Feasibility investigation of using waste laminated packaging as bitumen performance enhancer

Millions of tons of laminated packaging are extensively utilized in aseptic food packaging due to its advantages in transporting and storing liquid foods, leading to the annual generation of waste laminated packaging (WLP). To address this concern, this study processes WLP recycled from milk and fruit juice packages into particles. The properties of WLP-modified bitumen were characterized through conventional and rheological tests, and the results were compared with those of the base bitumen. The tests reveal that the addition of WLP increases the softening point and peak force while decreasing penetration and ductility. Additionally, higher WLP content results in a larger modification index, higher failure temperature, lower non-recoverable creep compliance, and lower stress sensitivity. Furthermore, the stabilizing effect of low-density polyethylene in WLP, combined with the complete cross-linking of cellulose fibers, contributes to enhancing the fatigue life of the bitumen.


Introduction
Laminated packaging, commonly known as beverage cartons, stands out as one of the most widely employed material structures in aseptic food packaging due to its advantages in transporting and storing liquid foods.In 2021 alone, over 192 billion Tetra Pak packages were sold globally (Tetra Pak 2021).Given the substantial production and consumption of laminated packaging, there is a pressing need for alternatives to mitigate environmental concerns arising from the landfill and incineration of waste laminated packaging (WLP).
At the same time, the asphalt mixture is one of the most common types of pavement surface materials used in the world.However, the climate environment and continuous traffic loads can significantly impact the asphalt mixture's ability to resist pavement diseases (Shen et al 2024, Fu et al 2023).To enhance the service life of asphalt mixtures in challenging conditions, bitumen, acting as the binder that binds individual aggregates in the asphalt mixture, becomes the primary component targeted for modification.Consequently, researchers have proposed the concept of utilizing various waste materials to modify bitumen, aiming for a mutually beneficial outcome.For instance, Li et al (2021) recycled waste polyethylene terephthalate (PET) from end-of-life plastic products to modify bitumen.Their findings revealed that PET can act as an anti-stripping agent, enhancing the asphalt mixture's resistance to moisture-induced damage.Additionally, Celauro et al (2023) investigated the impact of biochar, derived from the pyrolysis of birch and beech wood, on the aging resistance and mechanical performance of bitumen.They concluded that the presence of biochar in bitumen positively influences its oxidative resistance, resulting in more stable bitumen under UV irradiation.Furthermore, the high specific surface area and porous characteristics of biochar make it highly promising for runoff purification in permeable pavement (Liu et al 2022).These practices not only enhance the road and functional performance of bitumen and asphalt mixture but also contribute to the recycling of waste materials.
Based on the literature analysis, the use of WLP for bitumen modification is identified as a promising and viable approach.Previous studies reveal that the primary component of WLP is cellulose fibers, followed by low-density polyethylene (LDPE) and aluminum.Notably, cellulose fibers constitute 63%-75% by weight in WLP, while LDPE accounts for 25%-30% by weight (Haydary et al 2013, Andrés-Valeri et al 2018).Mohammed et al (2018) employed cellulose fibers and glass fibers to enhance bitumen.Their findings indicated that both types of fibers contributed positively to the resistance against permanent deformation in asphalt mixtures.However, cellulose fibers demonstrated superior effectiveness in enhancing the elasticity of bitumen.Rahman et al (2020) investigated the rheological performance of bitumen modified with cigarette butts (CBs).These CBs consist mainly of cellulose acetate-based fibers wrapped in paper.The study concluded that bitumen modified with 0.3% CBs met both workability and industry requirements, providing a sustainable solution for recycling a substantial amount of waste CBs.Simultaneously, Alghrafy et al (2021) incorporated varying proportions of LDPE recycled from polyethylene to modify virgin bitumen.Their observations revealed that as the LDPE content increased, the binders exhibited improved resistance to rutting under heavy traffic loading and hightemperature conditions.Geckil et al (2022) utilized waste LDPE to modify bitumen, concurrently introducing triethanolamine to establish chemical bonds between bitumen and LDPE.The chemical interaction between waste LDPE, TEOA, and bitumen results in the formation of a homogeneous single-phase structure.Moreover, the addition of LDPE, particularly at a 4% content, leads to substantial enhancements in the permanent deformation, fatigue resistance, and thermal crack resistance of bitumen.
In summary, both cellulose fibers and LDPE play a positive role in bitumen modification.Therefore, if WLP can be decomposed to obtain its constituent materials, it can be utilized for bitumen modification.However, the superior performance of WLP's multilayer structure makes it challenging to separate into distinct compounds.Hydro pulping has been employed as a practical method for recovering cellulose fibers, but its application is limited to the recycling of separated and cleaned cartons, as well as craft paper (Korkmaz et al 2009).Moreover, the separation of aluminum and LDPE from paper requires the redesign of certain equipment in paper mills.Alternatively, various chemical methods have been proposed for the efficient recycling of WLP, including hydrothermal treatment, pyrolysis, switchable hydrophilicity solvents, and sulfuric acid hydrolysis (Aziz et al 2017, Samorì et al 2017, Xing et al 2018).However, these methods have a limitation: the outcomes of WLP processing heavily depend on technical parameters such as processing temperature, time, and reactor specifications.Consequently, the process is considered expensive and cumbersome for achieving profitability through WLP recycling.Opting for the recycling and reuse of WLP as a whole, instead of separating its individual components, eliminates the need for intricate process parameters inherent in the aforementioned methods.Notably, based on the research mentioned above, WLP, consisting of cellulose fibers and LDPE, is expected to enhance bitumen performance.
To evaluate the feasibility and effectiveness of using WLP as a bitumen modifier, recycled WLP particles from milk and fruit juice packages are blended into the base bitumen with varying contents.Subsequently, standard conventional tests, covering penetration, softening point, and ductility, are conducted on the modified bitumen.This is followed by a series of rheological performance assessments, including temperature sweep tests, MSCR tests, frequency sweep tests, and LAS tests.

