•EP improved the low-temperature and fatigue properties of aged asphalt binder.•EP improved elongation and high-temperature properties of aged asphalt binder.•EP reduced the concentration of ...sulfoxide and carbonyl of aged asphalt binder.•The EP content had a greater impact on the properties than the asphalt ageing degree.•A recommended EP content of 40% is suggested.
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.
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•EP improved the low-temperature and fatigue properties of aged asphalt binder.•The fatigue properties of ERA binder steadily improved as the EP content increased.•After a phase ...transition occurred, the properties of the binder significantly changed.•EP changed the concentration of functional groups in aged asphalt binder.•The property gap between EA and ERA was not significant under the same EP content.
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.
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.
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•The degraded products of dry-method SBS reacted with epoxy resin molecules.•Phase separation occurred between EP and asphalt, as well as between asphalt and SBS.•Dry-method SBS increased the size of the asphalt binder phase in micro-morphology.•Dry-method SBS enhanced elongation, fatigue, and low-temperature properties of ERA.•The use of SERAM achieves material cost savings of around 46 USD (9%) per tonne.
•Recycled wax oils enhance low-temperature performance but trigger exudation, affecting binder properties.•Early-stage exudation is prominent, diminishing over time.•Accelerated exudation device ...reveals pressure, time, and temperature as pivotal factors.•The formation of fluorescent rings indicates the effect of recycled wax oil on asphalt stability.•Binder compatibility experiences significant changes based on the source of asphalt binder.
The tendency of asphalt to exude oil under certain conditions is often overlooked as a form of aging in asphalt pavement. To better understand the issue of oil exudation in asphalt during long term cold storage, two different oil sources of asphalt binders with recycled wax oils were investigated using the extended bending beam rheometer test (Ex-BBR), double edge notched tension test (DENT), extended Hansen solubility model, and fluorescence and polarizing microscopy. The results of the Ex-BBR and DENT tests demonstrate that the addition of recycled wax oils significantly enhances the low-temperature performance of asphalt. However, the use of fluorescing markers in cooling media indicates that recycled wax oil exudation can lead to ethanol diffusion in the asphalt binder. To further elucidate the factors influencing exudation, a device for accelerating the exudation of asphalt was developed. The research results show that, in addition to the intrinsic properties of asphalt and recycled wax oils, pressure, time, and temperature significantly influence the acceleration of exudation. The primary changes in recycled wax oil exudation occur early on, with the exudation rate decreasing over time. The fluorescent microscope reveals the separation of recycled wax oils as a fluorescent ring. Recycled wax oils alter the internal stability of asphalt, as evidenced by an increase in polarity and hydrogen bonding. This change is expected to impact the compatibility of asphalt binders. The mechanism of these interactions varies significantly depending on the source of the asphalt binder. After accelerated exudation, the three interaction forces representing sensitivity to chemical environments are further reduced.
•The applications of FTIR in asphalt materials research are reviewed.•The mechanisms of different ageing method are discussed from FTIR perspective.•The performance prediction models based on FTIR ...and chemometrics is discussed.•Multispectral data fusion approach is envisaged for future research.
Fourier-transform infrared spectroscopy (FTIR) has become a crucial method for both qualitative and quantitative analysis in characterizing asphalt materials. The present work aims to provide a comprehensive review of recent uses of FTIR in this field, that ranged from material quality control, material identification, to the analysis of modification mechanism, including ageing mechanisms, as well as for macroscopic performance prediction. The narrative unfolds within a broader context, with the basic principles, and insightful comparisons with ultraviolet–visible (UV–vis) spectroscopy, Raman spectroscopy, and fluorescence spectroscopy. The instrumentations employed in FTIR research are inspected in detail, delving into testing modes, sample preparation, and data analysis methods, with a particular emphasis on its ability to identify asphalt components at the molecular level. Furthermore, FTIR analysis provides useful indications for various applications: i) quality identification; ii) asphalt materials modifications and ageing states identification according to molecular changes; iii) prediction for the physical and rheological properties of asphalt binder based on chemometric method. The prospects in asphalt research are proposed stressing the relevance of combining FTIR analysis to high-throughput experimental methods and other spectroscopy technologies, and coupling to machine learning (ML) methods. This paper provides a reference for researchers who intend to explore the quality control and to analyze asphalt binders from a microscale perspective, fostering further research on relationships between microscopic compositions and macroscopic properties.
