Properties Of Aged Asphalt Binders Research Articles

Investigation of the Performance of Bio-Oils from Three Different Agricultural Wastes as Rejuvenators for Recycled Asphalt

The aim of this study was to investigate the possibility of using bio-oil obtained from pine cones, olive mill pomace, and wheat straw as rejuvenators for the reuse of aged asphalt binders. Additionally, the biomass used for bio-oil production was selected from waste materials. Therefore, it makes great contributions to both the environment and the economy. B50/70 bitumen was selected as the neat binder. The bio-oils used in the study were obtained as a result of pyrolysis. Bio-oil rejuvenators at 5%, 10% and 20% by the weight of the binder were added to the aged binder obtained from recycled asphalt mixtures to obtaine bioregenerated asphalts. The physical and rheological properties of bioregenerated asphalts were investigated and not compared on neat and aged binders through penetration, softening point, rotational viscometer and dynamic shear rheometer tests. In addition, the effects of temperature and biooil content on complex modulus properties were examined using response surface methods. It was foud that while the bio-oils increased the penetration values of the aged binders, they also decreased the softening point and viscosity values. The bio-oils significantly modified rutting resistance of the aged binder. The addition of bio-oil improved the viscous components and can rejuvenate the viscoelastic properties of aged asphalt binders to that of almost the original level. In addition, response surface methods results showed that the interactions between both independent variables were effective. Finally, high coefficient of determination (R2) values indicated good agreement between the actual and predicted values. It was recommended as a result of the study that 20% concentration of bio-oil should be used to rejuvenate the aged asphalt binder for reuse in pavement construction.

Utilization of dry-method styrene-butadiene-styrene and epoxy polymer to enhance the aged asphalt binder: Properties evaluation and cost discussion

To reduce the cost of epoxy asphalt mixture (EAM) pavement and increase the performance of mixture with high reclaimed asphalt pavement (RAP) content, three different dry-method styrene-butadiene-styrene (SBS) modifiers and an epoxy polymer (EP) were employed in this study to enhance the properties of aged asphalt binder and prepare SBS-modified epoxy reclaimed asphalt (SERA) binders. The chemical interaction between the dry-method SBS and EP was analyzed, and the microscopic structure and mechanical properties of the SERA binder were evaluated. Additionally, a discussion on the initial material cost of the newly proposed SERA mixture (SERAM) was conducted. Results indicated that the degraded products generated by the oxidization of dry-method SBS undergo interactive reactions with the epoxy rings present on the epoxy resin molecules. Phase separation occurred both between EP and SBS-containing aged asphalt binder, and between SBS and aged asphalt binder. The addition of dry-method SBS to epoxy reclaimed asphalt (ERA) increased the size of the asphalt binder phase in the fluorescence images. At EP contents ranging from 30% to 50%, the incorporation of dry-method SBS led to notable improvements in the elongation at peak, low-temperature properties, and fatigue resistance of ERA binder. The SERA binder exhibited comparable or even superior properties in terms of tensile strength, low-temperature behavior, and fatigue properties when compared to virgin epoxy asphalt (EA) binder. However, dry-method SBS may have a negative impact on the high-temperature properties and curing time of the binder. Dry-method SBS with rejuvenation capacity exhibited the greatest improvement in elongation at peak, low-temperature properties, and fatigue properties of ERA. Compared to EAM, the utilization of SERAM results in material cost-savings of approximately 46 USD (9%) per ton of mixture.

Chemical properties of the purified waste engine oil as recycling agents for restoring the properties of aged asphalt binder

In this study, the waste engine oil (WEO) was filtered manually and purified in a refinery, and the effect of the filtered and purified WEOs as recycling agents (RA) on the chemical properties of the aged asphalt binder was investigated. For this aim, the thermogravimetric analysis, scanning electron microscope, energy dispersive X-ray spectrometry, and Fourier transform infrared spectroscopy tests were conducted on the aged asphalt containing RAs. The results showed that both RAs could change the chemical properties of the aged asphalt binders to some extent. However, they cannot fully restore all the chemical properties of the aged asphalt binders.

