Superpave Binder Research Articles

Investigation of rheological properties of aged polymer modified binders

Bituminous pavement layers used in road flexible superstructure are the top layer that is directly exposed to the effects of traffic and the environment and therefore must be very robust in terms of mechanical properties. To enhance the resistance of pavements against traffic loads and permanent deformations, Styrene Butadiene-Styrene (SBS) polymer additive is generally preffered. The high demand for SBS often presents challenges in obtaining it when needed, leading to a consideration of alternative additives. In this study, three different polymers, namely 701, 611, and SBS, were compared to assess their effectiveness as modifiers for bituminous materials. Modified bitumens were prepared using SBS, 701 and 611 polymers prepared under specified conditions. The modified binders were subjected to long and short term ageing. For both pure and modified binders, the Superpave binder (dynamic shear rheometer) test was conducted. Consequently, these binders improved the performance of the pure binder when the Superpave binder test findings of the four distinct binders employed in the study were analyzed.

Benchmarking Recycled Binder Blends Using Statistical Analysis: A Case Study of Virginia and North Carolina

Recycling agents (RAs) are added to asphalt binder blends containing recycled materials to mitigate the negative effects of adding oxidized material to asphalt mixtures. Several methods exist to select a particular RA dosage to restore a specific Superpave performance parameter. However, the rheological similarities between the RA-modified systems and typical virgin binders across the complete range of temperatures remain to be ascertained. In this study, two RA dosage selection procedures, one aiming to restore high-temperature performance grade and the other aiming to restore low-temperature performance grade were statistically compared. Quality assurance datasets from Virginia and North Carolina were used to benchmark the typical virgin binder properties, and 17 recycled binder blends using constituent materials from the two states were studied with respect to Superpave binder properties. Both univariate and bivariate statistical analyses were applied to compare and contrast the rheological properties of these blends with the benchmarked virgin binder properties for the two states. Then, a statistical similarity analysis was done using the Mahalanobis distance to evaluate the rheological properties of these blends with those of the reference binders. The study found that both dosage selection procedures were successful in achieving rheological similarity at target-specific temperatures and for specific binder properties but might not necessarily yield similar properties at other temperatures. Finally, an example application is presented using statistical analysis to select an RA dosage that yields a rheological fingerprint more similar to that of virgin binder systems.

Experimental Analysis to Evaluate the Impact of Styrene-Butadiene-Styrene and Crumb Rubber on the Rutting and Moisture Resistance of Asphalt Mixtures

The most severe distresses in asphalt pavement are rutting, fatigue, and low-temperature cracking; therefore, to solve these problems, it is essential to modify asphalt binders in asphalt concrete mixtures. In this study, a comparison between using styrene-butadiene-styrene (SBS) and crumb rubber (CR) as modifiers for asphalt binders to overcome distress issues was conducted. Base and SBS or CR-modified binders were subjected to all conventional and Superpave binder tests. Engineering tests such as the Hamburg wheel tracker and indirect tensile strength ratio were also run to evaluate the engineering properties. The used SBS percentages were 1, 2, 3, 4, and 5%, while CR percentages were 3, 6, 9, 12, and 15% by total weight. The results showed lower penetration, higher softening point, viscosity, and elastic recovery for both additives. In addition, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests showed increasing values of both high and low temperatures of modified asphalt performance grade (PG) with increasing SBS or CR percent. The tensile strength ratio and Hamburg wheel tracker results showed the best engineering properties at 3% SBS or 9% CR, the optimum percent. A triple percentage of CR is needed to get the same effect of SBS for the asphalt mixture.

Improvement of Engineering Properties of Asphalt Binder and Mixture by Using SBS Additive Material

Rutting, thermal cracking, and stripping are among the most severe distress types in asphalt pavement. In this study, a specified type of styrene-butadiene-styrene (SBS) was used as a modifier for a low viscosity asphalt binder G80/100 (PG 58-22) to overcome the issues of the distresses in the asphalt mixture. The mixing process had been evaluated by using fluorescent microscopy. The control- and SBS-modified binders were subjected to all conventional and Superpave binder tests. The Hamburg wheel tracker (HWT) and indirect tensile strength ratio (ITSR) tests were conducted to evaluate the engineering properties of the control and modified asphalt mixtures. The used SBS percentages were 1, 2, 3, 4, and 5% of the total weight of the binder. The results showed lower penetration, higher softening point, viscosity, and elastic recovery. The dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests showed an increasing SBS% leading to an increase in both values of high and low temperatures of the asphalt performance grade (PG). The tensile strength ratio and Hamburg wheel tracker tests’ results showed that the highest TSR and rutting parameter values were obtained at 3% SBS, which was the optimum SBS content for the asphalt mixture and the resulted modified asphalt is PG76-16.