Materials
The binder chosen for the experimental program was a 50/70 penetration grade bitumen.To enhance the bitumen, WLP derived from recycled milk and fruit juice packages were utilized, which were manually collected from domestic waste.It's important to highlight that the WLP was collected manually, avoiding sorting equipment to prevent the introduction of impurities that automated sorting processes might bring.Automatic sorting processes can result in secondary pollution due to the mixing of dry and wet garbage.
After recycling the WLP, the first important aspect was to process the WLP for the preparation of the modifier.As shown in figure 1, firstly, the WLP was cut open, and the plastic caps and the food residue were removed.Secondly, the WLP sheets were cleaned under running water and dried in the air.Thirdly, the WLP was shredded twice through rotary shearing into particles with a diameter of less than 2 mm.Finally, these WLPs obtained from the rotary shearing were poured into the cutting mill, and were cut to the required size of at most 0.5 mm, which was checked with a sieve contained in the cutting mill.

Preparation of sample
In this section, recycled WLP particles were high-speed sheared with the base bitumen to prepare waste laminated packaging modified bitumen (WMB).The detailed process for preparation of WMB is shown in figure 2. Firstly, the bitumen, about 600 grams, was heated in the oven for 1 h.Then the heated bitumen was hung in a 180 °C oil-bath and the shear mixer at high speed was lowered into the bitumen.According to previous studies on reusing waste PE and waste packaging tape as bitumen modifiers (Yu et al 2015, Maharaj et al 2015 and Yu et al 2019), the shearing time was set as 60 min.In the first 15 min, WLP particles were gradually added into bitumen with a shearing speed of 2000 rounds per minute (rpm) to avoid the agglomeration and splashing of WLP particles.After this, the shearing speed was kept set at 2000 rpm for the remaining 45 min.The ratio of WLP to bitumen was determined based on the initial weight of the bitumen (e.g., for 100 grams of bitumen 1 gram of WLP was applied at a modification level of 1%).The preliminary tests of this study revealed that the WLP particles lacked the ability to evenly distribute in the base bitumen once its dosage exceeded 7%.Hence, the maximum dosage of WLP particles was set as 7%.In summary, to investigate the influences of WLP dosage on bitumen, the WLP dosages of 1%, 3%, 5% and 7% were used, and their modified bitumen was named as the 1%, 3%, 5% and 7%.

Conventional tests
The conventional tests were conducted based on DIN EN 1426, DIN EN 1427, andDIN EN 13589, respectively.Among them, the liquid is gradually heated at a uniform rate of 5 °C min −1 in the softening tests.In addition, the penetration tests and force ductility tests were completed at 25 °C and 15 °C, respectively.Three replicates of each test were prepared.

Temperature sweep tests
According to ASTM D6373, during the temperature sweep test, all the bituminous samples were oscillated with a constant strain amplitude of 12% at a fixed shear frequency of 10 rad s −1 .The test temperature increased from 58 °C with an interval of 6 °C until it reached the critical temperatures.The critical temperatures correspond to the temperature when the rutting factor, i.e., |G * |/sinδ, reaches 1 kPa.When the test temperature is more than 30 °C, the 25 mm plate and the 1 mm gap were chosen, while the test temperature is 30 °C or less, the 8 mm plate with a 2 mm gap was chosen.Three replicates of each test were completed.

