Aged Binder Research Articles

Effects of multiple recycling on the performance characteristics of asphalt binder using different recycling agents

The process of reclaimed asphalt pavement (RAP) recycling may occur multiple times during the life of the pavement. This study investigates the effect of multiple recycling on binder properties by employing a virgin 3045 PEN grade binder that was aged in the laboratory intended to simulate aging of binders in RAP. The aged binder was rejuvenated using two bio-oils and one softer binder. The doses of the bio-oils and softer binder were determined by matching the continuous high-temperature performance grade (PGH) of the rejuvenated RAP binder to that of the virgin binder. This aging and rejuvenation cycle was repeated three times. Finally, fatigue and rutting performance of the binder was evaluated for the three reuse levels. Results indicate that the material can be reused up to three cycles keeping good performance on fatigue or rutting. However, care should be taken regarding the cumulative effect of bio-oils causing an over-softening effect on the of the RAP.

Effect of crumb rubber and reclaimed asphalt pavement on viscoelastic property of asphalt mixture

Crumb rubber and reclaimed asphalt pavement have been widely used in the application of pavement engineering as they would greatly improve the high-temperature stability and rutting resistance of asphalt mixtures. This study aimed to give a comparative analysis of the viscoelastic improvement effect of crumb rubber and reclaimed asphalt pavement. In laboratory tests, 2 virgin binder contents, 2 crumb rubber contents, 2 sources of reclaimed asphalt pavement, and 2 reclaimed asphalt pavement contents were involved to produce 12 different types of asphalt mixtures with controlled aggregates gradation. Single axle creep test and dynamic modulus test were conducted to acquire stress-strain response under static and dynamic loading conditions. Creep performance was obtained under 20 °C, 35 °C and 50 °C, and dynamic modulus was obtained under 5 °C, 20 °C, 35 °C and 50 °C at 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz and 25 Hz. Master curves were constructed for creep compliance, complex modulus, phase angle, storage, and loss modulus in the time and frequency domains, and an optimal fitting model was selected. As a result, it was found that both crumb rubber and reclaimed asphalt pavement had a positive effect on the elasticity of the asphalt mixture. In most scenarios, the elasticity improvement was dominated by reclaimed asphalt pavement but it was dependent on the aged binder content. The effect of incorporating crumb rubber and reclaimed asphalt pavement together was comparable to the sum of the effect when incorporating each of them solely.

Unraveling the nano-cracking mechanism in aged asphalt binder with consideration of rejuvenation effects

For achieving the sustainable utilization of reclaimed asphalt pavement, a popular approach is to incorporate rejuvenators to restore the cracking resistance of aged asphalt. However, research on the nanoscale rejuvenation mechanisms and the relationship with the cracking behavior is limited. To address this challenge, this study utilizes molecular dynamics simulations to explore the fundamental cracking mechanism in aged asphalt and elucidate how rejuvenators affect this process. A multiphysics analysis, including mechanical response, morphology relationship, energy evolution, deagglomeration and lubrication behavior is developed to comprehend the nano-cracking mechanism. Computational findings reveal that the cracking failure originates form cavitation, and the process primarily includes nanovoid formation, enlargement, filamentation, and separation. Oxidation enhances the aggregation of asphaltene molecules and reduces intermolecular rearrangement and mobility, which fundamentally accelerates the nano-cracking process. Owing to the diffusion of rejuvenators and their disturbances to asphaltene π-π stacking, rejuvenators can penetrate into aged asphalt molecules, lubricate and reduce intermolecular friction. This facilitates molecular rearrangement during the cracking process, thereby improving the cracking resistance and energy performance of aged asphalt binder. The finding from this study contributes to elucidating the fundamental cracking mechanism in rejuvenated asphalt binder and promoting the sustainable utilization of recycled pavement materials.