Characterization of Sustainable Asphalt Binders Modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil

The current study aims to evaluate the viscosity and rheological properties of PG 64-22 modified with Styrene–Isoprene–Styrene (SIS) and Processed Oil (PO) to enhance asphalt binder properties. Performance properties were measured at high, intermediate, and low temperatures. PG 64-22 was blended with SIS and Processed Oil at three levels (5%, 10%, and 15% by weight of binder) and two concentrations (6% and 12% by weight of binder), respectively. Modified binders underwent two short and long artificial aging processes, through the spinning of the thin film in an RTFO oven and a pressure aging vessel (PAV). The Superpave binder evaluations were carried out using a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). According to the findings of the research, the addition of SIS caused higher values of viscosity, but when co-modified with processed oil, there was a substantial decrease in viscosity values. As a result, workability was improved. (1) It was observed that a greater reduction in viscosity was achieved when the processed oil was present at a higher concentration at 135 °C compared to a lower concentration. (2) The study showed that the incorporation of processed oil led to a reduction in rutting performance of the asphalt binder. However, the addition of SIS resulted in a notable enhancement of rutting resistance. (3) The role of processed oil as co-modifier at concentrations of 6% and 12% caused significant decreases in G*sin δ, based on the susceptibility of asphalt molecules to accept oil molecules in their network links. (4) The extracted measurements from the BBR tests indicated that modification with SIS and PO improved the low-temperature cracking resistance significantly. Comparison of asphalt binders modified with 6% and 12% PO and the same SIS content showed significant changes in modification with 12% PO rather than 6%.

Experimental investigation of usability of modified asphalt binder with waste expanded polystyrene (EPS)

EPS (Expanded polystyrene) is widely used in construction and packaging industries. Unfortunately, EPS is not mostly recyclable because it might not be economically feasible to store, transport, and process EPS so that it becomes recyclable. Therefore, alternative waste management strategies are urgently needed. The main objective of this study is to experimentally investigate the potential use of waste EPS in asphalt binder modification. As part of this study, a base asphalt binder with a Penetration grade of 70/100 was modified with waste EPS in four different ratios (0%, 1.5%, 3% and 4.5%, by weight of asphalt binder). The modified asphalt binder specimens were tested based on several physical (penetration, ductility, softening points and viscosity) as well as rheological/Superpave binder grading system tests including Rolling Thin Film Oven (RTFO), Pressure Aging Vessel (PAV), Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR). Based on the tests results, rheological and engineering properties of the modified asphalt binders were compared with the ones of the base binder so that effect of waste EPS addition on the properties of the base binder was evaluated; and how the Superpave binder grades of the modified binders were changed with the additions of waste EPS was discussed. It was found out that modifying asphalt binders with EPS provided them with a better rutting resistance at the expense of lowering their fatigue and low temperature cracking resistance. Overall, it could be concluded that waste EPS can be potentially used in the asphalt binder modification by paying special attention to these factors, and it should be noted that using waste EPS in the asphalt binder modification has many economic and environmental benefits.

Effects of modified binders obtained from different polymers on conventional and rheological properties

For the bituminous hot mix layers to resist the increased traffic load and number for a long time without deforming, binders modified with the Styrene-Butadiene-Styrene (SBS) polymer additive are commonly used in the asphalt material. The high demand for SBS makes its delivery difficult when needed and thus the use of alternative additives has been discussed. In this study, three different polymers (701, 611, and SBS) were compared. The effect of the bituminous binder on its physical, chemical, and rheological properties was examined. Conventional (force ductility, penetration, viscosity, softening point tests, etc.) and Superpave binder (bending beam rheometer and dynamic shear rheometer) tests were performed on pure and modified binders. Additionally, Fourier-transform Infrared Spectroscopy (FTIR) test was done on aged modified binder specimens. As a result, the conventional and Superpave binder test results of 4 different binders showed that the binders increased the performance levels of the pure binder. Furthermore, the results of the tests proved that 701 and 611 polymers could be used instead of SBS polymers. In particular, it was found that the rutting performance of the 611 polymer was better than other polymers.

