Aged Binder Research Articles

The investigation of rheological properties of rejuvenated asphalt binder with waste cooking oil as rejuvenator

Asphalt binder plays a significant role in the performance of asphalt pavement. However, due to the limited availability of crude oil and the increasing cost of asphalt, alternatives are being investigated. Reclaimed asphalt pavements (RAP) provide a sustainable solution for the increasing demand of asphalt. However, the amount of RAP which can be utilized in asphalt mixtures is limited due to production and performance issues. Incorporation of high RAP content calls for rejuvenators, which rejuvenate the aged binder and increases the degree of blending. Among various rejuvenators, waste cooking oil (WCO) is gaining increased attention due to its availability and concern towards environmental pollution. When combined in proper proportions with RAP, WCO is a potential rejuvenator, which restores the properties of aged binder to that of unaged asphalt binder. This addresses two problems simultaneously and can greatly benefit the economy and environment. This study focuses on the viscoelastic and rheological properties of the rejuvenated binder with WCO and RAP. The rheological properties are evaluated using frequency sweep test by assessing the complex shear modulus and rutting parameter of different binders. The viscoelastic properties are studied using multiple stress creep recovery (MSCR) test. The data of the MSCR test is analysed with the Burger model to understand the viscoelastic properties of the rejuvenated RAP binder. For each of 75, 60 and 45% RAP, three different oil proportions are selected, and the optimum WCO content is identified. The study concludes that higher RAP content results in lower viscous strain and higher elastic strain, whereas after mixing of higher WCO, the viscous strain increases, and elastic strain decreases. Hence, it is crucial to mix WCO and RAP in the optimum ratio to obtain the desired rheological and viscoelastic properties.

Evaluation of degree of blending and interaction between aged and virgin asphalt binders using rheological and fracture measurements

Evaluating the blending and interaction processes between aged and virgin asphalt binders is significant for enhancing the performance and longevity of asphalt pavements, particularly when using Reclaimed Asphalt Pavement (RAP). The primary aim of this research is to investigate the optimal conditioning time for diffusion process between virgin and aged binders. To simulate age-hardened RAP binder, asphalt binders were artificially aged in a forced draft oven at 163 °C for five hours, followed by additional aging at 85 °C and 110 °C over periods of 5, 7, and 10 days. The research assessed the degree of blending and interaction between aged and virgin binders in two phases using rheological and fracture measurements. In the first phase, the study explored the effects of various conditioning temperatures and durations (135 °C and 165 °C for 15, 30, and 60 minutes) on the diffusion and blending of the asphalt binders. Results indicated that the interaction between aged and virgin binders depends on the temperature and duration of conditioning; notably, complete blending was achieved at 165 °C after 60 minutes. The second phase investigated the impact of aged binder content on the rheological and fracture characteristics of the blended binders. Findings showed that fracture energy and peak load decrease with an increase in aged binder content. Specifically, increasing the aged binder content from 10 % to 30 % resulted in an approximate 23 % reduction in fracture-related parameters, while increasing the aged binder content from 50 % to 70 % led to an approximate 51 % reduction. Additionally, analysis of the complex shear modulus across different blends revealed an increase in modulus and high-temperature performance proportional to the percentage of aged binder, suggesting a hardening effect in the blended binder. Overall, this study underscores the significance of understanding the interactions between aged and virgin binders to optimize the diffusion and blending processes, ultimately enhancing the performance of asphalt pavements containing recycled materials.

Morphological, thermochemical, and rheomechanical evaluation of self-healing performance of asphalt binder modified with hybrid-structured phase change material capsules

Currently, sustainable pavement research focuses on modified asphalt binders with self-healing features for achieving durability and safety goals. This study assesses the self-healing behavior of asphalt binders incorporating innovative lab-manufactured hybrid-structured phase change material capsules (HPCMC). The HPCMC, using by-product paraffin oil as a core encapsulated by waste nano-silica fume as a shell, varied in core-to-shell ratios (0.5:1, 1:1, 2:1) and dosages (1 %, 3 %, 5 %, 7 %) by asphalt weight. Morphological, thermal, and chemical characterizations were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Healing efficiency of unaged and short-term aged HPCMC-modified binders was evaluated using SEM and energy dispersive X-ray (EDX) for morphological and chemical analysis. Rheomechanics were examined through rotational viscosity (RV), performance grading (PG), multiple stress creep recovery (MSCR), strain sweep (SS), frequency sweep (FS), linear amplitude sweep (LAS), and linear amplitude sweep-based healing (LASH). Study findings exhibit superior healing in HPCMC-modified binders compared to unmodified ones, particularly at a 3 % dosage and 1:1 core-to-shell ratio in unaged conditions. This study also evaluates healing assessment criteria and validates the self-healing mechanism, indicating significant potential for the proposed approach to revolutionize pavement construction and maintenance.