Effect of re-aging on chemical and rheological properties of waste engine oil rejuvenated asphalt binder

The use of rejuvenator can potentially restore original properties of reclaimed asphalt pavement (RAP) materials to achieve the purpose of reuse, but less attention has been paid to the aging properties of rejuvenated asphalt binders. In this study, original asphalt binder, aged binder and the rejuvenated binders with 3 %, 6 %, and 9 % of rejuvenator by total weight of binder were prepared first. Then the five rejuvenated binders were subjected to the oven aging. Based on the results from Fourier Transform Infrared Spectroscopy and Dynamic Shear Rheometer, the chemical and rheological properties of the five binders were investigated due to re-aging. It is showed that the of carbonyl index of the rejuvenated binders and original binder increase rapidly during the fast-aging state and then slowly during the constant-aging state, while aged binder increases approximately linearly. The rheological properties indexes such as complex shear modulus, phase angle δ, crossover frequency, crossover modulus, rheological index, G-R parameter and rutting factor of the five binders were determined, and the variation of these indexes are similar or opposite to carbonyl index during aging. Aging performances of the five binders were investigated using the oven aging indexes. It is showed the rejuvenated binders with more dosage of rejuvenator have faster aging rate and more obvious effects on the aging rheological behavior. The rheological properties of the aged binder are less affected by the re-aging. Among the rheological property indexes, the G-R-based oven aging index is most susceptible to the re-aging. There are some certain close relationships between the chemical property change and rheological property evolution during re-aging for the five binders, without considering the aging times and the dosage of rejuvenator.

Multiscale evaluation of asphalt binder rejuvenation dosing and efficacy

The final composition of asphalt binder in an asphalt mix can vary depending if it is a neat, virgin binder, or a blend of neat binder with reclaimed asphalt pavement (RAP), modifiers, and/or rejuvenators. As recycling of asphalt concrete becomes more commonplace worldwide, so too must be the use of chemical rejuvenators which can restore the original properties of the associated asphalt binder, contributing to the performance and therefore sustainability aspect of this material. In this context, this work aimed to evaluate the influence of rejuvenation in different proportions of aged and unaged binder, as well as the best way to dose rejuvenators, taking into consideration aspects that go beyond the Superpave Performance Grading characterization of binders. In the first phase of this study, when rejuvenator contents based on low PG recovery were proportionally added to different aged/unaged binder blends, it was observed that restoration of ductility and strength of the rejuvenated aged binder was limited. However, when an additional cycle of aging was applied to simulate the new service life of recycled material, the rejuvenated recycled material generally performed better than unrejuvenated recycled material. This long term effect can better differentiate the performance of different rejuvenators. Afterwards, the dosing procedure was investigated using an extensive range of dosages. An optimal dosage determination approach was developed and verified by means of the rejuvenation of aged asphalt mixtures from the rheological, mechanical, and chemical perspectives. Finally, the differences between laboratory-aged binder and laboratory-aged mixtures when rejuvenators are used was investigated, and it was determined that the mechanisms of rejuvenation at the two scales are not completely alike. Key findings also include the importance of re-aging asphalt binder blends before testing when a rejuvenator is used and the dominance of unaged binder within binder blends with limited replacement with recycled asphalt. Overall, this work opens the door to future studies of rejuvenation of asphalt using different approaches than those which have been conventionally used, including consideration of amount of replaced binder, using nonlinear viscoelastic characterization, fundamental chemical studies, and the method of addition based on mixture versus binder scale studies.

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.

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.

Effects of Fly Ash Geopolymer Hot Mix Asphalt Additive on the Rheological Properties of Unaged and Short-Term Aged Asphalt Binder

Asphalt pavement has the advantages of driving comfort and convenient maintenance, which has been widely applied to highway construction. However, due to the continuously increased traffic volume, it is recognized that asphalt binder and mixtures with enhanced characteristics are needed to guarantee the durability of the functional performance of transportation infrastructures. This study was carried to evaluate the effect of fly ash geopolymer additive on the rheological properties of unaged and short-term aged asphalt binder. In the respect, asphalt binder 80/100 and 60/70 penetration grade with 0, 3, 5, 7, 9 and 11% fly ash geopolymer by weight of asphalt binder were prepared. The results indicated that the addition of FAG significantly increases the stiffness (G*) and decreases the phase angle (δ) for both unaged and short-term aged modified asphalt binder compared to the control asphalt binder. This can be proved that presence of FAG significantly improved rutting parameter i.e G*/sin δ compared to control in which capable to resist rutting at higher temperature. In terms of failure temperature, highest failure temperature of 9% FAG modified asphalt binder indicated that the binder is less susceptible to be rutting at high pavement temperature for both unaged and short-term aged, respectively. Overall research conclusions are that 9% of FAG is proposed as the minimal content to be used as an additive in asphalt binder for further mixture evaluations.