Superpave performance graded asphalt binder selection for asphalt mixture design in Ghana

The Superior Performing Asphalt Pavements (Superpave) system – comprising asphalt binder grading, mixture design and mixture performance evaluation – has been in existence for nearly 30 years and has been implemented or evaluated for possible adoption in several countries to help address fatigue cracking, rutting and thermal cracking. These asphalt pavement distresses minimize pavement integrity to cause significant increase in maintenance cost, safety risks and roughness. Premature fatigue cracking and rutting failures are common in Ghana. Currently, only the mixture design component of the Superpave system is an option in the country's standard construction specification; asphalt binder selection is based on viscosity grading. Recently, very few projects have utilized Superpave-graded binders, and some of the binder grade selections were problematic. The use of Superpave-graded binders on high-volume roads is anticipated to become a common practice in the foreseeable future. However, there is no road agency guidance document on Superpave binder grade selection in Ghana currently, and this study sought to fill the gap. Such a guidance document will facilitate binder grade selection and streamline binder grade selection practices. This study utilized 42 years (1979–2020) of air temperature data collected from 24 weather stations across the country and measured asphalt pavement temperature to evaluate four existing Superpave binder grade prediction models. The model derived from the Long-Term Pavement Performance program better represented Ghana's climatic conditions and suggested the country may be partitioned into two Superpave binder grade selection zones: the Northern Savannah zone and the Transition/Forest/Coastal zone. At 98% reliability level, a binder grade of PG 70–10 was determined for the northern sector and PG 64–10 for the rest of the country. These are base binder grades (based on weather only) which must be adjusted for traffic conditions at the project site. Research should focus on local model formulation for refined Superpave binder grade selection and, during construction, selected binder grades must be verified through laboratory testing. Proper binder grade selection must be supplemented with effective pavement design, construction, axle load control and maintenance for good pavement performance and longevity.

Evaluation of Effect of Thermoplastic Polyurethane (TPU) on Crumb Rubber Modified (CRM) Asphalt Binder.

Crumb rubber binder with thermoplastic polyurethane (TPU) has been experimented with to characterize the performance properties considering the workability, rutting, fatigue cracking and cracking resistance at low temperatures depending on the temperatures and aging states. Physical and rheological properties were evaluated to proceed with the study by applying Superpave asphalt binder testing and multi-stress creep recovery (MSCR). Based on the targeted experiments, the binder samples were produced at three aging states (original, short-term aged and long-term aged) using a rolling thin film oven (RTFO) and pressure aging vessel (PAV). The results revealed that (i) the addition of TPU into CRM binders has a potential effect on increasing viscoelasticity at the original condition, (ii) CRM binders containing TPU showed improved anti-aging performance based on results of RTFO residues and (iii) the inclusion of TPU made it possible for CRM asphalt binder to improve its fatigue and cracking resistance at low temperature.

Effect of Processed Oil on Asphalt Binder Properties.

This study investigates the effectiveness of processed oil in the modification of PG 64-22 and PG 76-22 by assessing their physical and rheological properties, and multiple comparison was conducted between the two binders. The base binders PG 64-22 and PG 76-22 were blended with processed oil at four different percentages of contents (3%, 6%, 9% and 12% by the weight of the binder) and compared with the control binder in each test. The base and modified binders were artificially short-term and long-term aged using a rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were performed on the modified binders by applying a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). The comparisons and results presented in this study indicate that (1) the processed oil has a significant effect on the binders’ viscosity, which changes with respect to the increment of processed oil content. The viscosity of both modified binders decreased with the addition of 3, 6, 9 and 12% processed oil; (2) the performed DSR test showed that the addition of processed oil had a negative effect on the rutting resistance for both binders, since in PG 64-22, G*/Sin δ values decreased by 55, 65, 75 and 83% with the addition of 3, 6, 9 and 12% processed oil, respectively, while a decrement of G*/Sin δ of 24, 45, 58 and 65% with the addition of 3, 6, 9 and 12% processed oil was observed in PG 76-22; meanwhile, the fatigue cracking performance was improved and was found to be effective, while G* Sin δ in PG76-22 decreased by 9, 30, 36, and 52% and in PG 64-22 by 27, 44, 53, and 67% with the addition of 3, 6, 9 and 12% processed oil; (3) the results from the BBR test indicate significant improvement in the thermal cracking properties of the binders. The addition of 3, 6, 9 and 12% processed oil resulted in a decrease in the stiffness of both the PG 64-22 and PG 76-22 binders, with a positive effect consequently being observed on the m-values of the binders.

