O H * + R H   → R * + H 2 O

In the termination, the coupling termination is occurred by the reactions between radicals with each other. The reactions of termination are demonstrated below. R O O * + R O O * →   R O O R + O 2 R O O * + R *   → R O O R R * + R * → R − R

Figure 8 shows the trend of annual publications of utilizing polymers as bitumen modifier. It can be seen in the figure that the published articles on polymer-modified bitumen has been notably increased from 2011 onwards. The highest number of publications was in the year of 2021 with 235 articles, followed by the year of 2022 with 205 articles. However, the number of published articles slightly decreased in the year of 2022 as compared to the published articles in the year of 2011. It can be said that the interest in the use of polymer as binder modifier is increasing exponentially. This is attributed to the benefits of polymer-modified binder in terms of enhancing the physical and rheological properties that enhances the lifespan of modified binder.

The outputs of authors, number of documents, citations, and total link strength for the bibliometric analysis of bibliographic coupling versus authors are summarized in Table 4. In addition, the outputs of network visualization is used to highlight the top authors through size of node and link. The larger the size of node and the thicker the links indicate the significant contributing of an author. As highlighted in Table 4; Figure 9, the most contributing authors are Gallegos, C, Giustozzi, Filippo, and Partal, P. In addition, the highest link strength is between Gallegos, C and Partal, P, followed by the link strength between García-Morales, M and Partal, P. However, the link strength indicates the co-occurrence/co-authorship between studies. The higher the strength of link, the more the connections between the content/keywords of studies.

The bibliometric analysis for bibliographic coupling versus sources is used to identify the most contributing sources in a specific field. However, the name of sources, number of documents, citations, and total link strength are listed in Table 4, while the network visualization is shown in Figure 10. As can be seen in the table, the sources of Construction and Building Materials, Road Materials and Pavement Design, and Iop Conference Series Materials Science and Engineering are the top three in terms of number of published documents. While the sources of Construction and Building Materials, Fuel, and Road Materials and Pavement Design are the most contributing in terms of number of citations. In addition, the most contributing sources in terms of total link strength are Construction and Building Materials, Road Materials and Pavement Design, and International Journal of Pavement Engineering. However, the large size of node in the network visualization shown in Figure 10 indicates the most contributing sources in terms of number of published articles. The thicker link strength presented in the figure implies the strong connection between the documents of sources.

The most contributing organizations in modifying base binder with polymers is identified by the bibliometric analysis between bibliographic couplings versus organizations. Table 4 and Figure 11 shows the outputs of the bibliometric analysis. As observed in Table 4 and network visualization shown in Figure 11 the most contributing organizations in terms of number of documents are University of Alberta, University of Huelva, and University of Nottingham, while the top organizations in terms of citations are Royal Institute of Technology, University of Alberta, and University of Huelva. However, the top contributing organizations in terms of total link strength are University of Huelva, Rmit University, and Royal Institute of Technology. In addition, the link strength between organizations shown in Figure 11 implies the co-occurrence/co-authorship between published documents from organizations. The thicker the strength of link, the more the relatedness between published documents in terms of content/keywords. Otherwise, it is observed that the most contributing organizations are from the developed countries. Therefore, there should be a salient support for the organizations in developing countries in terms of publishing articles and case studies related to the modification of base bitumen with polymer.

The most contributing countries in modifying bitumen with polymer is determined through the bibliometric analysis between bibliographic couplings versus countries. The findings of bibliometric analysis are displayed in Table 4; Figure 12. It can be concluded from Table 4; Figure 12 that the top contributing countries in terms of published documents are Russia, China, and Iran, while the most contributing countries in terms of citations are United Kingdom, Spain, and Canada. The higher the number of citations, the more the impact of documents. However, China, Italy, and Iran are the top contributing countries in terms of total link strength. It can be concluded that the published articles from developing countries still limited as compared to the published documents from developed countries.

