Saturates, Aromatics, Resins And Asphaltenes Fractions Research Articles

Effect of oxidation kinetic aging on the adhesion behaviour of asphalt-aggregate interfaces from molecular view

ABSTRACT Asphalt oxidation kinetic aging effect on the adhesion behavior of asphalt-aggregate interfaces at atomistic scale was investigated in this study. The asphalts were aged at different aging durations. The sulfoxide and carbonyl functional group content as well as SARA fractions of the asphalts at different aging times were studied through the tests of Fourier Transform Infrared Spectroscopy (FTIR) and Saturate, Aromatic, Resin and Asphaltene (SARA) fractions. Asphalt molecular models of virgin, rapid-rate aged, slow-rate aged and full-aged were established based on SARA fractions and FTIR results, to construct asphalt quartz and asphalt-calcite interface systems at different aging stages. The simulation results showed that the nanostructure of asphalt is influenced by the aggregate type and asphalt oxidative aging. The growth rates of adhesion energy of asphalt-quartz and asphalt-calcite systems increase rapidly first and then slowly with aging time, but the growth rates are different. Meanwhile, the Van der Waals energy is the major energy source of adhesion energy, and the contribution of van der Waals and electrostatic energy to adhesion energy is different. The aging of asphaltene and resin promotes the adhesion ability to quartz or calcite, while the aging of aromatic components is not conducive and the saturate has almost no effect.

Simplified regular solution model for asphaltenes precipitation in crude oil blends

The regular solution model is used with Hankinson-Brobst-Thomson (HBT) molar volume correlation for saturates, aromatics, resins and asphaltenes (SARA) fractions for pure crude oils and blends to predict the precipitation of asphaltenes. The parameters of the HBT correlation were tuned with experimental data for SARA fractions densities. At the same temperature and pressure conditions, the precipitation of asphaltenes is greatly influenced by the presence of other compounds. SARA fractions were obtained according with ASTM D2007 using n-heptane as precipitant solvent. The use of average properties for saturates, aromatics and resins and the assumptions made in the model could reproduce precipitation curves for all study cases. Calculations of asphaltene precipitation prediction for pure oils showed an average absolute deviation between 0.12 and 0.69% for oil of Gulf of Mexico and Cold Lake oil, respectively. For blends it showed values between 0.08 and 0.65% for Cold Lake/Lloydminster-Asphaltene free blend and Cold Lake/Lloydminster-Gulf of Mexico blend respectively. The proposed model maintains its simplicity and can predict the asphaltene precipitation accurately.

Comparison of column chromatography and solid-phase extraction on virgin and aged bituminous maltene phases

Bitumen is a complex mixture consisting of different hydrocarbons, which can be categorised into substance classes called SARA (saturates, aromatics, resins and asphaltenes) fractions. The saturates, aromatics and resins are further referred to as maltenes or maltene phase. To determine the SARA fractions the asphaltenes were separated from the maltenes in a first step. A standard method to further separate the maltenes is column chromatography (CC). Since column chromatography is a time-consuming and solvent-intensive process, an alternative method for separating maltenes using solid-phase extraction (SPE) was investigated. A total of nine bitumen samples of the same type in different ageing states but from different manufacturers were separated with both methods to determine the mass percentages of the fractions for investigating their comparability. The results show that both methods led to different mass percentages of the fractions. However, with the SPE, separating smaller amounts of maltenes is possible while saving a large amount of material, costs, and workload. Linear regression analyses between the colloidal indices with conventional and rheological parameters revealed that the fractions obtained from SPE led to higher coefficients of determination of the linear regression model. The obtained fractions were further structurally compared with FTIR spectroscopy, whereby the spectra of the SPE fractions and the CC fractions did not show any significant differences. The overall consideration of the results concludes that the SPE can replace the CC.