Enhancing Pavement Durability: Comparative Rheological Evaluation of Conventional and Rejuvenated Reclaimed Binders under Aging Conditions.

A drawback of recycled mixtures containing reclaimed asphalt is their increased stiffness, further worsened by the accelerated aging of binders in extreme weather conditions. Previous studies have shown that while rejuvenating agents can mitigate some of these issues by improving flexibility and reducing brittleness, they often present challenges, such as performance variability and the potential for rutting. This study aims to develop an optimal blend of reclaimed bitumen, a rejuvenating agent, and pure bitumen to achieve rheological properties similar to a control 35/50 pen-grade bitumen for road paving. Hence, the rejuvenated binders comprised 30:70 blends of reclaimed asphalt bitumen and 50/70 pen-grade bitumen, adding 0.2% to 0.6% of a rejuvenating agent by mass of the reclaimed asphalt. Sample testing included conventional penetration grade, softening point, and viscosity tests, followed by dynamic shear rheometer tests under unaged, short-term, and long-term aging conditions. The results show that the binder blend with 0.4% rejuvenator closely resembles the rheological properties of 35/50 pen-grade bitumen. This blend exhibits a 20% to 55% stiffness reduction for recycled mixtures with 30% reclaimed asphalt. Notably, the rejuvenated binders exhibited a similar level of aging resistance to the control bitumen, with a marginal difference of less than 5% in aging ratios. Meanwhile, large strain amplitude tests showed the importance of defining maximum rejuvenating incorporation rates in recycled mixtures to avoid rutting problems, where binders with 0.4% rejuvenator doubled the rutting potential (Jnr values). This innovative study highlights the potential for enhancing recycled mixtures' performance by evaluating rejuvenated reclaimed binders' rheology subjected to different aging conditions, thus contributing to sustainability in pavement construction.

Effect of waste engine oil and warm mix additive on the physical, rheological, and short-term aging attributes of Styrene–Butadiene Rubber-modified asphalt binders

Styrene-butadiene rubber (SBR) latex is used widely to increase the low-temperature resistance of asphalt binders. However, the high content of butadiene copolymer in SBR-treated asphalt causes oxidation and aging. Furthermore, following the SBR modification, the compatibility and thermal storage stability of SBR-modified asphalt is not satisfactory. Therefore, the best approach to improve the quality of short-term aged SBR-modified asphalt is to lower the manufacturing temperatures of the SBR-modified asphalt mixture. In this study, to reduce the preparation temperatures of SBR-modified asphalt mixes and improve their performance after short-term aging, several additives i.e., waste engine oil (WEO), warm mix agent i.e., ZycoTherm, and WEO/ZycoTherm combination (WEO+ ZycoTherm) were selected. The rheological properties and aging performance of binder samples were evaluated through the rational viscosity, dynamic shear rheometer, bending beam rheometer and Fourier transform infrared spectroscopy tests. The results showed that adding WEO together with ZycoTherm into an SBR-modified binder contributed to reducing the compaction and mixing temperatures. The chemical analysis showed that the three additives i.e., WEO, ZycoTherm, and ZycoTherm/WEO declined the aromaticity and chemical aging indicators of aged SBR-modified binders. Furthermore, it was demonstrated that both the ZycoTherm and WEO/ZycoTherm improved the asphalt resistance to rutting at elevated temperatures in both conditions i.e., before and after short-term aging. In addition, the findings revealed ZycoTherm /WEO compound yielded the best performance to improve the minimal-temperature cracking resistance of the SBR-modified binder, resulting in lower short-term aging temperatures. In summary, this study highlights the necessity of lowering preparation temperatures in asphalt mixes containing SBR to enhance binder resistance to rutting and cracking and reduce susceptibility to oxidation during short-term aging.

Exploring the impact of humidity and water on bituminous binder aging: a multivariate analysis approach (TI CAB)

Bituminous binders naturally age, affecting the properties and performance of asphalt pavements. The physical and chemical characteristics of binders are influenced by environmental factors, leading to a decline in their performance and durability. Therefore, it is essential to understand the mechanisms of binder environmental aging to design more resilient and long-lasting asphalt pavements. This study examines the effects of temperature, liquid, and vapor water on binder aging to develop more durable pavements. Aging was induced at three temperatures (60°C, 70°C, 85°C) under dry air, 90% relative humidity, and water immersion conditions. Field-aged samples were also analyzed to compare with laboratory-aged samples. Fourier-transform infrared spectroscopy (FTIR) and dynamic shear rheometer (DSR) were used to assess chemical and rheological changes. To assess the similarity between samples and identify the lab aging protocol closest to field aging, Hierarchical Cluster Analysis (HCA) was employed for data analysis..