Multi-stress creep recovery (MSCR) tests
The MSCR tests were completed at 64 °C, and three stress levels (0.1 kPa, 1.6 kPa, and 3.2 kPa) were selected according to DIN EN 16659.The non-recoverable creep compliance (J nr ) and stress sensitivity parameter (J nr-diff ) are utilized as the evaluation indicator, as shown in equations ( 1  where ε nr and σ respectively represent the non-recovery strain at the end of the recovery period and the applied stress.The 25 mm plate and the 1 mm gap were chosen in this test, and three replicates of each test were completed.

Frequency sweep tests
The frequency sweep tests were conducted within the linear viscoelastic (LVE) range.Based on this test, the master curves of WMBs were constructed, which presents the overall rheological properties of bitumen.Before conducting the frequency sweep tests, a stress amplitude sweep test was performed on the base bitumen to determine the LVE range.During the frequency sweep test, all the bituminous samples were oscillated from 0.1 Hz to 10 Hz.The temperature range is between 10 °C to 50 °C.Based on the Time-Temperature Superposition Principle (TTSP), the 20 °C was selected as reference temperature to construct the master curve.The Christensen-Anderson-Marasteanu (CAM) model, which is feasible for both base and WLP modified bitumen, was used to smooth the master curve.The CAM model is mathematically represented as the following: where G g is the glassy modulus, ω c is the crossover frequency, and υ and w are parameters of model.The construction of the curves was conducted with the aid of the Microsoft Excel Solver.The nonlinear least square regression techniques were used to obtain the model parameters.The goal function used was the sum of square error (SSE), as shown in equation ( 4) where G * exp and G * model respectively represent the measured complex modulus and predicted modulus by the CAM model.

Linear amplitude sweep (LAS) tests
LAS tests were conducted at 25 °C to compare the fatigue performance of different WMBs.According to AASHTO 101-14, the LAS test includes a frequency sweep phase and an amplitude sweep phase.The frequency sweep phase employed a shear strain of 0.1% and the frequency range is between 0.2 Hz and 30 Hz.The amplitude sweep phase was conducted in a strain-control mode.The frequency is 10 Hz and the strain range is 0%-30%.The viscoelastic continuum damage method was used to predict the fatigue performance at strains of 2.5% and 5%.

Conventional tests
The penetration and softening points of WMBs with varying WLP content are illustrated in figure 3. Penetration is used to assess bitumen hardness, and the softening points are indicative of the permanent deformation of asphalt mixtures.It was observed that the penetration values decrease and softening points increase significantly with the addition of WLP, especially as the WLP dosages increase.For instance, when the WLP content increases from 1% to 7%, the softening point rises from 50.59 °C to 64.5 °C, and the penetration decreases from 51.8 (0.1 mm) to 33.0 (0.1 mm).However, an interesting phenomenon emerged: when 1% WLP was added, the penetration of WMB decreased by almost 10 (0.1 mm).As the WLP content continued to increase, the rate of decline in penetration slowed down significantly.Conversely, the softening point exhibited the opposite trend.This may be attributed to the distinct effects and content of LDPE and cellulose fibers in WLP on the penetration and softening point of bitumen.Previous studies support these findings.AI-Hadidy and Tan (2009) found that with an increase in LDPE content from 2% to 8%, the softening point increased from 52.5 °C to 68.5 °C, while the penetration decreased from 51 (0.1 mm) to 23.5 (0.1 mm).Additionally, Mohammed et al (2020) observed an increase in the softening point from 55.85 °C for the base bitumen to 65.4 °C for the 0.9% LDPE modified bitumen, and the penetration decreased from 41.9 (0.1 mm) to 24.4 (0.1 mm).This suggests that the presence of LDPE not only increases the softening point but also reduces penetration.Moreover, Mohammed et al (2018) found that unevenly distributed and relatively short cellulose fibers are less likely to form a rigid network in bitumen, resulting in a minimal impact on penetration.However, as the content of cellulose fibers increases, there is a significant improvement in the softening point.For WLP, cellulose fibers have the highest content, followed by LDPE.A lower content of LDPE in WLP has a minor impact on penetration, while both components in WLP positively contribute to the softening point.In this case, the softening point will be more significantly influenced by WLP.
During the force ductility test, the relationship between the applied force and the corresponding displacement were collected, as shown in figure 4. Initially, the applied load increased with the displacement.After reaching a peak, the applied load nonlinearly decreased as displacement continued until the test sample fractured.The peak force indicates the bearing capacity of bitumen to the monotonic loads, while the fracture displacement, representing the displacement at the point of sample fracture, indicates the ductility of bitumen.Therefore, both peak force and fracture displacement offer insights into bitumen ductility.It can be observed that peak force of WMB increases with the rise in WLP content.This may be attributed to the presence of WLP, which could lead to an increase in the viscosity and elastic modulus of the bitumen.Such enhancements might result in the need for greater force to stretch or deform the material during the ductility test.However, the fracture displacement decreases with the increase in content.This may be attributed to the presence of insoluble paper fibers in WLP could make the bitumen more brittle and less homogeneous, consequently reducing its deformability.