Investigating the relationship between chemical composition and mechanical properties of asphalt binders using atomic force microscopy (AFM)

As a complex mixture, the composition-structure-mechanics relationship of asphalt binders is not well-understood. Thus, it is essential to understand the relationship between chemical composition and mechanical properties. Saturate, aromatic, resin and asphaltene (SARA) fractions are crucial chemical components of asphalt binders. At present, the main challenge faced by many researchers is the relationship between the SARA fractions and the microstructure, and how the SARA fractions affect the micro-mechanical properties of asphalt binders. In this paper, the composition-structure-mechanics relationship were studied using atomic force microscopy. The asphalt samples were divided into two groups. Firstly, different kinds of asphalt binders with different SARA content were compared. Then, new asphalt binders were derived and their properties were analyzed. Results show that bee structure appears on the surface of asphalt binders with higher asphaltene and resin contents, it means that the formation of bee structures is related to the aggregate of asphaltene and resin. Moreover, the micro-mechanical properties of the asphalt binders are affected by two fractions rather than a single fraction. The adhesion force increases with the increase in saturate and aromatic contents, and decreases with the increase in asphaltene and resin contents. The Derjaguin–Müller–Toporov (DMT) modulus, storage and loss modulus increase with the increase in asphaltene and resin contents, and decreases with the increase in saturate and aromatic contents. Furthermore, SARA fractions have the same effect on both the micro- and macro-rheological properties of asphalt binders. These findings will help to improve the understanding of the composition-structure-mechanics relationship of asphalt binders, which in turn will aid in optimizing their performance.

Determination of SARA fractions in asphalts by mid-infrared spectroscopy and multivariate calibration

The SARA fractions in petroleum asphalts for road paving play a dominant role in the pavement performance of asphalt binders. In this study, a rapid and accurate determination method of SARA fractions in asphalts was proposed using Mid-Infrared (MIR) spectra and Partial Least Square Regression (PLSR) modeling method. Firstly, the blending and progressive aging process employed in this study successfully prepared 84 asphalt samples with fair differences in their Saturates, Aromatics, Resins and Asphaltenes (SARA) fractions. Secondly, the SARA fractions and MIR spectra of these samples were measured and collected by standard test methods, respectively. Finally, four quantitative calibration models were developed for each fraction using MIR spectra and PLSR method, and the validation results verified the high consistency between the measured values and the predicted values as well as the reproducibility and repeatability of the proposed method. This MIR-PLSR method was able to provide a faster SARA determination than the standard test methods through a single MIR spectrum. It could probably be used for the real-time quality control of asphalt production and the in-situ quality inspection of asphalt materials in road construction using portable equipment.

Algorithm for estimating SARA fraction properties and its application in predicting the densities of heavy oils, bitumen and diluted bitumen with solvents

Using aromatic ring index (ARI) and the densities of saturates, aromatics, resins and asphaltenes (SARA) at any temperature, an algorithm was developed to iteratively estimate the molecular weights and specific gravities (60 °F) of the SARA fractions. The algorithm circumvents molecular weight measurements in reporting SARA fractions properties. Then, using the corresponding state principles the critical properties and acentric factor of the fractions were estimated using the correlations available in literature. Further, applying regular solution theory the densities of heavy oils, bitumen, and five diluted Athabasca bitumen with 5 solvents were predicted from Hankinson-Thomson and a compressed liquid density correlation. The average absolute deviation (AAD) in predicting the densities was found to be 1.33% for 1524 points with temperature range from 288 K to 463 K and pressure from 0.1 to 10 MPa. The method exhibits predictive ability and can be used satisfactorily for any heavy oil/bitumen/solvent system. In order to improve the accuracy of the calculated densities, a constant density translation method can also be applied to the bitumen/oil mixtures. When the translation method was used, the AAD of mixtures was improved to 0.69%. The proposed method was found to be better or comparable to other models in predicting densities.

Solubility of carbon dioxide and ethane in Lloydminster heavy oil: Experimental study and modelling

AbstractHeavy oil reserves in the world represent 5.5 trillion barrels, which are equivalent to five times the conventional crude oil reserves. Heavy oil reserves will be the main petroleum source for the world's future demand for energy. To enhance the recovery of heavy oil/bitumen, solvent‐based recovery seems to be one of the most promising alternatives to costly thermal methods. Phase behaviour studies of light gases in heavy oil are therefore very important when designing surface facilities and for enhanced oil recovery operations. In this study, we present solubility data for carbon dioxide and ethane in Lloydminster heavy oil. Measurements were carried out using a microbalance at 290.2, 298.2, and 313.2 K and at pressures varying from 200–2000 kPa. Experimental data were regressed with the Peng‐Robinson (PR) equation of state. We also report results of the fractionation of the heavy oil and its characterization in terms of SARA (saturates, aromatics, resins, and asphaltenes) fractions. Henry's law constants for gaseous solvents were also regressed and reported. As expected, ethane had a higher solubility than CO2 in the heavy oil at all temperatures.