The property evaluation of recycled asphalt binder composed of an epoxy resin polymer and aged asphalt binder

The reutilization of reclaimed asphalt pavement (RAP) is gaining importance in meeting the objectives of green and sustainable environmental policies. Meanwhile, epoxy asphalt (EA) is not widely used due to its high price. To facilitate the utilization of EA in RAP recycling, this study adopted an epoxy polymer (EP) to prepare the recycled asphalt binder and investigate the effects of different EP content on the properties of aged asphalt binder. Evaluation encompassed mechanical, microstructural, and chemical characteristics of EP-recycled asphalt (ERA) binders, which were compared against virgin EA binders. The addition of EP can significantly enhance the tensile strength, high-temperature properties, low-temperature properties, and fatigue resistance of the aged asphalt binder. However, the elongation of the aged asphalt binder became worse. As the EP content increased from 30% to 50%, the tensile strength, high-temperature properties, fatigue resistance, and construction allowance time of ERA consistently improved, while the elongation of ERA steadily decreased. A phase transition occurred between asphalt binder and EP phase as EP increased from 40% to 50%, resulting in a rapid increase in tensile strength, high-temperature properties, and fatigue resistance of ERA, as well as a significant reduction in elongation and low-temperature properties of ERA. The concentration of sulfoxide decreased as the EP content increased. The performance gap between EA and ERA was not significant under the same EP content. The EP content had a greater impact than the aging degree of asphalt binder on the properties of the ERA. A recommended EP content of 40% was suggested.

Operando FTIR-ATR with molecular dynamic simulations to understand the diffusion mechanism of waste tire-derived pyrolytic oil for asphalt self-healing

Recent research proves that pyrolytic oils from waste tires are effective in restoring the chemical and rheological properties of aged asphalt binders. Nonetheless, the role of oil-binder molecular interactions and bindeŕs aging degree on the diffusional behavior of the pyro-oils is still unclear. In this study, authors propose integrating operando Fourier Transformed Infrared Spectroscopy (FTIR) measurements with molecular dynamics (MD) simulations as a novel approach to unravel the diffusion mechanisms of pyro-oils in asphalt binders with self-healing purposes. The produced pyro-oils contains aliphatic and single-ring alkyl aromatic compounds as the most abundant species (ca. 80%). The operando FTIR measurements were correlated by a Fickian model, resulting in diffusion coefficients (D0) between 10-12 and 10-11 m2s−1. Moreover, MD simulations, with a molecular model of aged asphalt containing benzylic rings, sulfoxides, and hydroxyl functional groups, demonstrated that interactions of functional groups in the pyro-oil with the binder, hinder the diffusion behavior of the pyro-oil. The D0 estimated from the MD simulations agreed with those calculated from experimental data and previous reports for petro- and bio-derived rejuvenators. The predictive performance of the MD simulations developed in this study confirms to design of more resilient self-healing asphalt binders using a bottom-up strategy.

An atomistic model of aged asphalt guided by the oxidation chemistry of benzylic carbon with application to asphalt rejuvenated with a triglyceride

Waste cooking oil (WCO) shows promise for restoring physical properties of aged asphalt binder to enable pavement recycling. Its use as a rejuvenator lessens the environmental burden on land fills with its disposal. In this study, we report our initial development of an aged asphalt model and the computational investigation of the effect of triglycerides, the main component of WCO, on the viscosity, self-diffusion, and microstructural properties of aged asphalt at 1 atm and 404 K. The fundamental research question in this work involves understanding the underlying mechanism(s) by which WCO rejuvenates aged asphalt binder. A central feature of this aged asphalt model is consideration of oxidation chemistry and reported functional group concentrations since properties like viscosity are known to be related to the amounts of moieties such as ketones and sulfoxides. Model oxidation compounds include proposed representative asphalt structures based on Peterson’s dual reaction pathways, leading to polycyclic aromatic hydrocarbon molecules resulting from fast phase aromatization and multiple species from a slow phase degradation of benzylic hydroperoxide intermediates. The new model takes into account the observed product distribution of aryl alcohols and aryl ketones based on findings for cumene oxidation in the literature. Other oxygen-containing functional groups, such as anhydrides, carboxylic acids, and polynuclear aromatics, have been incorporated to account for the critical physical characteristics of aged asphalt. By extending the molecular basis set of asphalt components, we can now construct more realistic asphalt models to represent varying SARA (Saturates, Aromatics, Resins, Asphaltents) content, different oxidation levels and functional group composition. Virtual representations of the molecules in the basis set were created and molecular dynamics simulations of the aged asphalt model conducted. Results with aged asphalt basis set provided good agreement with reported physical properties. With the developed aged asphalt model, our molecular dynamics simulations reveal that triglyceride (tristearin) has preferential interactions with asphaltene molecules. On addition of 10 wt% triglyceride to aged asphalt, the asphaltene-asphaltene interaction was most significantly affected. The radial distribution functional analysis revealed that the asphaltene-asphaltene nearest neighbor distance increased from 4.0 Å to 7.5 Å. Thus, adding triglyceride to aged asphalt helps to reduce the aggregation of asphalt components and as such promotes a decrease in viscosity of the aged asphalt, from 83 cP to 69 cP. In addition, the asphaltene components have larger self-diffusion coefficients upon the addition of triglyceride, changing from 3.57 × 10−8 cm2/s in the aged asphalt to 1.41 × 10−7 cm2/s in the triglyceride/aged asphalt mixture. Those findings are consistent with the observed effectiveness of utilizing waste cooking oil to rejuvenate aged asphalt.