Laboratory Characterization of Asphalt Binders Modified with Styrene Butadiene Rubber (SBR).

The study describes the laboratory assessment (physical and rheological properties) of the binders (PG 64-22 and PG 76-22) modified with Styrene Butadiene Rubber (SBR), and a comprehensive comparison between these two modified binder types. PG 64-22 and PG 76-22 were used as base binders. Both of the base binders were blended with SBR at four different percentages of content (0%, 4%, 6%, and 8% by the weight of the binder). The base and modified binders were artificially short-term and long-term aged using a rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were conducted on the SBR modified binder using rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). In depth rutting performance was investigated using Multiple Stress Creep Recovery (MSCR). The results of this study indicated that (1) the addition of SBR into both binders increased the viscosity and polymer modified asphalt (PMA) binders observed to have more significant effect on its viscosity property; (2) the higher the SBR content, the better the rutting resistance of the binder and it is observed that the effect is prominent on the control binder; (3) MSCR test results showed that the SBR modified binders improved the binder percentage recovery and found to have a more significant effect on the PG 76-22 binder compared to PG 64-22; and (4) both the control PG 64-22 and PMA PG 76-22 binders resulted in similar trends on the cracking properties and were found to have insignificant effects due to the addition of an SBR modifier.

Evaluation of Petroleum Resin in Rubberized Asphalt Binder

The crumb rubber modified (CRM) binder was evaluated considering the general operating temperatures of high, intermediate, and low temperatures. CRM binders were produced with four different contents (0, 5, 10, and 15%) using the base asphalt binder (PG64-22). Then, they were artificially aged by a rolling thin-film oven (RTFO) and pressure aging vessel (PAV). Superpave binder tests using a rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR) was applied to characterize the performance of the original and aged binders. Multiple stress creep recovery (MSCR) tests were also performed for deeper rutting characterization. The results of this study are as follows: (1) the presence of PR increases the binder viscosity, (2) the integration of CRM greatly improved the rutting resistance of the binder, and it was found that PR also improved the rutting characteristics, and (3) it is observed that PR is detrimental to the cracking properties of CRM binders.

Investigating the potential of using dry battery waste powders (DBWPs) as a modifier for asphalt binders

This study aims at investigating the potential of using dry battery waste powders (DBWPs) as modifiers in asphalt binder. A 60/70 penetration grade asphalt binder was used in this study. DBWPs, which were extracted from spent batteries, were mixed with the asphalt binder at seven different percentages [0% (control sample), 2%, 4%, 6%, 8%, 10%, 15%, and 20% by weight of asphalt binder]. The mixing process was performed at 175 °C for 30 min using a high-speed mechanical mixer. To study the effect of DBWPs on asphalt binder properties, both traditional and Superpave binder tests were carried out. Consistency tests included penetration, softening point, and ductility, while Superpave tests included Rotational Viscometer (RV), Dynamic Shear Rheometer (DSR), and Bending Beam Rheometer (BBR). Flash and fire point tests were also conducted. The test results indicated that the addition of DBWP to the asphalt binder decreased ductility and penetration values and increased the softening and the flash and fire points of the asphalt binder. High-temperature rutting performance of asphalt binder, as presented by DSR rutting parameter (G*/sinδ), was improved by adding DBWP. The high-temperature performance grade of asphalt binder was raised by one grade by adding DBWP up to 10%, two grades at 15%, and three grades at 20%. On the other hand, fatigue and low-temperature performance of asphalt binder were adversely affected by adding DBWP. The Superpave fatigue parameter (G*.sinδ) was negatively increased by increasing the content of DBWP but remained less than the Superpave limit (≤ 5000 kPa). The low-temperature asphalt binder grade was decreased from − 22 °C (for control asphalt binder) to − 16 °C at 15% DBWP and then to − 10 °C at 20% DBWP. Therefore, it is recommended to use DBWP modifier in high-temperature regions to resist rutting distresses.

