Extended Bending Beam Rheometer Research Articles

Revealing time-dependent behavior of asphalt binder at low-temperature by crystallization kinetics

To gain deeper insights into the influence of thermal history on wax crystallization and thermoreversible aging for enhanced asphalt pavement durability, this study employed the extended bending beam rheometer (ExBBR) test and modulated differential scanning calorimetry (MDSC) analysis. These techniques were utilized to analyze the crystallization kinetics of diverse asphalt binders under both isothermal and non-isothermal conditions. The ExBBR test results demonstrated that the cold-temperature performance of asphalt binders experiences continuous degradation with an increasing grade loss during conditioning. The Avrami isothermal crystallization kinetic theory proved to be an accurate descriptor of the thermoreversible aging tendency in asphalt binders. MDSC test findings revealed that distinct cooling rates exert an influence solely on specific asphalt varieties, with discrepancies in thermal signals arising from diverse oil sources. The Ozawa exponent, determined through the endothermic background area selected from the baseline, serves as a reliable guide for assessing the degree of thermoreversible aging in different asphalt binders. Crucially, the appearance of crystallizable fractions in asphalt binders with varying thermal histories can be effectively modeled using both isothermal Avrami and non-isothermal Ozawa theoretical frameworks. To conclude, the study undertook the separation of four components of asphalt, analyzing the microstructural evolution of these components under identical test conditions. The contribution of each component to the asphalt crystallization process is comprehensively expounded through considerations of glass transition temperatures, as well as endothermic and exothermic peaks associated with distinct components.

Effect of polyisobutylene on low-temperature thermoreversible aging properties in asphalt binders

In order to study the influence of polyisobutylene (PIB) on pavement performance of asphalt binders, two asphalt binders with large differences in wax content and the similar performance grades were selected as the base asphalt binders, and three kinds of waxes and PIB were selected as additives. Extended bending beam rheometer (Ex-BBR) test, double-edge-notched tension (DENT) test, multiple stress creep recovery (MSCR) test and rotational viscosity test were used to study the effect of PIB on the low, medium and high temperature properties of asphalt binders, respectively. The phase transition pattern of PIB when interacting with waxes was analyzed by variable temperature polarizing microscope (VT-PLM). The results show that PIB can be miscible with waxes and reduce the melting point of waxes by about 20∼60%. PIB can improve the low-temperature performance (reducing creep stiffness), medium-temperature performance (increasing toughness and fracture resistance), high-temperature performance (improving high-temperature deformation resistance and deformation recovery ability) and workability (reducing mixing and compaction temperature) of asphalt binders (including high-wax and wax-based warm-mixed asphalt binders). It is worth noting that PIB will aggravate the thermoreversible aging (the results of P-value analysis showed that PIB had a significant effect on the grade loss (GL) of asphalt binders), which will affect the low-temperature performance of asphalt binders during the isothermal low-temperature storage, resulting in premature damage to the pavement.

The Applicability of Limiting Phase Angle Temperatures for Specifying Asphalt Binder Low Temperature Performance

The paper discusses the applicability of using limiting phase angle temperatures, measured in the Dynamic Shear Rheometer, for low temperature ranking of performance, in comparison with limiting low temperature grades in accordance with AASHTO TP 122-16 extended Bending Beam Rheometer method. During this study, also other low-temperature test methods were compared to each other. For this purpose, 13 asphalt binders were sourced from around North-Eastern Europe, twelve of which are currently used throughout Estonia as well as the neighbouring countries. The thirteenth was a high-quality Laguna Venezuela binder that is no longer commercially available in the region but was deemed suitable for comparison. Samples were tested to measure their needle penetration, Superpave Grades, Fraass breaking points, AASHTO TP 122-16 limiting low temperature grades and limiting 30° phase angle temperatures. Additionally, a correlation found in previous work was applied to the set of samples studied in this paper. Of the binders tested, the low temperature behaviour of the Venezuelan binder stands out with better performance. The analysis suggests that the twelve commercially available binders are from a similar source which was observed through their tendency to undergo thermo-reversible aging. The study shows that the phase angle approach provides a reasonable surrogate for the AASHTO TP 122-16 limiting low temperature grade. However, the latter should currently remain the preferred approach.