Hydrogen donating capacity of water in catalytic and non-catalytic aquathermolysis of extra-heavy oil: Deuterium tracing study

The goal of this work is to try to figure out the role of water in catalytic and non-catalytic aquathermolysis by using isotope tracing techniques. For this purpose, heavy water (deuterium oxide, D2O) was used to replace the ordinary water (H2O) for catalytic and non-catalytic aquathermolysis processes of extra-heavy oil with high sulfur content in autoclave. The donating and upgrading performance of D2O were deeply investigated by analyzing the upgraded (deuterated) oil and their SARA (saturates, aromatics, resins and asphaltenes) fractions using different tracing techniques (FTIR, isotope and elemental analysis), evolved gases by GC, and change in physical-chemical properties of upgraded (deuterated) oils by viscosity measurement, SARA analysis, elemental analysis and GC, etc. The results proved the chemical role of water as a green and environmental hydrogen-donor solvent during aquathermolysis process, verified by considerable deuterium substitution (deuteration) obtained from isotope analysis both in upgraded oil and SARA fractions. The results are further supported by significant deuterium exchanges (deuteration) of aliphatic and aromatics parts in the initial and deuterated oil samples and their individual SARA fractions in FTIR spectra. Simultaneously, introducing Ni-tallate as an oil-soluble catalyst promoted the donating capacity of water, thus significantly improving the upgrading performance. The important finding about the role of water in catalytic and non-catalytic aquathermolysis not only enriches the theoretical basis in this area, but also provides a strong support for the use of catalysts in aquathermolysis for improving in-situ heavy oil upgrading performance.

Thermal effects of asphalt SARA fractions, kinetic parameter calculation using isoconversional method and distribution models

To discuss the thermal decomposition mechanism of asphalt materials, the kinetic parameters were calculated and their distribution models were established based on differential scanning calorimetry (DSC) test results of saturates, aromatics, resins and asphaltenes (SARA) fractions in asphalt. Results indicate that the thermal decomposition processes of SARA fractions are accompanied by complicated endothermic and exothermic reactions, and the exothermic reactions are predominant. The DSC curve is shifted to higher temperature when the heating rate is elevated, and the thermal effects, reaction progress and decomposition rate are increased simultaneously. Also, the Friedman–Reich–Levi (FRL) isoconversional method is suitable to calculate the kinetic parameters during the thermal decomposition of SARA fractions. The conversion ratio (α) of each SARA fraction shows obvious effects on the calculated activation energy (E). As the α of each SARA fraction is increased, the calculated E of saturates is more accurate at a lower α at the decomposition stages 1 and 3, but is always accurate at stage 2. Additionally, the calculated E is more accurate at the lower and higher α than that at the middle α at the two decomposition stages of aromatics. The calculated E of resins is fluctuated between 99 and 112 kJ mol−1, and its accuracy is satisfactory. The calculated E of asphaltenes is changed between 8 and 80 kJ mol−1, and is more accurate at the lower and higher α than that at the middle α. Finally, the distributed activation energy models of each SARA fraction are established to provide an insight into thermal decomposition mechanism of asphalt materials.

Effects of SARA fractions on pyrolysis behavior and kinetics of heavy crude oil

This research aims to explore the effects of saturates, aromatics, resins and asphaltenes (SARA) fractions on the heavy crude oil pyrolysis behavior. The results showed that resins and asphaltenes had more pyrolysis residues (22.04% and 45.66%) relative to other samples. However, no residue was found after pyrolysis reactions when the oil mixed with SARA fractions. In addition, high temperature pyrolysis (HTP) activation energies of oil + saturate/resins/asphaltenes (112.50/128.36/119.45 kJ/mol) were less than that of the heavy oil (146.20 kJ/mol). The addition of saturates, resins, and asphaltenes could reduce the difficulty of the heavy oil HTP reactions.