Laboratory Evaluation of Sustainable PMA Binder Containing Styrene-Isoprene-Styrene (SIS) and Thermoplastic Polyurethane

In this study, thermoplastic polyurethane (TPU) and styrene-isoprene-styrene (SIS) were utilized to enhance asphalt binder properties. Superpave asphalt binder tests and multiple stress creep recovery (MSCR) were conducted to evaluate the physical and rheological performance (viscosity, rutting, and cracking properties) of the asphalt binders before and after short-term aging and after the long-term aging process. The results showed that (i) TPU has a positive effect on workability, including the mixing and compaction processes, which was evident from the reduced binder viscosity; (ii) asphalt binders with TPU and SIS showed better rutting resistance compared to the SIS binders without TPU; (iii) the cracking resistance of asphalt binders was found to be improved significantly with the addition of TPU; and (iv) TPU has the potential to be considered as a sustainable polymer modifier for producing bearable asphalt binders by improving rutting and crack resistance without increasing the melting temperature of the asphalt binders.

Fatigue and Healing Characteristics of RAP Mixtures

The healing properties of bituminous mixes prepared using reclaimed asphalt pavement (RAP) material are different from those of virgin mixes because the chemical characteristics of RAP binder blends are different (depending on the extent of aging) compared to virgin binders. Very limited research work has been reported in the literature on the healing potential of RAP mixtures. The current study aims to examine the fatigue and healing characteristics of RAP mixtures with varying rest periods between loads. To this end, different blends of RAP and virgin binders (VG30) were prepared at varying proportions (0%, 15%, 25%, 35%, and 45%) of RAP material in mix. The fatigue lives of different RAP mixes were evaluated by varying the rest period (400, 650, 900, and 1,400 ms) between load pulses. The healing potential of the mixes was evaluated in terms of the slopes of the lines drawn between fatigue life and rest period. The fatigue life of a mix increased with increases in the proportion of RAP in the mix. The degree of healing indicated by the slope of log (fatigue life) versus log (rest period) line was found to depend on RAP content and rest period. Mix time lag (between the peaks of stress and strain), a viscoelastic property of the mixes, was determined from the stiffness modulus test. Different rheological and chemical characteristics of the binder blends and the time lag values of the mixes were correlated with the fatigue lives and healing indexes of the mixes. The Superpave binder fatigue parameter (G*sinδ) and the mix time lag were observed to have good correlation with the fatigue life of RAP mixes. Surface free energy and different aging indexes of the binders (ICO and ICH) showed good correlation with the healing index of the mixes. Flow (consistency) parameters, such as softening point and viscosity at 60°C, correlated well with the healing index. These correlations are expected to improve understanding of the fatigue and healing behavior of RAP mixes.

Compound modification of asphalt with styrene-butadiene-styrene and waste polyethylene terephthalate functionalized additives

The modification of asphalt binder using recycled plastics such as polyethylene terephthalate (PET) may improve its rheological characteristics while providing secondary environmental benefits. In this study, the chemical recycling of PET was conducted to synthesize additives and used in conjunction with styrene-butadiene-styrene (SBS) to modify asphalt binder. The properties of the modified asphalt binder (PS-MB) were characterized through both conventional binder tests, including penetration, softening point, viscosity, and storage stability tests, and Superpave binder tests, such as multiple stress creep recovery (MSCR), rutting factor (G∗/Sinδ), fatigue factor (G∗Sinδ), and low temperature creep stiffness tests. These properties were then compared with those of the unmodified asphalt binder and asphalt binder modified with SBS (S-MB). To study the effects of PET additives on the physical and chemical structures of S-MB, additional analyses were done using scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. The outcomes of the laboratory investigation indicated that using waste PET derived additives as modifiers for SBS modified asphalt binder not only provides a functioning way to recycle waste PET, but also enhances the rheological properties of SBS modified asphalt binder as a paving material.

Predicting rutting performance of asphalt mixture from binder properties and mixture design variables

Rutting is one of the main asphalt pavement distresses, and it is believed that binder properties play an important role in mixture’s potential rutting resistance. Generally, in the Superpave design system asphalt binder is selected based on the binder PG grade required for the climate. However, to implement performance control through the traditional Superpave PG system during mix design faces more challenges due to the changes of oil refinery, asphalt binder modification, and the use of recycled materials in the mixture. This paper aims to investigate the role of asphalt binders and mix designs in the rutting resistance of asphalt mixtures. A total of 22 plant-produced mixtures from 10 states and 5 laboratory-produced mixtures were investigated for their rutting performance in this study. Those tested mixtures include various binder grades, aggregate sources, RAP contents, and mix designs. The Superpave binder rutting parameter G*/sinδ and Multiple Stress Creep and Recovery (MSCR) grade parameter Jnr3.2 are correlated with the mixture dynamic modulus and Hamburg Wheel Tracking (HWT) rutting parameters. In addition, the effects of other mix design variables on the rutting resistance are evaluated using a statistical analysis. The results show that by incorporating the binder properties and mix design variables, the stepwise regression fitting provides a much better prediction for HWT rutting parameters as compared to using only the binder properties. This indicates the importance of proper selection of the binder grade for mixture performance, and it also calls for justifying more focus on including mixture design variables to ensure acceptable mixture rutting performance. The statistical analysis can provide an insight into the use of artificial intelligence and machine learning by generating mathematical models for evaluating which mixture design variables are needed for better prediction of rutting performance.