Volumetric Dilatometer Study of Thermoreversible Aging Properties in Crumb Rubber–Modified Asphalt Binders

Abstract The primary objective of this paper is to investigate the thermoreversible aging mechanism of crumb rubber–modified asphalt binders (CRMAs). In order to achieve this goal, an extended bending beam rheometer (Ex-BBR) test and volumetric dilatometer test were conducted. Additionally, isothermal crystallization kinetics (Avrami theory) and thermal stress calculation using the Hopkins and Hamming algorithm were employed to process the test data. The low-temperature properties of the asphalt specimens were characterized through calculations of creep stiffness (S), creep rate (m-value), grade loss (GL), thermal stress, and Avrami index (n). The experimental results indicate that thermoreversible aging is present in all asphalt samples during the long-term isothermal hardening process. This aging is characterized by continuous macroscopic volume shrinkage, accumulation of thermal stress, a crystallization process, and a process akin to crystallization (i.e., crumb rubber adsorbed oil at low temperatures). It was observed that CRMAs exhibit more severe thermoreversible aging and faster physical hardening rates due to their unique properties at a constant low temperature when compared with base asphalts. However, it was also observed that CRMAs can reduce the thermal stress by reducing the volumetric shrinkage coefficients and S. It is important to note that the volumetric shrinkage coefficients are not constant, which are related to the base asphalts, crumb rubber, and conditioning time. Therefore, it is not appropriate to use a single empirical constant to calculate thermal stress. Instead, multiple coefficients may need to be incorporated to account for the variability in shrinkage behavior.

Effects of cold storage temperature on thermoreversible aging in heavily oxidized asphalt binders

In order to better understand the thermoreversible aging characteristics of asphalt after heavy oxidation, six selected heavily oxidized asphalt containing different proportions of C20H42 are subjected to extended bending beam rheometer (ExBBR) tests, while modulated differential scanning calorimetry (MDSC) and atomic force microscope (AFM) are also performed on the asphalt. The results indicate that the introduction of heavy oxidation will not only affect the low temperature properties of the asphalt but also its thermoreversible aging characteristics, but this effect will receive an influence of the storage temperature. This is due to the increase in viscosity of the asphalt after heavy oxidation, which makes it difficult for C20H42 to migrate, while the increase in storage temperature can release the potential of the degree of thermoreversible aging of the asphalt by accelerating the movement of wax molecules. And like C20H42, the grade loss of asphalt blended with C30H62 is different at different storage temperatures and oxidation levels, which proves that for heavily oxidized asphalt, multiple storage temperatures should be selected for testing its grade loss. Combined with thermal and morphological analysis, the introduction of heavy oxidation not only increases the amount of wax precipitation, but also significantly increases the thermoreversible aging of the asphalt by lowering the Tg of the asphalt and forming more perfect crystals during low temperature storage. Finally, by comparing the grade loss due to cold storage and extended oxidation, it can be found that the incorporation of C20H42 will make the asphalt more influenced to physical hardening. Therefore, it is necessary to study the effect of asphalt wax content on the degree of thermoreversible aging of heavily oxidized asphalt.

Effects of Physical Hardening on Low-Temperature Properties of Asphalt Binders Containing Reclaimed Asphalt Pavement

Abstract Reclaimed asphalt pavement (RAP) materials are widely used in sustainable construction of the asphalt pavement, which has evident advantages in solving the problem of material costs and waste disposals. However, there are few studies on the influence of RAP materials on the physical hardening of asphalt binders. In this paper, the physical hardening rate from the dynamic mechanical analysis test and grade loss deduced by the extended bending beam rheometer experiment were used to characterize the physical hardening of the RAP-modified asphalt binder at low temperatures. The results show that the loading time–conditioning time superposition principle is suitable to determine the physical hardening rate of RAP-modified asphalt binder through a smooth master curve and verification of the typical 2S2P1D rheological model, and grade loss can be predicted by the physical hardening rate using their good correlation. The RAP binders can accelerate the degree of physical hardening and increase the thermal stresses of the asphalt binder, and these effects are more evident for the RAP binder with longer aging time and higher content. The base asphalt with less wax content will act as a regenerant, which can accommodate more content of the RAP materials to produce a new usable asphalt binder.