Thermal-oxidative aging mechanism of asphalt binder based on isothermal thermal analysis at the SARA level

To better understand the thermal-oxidative aging mechanism of asphalt binder at the component level, a new isothermal agingmethod was developed to discuss thermal behaviors of saturates, aromatics, resins and asphaltenes (SARA) fractions. Volatile constituents released from SARA fractions were identified and the changes in chemical compositions, morphology and elements of SARA fractions were characterized before and after the thermal-oxidative aging. Results indicate that the mass losses of saturates and resins are 2.1% and 0.7%, respectively. However, the aromatics and asphaltenes masses are increased by 2.0% and 5.2%, respectively. Also, endothermic reactions occur in saturates and aromatics, and endothermic and exothermic reactions are basically equivalent in resins, and exothermic reactions occur in asphaltenes. Further, CO, CO2, CH4 and light oxygen-containingcompounds are released during the aging of SARA fractions, and short-chain alkanes are generated in saturates. Low molecular hydrocarbons, CO2, and SO2 are emitted, and more aromatic ring products are generated in aromatics. Carboxylic acids, small molecular unsaturated hydrocarbons and SO2 are volatilized, and fused aromatic rings, alcohols and ethers are produced in resins. Unsaturated hydrocarbons are released, and the molecular polymerization becomes obvious in asphaltenes. Additionally, after the isothermal aging, pores or bulges are left in saturates, and obvious folds and pores appear on aromatics. Cluster whiskers, lumps and disordered lamellar layers are observed on resins, and resins and asphaltenes become loose, dry and rough. C element content is increased, but O element content is decreased. Finally, various volatiles are released from SARA fractions at different aging stages. The thermal-oxidative aging of asphalt binder consists of the volatilization of light components and the oxidation of side chains in benzene methyls and aliphatic hydrocarbons, leading to the content changes of SARA fractions in asphalt binder.

The use of thermogravimetry as a means of predicting the performance of coke in delayed coking of a residue of Venezuelan origin

A study, which shows the similarities in the results obtained through this technique and those corresponding to a process of delayed coking at laboratory scale, is presented. Fifteen mixtures with a controlled composition of SARA (saturate, aromatic, resin and asphaltene) fractions which make up the crude were processed both in a delayed coking laboratory unit (DCLU) and in a thermogravimetric analyzer (TG). The comparison of the behavior of the yield of the coke and volatile material obtained through both mediums, DCLU and TG, showed similarities in the mixtures with high aromatic and asphaltene content, but differences in the mixtures with high resin content which would be associated with the formulation of the same, thus indicating the synergy of the fractions within the chemical reaction process taking place, which lead to different reaction pathways depending on the composition of the mixture fed. The similarities in the results obtained through TG and those from DCLU, while not reproducing the exact magnitude of the results, may lead to this technique being a valid reference for the study of changes in the diets used in the process with low resource consumption at both laboratory and industrial scale.

Effects of SARA fractions on low temperature properties of asphalt binders

Effects of the chemical fraction on the low temperature rheological behaviours of asphalt binders were explored in this study. Four fractions, namely saturate, aromatic, resin and asphaltene (SARA), were obtained from eleven asphalt binders by a novel column chromatography separation method. In addition, the viscoelastic master curves for binders and their subsets were characterised by dynamic shear rheometer (DSR) at high frequencies (low temperatures). The results showed that the complex modulus and phase angle of asphalt binders were closely related to the changes of SARA fractions. Moreover, low temperature properties of asphalt binders characterised by the creep stiffness modulus and m-value were measured using bending beam rheometer (BBR) test. The increases of asphaltene in asphalt binder resulted in the decreases of creep stiffness modulus of asphalt as well as m-value. Further, the glass transition temperature (Tg) of resins, asphaltenes and asphalt binders were measured by differential scanning calorimetry (DSC) test. The results showed that the Tg values of asphalt binders were mainly determined by saturates and aromatics fractions. However, the Tg values of the asphalt binder would increase with the increase of asphaltene content. Finally, significant relationships between SARA fractions and low temperature parameters of asphalt binder specimens were found and conducted using linear regression analysis, indicating that the SARA fractions would perform significant effects on the low temperature properties of asphalt binders.

Thermal behaviors and harmful volatile constituents released from asphalt components at high temperature.