Rheology and mix performance of rejuvenated high RAP field produced hot mix asphalt with a soybean derived rejuvenator

A laboratory study was conducted to determine the optimum dosage of a bio-based rejuvenator, epoxidised methyl soyate (EMS), needed to obtain a mix design containing 30% unfractionated recycled asphalt pavement (RAP) using a neat asphalt binder with performance grade (PG) 58-28S, rated for standard traffic to meet performance criteria for a PG 58-28S. Based on running a comprehensive rheological characterisation using Superpave binder criteria, 3% EMS by weight of the neat binder was needed to obtain a PG 58-28S at proportions of (75.5% neat binder w/ 3% EMS, and 24.5% RAP extracted binder). The 3% EMS is equivalent to 0.126% by weight of the total mix. Through lab verification, the mix design with 0.126% EMS was shown to meet performance criteria for moisture susceptibility/rutting and low temperature cracking. Field produced mix with 0.126% EMS by weight of total mix was also shown to pass the performance criteria as well for the aforementioned properties. However, the field produced control mix with 20% RAP was not shown to pass criteria for low temperature at −18°C, and thus the field produced control mix became rated as a PG 64-22S. In addition, field density was checked for both the control mix and EMS RAP mix, where both sections had pay bonuses of 3.1% and 4%, respectively.

Laboratory Evaluation of SBS Modified Asphalt Binder Containing GTR, SIS, and PE

Performance properties of polymer modified asphalt (PMA) binders with Styrene‐isoprene‐styrene (SIS), petroleum resin (PE), and ground tire rubber (GTR) were evaluated at high, intermediate, and low temperatures. Styrene‐butadiene‐styrene (SBS) PMA binder of PG 76‐22 was used as a base binder. The PG76 SBS PMA binders were blended with SIS, PE, and three different GTR contents (0, 5, and 10%). The binders were artificially short‐term and long‐term aged using rolling thin film oven (RTFO) and pressure aging vessel (PAV) procedures. Superpave binder tests were conducted on the binders through rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR). Multiple stress creep recovery (MSCR) test was also performed to evaluate the rutting property. The results of this study indicated that (1) the addition of PE can decrease the binder viscosity, (2) although the incorporation of GTR and SIS significantly improve the rutting resistance of the binders, the effect of PE is found to be insignificant, (3) PE is observed to have positive effect on the cracking properties of control PG76 SBS PMA binder blended with SIS and GTR, and (4) incorporation of PE might be an useful option to improve the workability of high performance PMA binder in lieu with maintaining good rutting and cracking resistance.

Colloidal stability and dynamic mechanical properties of asphalt modified with unsaturated polyester prepared from waste polyethylene terephthalate.

This research aims to prepare unsaturated polyesters (UP) from polyethylene terephthalate waste (WPET) and studying their effects on the colloidal stability and dynamic mechanical properties of the prepared modified asphalt samples. To achieve this aim WPET is chemically recycled through glycolysis reaction using different glycols namely, diethylene glycol (DEG), triethylene glycol (TEG) and propylene glycol(PG) at molar ratios of PET wastes/glycol; 1:1.2 separately. The glycolyzed products were converted into unsaturated polyester (UP) via reaction with maleic anhydride. The prepared unsaturated polyesters (UPd, UPt and UPpg) were characterized using FTIR, GPC and TGA and then added to asphalt 60/70 in percentages ranging from 2wt% to 8wt% using wet process to prepare modified asphalt binder with desirable physical and engineering properties. The prepared modified asphalt samples were evaluated for thermal stability using TGA, physical and chemical properties using conventional tests, colloidal stability index while their rheological properties were investigated using Superpave binder tester, namely, dynamic shear rheometer (DSR) to determine the rutting and stiffness resistance of the prepared samples. The results showed an improvement in asphalt properties which became more thermally, colloidally stable and resistant to rutting and plastic deformation.