Temperature sweep tests
The correlation between complex shear modulus and temperature, as well as the correlation between phase angle and temperature, is depicted in figure 5.This figure allows researchers to intuitively observe the temperature sensitivity of bituminous stiffness.From figure 5(a), as the test temperature increased, the complex modulus of all the bituminous samples decreased, which complied with base bitumen behavior.In addition, it was observed that the incorporation of WLP enhanced the stiffness of bitumen, and an increase in the dosage of WLP showed positive effects on the complex modulus of bitumen in the temperature range from 58 °C to 76 °C.This may be attributed to the high molecular weight and relatively long molecular chains of LDPE, which could result in the formation of a stronger network structure at higher temperatures, thereby increasing the shear modulus.However, the improvement effect of 1% was almost identical to that of 3%, which means that only bitumen with higher WLP content showed better-rutting resistance performance at high temperatures.WLP dosage is recommended to be higher than 3% to obtain significant modification effects on bitumen.
In figure 5(b), it can be found that the phase angle of WMBs showed a reversed tendency.Typically, the phase angle of the base bitumen increases with rising temperature, indicating a progressively dominant influence of viscosity until the bitumen approximates a Newtonian fluid.However, after being blended with WLP, the viscoelastic property of bitumen was essentially altered.As temperature increases, the phase angle decreases, especially at relatively high temperatures.With an increase in WLP content, WMBs performed more elastically at temperatures below 64 °C.A plausible reason is the viscosity, i.e., flow resistance, of WMBs is strongly affected by the particle effect from WLP and the viscosity of base bitumen.With temperature increases, the influences of bitumen viscosity reduce, allowing the particle effect of WLP to govern the viscosity of WMBs, consequently reducing the phase angle of WMBs.
Figure 6(a) illustrates the rutting parameter and failure temperature derived from temperature sweep test results.The rutting parameter is considered to be an indicator for the evaluation of the high-temperature performance of bitumen.Based on this indicator, it can be concluded that the WLP-modification favorably influences the high temperature performance.This would imply a higher resistance to rutting.The temperature sweep test, also known as the Superpave rutting factor test, begins at 58 °C.Subsequently, the temperature increases by 6 °C, and the sequence repeats.This cycle continues until the rutting factor |G * |/sinδ falls below 1.The failure temperature is determined when |G * |/sinδ equals 1.It is evident that the failure temperatures for base bitumen, 1% WMB, and 3% WMB are 68.3 °C, 74.1 °C, and 75.7 °C, respectively.As discussed in the preceding results, the 1% and 3% modifications show a slight increase in the failure temperature.However, beyond 3% modification, each increase raises the failure temperature by roughly 4 °C, reaching 83.63 °C for 7%.The same phenomenon can also be observed from the modification index of base bitumen and modified bitumen in figure 6.The modification index is the ratio of the failure temperature of WMBs to that of base bitumen.A higher WLP content led to a greater modification index, indicating the positive effect of WLP on the hightemperature performance of bitumen.Further, the WLP dosage of 3% appears to be a critical value, beyond which the modification effect became considerable.This suggests a nearly linear improvement from this modification level onward.In addition, in a previous study (Duarte and Faxina 2021), the failure temperature of 4% LDPE-modified bitumen is reported as 71.2 °C, lower than that of 1% WMB.This indicates that the enhancing effect of WLP on the high-temperature performance of bitumen surpasses that of LDPE.This could be attributed to the presence of many cellulose fibers in WLP, which have low viscosity and high absorption.