The incorporation of polymers with bitumen significantly increases the physical properties of binder in terms of softening point and viscosity. On the contrary, the addition of polymers notably decreases penetration and ductility. It is documented that the addition of SBS to a base binder increased viscosity and softening point, while the penetration and ductility are reduced (Bai, 2017; Hao et al., 2017; Shah and Mir, 2020; Tang et al., 2021; Kong et al., 2021). Similarly, various studied (Zhang et al., 2012; Liang et al., 2017; Li et al., 2021), concluded that modifying a base bitumen with SBR significantly improved the physical properties of aged and unaged binder. However, introducing SIS to a bitumen notably enhanced penetration, softening point, viscosity, and ductility (Kim et al., 2019; Ji et al., 2020; Mazumder et al., 2020). According to the findings of studies (Bachir et al., 2016; Zapién-Castillo et al., 2016; Zhang et al., 2018), SEBS amended-bitumen improved physical properties of unaged and aged modified binder. It is confirmed that the physical properties of bitumen subjected to short-term aging and long-term aging could be enhanced by the addition of EVA (Al-Mansob et al., 2014; Jiang et al., 2017; Keymanesh et al., 2017). Furthermore, adding PE to a base binder produces a modified bitumen with superior physical properties (Yan et al., 2020; Liang et al., 2021; Yan et al., 2021).

Morphology properties are used to identify the size, shape, and structure of polymer-modified bitumen. In addition, the compatibility between polymer and binder is evaluated through morphology properties. Fluorescence microscopy is the common test utilized in the evaluation of morphology properties. It is reported that the addition of polymers to a binder negatively affects the homogeneity between bitumen and polymer due to the difference in the densities. Tang et al. (2021) noticed the incompatibility of 9% SBS-amended binder, in which the structure of polymers was like honeycomb. Furthermore, the concertation of polymers remarkably decreased after subjecting modified binder to short-term aging (RTFO) and long-term aging (PAV). However, authors observed the enhancement in the compatibility and aging resistance of 9% SBS-modified bitumen by introducing 0.15% sulfur. Similarly, Hao et al. (2017) concluded that adding 0.15% sulfur to 4.5% SBS-modified binder significantly enhanced compatibility and decreased degradation of polymer. On the contrary; Zhang et al. (2012) pointed out that modifying base binder with 4% SBR caused incompatibility and subjecting SBR-amended binder to aging significantly decreased the existence of polymers due to degradation. In addition, researchers stated that the addition of 0.03% sulfur improved compatibility, but sulfur is more susceptible to degradation due to aging; Li et al. (2021) confirmed that the incorporation of 4% Sasobit and 4% epoxidized soybean pol (ESO) to 4% SBS-modified binder significantly enhanced homogeneity and resistance to aging. Authors claimed that the addition of Sasobit and ESO maintained structure and concertation of polymers after aging. Liang et al. (2017) confirmed that the addition of 1.5% polyphosphoric acid (PPA) to 3% SBR-modified bitumen notably improved the compatibility. Mazumder et al. (2020) noticed that the addition of 15% SIS to a base binder significantly reduced the honeycomb structure of binder. Researchers stated that the reduction in bee structure is attributed to the dissolution of waxy particles by the addition of SIS. Zapién-Castillo et al. (2016) assured that modifying bitumen with 6% SEBS displayed poor compatibility. However, researchers observed the remarkable enhancement in compatibility after adding 6% nanoclay to SEBS-amended bitumen. Authors stated that the addition of nanoclay balanced the difference in the densities of polymer and bitumen. Al-Mansob et al. (2014) demonstrated that the addition of 6% natural rubber to a base binder showed satisfactory compatibility. Jiang et al. (2017) evaluated the compatibility of bitumen-modified with 5% EVA, 2% SBS, and 0.05% sulfur. The morphological evaluation results exhibited that before aging the modified binder with EVA showed incompatibility between bitumen and polymers, in which the interface of polymer was like honeycomb. However, the addition of SBS to EVA-modified binder improved the compatibility through the appearance of the polymer particles in the form of a continuous filament network. Furthermore, the addition of sulfur to modified bitumen with EVA and SBS displayed the best compatibility. After aging, researchers noticed that the concentration of polymer particles significantly decreased for all modified bitumen. Authors stated that the crosslinked of polymers were destroyed due to aging processes. Yan et al. (2021) indicated that the addition of 4% PE to a base binder displayed poor compatibility. However, authors declared that introducing 4% EVA to PE-modified binder enhanced the compatibility.