Influence of epoxy resin polymer on recycled asphalt binder properties

Utilization of high-performance pavement materials with a high reclaimed asphalt pavement (RAP) content is gradually gaining importance given the impetus of green environmental policies. Epoxy resin polymer (EP) can greatly enhance the reuse of RAP materials in asphalt mixture. The influence of EP on the properties of aged asphalt binder was investigated wherein mechanical and chemical properties, and the micro-morphology of binders composed of aged asphalt binder and EP were also evaluated. EP significantly improved tensile, high-temperature, low-temperature, and fatigue properties of aged asphalt binder, and simultaneously reduced concentration of sulfoxide and carbonyl of aged asphalt binder. Increasing EP content reduced the impact of asphalt ageing degree on mechanical properties, micro-morphology, and chemical composition. Furthermore, the construction allowance time of the binder was increased with increasing EP content. At 40% EP content, an effective network structure was formed in the aged asphalt binder, leading to higher tensile elongation, high-temperature rheological properties, and fatigue life as compared to virgin asphalt binder. Meanwhile, low-temperature modulus and sulfoxide and carbonyl concentrations were lower than those of virgin asphalt binder. For application, a recommended EP content of 40% is suggested.

Physical and chemical evaluation of adhesion recovery property of aged high-viscosity asphalt based on specialized composite rejuvenators

With the wide application of porous asphalt pavement, the techniques for recycling aged porous asphalt mixture have attracted more attention for facilitating its sustainable development. One of the most critical issues is how to recover the adhesion properties of aged high-viscosity asphalt (HVA). In this study, different specialized composite rejuvenators types on the adhesive properties of aged asphalt binder were designed and evaluated for the goal of adhesion recovery. A bond strength test was used to evaluate the macroscale adhesion properties between the regenerated asphalt and aggregate. Micro-scale chemical and physical tests were utilized to discover the regeneration mechanism of specialized composite rejuvenators on asphalt adhesion. The results showed that the proposed three kinds of composite rejuvenators can effectively restore and improve the adhesive properties of aged HVA. The results of differential scanning calorimetry (DSC) represented that recycled HVA with smaller Tg and total heat absorption showed better adhesion properties. The FT-IR and AFM test results showed that the adhesion of recycled HVA is highly correlated with the C–O functional group index and micro adhesion. In addition, the concave structure in the asphalt surface is more beneficial to improve the asphalt-aggregate interface bonding, and the scheme of adding 8% optimized rejuvenator based on graft co-polymerization had the best effect, which could be promoted for the future application in the recycling of HVA in porous asphalt pavement.

Thermodynamic properties analysis of warm-mix recycled asphalt binders using molecular dynamics simulation

This study aims at investigating the effect of warm-mix recycled on the thermodynamic properties of aged asphalt binders using molecular dynamics simulation. The molecular models of asphalt binders in the virgin, long-term aged, recycled and warm-mix recycled states were developed based on the proportional relationships between the asphalt components as well as oxidation functional indicators. The mean square displacement, molecular radial distribution function and fractional free volume were used to evaluate the molecular structure variations in different asphalt states. Based on this study, it is found that the composite regenerator cannot completely degrade the oxidation functional groups in the aged asphalt, but rather mainly rely on small molecular structures penetrating and filling the intermolecular aggregation spaces of the asphaltene to reduce asphalt brittleness and hardness. The warm mix recycling processes mainly depend on increasing the activity of the lighter components to improve the diffusion properties of the aged asphalt.