Nanoscale evolution of rubber-oil modified asphalt binder after thermal and UV aging

Thermal oxidation and ultraviolet exposure cause complex micro-scale chemical changes in asphalt binders, leading to severe deterioration of pavements. The aging-induced evolution of nanoscale domains in asphalt binders was investigated using multiple nanoscale characterizations. This in turn provides insights to develop means of alleviating the aging of asphalt binders to extend pavement service life. The chemical composition, surface topography, and mechanical properties of four asphalt binders (base asphalt and modified asphalt with bio-oils and crumb rubber) are investigated by atomic force microscopy during thermal aging and UV aging and a combination thereof. It was shown that the three domains in the asphalt binder react differently to aging. Abundant carbonyl and sulfoxide compositions are observed in the aged base asphalt binder, which is mainly generated and concentrated in the para domains. The addition of rubber and bio-modified rubber reduces the formation of aging-related compositions in para domains, thereby enhancing the aging resistance of asphalt binder. Aging also significantly changes the surface roughness and domain structures of asphalt binders. Furthermore, it was shown that the domain stability during thermal aging and UV aging can be enhanced by crumb rubber and bio-oils, respectively. Nano-mechanical characterization shows the surface of asphalt binders becomes stiffer, and its adhesion is reduced after aging. Significant reduction (up to 26%) in latter aging indicators was observed with the bio-modifier used in rubberized asphalt. This paper provides insights pertaining to the aging-induced evolution of asphalt binders while examining the efficacy of bio-modification of rubberized asphalt to delay aging. It is recommended to include hybrid aging in future studies and to test bio-modified rubberized asphalt at a larger scale.

Development and Performance Evaluation of an Asphalt Regenerant Derived from Waste Engine Oil Residue.

This study assessed the fundamental physical properties and chemical composition of three specific waste engine oil residue (WEORs) asphalt regenerants. Through dynamic shear rheometer and rolling thin-film oven tests, the performance of aged asphalt was evaluated using three key indicators. Thin-layer chromatography investigations probed the WEOR-induced changes in the aging asphalt components, leading to the creation of two novel asphalt regenerants, WEOR-H and WEOR-G. WEOR-G was developed from WEOR-1, liquid rubber, ultraviolet absorber, light shielding agent, and antioxidant, while WEOR-H was formulated from WEOR-2, aromatic oil, and liquid rubber. The study employed differential scanning calorimetry and conventional laboratory tests to analyze the road performance attributes of Ingevity J type regenerant (J), WEOR-G, and WEOR-H. The results indicated that WEORs increase the saturate and aromatic content in asphalt and partially replenish the missing lightweight components of aged asphalt, moderately improving the three key indicators, though the regenerative effect is restricted. Achieving a full restoration of component proportions within aged asphalt to their initial levels proved unattainable, and direct application of any of the three WEORs as asphalt regenerants is impractical. WEOR-H and WEOR-G demonstrated potential in enhancing aged asphalt binder road performance, outpacing three other WEORs. At a 14% dosage, WEOR-G and WEOR-H could increase the 10 °C ductility to 23.5 and 21.4 cm, respectively, effectively counterbalancing the insufficient ability of WEOR-1 and WEOR-2 to restore the low-temperature performance of aged asphalt. Among the regenerants, WEOR-G, possessing superior regenerative effects, the lowest glass transition temperature, and optimal low-temperature deformation resistance, emerged as the most efficacious. This inquiry furnishes vital data support for future applications of WEOR-G asphalt regenerant.