Asphalt binder releases lots of heat and harmful volatiles at high temperature. To further understand thermal behaviors, dynamic release and toxic constituents of emitted volatiles during the combustion of asphalt binder, such fractions as saturates, aromatics, resins and asphaltenes (SARA) were first prepared. Thermal behaviors, volatile constituents and combustion residue microstructures of SARA fractions are discussed. Results indicate that polymerization degree of asphalt binder is high and the content of polycyclic aromatic compounds is large. Combustion processes of resins and asphaltenes only show single-stage exothermic reactions, but other two fractions present obvious multi-stage combustion reactions. As the heating rate is raised, the incomplete combustion of SARA fractions is increased, and more volatiles are released. Main volatiles released from SARA fractions are inflammable, toxic, corrosive or explosive compounds, and such common volatiles as acetaldehyde and propane are released from each SARA fraction. More toxic volatiles are released at combustion stage I, but macromolecular volatiles are mainly released at stage II. Volatile release behaviors of saturates and aromatics are more obviously affected by the heating rate. Combustion residues show more intact morphologies from saturates to asphaltenes, and mainly contain C, O and S elements. Asphalt binder is hazardous material at high temperature.

Modelling of rheological and chemical properties of asphalt binder considering SARA fraction

Modelling the rheological properties and chemical characteristics of asphalt material has been a hotspot. In this study, 20/40 and 60/80 pen grade asphalt binders named binder A and binder B were used to blend eleven binder samples. After that, a novel column chromatography was applied to collect sufficient SARA (Saturates, Aromatics, Resins and Asphaltenes). The Dynamic Shear Rheometer (DSR) test was used to develop the viscoelastic master curves for binders and their subsets. The Fourier Transform Infrared Spectroscopy (FTIR) test was conducted to identify and semi-quantitatively analyze the notable functional groups. Linear combination models were conducted between rheological model parameters and chemical components. It was found that the contents of Asphaltenes and Saturates increased, while those of Resins and Aromatics decreaed with the addition of binder A, resulting in the increased colloidal instability index (CII) values. In addition, the Saturates had constant value of phase angle, while the phase angle master curves of Aromatics and Resins showed plateau values of 80°. Resins containing more aromatic structures had a lower frequency (high temperature) value at this plateau value. Furthermore, the main findings were that ICC and ICH of Aromatics as well as ICH and ISO of Resins had significant relationships with binder A content. Statistically, several parameters such as CResins, CAsphaltenes, CII, ICC of Aromatics, ICH of Aromatics, ICH of Resins, and ISO of Resins had significant effects to develop multiple linear regression model on asphalt rheological properties.

Crude oil spectral signatures and empirical models to derive API gravity

Infrared spectroscopy is presented as a quick alternative method for establishing crude oil properties such as density (°API gravity) and content of saturates, aromatics, resins and asphaltenes (SARA). Here, thirty seven (37) samples of crude oils with different °API gravities and SARA fractions were measured in the visible, near infrared and short wave infrared (VIS – NIR – SWIR/350–2500 nm), and in the middle and longwave infrared (MWIR – LWIR/3000–15,000 nm) ranges. Main CH absorption bands and optimal intervals for the discrimination among oil types were identified in all spectral regions. Based on diffuse reflectance spectroscopy and equivalent wavelet spectra, Principal Component Analysis allowed distinguishing between three major groups of crude oils with varied densities. Partial Least Squares Regression analysis yielded sixteen predictive models tailored to estimate the °API of crude oils based on their spectral signatures in the NIR – SWIR – MWIR – LWIR intervals. These data and methods are swift and nondestructive ways to estimate the °API of crude oils, with latent applications in several chains of the petroleum industry, particularly to assess and manage the environmental impact caused by oil discharge, leakage and spill events. Additionally, considering that airborne and orbital sensor systems currently in operation can sense some of the crude oil absorption bands highlighted in this study, the oil signatures revealed here could be potentially used to map oil contamination in diverse settings and globally using remote sensing.

Comparing Crude Oils with Different API Gravities on a Molecular Level Using Mass Spectrometric Analysis. Part 2: Resins and Asphaltenes

The combination of fractionation methods for crude oils, such as saturate, aromatic, resin and asphaltene (SARA) fractionation, in combination with analysis by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been used for reducing the complexity and improving the characterization of crude oils. We have used the FT-ICR MS techniques in conjunction with electrospray ionization (ESI(±)) and atmospheric pressure photoionization (APPI(+)) to find trends between MS data of SARA fractions of crude oils with different American Petroleum Institute (API) gravities from the Sergipe-Alagoas basin (Brazil), focusing on the resin and asphaltene fractions. For the first time, an adaptation of the SARA fractionation has been performed to obtain a second resin fraction, which presented compounds with an intermediate aromaticity level between the first resins and asphaltene fraction. Both the first and second resin and the asphaltene fractions were studied on a molecular level using multiple ionization techniques and FT-ICR MS to find a direct relationship between the API gravities of a heavy, medium and light crude oil. For the FT-ICR MS data and the API gravities an aromaticity tendency was found. The data show that the use of SARA fractionation with FT-ICR MS offers a tool for comprehensive characterization of individual fractions and selective chemical characterization of the components in crude oils.