Investigation of wax inhibition efficiency based on alkane structures in model asphalt for sustainable utilization of wax inhibitors

In recent years, the wax inhibitors (WIs) are used to inhibit premature crystallization of alkane molecules in asphalt at low temperatures has yielded certain benefits. However, the method for effective and sustainable use of WIs in asphalt to avoid inefficient and expensive “trial and error” procedures has not yet been determined. In this paper, the model asphalts were established through non-waxy base asphalt doped with n-alkanes (Eicosane, triacontane and tetradecane) and isoalkane (Squalene), and the wax inhibition efficiencies and cracking resistance of model asphalt with addition of three typical WIs (poly (methyl methacrylate) (PMMA), nano-SiO2 hybrid PMMA and ionic liquid (IL) modified with graphene oxide (GO)) were directly characterized by wax precipitation temperature (WPT) and extended bending beam rheometer (Ex-BBR), double edge notched tension (DENT) and thermal fatigue tests, respectively. On this basis, the microscopic mechanism of wax inhibition was investigated by molecular dynamic simulation. The results show that the wax inhibition efficiencies are higher for the short-chain n-alkanes and ordered isoalkanes to improve the low-temperature cracking, ductile and thermal fatigue resistances more significantly, but the disordered isoalkanes and high content of long-chain n-alkanes will decrease the wax inhibition efficiencies of WIs. The WIs can increase diffusion coefficient and bond stretching, angle bending and dihedral angle torsion energies but decrease the Coulomb and van der waals (VDW) energies of wax molecules to inhibit the formation of wax crystals network. It is recommended to add WIs with higher content or efficiency for asphalts with heavy n-paraffins and low concentration of branched paraffins to inhibit wax precipitation. As for asphalts containing light n-alkanes and high concentration of branched alkanes, it is suggested to add smaller amount of WIs to save resources.

Thermoreversible aging in biorejuvenated asphalt binder

Biorejuvenators are widely investigated for the restoration of performance properties of aged asphalt. However, thermoreversible aging phenomena in rejuvenated asphalt binder at cold temperatures remain largely unexplored. Three rejuvenators were used to restore aged binder. Extended bending beam rheometer (EBBR) and modulated differential scanning calorimetry (MDSC) testing were used to assess reversible aging tendencies, wax crystallization, and phase separation. Biorejuvenator was found to reduce physical aging in a dose dependent manner. Non-isothermal kinetic analysis based on the Ozawa theory showed that crystallization rate increases with dosage. However, isothermal analysis based on the Avrami theory showed no consistent changes, likely due to the relatively low conditioning temperature employed. Surprisingly, both isothermal and non-isothermal analyses indicated a risk for phase separation, especially at higher dosage levels around 0 °C. Hence, it is critical to determine optimum rejuvenator contents for an effective use in the recycled pavement.

Role of asphalt binder compositions in the thermoreversible aging Process

ABSTRACT In order to understand the contribution of asphalt components to thermoreversible aging, the extended bending beam rheometer (Ex-BBR) test, SARA fractions separation, and thermal analysis were performed on a series of asphalt binders from different sources. The results indicated that thermoreversible aging is not an inherent characteristic of asphalt, and some binders were not affected by thermoreversible aging. Grade loss caused by thermoreversible aging showed a high correlation with wax content in asphalt but had no apparent relationship with asphaltenes content and colloidal structure index used. Moreover, the thermal analysis results well explained the degree of thermoreversible aging in the asphalt binder. Finally, the endothermic peak and crystallites formed in asphalt binder could have resulted from the long side chains in naphthene aromatic molecules.

Relationship between thermoreversible and irreversible aging in rejuvenated asphalt binder

Rejuvenators are now widely used to restore performance of aged asphalt. A critical factor that controls performance of pavements in service is age hardening of the binder. Hence, both reversible and irreversible processes need to be accounted for in order to ensure durable designs. Thermoreversible processes are affected by irreversible aging, but how the two interact remains largely unexplored for rejuvenated binders. A straight Cold Lake PG 58-28 binder was blended with castor oil residue (COR), soybean oil residue (SOR) and petroleum-based aromatic oil (ARO) rejuvenators. Standard Extended Bending Beam Rheometer (EBBR, AASHTO TP 122) tests were conducted to assess thermoreversible aging. Non-isothermal crystallization kinetics were investigated using Modulated Differential Scanning Calorimetry (MDSC) and Thermogravimetric Analysis (TGA). Standard Rolling Thin-Film Oven (RTFO) followed by 20 h of Pressure Aging Vessel (PAV) conditioning proved sufficient to differentiate thermoreversible aging tendencies. However, EBBR grade losses increased significantly upon extended aging. Rejuvenated compositions fared worse in comparison to straight Cold Lake binder. Three-day grade losses for the PG 58-28 ranged from 1.8 °C (unaged) to 9 °C (100 h PAV). In contrast, the ARO blend lost 0.8 °C (unaged) increasing to a significant 15 °C (100 h PAV).