This study evaluates the ability of softer virgin binders, recycling agents (RAs), and extenders to restore the rheology of reclaimed asphalt pavement (RAP) binders to that of control binders. ...Control binders are those binders that would be specified for use with virgin mixtures. Two procedures for RA dosage selection are examined: 1) dose to restore the intended high-temperature grade; and 2) dose to restore the intended low-temperature grade. A broad range of point parameters and rheological parameters that measure the balance of relaxation and stiffness characteristics are examined at two long-term age levels. The results of recycled binder blends are compared with the control virgin binders statistically. Using softer virgin binders generally resulted in blended binder performance-graded properties that were similar to or better than the control. However, these softer binder systems often exhibited other rheological properties that were inferior to the control. The rheological characteristics of the RA blends varied with the RA type and dosage. Blends with dosages that restored the intended high-temperature grade generally yielded the most favorable comparisons to the control binders. RAs derived from triglycerides and fatty acids and from tall oils generally yield more favorable rheological characteristics than those derived from aromatic extracts. In addition, a vacuum gas oil extender achieved similar blend rheological characteristics to RAs but extenders containing re-refined engine oil bottoms generally yielded a poor balance of stiffness and relaxation characteristics. Rheological balance parameters are generally weakly correlated, suggesting they provide unique insight into the rheological behavior of binders.
•The periodic perturbation method is adopted to calculate the ZSV of asphalt binder MD models.•Asphaltene and saturates more easily reorient their conformation in shear flow.•Short, unordered planar ...accumulations structures dominate asphalt binder microstructure.
This study aims to develop molecular model of asphalt binder and investigate the reasonable simulation scale of molecular dynamics (MD) in researching the viscosity property and microstructure of asphalt binder. Eighteen MD models with atom numbers in the range of 10,000–750,000 for the three typical asphalt binder AAA-1, AAK-1, and AAM-1 in the Strategic Highway Research Program (SHRP) were constructed. Density, Zero Shear Viscosity (ZSV), and microstructure characters of the asphalt binders were analyzed by MD to compare with experiment data. The result shows that densities and the ZSV values of the MD models are all close to the experimental values. These models with atom numbers of 130,000–375,000 are well stabilized and have lower errors, which is recommended to research the density and viscosity properties. In the shearing process, the shear flow induces the conformational transitions of the asphalt binder, and most molecules tend to parallel the shear direction. Asphaltenes and saturates components are easier to reorient their conformation in shear flow. Through the density map obtained by MD simulation and the asphaltenes image from the High-resolution transmission electron microscopy in literature, we speculate that short and unordered planar accumulations structures dominate the asphalt binder microstructure, which is a further explanation of the colloidal theory.
Crumb rubber modified bitumen (CRMB) can be regarded as a binary composite system in which swollen rubber particles are embedded in the bitumen matrix. Previous study has successfully implemented the ...micromechanics models in predicting the complex moduli of CRMB binders using more representative constituent parameters. In the regime of master curves, while the micromechanics models used predicted well in the high-frequency range, they underestimated the complex modulus in the low-frequency range. The current study aims to further improve the prediction accuracy of micromechanics models for CRMB by considering the interparticle interactions. To accomplish this goal, a new reinforcement mechanism called chain entanglement effect was introduced to account for the interparticle interaction effect. Results show that the polymer chain entanglement effect accounts for the underestimation of complex modulus and lack of elasticity (overestimation of phase angle) for CRMB at high temperatures/low frequencies. The mechanical properties of bitumen matrix and entangled polymer network can be determined based on the rubber content. The introduction of the entangled polymer network to the generalized self-consistent model significantly improved the prediction accuracy for both complex modulus and phase angle in the whole frequency range. In summary, by incorporating the physio-chemical interaction mechanism into the currently available models, a new dedicated micromechanics model for predicting the mechanical properties of CRMB has been developed. The predicted viscoelastic behaviors can thereafter be used as inputs for an improved mix design.