Molecular dynamics simulation on the rejuvenation effects of waste cooking oil on aged asphalt binder

Waste cooking oil (WCO) has received attention on rejuvenating aged asphalt binder widely in recent years. This study evaluated the rejuvenation effects of WCO on aged asphalt binder on the micro-scale using molecular dynamics (MD) simulation. First, the representative molecules of WCO and asphalt binders were selected. The molecular mixture model was then developed. The thermodynamic properties were investigated, including density, cohesive energy density, solubility parameter, and surface free energy. The results show that WCO can restore the thermodynamic properties of aged asphalt binder to some extent and WCO has different influences on electrostatic interactions and van der Waals effects. From the diffusion behavior and molecular structure of asphalt binder, WCO can improve the molecular mobility and restore the colloidal structure. Besides, the adhesion work and moisture susceptibility of asphalt binder-aggregate interfaces (calcite and quartz) were evaluated. The results show that WCO can improve adhesion work between asphalt binder and aggregates since WCO can change molecular structure of asphalt binders and certain adhesion work exists between WCO and aggregates. Also, it can mitigate the moisture susceptibility of asphalt binder-aggregate interfaces (calcite and quartz). The study demonstrates that the MD simulation can help to understand the rejuvenation effects of WCO on aged asphalt binder on the micro-scale. • WCO can improve the mobility of the saturates best of aged asphalt binder. • WCO can weaken both the self-aggregation of asphaltenes and interactions between asphaltenes and saturates. • WCO can change the molecular structure of asphalt binders.

Fatigue Behavior and Healing Properties of Aged Asphalt Binders

This study aims to investigate the fatigue behavior and healing properties of aged asphalt binders. Both 70# and SBS-modified asphalt binders were aged using a rolling thin-film oven test (RTFOT), and their physical properties were analyzed. Their fatigue behavior and healing properties were investigated using a dynamic-shear-rheometer time-sweep test. The influence of healing on fatigue behavior was evaluated in terms of the fatigue life ratio (FLR), and a new index was defined (accumulated dissipation-energy ratio, ADER) to evaluate the healing properties of aged asphalt binders. Aging reduced the penetration and ductility of both the asphalt binders, and large aging degrees increased their softening points. Small aging degrees slightly decreased the softening point of the SBS-modified asphalt binder but increased that of 70# asphalt binder. The former had a better thermal-oxidative aging resistance than the latter. Aging increased the complex shear modulus of the binders, resulting in a longer fatigue life under controlled-stress conditions. The fatigue life of aging asphalt binders obeyed a good (R2>0.90) double-logarithmic linear relationship with the stress level. Healing recovers the asphalt complex shear modulus and extends its fatigue life. Additionally, the FLR and ADER increased with a decrease in aging degree and an increase in the healing period.

Synergistic effect of SBS copolymers and aromatic oil on the characteristics of asphalt binders and mixtures containing reclaimed asphalt pavement

Rejuvenators have been utilized to restore the physical and rheological properties of aged asphalt binders found in the reclaimed asphalt pavement (RAP). Also, the rejuvenators are utilized to enhance the cracking resistance of asphalt containing RAP. In addition, polymers have been efficiently applied to enhance the rutting performance of rejuvenated mixtures. The purpose of this study was to assess the influence of combining SBS copolymers and aromatic oil (AO) at the same time as a hybrid rejuvenator (HR) on the performance of high RAP asphalt binders and mixtures. HR is a mixture of 25% SBS and 75% AO. The properties of the rejuvenated binders were assessed by SARA (Saturates, Asphaltene, Resin, and Aromatics) fractions analysis, Fourier Transform Infrared Spectrum (FTIR), physical tests, high-temperature storage stability test, Dynamic Shear Rheometer (DSR) test, and Bending Beam Rheological (BBR) test. In addition, the mechanical behaviour of the rejuvenated mixtures was assessed using the Indirect Tensile Strength (ITS) test, moisture susceptibility test, resilient modulus test, and wheel tracking rutting test. The results showed that appropriate adjustment of the SARA fractions and SBS copolymer could improve the overall performance of mixtures and binders with high RAP content. However, it is asserted that a field investigation of this compound rejuvenator should be done to further analyze its influence on the long-term field behavior of high RAP mixtures.