Study on the effect of aging on cracking resistance of virgin asphalt binder and its evolution model

The cracking resistance of asphalt pavement is significantly affected by the aging of asphalt binder. A better understanding of the effect of aging on the cracking resistance of virgin asphalt binders can help to determine the optimum maintenance time. In this study, the rolling thin film oven test (RTFOT) and pressure aging vessel (PAV) test were conducted to simulate short-term aging and long-term aging of asphalt binders, respectively. Frequency sweep tests were conducted on two asphalt binders at different aging conditions. The Glover-Rowe (G-R) parameter, stiffness modulus (S), creep rate (m), continuous grading temperature (Tc), critical temperature difference (ΔTc), relaxation time (λ), dissipation energy ratio (Wd/Ws), low-temperature indicator ratio (m/S), low-temperature comprehensive compliance parameter (Jc) were obtained. Meanwhile, the sensitivities of different indicators to aging were analyzed and the correlations between G-R parameter and various low-temperature indicators were discussed. Subsequently, a nonlinear model of asphalt binder aging was established by a rheological indicator. The results showed that aging had a significant impact on the low-temperature properties of asphalt binder. G-R parameter, Tc, λ increased with the growth of aging severity, whereas m, ΔTc, Wd/Ws were contrary to this trend. S, m/S, Jc had no significant relationship with the degree of aging. Moreover, G-R parameter and ΔTc were very sensitive to aging. The G-R parameter had a good correlation with m, Tc, λ, ΔTc and Wd/Ws, respectively. It indicated that G-R parameter was closely related to the low-temperature properties of asphalt binders. The aging nonlinear model containing G-R parameter could exactly describe the aging evolution of virgin asphalt binder. It is helpful for the prediction of cracking resistance of asphalt binder and determination of maintenance plan.

Molecular study on diffusion behavior and performance recovery of aged asphalt binder containing functional rejuvenators

In hot in-place recycling (HIR) technology, there are many shortcomings and challenges such as low mixing temperature, short mixing time and less virgin asphalt binder, demanding multifunctional rejuvenators with higher diffusion rates. Therefore, there is an urgent need to develop a rejuvenator that balances diffusion rate and performance recovery. In this study, molecular dynamics (MD) simulation was employed to establish the basic structure of oil fractions, including chain alkanes, cycloalkanes and aromatic hydrocarbons. To improve the diffusion rate of rejuvenators, functional groups in penetrants and surfactants, such as hydroxyl, carboxyl, amide, ether, and ester groups, were incorporated into the basic structure for artificial design and enhancement. The diffusion rates of the primary and enhanced structures were investigated, and the internal factors for diffusion were analyzed. Furthermore, two rejuvenation methods for rejuvenators were proposed based on the changes in non-bond interaction energy in different asphalt binder systems. Moreover, the performance recovery of different rejuvenators were investigated. The results show that the diffusion rate of chain alkanes in the basic structure is the fastest, while that of aromatic hydrocarbons is the slowest. When ether and ester groups are used as enhanced structures, the diffusion rates of chain alkanes increase by 34.7% and 61.1%, respectively. Regarding performance recovery, chain alkanes exhibit the best performance recovery effect, which is further enhanced when ether and ester groups are employed as enhanced structures.

UV aging behavior evolution characterization of HALS-modified asphalt based on micro-morphological features

Abstract To clarify the effect of Hindered amine light stabilizer (HALS) on ultraviolet (UV) aging behavior of asphalt binder, the evolution history and characteristics of the UV induced micro-structure of modified asphalt were characterized. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) were used to analyze the microscopic morphology evolution of light stabilizer-modified asphalt during UV aging. By defining the micro-structure of asphalt in aging joints induced by UV, the identification and classification of typical micro-structure are proposed. On this basis, an evaluation method based on the morphology evolution process of modified asphalt aging was proposed to quantitatively analyze the effect of HALS on the UV aging of asphalt binder. The results show that the control effect of HALS on the UV aging behavior of asphalt can be verified by SEM and AFM detection methods. At the same time, the aging interval of the asphalt modified by hindered amine was divided by the method, and it was verified that the HALS could significantly prolong the service life of the asphalt binder. The micro-morphology of asphalt binder undergoes the process of crack generation and propagation during UV aging. The micro-morphological changes of UV aged asphalt were interfered effectively by HALS, which could alleviate and control the development of UV induced micro-cracks, and promote the fusion of micro-cracks. This study provides an effective evaluation method for detecting UV aging microscopic evolution of HALS.

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.