Singlet Oxygen Production by a Crude Oil from the San Jorge Gulf Basin, Argentina.

The quantum yields for singlet oxygen production by diluted solutions of an Argentine crude oil and its SARA (saturates, aromatics, resins and asphaltenes) fractions were obtained by direct detection of the characteristic phosphorescence following monochromatic excitation at 355nm. The most efficient sensitizers of singlet oxygen in organic media are crude oil, maltenes and aromatics fractions (values of singlet oxygen quantum yield are around 0.7), and resins (values around 0.1) are the poorest. Also, the quenching of singlet oxygen by the crude oil and its fractions was investigated; the asphaltenes and the petroleum are relatively efficient quenchers of singlet oxygen.

Effects of flame retardants on thermal decomposition of SARA fractions separated from asphalt binder

To better understand effects of flame retardants on thermal decomposition of saturates, aromatics, resins and asphaltenes (SARA) fractions in asphalt binder, different flame retardants were selected to match the thermal decomposition temperature range of each SARA fraction, respectively. Then inhibitory effects of matched flame retardants were discussed and microscopic morphology of combustion residues were observed. The results indicate that the decomposition process of each SARA fraction still includes two thermal mass loss stages after adding the matched flame retardants. However, the thermal decomposition rates are lowered, and the initial decomposition temperatures and maximum decomposition temperatures of each SARA fraction are elevated. Also, the matched flame retardants have few effects on the volatile constituents of four SARA fractions, but show an obvious influence on the release amount of gaseous products. CO2 and H2O are still the two main products of each SARA fraction after adding matched flame retardants. Few chemical reactions between SARA fractions and flame retardants are found during their decomposition. Additionally, the superposed and densified charring layers are formed due to the synergic effects of the composite flame retardants. The thick charring layer prevents the heat from transferring, and hinders the oxygen supply, and inhibits the release of flammable volatiles. Finally, the thermal stability of each SARA fraction is greatly improved by the matched flame retardants. The composite flame retardants show a synergistic flame retarding and smoke suppressing effects. This study is beneficial to develop new composite flame retardants for asphalt binder with a satisfactory flaming retarding and smoke suppressing effects.

Analysis of the Relationships between Waste Cooking Oil Qualities and Rejuvenated Asphalt Properties.

Waste cooking oil (WCO), in many cases, can rejuvenate aged asphalt and restore its properties. However, the influence of WCO qualities on rejuvenation behaviors of aged asphalt has not been investigated in detail. The objective of this paper was to evaluate the effects of WCO viscosity and acid value on the basic, rheological, and chemical properties of a typical rejuvenated asphalt. Penetration, ring and ball (R and B) softening point, and ductility were tested to evaluate the influence of WCO qualities on basic properties of rejuvenated asphalts. Then, the rheological properties of rejuvenated asphalt were characterized based on rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR) test results. Further, SARA (saturates, aromatics, resins, and asphaltenes) fraction analysis and Fourier transform infrared spectroscopy (FTIR) tests were performed to investigate the effects of WCO qualities on asphalt chemical composition. Finally, grey correlation coefficients were calculated and the relationships between WCO qualities and rejuvenated asphalt properties were quantitatively evaluated. The experimental results indicated that WCO qualities influence the rejuvenation behaviors of aged asphalt significantly, and the WCO with higher qualities (low acid value and viscosity, as defined in this research) tends to achieve better rejuvenation effects. Based on the results of grey correlation analyses, the acid value is, relatively, a better indicator than viscosity in predicting the rejuvenation efficiency of WCO. The rejuvenation thresholds of WCO are varied with the categories of properties of rejuvenated asphalts, and WCO with an acid value of 0.4–0.7 mg KOH/g, or a viscosity of 140–540 mm2/s, can meet all of the performance requirements for asphalt rejuvenation used in this research.