In a study conducted by Hao et al. (2017), the chemical composition of 4.5% SBS-modified bitumen was investigated by means of gel permeation chromatography (GPC). The findings of study demonstrated that subjecting modified binder to short-term aging (RTFTO) and long-term aging (PAV) decreased the molecular weight of polymer. Additionally, the asphaltenes components notably increased, while the maltenes composition decreased after subjecting modified bitumen to RTFTO and PAV. Authors indicated that the decrease in molecular weight is attributed to the degrading of polymer. However, researchers concluded that the addition of 0.15% sulfur to 4.5% SBS-modified binder further reduced the molecular weight of polymers. In similar content, Hu et al. (2020) noticed that subjecting 4.5% SBS-modified binder to PAV decreased percentage molecular weight of polymers from 3.5% to 0.8%, while asphaltenes content increased by about 30%; Tang et al. (2021) observed that subjecting 9% SBS-modified bitumen to PAV significantly decreased the average molecular weight of polymers and increased the average molecular weight of asphaltenes. However, researchers found that the addition of 0.15% sulfur to 9% SBS-modified binder further decreased molecular weight of polymers and increased the average molecular weight of asphaltenes. Authors attributed this change in the average molecular weight to filtration of gel permeation chromatography (GPC) specimens. Bachir et al. (2016) obtained similar findings, in which the addition of 5% SEBS to base bitumen increased the content of asphaltenes before aging and after aging.

The aim of adding polymers to a base binder is to improve the rheological properties. The rheological properties are evaluated through complex shear modulus (G*) and phase angle (δ). Complex shear modulus refers to the resistance of binder to rutting, while phase angle implies the elastic behavior of binder. The higher the complex shear modulus, the better the resistance to rutting. On the contrary, the low phase angle indicates the better elastic behavior. Furthermore, rutting factor (G*/sinδ) and fatigue factor (G*sinδ) are used to assess the resistance of bitumen to rutting and fatigue cracking. The higher the rutting factor the better the resistance to rutting, while the low value of fatigue factor indicates the better resistance of binder to fatigue cracking. However, numerous studies have investigated of modifying a base binder with polymers. In a comparative study conducted by Hu et al. (2020), a base binder was modified with 4.5% SBS, 12% high viscosity modified asphalt (HVMA), and 16% HVMA. However, the rheological properties of modified bitumen subjected to RTFO and PAV were investigated. The findings of study demonstrated that the unaged and aged of 12% and 16% HVMA-modified bitumen showed better complex shear modulus and phase angle than the modified bitumen with 4.5% SBS. Hao et al. (2017) concluded that subjecting 4.5% SBS-modified bitumen to RTFTO and PVA significantly increased complex modulus and reduced phase angle. Authors noticed that the addition of 0.15% sulfur improved complex shear modulus and phase angle. According to Shah and Mir. (2020), the addition of 2% montmorillonite clay (OMMT) to 4% SBS-amended binder notably enhanced rutting factor and fatigue factor. However, the authors noticed that subjecting 4% SBS modified-bitumen decreased rutting and fatigue factor. Researchers confirmed that the addition of OMMT improved rutting and fatigue factor of aged bitumen. Similarly, Zhang et al. (2012) indicated that the phase angle of 4% SBR modified-binder significantly decreased after modified bitumen exposed to PAV; Li et al. (2021) observed that the addition of 4% Sasobit and 6% epoxidized soybean pol (ESO) to 4% SBR amended-bitumen notably enhanced complex shear modulus and phase angle of subjected modified binder to short and long-term aging. Mazumder et al. (2020) confirmed that modifying base binder with 15% SIS significantly improved rutting and fatigue factor as compared to unmodified binder. Bachir et al. (2016) concluded that adding 5% SEBS to a base binder improved complex shear modulus and phase angle before and after aging. In a research conducted by Al-Mansob et al. (2014), natural rubber was introduced to a base binder at different contents 0%–12% in 3% increment by bitumen weight. The study findings displayed that adding natural rubber at content of 6% improved unaged bitumen performance to rutting and fatigue cracking in comparison with unmodified binder. In a comparative study conducted by Jiang et al. (2017) a base binder was modified with EVA, SBS, and sulfur to investigate the impact of utilizing these polymers on the rheological, properties of modified binder. Three types of modified binder were prepared, the first type was prepared by modifying a base bitumen with 5% EVA, the second type was fabricated by amending base binder with 5% EVA and 2% SBS, the third type was equipped by introducing 0.05% sulfur to a bitumen incorporated 5% EVA and 2% SBS. According to dynamic shear rheometer evaluation, the short-term aged modified bitumen with EVA exhibited the highest complex shear modulus and phase angle, followed by the modified bitumen with EVA and SBS, while the modified bitumen with EVA, SBS, and sulfur showed the lowest complex shear modulus and phase angle. However, the higher complex shear modulus indicates the better resistance to rutting, while the lowest phase angle implies the better elastic behavior. Thus, the addition of sulfurificantly improved aging resistance of bitumen. Yan et al. (2021) assessed the performance of modified bitumen with EVA and low-density polyethylene (LDPE). In the study, EVA was introduced to a base binder at different proportions 0, 4, 6, 8% by binder weight. Furthermore, EVA modified-binder was also amended with 4% of LDPE. Researches noticed that the unaged modified bitumen with 4% LDPE showed the best complex shear modulus, phase angle, followed by the modified bitumen with 4% LDPE and 8% EVA. Senise et al. (2017) evaluated the performance of different polymers modified-bitumen (3% SBS/0.05% sulfur, 3% EVA/0.05% sulfur, and 3% EBA/0.05% sulfur). The findings of study demonstrated that SBS/sulfur showed the best complex shear modulus and phase angle, followed by EBA/sulfur, and EVA/sulfur modified bitumen.