MSCR tests
MSCR testing was conducted on all the involved bitumen samples to assess their high-temperature performance and the corresponding stress sensitivity.Table 1 presents the J nr and J nr-diff for each stress phase at every modification level.A lower J nr indicates better rutting resistance.It can be easily found that the 7% WMB exhibits the lowest J nr across all stress levels.This is because the addition of WLP is beneficial to an increase in the elastic component of bitumen, which results in better recovery behavior at high temperatures.The previous study (Duarte and Faxina 2021) found that the J nr values at 0.1 and 3.2 kPa for the 2% LDPE modified 50/70 bitumen base asphalt were 3.051 and 3.395, respectively, which are approximately 1.2 times those of the corresponding values for 1% WMB.This means that the improvement effect of WLP on the high-temperature performance of bitumen is better than that of LDPE.In addition, the J nr-diff reflects the sample's reaction to stress increases.According to the value of J nr-diff , it can be found that the stress sensitivity of WMB increases significantly with the increase of WLP content.For example, the J nr-diff (0.1-3.2 kPa) of WMB containing 1% WLP is 20.90%, while the J nr-diff (0.1-3.2 kPa) of WMB containing 7% WLP is 196.77%.Meanwhile, the J nr value of 2% LDPE is 1.25 times that of 1% WMB.The J nr-diff results indicate that the increase in WLP content significantly influences the stress sensitivity of the base bitumen.However, it's worth noting that, per previous studies, the above method for assessing stress may not be accurate bitumen with high content of WLP.In this case, an alternative calculation equation in another study was proposed to assess the stress sensitivity of modified bitumen (Stempihar et al 2018), as shown in equation (5).
where - J nr slope is the slope of the J nr value between 0.1 and 3.2 kPa stress level.- J nr slope does not include J nr, 0.1 in the denominator; thus, the J nr, 3.2 magnitudes will not influence the results.Based on the equation (5), the -J nr slope (0.1-3.2 kPa) of base bitumen and WMBs is shown in table 1.It can be clearly seen that the values of -J nr slope (0.1-3.2 kPa) and J nr-diff (0.1-3.2 kPa) obtained for the same bitumen are completely different, especially when the bitumen is modified with a high content of WLP.For example, when the WLP content is 5% and 7%, the J nr-slop (0.1-3.2 kPa) is 23.55% and 19.68%, respectively.This result indicates that WMBs exhibit lower stress sensitivity.

Frequency sweep tests
The black diagrams obtained from the frequency sweep tests for both the base bitumen and WMBs are presented in figure 7. Notably, the black diagrams exhibited inconsistency, particularly for those with higher dosages of WLP.It indicated that the WMB does not strictly conform to the thermal-simple viscoelastic.The departure from thermo-rheological simplicity can be attributed to polymer modification, a phenomenon reported in previous studies (Airey 2002).The presence of WLP causes discontinuous waves or branches in the diagrams.At high temperatures, the stiffness and the viscoelastic properties were strongly affected by the WLP, especially when the temperature surpasses the softening point of the base bitumen.As the temperature increases, the impact of bitumen viscosity diminishes, enabling the particle effect of WLP to control the viscosity of WMBs.Consequently, WMBs and base bitumen exhibited different black diagrams.Nevertheless, despite this variation, all samples exhibit a monotonous tendency in their black diagrams, indicating that the time-temperature superposition principle remains applicable for WMBs.
Accordingly, the master curves of base bitumen and WMBs were shown in figure 8 based on the CAM model and the parameters involved in the CAM model were presented in table 2. As shown in figure 8, for all the bitumen, the lower the frequency, the smaller the corresponding complex modulus.Compared with the base bitumen, WMBs had higher modulus in all the frequency ranges, indicating a good anti-rutting resistance.This could be attributed to the incorporation of LDPE molecular chains, resulting in the development of more robust network structures, especially at elevated temperatures.Such a network structure has the potential to elevate the shear modulus, imparting greater stiffness to the bitumen.In addition, as seen in table 2, the glassy modulus is 1 GPa.Therefore, the master curves approximated to a horizontal asymptote with increasing frequency for all samples.