Use of linear amplitude sweep test as a damage tolerance or fracture test to determine the optimum content of asphalt rejuvenator

A procedure based on the linear amplitude sweep (LAS) test has been developed to determine the optimum rejuvenator content for restoring the properties of aged asphalt binders. The LAS test was employed to assess the damage tolerance, fatigue resistance, and fracture behavior of rejuvenated aged binders. In case of fracture analysis, a crack-based indicator to govern the stable crack propagation was defined to characterize fracture resistance of asphalt binders. While rejuvenators improved all of these properties, higher contents were required to restore the cracking behavior of the original binder. The linear relationship between the integrated damage-fatigue-fracture indicator and rejuvenator content was used to determine the optimum content. Unlike the similar permissible range based on restoration of the low and high-temperature performance, the LAS-based approach demonstrated superior performance of the aromatic extract rejuvenator over the waste cooking oil at higher contents.

Increasing the efficacy of recycling agents with simultaneous addition of zinc diethyldithiocarbamate as an antioxidant

Recycling agents are commonly used to enhance the properties of aged asphalt binder. The aged asphalt binder found in reclaimed asphalt pavement is considerably oxidized and has lost a significant amount of its volatiles during its service life. Therefore, its performance characteristics need to be improved before it can fully function in new–pavement construction. Recycling agents are intended to modify performance characteristics; however, typical recycling agents are prone to oxidation, which renders them ineffective. It is hypothesized that the efficacy of recycling agents can be enhanced by simultaneous addition of antioxidants to the binder system. Therefore, in this paper, the synergy between three types of recycling agents (paraffinic oil, triglycerides and fatty acids, and tall oil) and zinc diethyldithiocarbamate (ZnDEC) as an antioxidant is examined using rheological characterization at high, ambient, and sub-zero temperatures. The study results show that the efficacy of recycling agents was improved with the addition of ZnDEC; however, the efficacy of the ZnDEC varied depending on the recycling agent used. The latter was attributed to the susceptibility of recycling agents to oxidation as well as the extent of synergy between a recycling agent and ZnDEC.

Investigation into possibility of rejuvenating aged asphalt binder using mustard oil

ABSTRACT Incorporation of high content of Reclaimed Asphalt Pavement (RAP) into fresh asphalt mixtures make them prone to thermal cracking and fatigue failure. Rejuvenators are usually recommended to overcome this problem by restoring the aged asphalt binder properties. This study aims to investigate the feasibility of using Mustard oil as a rejuvenator and to evaluate its effectiveness as a rejuvenator by determining the extent to which it restores the chemical and physical properties of aged asphalt binder extracted from RAP. The effect of Mustard oil on physical, rheological, chemical and thermal properties of aged asphalt binder was studied by employing Rotational Viscometer, Dynamic Shear Rheometer, Bending Beam Rheometer, Fourier Transform Infrared Spectroscopy, Thermogravimetric analysis, Gas-Chromatography-Mass Spectrometry and Rolling bottle equipment. Results indicated that Mustard oil effectively restores the properties of aged asphalt binder and can be used as a suitable rejuvenator. Ten per cent of Mustard oil is recommended as an optimum dose for rejuvenation of aged asphalt binder. This dose is based on restoring the RAP binder to match the properties of neat binder having PG64 and is specific to the stiffness of RAP material being used.

Comparative Evaluation of Methods for Removing Residual Mineral Fillers during Bitumen Extraction and Recovery Based on FTIR

AbstractAsphalt extraction and recovery are essential steps before characterizing components and properties of aged asphalt binders for recycling the reclaimed asphalt pavement (RAP). To accurately...