Polymer-modified asphalts (PMAs) are known to improve the rutting, cracking, and durability of pavements, especially creating better resistance to aging susceptibility. Although the properties, ...benefits, and performance of PMAs overall are fairly well known and talked about in the asphalt industry, the key aspect of selecting a good base binder for effective styrene–butadiene–styrene compatibility and enhanced performance still remains largely unexplored, and is generally based on trial-and-error methodologies. The main objective of this study was to perform in-depth physical, chemical, rheological, and microstructure characterization of base (neat/unmodified) and corresponding PMA binders to understand and quantify important aspects of their composition that would contribute to developing robust and better-performing PMAs. The experimental matrix included three base asphalt binders from different sources but similar Superpave
TM
performance grades (PG) and three corresponding PMAs. A comprehensive characterization effort was carried out on these binders that included PG grading, Black Space analysis, G* master curves, determination of ΔT
c
, determination of saturates, aromatics, resins, and asphaltenes fractions, differential scanning calorimetry, size-exclusion chromatography, Fourier transform infrared, and microscopy. The key outcome of this study is a set of guidelines and recommendations for preferable characteristics of base binders that contribute to formulating effective PMAs and certain “dos and don’ts” with respect to the interpretation of data and/or the analysis approach. It is expected that the outcome of this study will become an important tool for formulating well-performing PMAs that will be useful to asphalt and additive suppliers as well as contractors, agencies, or both, that procure, handle, and use PMAs for pavement applications in general.
Cathode-ray-tube (CRT) is the ingredient of glass used in obsolescent televisions or computer monitors. CRT glass contains a considerable amount of heavy metals, and the landfilling of CRT glass is ...significantly harmful to the environment. In an effort to recycle waste CRT glass instead of landfilling it, recycled CRT glass powders were introduced to asphalt binders as a modifier in this preliminary investigation. The recycled CRT glass was processed to a particle size smaller than 0.075 mm and mixed with asphalt binder (PG 58–28) to produce asphalt mastics with four different concentrations (0, 5, 10, and 15 wt%). The rheological performance was characterized with the rotational viscosity (RV), dynamic shear rheometer (DSR), and multiple stress creep recovery (MSCR) tests. The fatigue performance was evaluated by linear amplitude sweep (LAS) test. Meanwhile, the low-temperature properties were measured by the asphalt binder cracking device (ABCD). The hazard materials leaching test was applied to evaluate the leaching potential of lead content into the external environment due to the high lead content in the modified asphalt. The test results revealed that the increase of CRT glass powder content improved the energy of activation compared with that of virgin binder, as well as the resistance of permanent deformation. Furthermore, the incorporation of CRT glass powder may slightly increase the fatigue life of asphalt because of the improved physicochemical interaction between glass and bitumen. The low-temperature cracking temperature first decreased with the increase of CRT glass powder content and then increased as the CRT content increased further. The leaching test demonstrated that the CRT glass powders incorporated into asphalt binders represented a lower lead leaching content than that of the original CRT glass powder, where the lead leaching amount of CRT glass modified asphalt binder is obviously lower than the specified level of 5 mg/L. Therefore, it is possibly acceptable to recycle CRT glass powders in asphalt binders as an additive as an environmental-friendly recycling method, in which the optimal addition content of CRT glass powders could be up to 10% (wt.).