Evaluation of cracking resistance of asphalt concrete under long-term aging condition

Cracking is one of the primary distresses in asphalt pavements under traffic loading and climate. Asphalt cracking can be caused by aging asphalt binders in production, transportation, construction, and exploitation. Therefore, it is very necessary to study the influence of aging on cracking resistance for asphalt concrete. This paper initially evaluated the cracking resistance of asphalt concrete with a nominal maximum aggregate size of 12.5mm (AC 12.5) under long-term aging conditions. Based on the laboratory experiments, the study evaluated the required technical parameters of 60/70 binder, PMBIII binder, and AC 12.5 considering long-term aging conditions. Test results indicated that the aging of asphalt binder can significantly affect the cracking resistance of asphalt concrete.

Aging Resistance of Bitumen Modifiers: A Comprehensive Review

Abstract The deterioration of physical and mechanical properties of bituminous materials that are attributable to the aging of bitumen is one of the major causes of reduction in service life of flexible pavements. Thermal-oxidation and photo-oxidation aging are the two major types of aging of bitumen. Heat and oxygen cause thermal-oxidative aging, whereas ultraviolet irradiation and oxygen causes ultraviolet photo-oxidative aging of bitumen. Aging of binder leads to significant changes in the chemical composition of bitumen resulting in reduction of cracking resistance of bituminous mixes because of hardening of bitumen. So, it is quintessential to reduce the rate of hardening of bitumen induced by aging for prevention of premature failure of flexible pavements. The type of bitumen used for production of bituminous mixes have a significant effect on aging resistance of bitumen. The bitumen can be modified by using different types of modifiers such as antioxidants, bio-oils, nanomaterials, polymers, rubber, and ultraviolet absorbers. In addition to this, the modifiers such as fillers, warm mix additives, and rejuvenators also affect the aging resistance of bitumen. However, the effectiveness of these modifiers in preventing the hardening of bitumen because of aging varies with type of aging. The modifiers that exhibit improvement in thermal-oxidative aging resistance of bitumen are found to be less effective in improvement in photo-oxidative aging resistance and vice-versa. So, it is imperative to understand the effectiveness of different types of bitumen modifiers for the prevention of thermal-oxidative and photo-oxidative aging of bitumen. This review documents the resistance of different types of modifiers to thermal-oxidative and photo-oxidative aging. Finally, the scope for future work based on the critical gaps identified from existing works is also provided to assist further research.

Analysis of SBS content quantitative determination and rheological properties of aged modified asphalt binder

The content of styrene–butadiene–styrene (SBS) modifier has a significant influence on the physical and chemical characteristics of asphalt. However, determining the SBS content in SBS modified asphalt (SBS MA) after aging remains a challenge. To facilitate the understanding of the relationship between physical properties and SBS content, the Fourier transform infrared (FTIR) and potentiometric titration test were utilized to detect SBS content of aged binders. In this paper, radial and linear SBS were incorporated into asphalt binders at three levels, and their rheological properties were investigated after thin film oven aging (TFOT) and long-term aging. Furthermore, the actual SBS content versus the rheological index at different aging stages was investigated. The results showed that both IC=C and Na2S2O3 titration volume highly correlated with SBS content (R2 > 0.99), and there was only a slight difference between the actual content of SBS determined by the two methods. The fatigue resistance, high-temperature elastic, and low-temperature cracking characteristics of asphalt were weakened after aging, due to SBS degradation, especially in the early stage. In addition, the resistance to deformation, elastic recovery, anti-fatigue properties of radial SBS MA were superior to that of linear SBS MA at the same SBS content, while the low-temperature cracking performance demonstrated an opposite trend. The actual SBS content versus the rheological indexes after aging can be well-fitted by a nonlinear equation. Therefore, FTIR and potentiometric titration tests can effectively predict SBS content and analyze the aging degree of SBS MA.