The low-temperature performance of bitumen are evaluated by means of bending beam rheometer (BBR) and direct tension tester (DTT). The parameters of relaxation ratio (m-value) and elongation are used to identify the performance of bitumen at low temperature. The higher the m-value and elongation, the better the resistance of binder to cracking at low temperature. However, several studies investigated the performance of polymer-modified bitumen at low temperature. Liang et al. (2021) investigated low-temperature performance of bitumen modified with 3% SBR and different proportions of polyphosphoric acid (PPA) i.e. 0%–2% in 0.5% increment. The findings of bending beam rheometer test showed that the base binder at low temperature exhibited higher stiffens and lower relaxation rate (m-value) than the modified binder, while the addition of 3% improved the performance of binder at low-temperature, in which relaxation rate (m-value) was increased. Researchers stated that the optimum content of PPA is 1.5% by binder weight. Mazumder et al. (2020) indicated that modifying a base binder with 15% SIS displayed superior performance at low-temperature, in which the relaxation ratio (m-value) of 15% SIS modified-bitumen remarkably increased. Zhang et al. (2018) noticed that adding 0.8% PPA to 4% SEBES significantly enhanced m-value of aged and unaged bitumen. In a comparative study conducted by Jiang et al. (2017), a base binder was modified with EVA, SBS, and sulfur to investigate the impact of utilizing these polymers on the low-temperature performance of binder. Three types of modified binder were prepared. The first type was prepared by modifying base bitumen with 5% EVA, the second type was fabricated by amending base binder with 5% EVA and 2% SBS, the third type was equipped with introducing 0.05% sulfur to bitumen incorporated 5% EVA and 2% SBS. The low-temperature assessment findings demonstrated that the unaged and aged modified binder with EVA and SBS displayed the highest m-value, followed by the modified bitumen with EVA, SBS, and sulfur. Yan et al. (2021) assessed the low-temperature performance of modified bitumen with EVA and low-density polyethylene (LDPE). In the study, EVA was introduced to a base binder at different proportions, i.e. 0, 4, 6, 8% by binder weight. Thereafter, EVA modified binder was also amended with 4% of LDPE. Authors observed that unaged modified bitumen with 4% LDPE showed the best m-value, followed by the modified bitumen with 4% LDPE and 8% EVA. Table 5 summarizes the findings of the literature review.

Incompatibility is considered as the main drawback of polymer-amended bitumen However; different strategies have been used to decrease the incompatibility of polymer-modified bitumen such as adding waste oil, nanomaterials/nanoclay, sulfur, wax, polymers, and compatibilizers (reactive elastomeric terpolymer, PE-g-MA). It is documented that the addition of waste oil into polymer-amended bitumen significantly improves compatibility, aging resistance, and low-temperature performance. This is because adding oil reduces the viscosity of the major phase (bitumen) in the blend, which, in turn, decreases the phase separation. In addition, introducing oil to a modified binder with polymers reduces viscosity, softening point, rutting factor, and increases penetration, elastic recovery, and ductility. This is attributed to the improvement of elastic behavior of blend, which, in turn, increases the resistance of polymer blend to aging and improves low-temperature performance (Nie et al., 2020; Ren et al., 2021). Otherwise, the decrease in the performance of polymer-amended bitumen incorporating oil is attributed to the fact that the introduction of oil softens the blend. Furthermore, it is proven that adding nanomaterials such as (nanoclay, nanosilica, nano-ZnO, nano-TiO₂, and nano-CaCO₃) to a polymer-modified binder improves compatibility, aging resistance, physical properties, and rheological properties. The improvement in the compatibility of polymer-amended binder is attributed to the reduction in dispersed phase by decreasing the interfacial tension (Luo et al., 2017; Peng et al. 202; Zhang et al., 2016). Moreover, introducing EVA to SBS/GTR/PE-amended base binder significantly enhances compatibility, physical properties, and rheological properties of the modified binder.