LAS tests
Figure 9 presents the fatigue life of the involved bitumen determined by the LAS test at different strain levels.A higher fatigue life indicates better resistance to damage.As shown, the fatigue life of WMB was higher than that of base bitumen.This means that the positive effect of WLP on fatigue damage resistance.It can be observed that the fatigue life of 5% WMB and WMB was higher than that 3% WMB.This is because the LDPE in WLP has stabilizing effect and the cellulose fibers in WLP have formed sufficient crosslinks when the bitumen contains a high content of WLP.However, the fatigue life of 7% WMB was slightly lower than that of 5% WMB at 5% strain degrees.This may be attributed to the decrease in fatigue life caused by insoluble cellulose fiber, which was also found in the previous study of Norgbey et al (2020).In addition, previous studies added the 7.5% LDPE into the 85/100 pen grade bitumen, and they found that the fatigue life of the LDPE-modified bitumen was 14075 and 721 at two strain levels (2.5% and 5%) (Mansourian et al 2022).In this study, the fatigue life of the WMB modified by 1% WLP can be up to 18286 (2.5%) and 2988 (5%) at the different strain levels.In summary, it is feasible to recycle waste WLP as bitumen modification material, and it shows a beneficial effect on the fatigue property of bitumen.

Conclusion
The main components of WLP are the cellulose fibers, followed by the LDPE and aluminum.The enhancement effects of the LDPE and cellulose fibers as bitumen modifiers have been demonstrated previous studies.In this study, feasibility and effectiveness of using WLP as a bitumen modifier were evaluated.In this case, the WLPs were manually collected from domestic waste and then processed into particles with 0.5 mm.Subsequently, the waste laminated packaging modified bitumen (WMB) was prepared by blending the WLP with base bitumen.Meanwhile, the experiments were conducted on WMB and base bitumen, including conventional tests and rheological tests.Based on the analysis, the following conclusions can be drawn: (1) Incorporating WLP affected the conventional properties of base bitumen, i.e., WLP increases the softening point and peak force, and reduces the penetration and ductility of WMBs.
(2) The WLP dosage showed positive influences on the complex modulus of bitumen in a broad temperature range.However, as the temperature increases, the phase angle of WMB shows an opposite trend compared to the base bitumen.This is because with rising temperatures, the influence of bitumen viscosity decreases, allowing the particle effect of WLP to dominate the viscosity of WMB.
(3) A higher WLP content led to a greater modification index, higher failure temperature, and lower nonrecoverable creep compliance, indicating the positive effect of WLP on high-temperature performance.Meanwhile, it can be concluded that the stress sensitivity of WMB is not significantly influenced by the content of WLP, regardless of lower and higher WLP content.
(4) The black diagrams for base bitumen and WBMs showed a monotonous tendency, which suggested that the time-temperature superposition principle was still applicable for WMBs Meanwhile, the WMBs had higher modulus in all the frequency ranges, indicating a better anti-rutting property.The fatigue life of WMB was higher than that of base bitumen.In addition, the fatigue life of 5% WMB and 7% WMB was higher than that of 3% WMB.This is because the LDPE in WLP has a stabilizing effect and the cellulose fibers in WLP have formed sufficient crosslinks when the bitumen contains a high content of WLP.However, the fatigue life of 7% WMB was slightly lower than that of 5% WMB at 5% strain level.This may be attributed to the decrease in fatigue life caused by insoluble cellulose fiber.In general, the WLP shows a beneficial effect on the fatigue property of bitumen.
The conclusions drawn above are based on a limited set of tests.Therefore, further research efforts should be dedicated to conducting a comprehensive test program to unveil additional mechanical properties of WMBs, such as moisture susceptibility and bending beam rheometer tests.The modification mechanism of WLP at the microscale should be investigated using advanced testing methods, such as a scanning electron microscope.Subsequently, WMBs could be applied more extensively in the manufacturing of asphalt mixtures.Simultaneously, the performance of these asphalt mixtures should undergo thorough testing.Ultimately, reusing and recycling waste packages can contribute to saving natural resources and mitigating environmental and energy pressures.In this context, an economic benefits analysis and life cycle assessment method can be employed, encompassing related costs, as well as fossil fuel and gas emissions throughout the life cycle stages.

Figure 1 .
Figure 1.Recycling and processing of the WLP.

Figure 2 .
Figure 2. Mixing process for preparation of WMB.

Figure 3 .
Figure 3. Penetration and softening point of bituminous sample.

Figure 4 .
Figure 4. Force ductility test results of test sample.

Figure 5 .
Figure 5. Isochronal plots of complex shear modulus phase angle for base bitumen and WMBs: (a) Complex modulus versus temperature; (b) Phase angle versus temperature.

Figure 6 .
Figure 6.Results of test: (a) Superpave rutting factors and failure temperature; (b) Modification index.

Figure 9 .
Figure 9. Fatigue life of involved bitumen derived from LAS test results.

Table 2 .
CAM model parameters for master curve construction.