Effect of modifier on Low-Temperature reversible aging behavior of asphalt binder and its morphology analysis

• Rubber powder can alleviate the effect of reversible hardening on asphalt binders. • The addition of modifiers can reduce the reversible hardening degree of the asphalt binder. • Cone penetration test can be used to characterize the reversible hardening degree of the asphalt binder. • With the extension of conditioning time, the average area of asphalt binder “bee” structure increases gradually. Reversible aging of asphalt binders is one of the reasons for the premature failure of asphalt pavements. To better understand the effect of modifier types on the reversible aging in asphalt binder, styrene–butadienestyrene (SBS), styrene-butadiene rubber (SBR), crumb rubber (CR), and Nano-CaCO 3 were selected to prepare modified asphalt binder. Firstly, an extended bending beam rheometer (Ex-BBR) test and a cone penetration test (CPT) were carried out on base asphalt (BA) and modified asphalt binders under different conditions. Secondly, the reversible aging behavior of asphalt binders was characterized using a logistic regression model. Furthermore, the mechanisms of asphalt reversible aging were analyzed by atomic force microscopy (AFM) and molecular dynamics (MD) simulation. The results show that the addition of modifiers affects the reversible aging behavior of asphalt binders. Compared with SBS, SBR, and nano-CaCO 3 , CR can improve the mobility of asphalt molecules and mitigate the aggregation of asphalt molecules, thereby alleviating the impact of reversible aging on asphalt binder performance. After 72 h low-temperature conditioning, CR modified asphalt binder has the smallest grade loss of 1.7 °C. The low-temperature conditioning time can greatly affect the microstructure of the asphalt binder. With the increase of low-temperature conditioning time, the average area of the asphalt binder’s “bee” structures increases linearly. Furthermore, the reversible aging behavior of asphalt binders can be better understood using MD simulation.

On the use of empirical phase angle limits for the grading of asphalt binder

• Asphalt phase angles can be measured most precisely and rapidly. • Limiting phase angle temperatures correlate with DENT properties. • Limiting phase angle temperatures correlate with EBBR properties. • Divergent behavior is seen for softer binders where correlations weaken. In recent years, Ontario paving contracts have specified asphalt binders based on limits for: (1) critical crack tip opening displacements (CTOD) obtained in the double-edge-notched tension (DENT) test, (2) limiting low temperature performance grades (LLTPG) obtained in the extended bending beam rheometer test (EBBR), and (3) EBBR grade losses, in addition to (4) regular American Association of State and Highway Transportation Officials (AASHTO) M320 criteria. While the enhanced performance measures are expected to provide significant improvements in pavement performance, both DENT and EBBR protocols are cumbersome. A total of 371 sets of binder test results are used to assess if CTOD, EBBR LLTPG and grade losses can be replaced with limiting phase angle temperatures T 30° and T 45° , in an effort to make the binder specification more practical. The CTOD, LLTPG and grade loss correlate strongly with phase angle but variation for softer grades were found to be significant, which likely relates to differences in aging mechanisms in the laboratory and service (chemistry and/or thermal history, exudation of oils). A phase angle specification for the control of pavement cracking deserves further consideration for its accuracy, sensitivity, precision and thus usefulness.

Thermoreversible aging in model asphalt binders

Thermoreversible aging is an important factor leading to premature cracking in asphalt pavement. In order to better understant the contribution of various pure waxes in asphalt binder to thermoreversible aging, model asphalts are prepared with three kinds of alkanes (eicosane, triacontane, and squalane). The effects of alkane dopant crystallization on the thermoreversible aging properites of low- and high-wax asphalts are examined using extended bending beam rheometer (ExBBR) test and limiting phase angle temperatures. The results show that eicosane is an additive that improves the conventional 1 h low-temperature performance of asphalt binder, but it will aggravate the thermoreversible aging and the magnitude depends on the base asphalt and concentration of additive. The branching of straight-chain hydrocarbons can improve the low-temperature performance of the corresponding asphalt without aggravating the degree of thermoreversible aging. Limiting phase angle temperature is more sensitive to the dosage of C30 and squalane additives. But poor correlation is found for C20 doped asphalts.