Investigating molecular-level factors that affect the durability of restored aged asphalt binder

This paper examines the durability of restored aged asphalt in terms of its susceptibility to moisture and aging. The study is motivated by the increasing use of modifiers called rejuvenators that are added to paving mixtures containing reclaimed asphalt pavements to restore the original rheological properties of asphalt binder that have been lost during service life. Although several test methods have been proposed to quantify the restoration capability of rejuvenators, not much attention has been given to the side-effects that the rejuvenators may impart to the resulting mix. Due to the specific chemical composition of certain rejuvenators, they may negatively impact the durability of the mixture, especially pertaining to its resistance to moisture damage and aging. This paper examines several rejuvenators that are all effective at restoring aged asphalt binder’s rheological properties, to highlight plausible side effects that may be overlooked when selection criteria are based solely on the restoration capacity of rejuvenators. Our laboratory experiments and computational analysis geared toward the use of rheometry and density functional theory showed that while all studied rejuvenators restored the rheological properties of aged asphalt binders, they had very different durability in terms of resistance to aging and moisture damage. Results obtained from the dynamic shear rheometer showed the rejuvenators with the highest restoration capacity did not have the best durability. Computational analysis showed that while the restoration capacity of rejuvenators is related to their penetration into and peptizing of asphaltene nanoaggregates, durability is mainly related to their polarizability values. Rejuvenators with lower polarizability showed better resistance to aging and moisture damage. The outcome of the study facilitates production of effective rejuvenators without compromising the long-term durability of restored asphalt binder. It also helps road authorities develop selection metrics that account for durability along with rheological properties, to prevent non-durable rejuvenators from entering the market. Accordingly, the study results promote sustainability and resource conservation by providing an in-depth understanding of the relation between rejuvenators’ chemical structure and the durability of restored aged asphalt binder.

Use of recycling agents in asphalt mixtures with high recycled materials contents in the United States: A literature review

Abstract Recycling agents, or rejuvenators, are products with chemical and physical characteristics designed to restore the rheological properties of aged asphalt binders to improve the performance of recycled asphalt mixtures with large quantities of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) that promote economic and environmental benefits. This paper summarizes current knowledge related to the use of recycling agents in the asphalt pavement industry, including properties of recycled and rejuvenated asphalt mixtures. This information is further used to identify current and future challenges that could prevent utilization of recycling agents and production of rejuvenated asphalt mixtures with adequate performance.

Predict the rheological properties of aged asphalt binders using a universal kinetic model

In this study, universal models were proposed to predict the aging behaviors of five different asphalt binders, where the rheological properties were emphasized on. The carbonyl content and crossover modulus of binders during oxidative aging process were predicted using the proposed universal kinetic models. The carbonyl content test using the Fourier Transform infrared spectroscopy (FTIR) technique and the frequency sweep test using a Dynamic Shear Rheometer (DSR) were performed to obtain the optimum model parameters. From the testing results, the crossover modulus of binders under oxidative aging effect showed similar growth trend to the carbonyl content that follows the two-reaction kinetics of aging. An approximately linear relation was established between the log crossover frequency and the inverse of log crossover modulus. A sufficient good agreement was achieved between the measured and predicted results of carbonyl content and crossover modulus of asphalt binders at given aging temperature and duration. However, it lost a little prediction accuracy when using the universal model parameters, compared to the specific model parameters. Moreover, based on the calculated crossover modulus and crossover frequency, the complex shear modulus and phase angle were successfully predicted based on the Christensen-Anderson model. The proposed universal model provides an effective approach of predicting the rheological properties of aged asphalt binders.

A Comprehensive Evaluation of Rejuvenator on Mechanical Properties, Durability, and Dynamic Characteristics of Artificially Aged Asphalt Mixture.

In this study, the aged asphalt binder and mixture were laboratory prepared through short-term ageing testing and long-term ageing testing. Firstly, the effect of rejuvenator on physical properties of aged asphalt binders was investigated. In addition, a series of laboratory tests were performed to evaluate the influence of ageing and rejuvenator content on the mechanical properties, durability and dynamic characteristics of asphalt mixtures. Physical test results of asphalt binder testified that rejuvenator used can efficiently recover the aged asphalt binder. However, the effect of ageing and rejuvenator content exhibits different trends depending on the physical property tests conducted. Moreover, artificially aged asphalt mixture with rejuvenator has better ability to resist moisture damage and ravelling. In addition, the ITSR value is more suitable to evaluate the moisture susceptibility for asphalt recycling. Although rejuvenator improves the thermal cracking resistance and fatigue property of aged asphalt mixture, rejuvenated mixture shows greater modulus and inferior ability to resist reflective cracking than the unaged mixture. Moreover, rejuvenated mixture shows less dependence on frequency at high temperature regions and stronger dependence at low temperature regions compared to unaged and long-term aged mixtures.