Quantitative analysis of oxidative aging effects on the fatigue resistance of asphalt mixtures based on the simplified viscoelastic continuum damage (S-VECD) model

Fatigue cracking evolution in asphalt pavement is coupled by the oxidative aging of asphalt binder throughout its lifespan. Identifying the quantitative effects of asphalt binder aging on the fatigue resistance of asphalt mixture is important for the long-life design of asphalt pavements. In this study, two fatigue indexes (DR and Sapp) derived from the simplified viscoelastic continuum damage (S-VECD) model, were used to evaluate the fatigue resistance of laboratory-aged asphalt mixtures. Asphalt binders were extracted from aged asphalt mixtures and tested by using Fourier transform infrared spectroscopy (FTIR) to assess their aging state based on two aging indexes, the carbonyl index and the sulfoxide index. It was found that the aging indexes and fatigue indexes are well related through two power functions. Hence, the relationship between aging evolution and fatigue modelling of asphalt mixtures can be well quantified. It is anticipated that these aging-fatigue functions can assist in modelling and predicting the fatigue resistance for asphalt pavements in the field.

Molecular dynamics simulation and experimental analysis on fluidity improvement of liquid rubber modified asphalt binder

Liquid styrene-butadiene rubber (LSBR) has been used as a modifier to improve high-temperature storage stability and cracking resistance of asphalt binder. However, the interaction mechanism between LSBR and asphalt binder at both micro and macro scales has not been well understood. In this study, the intermolecular dynamics, rheological and chemical properties of liquid rubber modified asphalt (LRMA) binder by laboratory experiments and molecular dynamics simulation. Five LSBR dosages (0, 0.5, 1.0, 1.5, 2.0, and 2.5% by weight of asphalt binder) were applied to prepare the LRMA binders. Frequency sweep, performance grading, and multiple stress creep recovery (MSCR) tests were conducted to assess the intermediate- and high-temperatures rheological properties of modified asphalt binders. Fourier transforms infrared (FTIR) spectroscopy was applied to evaluate the chemical properties. Molecular dynamics (MD) simulation was performed to evaluate compatibility and molecular mobility during self-healing process. The results indicated that the addition of LSBR improved the fluidity of asphalt binder at intermediate- and high- temperature, and also enhanced the susceptibility to temperature changes. FTIR results showed that LSBR could effectively delay aging of asphalt binder and ameliorate the service performance degradation. The MD simulation results indicated that the addition of LSBR could improve the solubility of different components in asphalt and the homogeneity of asphalt system. LRMA had a better capability to heal micro-crack than the unmodified asphalt binder. LSBR could improve the fluidity of base asphalt and aged asphalt. It is feasible and appropriate to use liquid styrene-butadiene rubber to improve fluidity of asphalt to meet the requirements of construction and production. Keywords: asphalt fluidity, molecular dynamics simulation, liquid styrene-butadiene rubber, self-healing, rheological property.

Long-Term Performance Analysis of Epoxy Resin Ultra-Thin Wearing Course Overlay on Cement Concrete Pavement

The overall rigidity of the cement concrete pavement is high, but there are defects such as easy cracking and insufficient anti-slip performance. The epoxy resin ultra-thin wearing course overlay can effectively solve these issues. However, there is still a lack of knowledge about the long-term performance of epoxy resin ultra-thin wearing course overlay on cement concrete pavement. Therefore, this article analyzed the interlayer adhesion and durability of epoxy resin ultra-thin wearing course overlay through the Hamburg rutting test and a series of shear tests under damp heat, thermal oxygen aging, and ultraviolet (UV) aging conditions. Shear test results indicated that the shear performance of epoxy resin overlay grew with the increase in epoxy resin content and was severely affected by high temperature, and the optimal content was set as 3.4 kg/m2. The Hamburg rutting test results showed that the epoxy resin overlay exhibited satisfactory high-temperature performance and water resistance. For the damp heat effect, it was revealed that damp heat led to more significant shear strength loss compared with the overlay specimens without damp heat. The water immersion caused the shear strength decline due to the water damage to the overlay interface. As for the thermal oxygen aging effect, it was reflected that the short-term thermal oxygen aging had a minor impact on the shear performance of the epoxy resin overlay. However, with the increase in thermal oxygen aging duration, the shear strength of the epoxy resin overlay significantly decreased due to the aging of epoxy resin binders. Regarding the UV aging impact, it was also found that the shear performance of the epoxy resin overlay rapidly decreased as the UV aging duration grew whether at 20 °C or 60 °C. Moreover, UV aging led to a more significant impact on the shear performance of the epoxy resin overlay than thermal oxygen aging.