Effect of physical hardening on low temperature performance of DCLR modified asphalt

This study aims to investigate the effect of physical hardening on the low temperature performance of direct coal liquefaction residue (DCLR) modified asphalt. The extended bending beam rheometer (EBBR) method was used to evaluate the low temperature performance of DCLR modified asphalt with benzaldehyde, silane coupling agent and xylene compatibilizer. Meanwhile, the microstructure and morphology of DCLR modified asphalt before and after physical hardening were quantitatively characterized by atomic force microscope (AFM) and image processing software. In this study, the physical hardening was performed by placing the DCLR modified asphalt at low temperature conditions for a certain time. The test results show that as the conditioning temperature decreased and the conditioning period increased, both low temperature grade loss and hardening rate of asphalt increased, indicating that the low temperature performance deteriorated. Compared to the room-temperature conditions, the total number of “bee-structures” of DCLR modified asphalt under low temperature conditions were less, but the shape of a single “bee-structure” became larger and longer. The compatibilizers hindered the growth of “bee-structure”, which demonstrated that the compatibilizers could improve the low temperature performance of asphalt. The three compatibilizers had different effects on low temperature performance of DCLR modified asphalt. Among them, the silane coupling agent was the most effective, followed by benzaldehyde and xylene.

Study on the effects of reversible aging on the low temperature performance of asphalt binders

Reversible aging refers to a time-dependent stiffening of asphalt binder that results from the time-delayed increase in stiffness when the asphalt binder is stored at low temperatures. The increase in stiffness will distinctly affect the low temperature performance of the asphalt binder, but existing researches rarely consider this. This paper aims to investigate the effects of reversible aging on the low temperature performance of asphalt binders, and to reveal the underlying mechanism of reversible aging. To this end, four different types of asphalt binders were selected for the extended bending beam rheometer (EBBR) test at different conditioning times. The thermal stress was computed based on the rheological data obtained from the EBBR test to quantify the influence of low temperature reversible aging on the cracking resistance of the asphalt binders. The Avrami isothermal crystallization kinetics theory was used to analyse the reversible aging process of asphalt binders from the perspective of macro-crystal structure. Furthermore, the molecular dynamics was performed to simulate the reversible aging process of asphalt binders from a microscopic point of view. The results from this study show that the low temperature performance of asphalt binders continues to decline with the extension of the conditioning time, which is manifested by the increase in grade loss, thermal stress and critical cracking temperature. Reversible aging exhibits great impact on the low temperature performance of asphalt binders by lowering the low temperature grade of asphalt binders up to one grade. The Avrami isothermal crystallization kinetic theory can accurately characterize the reversible aging tendency of asphalt binders. The molecular dynamics simulation results show that the asphaltene component contributes the most to the reversible aging of asphalt binder.

Effective control of flexible asphalt pavement cracking through quality assurance testing of extracted and recovered binders

A total of 54 asphalt binders were obtained from six different Canadian (four municipalities) and United States (two State Departments of Transportation (DOTs)) user agencies. Regular AASHTO M 320 grades, critical crack tip opening displacements (CTOD), extended bending beam rheometer (EBBR) limiting low temperature grades (LLTG), and limiting phase angles grades T(δ = 30°) and T(δ = 45°), were determined for tank-sampled and extracted and recovered materials.While nearly all binders sampled from storage tanks at asphalt plants pass regular contract quality assurance (QA) requirements with ease, enhanced test methods showed major variability for materials of ostensibly the same AASHTO M 320 grade. The CTOD provides a measure of strain tolerance in the ductile state around the freeze-thaw regime. It ranged from a low of 8.4 mm for a contract in a PG minus 28 zone—likely burdened by too much reclaimed asphalt pavement (RAP) and/or poor virgin binder quality—to a high of 48.4 mm for a contract in a PG minus 34 zone. The CTOD varied by as much as threefold within the same climatic zone. Tank samples graded consistently better according to the CTOD compared to recovered binders, at times in a major way.Grade losses due to cold conditioning in the extended BBR protocol, which provide a measure of durability, ranged from a negligible 0.9 °C to a very significant 9.1 °C after only 72 h of cold conditioning. The EBBR LLTG was found to be highly correlated with the T(δ = 30°) grade (R2 = 0.85), and somewhat less correlated with T(δ = 45°) (R2 = 0.74). The CTOD was found to be highly correlated with the T(δ = 45°) (R2 = 0.90), and somewhat less correlated with the T(δ = 30°) grade (R2 = 0.86). Hence, the two limiting phase angle temperatures may be used, in the future, in a more precise, accurate, and practical specification protocol for the control of cold temperature cracking.

Variable-temperature Fourier-transform infrared spectroscopy study of wax precipitation and melting in Canadian and Venezuelan asphalt binders

Variable-temperature Fourier-transform infrared (FTIR) spectroscopy was used to improve our understanding of chemical and physical properties of importance to gradual, thermoreversible aging in asphalt at cold temperatures. The FTIR peak area growth between 735 and 715 cm−1 follows a straight line upon cooling. Abrupt and significant changes in slope signify wax precipitation onset temperatures (WPT). Cold conditioning increased wax melt out temperatures (WMT), while chemical oxidation increased both WMT and WPT. Thermoreversible aging in an extended bending beam rheometer (EBBR) protocol shows Cold Lake, Alberta, and Laguna, Venezuela binders performing exceptionally well, likely because they are very low in crystallizable fractions (CF).

Non-isothermal low-temperature reversible aging of commercial wax-based warm mix asphalts

ABSTRACT Low-temperature reversible aging is one of the most important forms of asphalt hardening, especially for cold regions. However, there are few researches about the influence of wax-based warm additive on the low-temperature reversible aging of asphalt, especially under non-isothermal conditioning. For this reason, simplified extended bending beam rheometer (Ex-BBR) test, non-isothermal rheological analysis and differential scanning calorimetry (DSC) test are performed on asphalt binders containing selected four kinds of commercial wax modifiers (Fischer-Tropschbased wax, linear aliphatic hydrocarbon-based wax, polyethylene-based wax, and fatty acid amides based wax). The results show that all commercial waxes used in this study will accelerate the degree of physical hardening in unaged asphalt binders. Compared with wax-based warm mix additive, oxidative aging has a greater impact on the low-temperature reversible aging properties of asphalt binder. Independent of cooling rate, the base asphalt has the highest phase angle value while the F–T wax modified asphalt has the lowest value. The crystallizable fraction increases with the decrease of cooling rate for both unaged and PAV aged sample. The magnitude of Ozawa exponent has the same order as grade loss for PAV aged sample. However, no obvious rule is observed for unaged asphalt binders.

Toward a better understanding of the low-temperature reversible aging phenomenon in asphalt binder

ABSTRACT Asphalt aging with time is one of the main causes that leads to the performance deterioration of asphalt pavement. Compared with non-reversible oxidation aging, reversible aging which resulted from molecular structuring gets little attention in asphalt materical specification, especialy at low-temperature. This paper aims to compare the effect of oxidation and isothermal conditioning on original asphalt binder’s low-temperature properties. Firstly, the mechanisms of asphalt reversible aging are systematically reviewed in this paper. Secondly, extended bending beam rheometer (Ex-BBR) test and modulated differential scanning calorimetry (MDSC) test are carried out on original asphalt and its oxidative residue. The results show that oxidation has apparently different influence on two physical hardening indicators used in this study. Only three days of non-accelerated physical hardening may produce a more brittle material than accelerated oxidative residue. There is an obvious peak around 25°C in non-reversing heat flow curve of asphalt binder after long-term isothermal conditioning, and it is caused by some imperfect crystals forming fully crystallized structure after long-term conditioning. Both long-term isothermal conditioning and oxidation will increase the amount of crystalline phase and rigid amorphous phase.

Characterizing mechanical response of bio-modified bitumen at sub zero temperatures

Cracks associated with large temperature fluctuation especially in cold regions are among prevalent pavement distresses. Binder rheology is typically found to the key factor affecting low temperature cracking resistance. Recognizing the importance of binder properties, many road authorities are requiring the use of special additives to enhance low temperature properties of binder to alleviate low temperature cracking problems. However, most of these modifiers are petroleum-based products with unstable price and depleting resources. Therefore, the asphalt industry is looking for renewable alternatives for modifying bitumen and improving its low temperature performance. Accordingly, this paper incorporates laboratory experiments and modeling to study merits of modifying bitumen with several bio-binders to enhance low temperature properties of bitumen. To investigate rheological properties at low temperatures, an extended bending beam rheometer test was used incorporating a simple fractional viscoelastic model based on the general power law. The data collected during loading and unloading portion of the test was used to evaluate the effect of introduction of bio-modifiers on low temperature properties of bitumen. The experimental results showed that introduction of bio-modifiers to bitumen significantly enhanced bitumen behavior both during creep loading and relaxation. The results of finite element modeling based on the extended bending beam rheometer geometry and boundary conditions proved that the simple fractional viscoelastic model can accurately characterize low-temperature mechanical behavior of bio-modified bitumen.