Comparative analysis of several short-term aging simulation methods and their impact on long-term aging performance of asphalt binders

The aging of the asphalt pavement is an essential factor to consider when constructing a road. Several methods, such as the Thin Film Oven Test (TFOT) and Rolling Thin Film Oven Test (RTFOT), have been used to simulate the short-term aging of asphalt binders. Based on the wide use of polymer-modified asphalt binder and the idea of research facilitation, 5 hours of Pressure Aging Vessel (5 h PAV) was proposed as an alternative to previous short-term aging methods of asphalt binders. However, the efficacy of this technique still needs to be wholly explored in all aspects and requires advanced research. The frequency sweep, temperature sweep, and Multiple Stress Creep Recovery tests were performed to evaluate the high-temperature performance of asphalt binders under aging conditions. In addition, the relaxation test was carried out to determine the low-temperature stress relaxation change and the fatigue cracking resistance of asphalt binders. The Chemical test explored the chemical change of asphalt binders under different aging conditions. The findings revealed that, in the case of neat asphalt binders N50, N70, and N90, the maximum disparity between the aging conditions of TFOT and 5 h PAV was found to be below 6 %. However, the difference between the aging conditions of 5 h PAV and RTFOT was observed to be approximately 20 %. Then, 5 h PAV can be highly recommended as an alternative to replacing TFOT. For SBS and high viscosity-modified asphalt binders HVMA-I and HVMA-II, the maximum gap between 5 h PAV and TFOT was estimated to be approximately 19.71 %. However, the gap between 5 h PAV and RTFOT was estimated to be less than 7 %. Then, 5 h PAV can be an alternative to replace RTFOT for modified asphalt binders if necessary. This study offers a thorough explanation and dispels doubts regarding the suitability of the 5-hour PAV as an alternative for simulating the short-term aging of asphalt binders, thereby enhancing research facilitation. Furthermore, the research delineates the impact of various short-term aging simulation methods on the long-term aging properties of asphalt binders, including the variation rates between them.

Laboratory-accelerated simulation and calibration method for ultraviolet aging of asphalt binders based on radiation equivalent conversion

Ultraviolet (UV) radiation is a significant environmental factor that accelerates the aging of asphalt pavements. To address the gap in the equivalence conversion relationship between laboratory simulation parameters and field environmental factors for asphalt pavement aging in the Tibet area of China, this study investigates the relationship between laboratory simulations and field service for asphalt aging. The results indicate that using macroscopic rheological parameters (rutting factor (G*/sin δ), average recovery rate (R), and average non-recoverable creep compliance (Jnr)) and microscopic parameters (sulfoxide index (SI) and glass transition temperature (Tg)) as quantitative indicators can evaluate the equivalent degrees of laboratory and field aging. Furthermore, this study introduces a correction coefficient for laboratory-accelerated simulated aging to improve the accuracy of the equivalent radiation conversion formula. The correction coefficient range for 90# matrix asphalt is 1.36–2.05, while the range for SBS modified asphalt is 0.82–1.64. This study provides a valuable database for establishing the relationship between laboratory simulations and field service for asphalt aging and offers a parameter basis and technical support for designing durable asphalt pavements in areas with intense UV radiation.

Assessment of the effectiveness of binder fatigue, rheology and chemistry parameters in evaluating cracking resistance in high RAP mixtures modified with recycling agents

The utilization of Reclaimed Asphalt Pavement (RAP) in pavement construction has gained prominence as a sustainable approach to reduce material costs and environmental effect. However, a significant challenge associated with increased RAP incorporation lies in the potential fracture distress caused by the aged binder. The purpose of this study is to assess the cracking performance of asphalt mixtures incorporating three levels of recycled materials (30% RAP, 50% RAP, and 30% RAP along with 5% Reclaimed Asphalt Shingles (RAS)). Three softening oils were employed to improve the cracking performances at two aging levels. Performance evaluations, including cracking performance assessments at intermediate and low temperatures, were carried out and compared with control mixtures. The findings of this study reveal that the incorporation of softening oils, as investigated herein, offers a viable means of producing asphalt mixtures featuring high RAP content while preserving performance comparable to that of a virgin mix. From a binder perspective, the Glover–Rowe (G–R) parameter and fatigue life at 10% strain level emerge as robust indicators for evaluating cracking resistance under conditions pertaining to intermediate and low temperatures.

Comparative analysis of time sweep testing evaluation methods for the fatigue characterisation of aged bitumen

Ageing of bitumen changes its stiffness related properties and is thought to have a considerable impact on its fatigue performance. Time sweep tests are a commonly used methodology to evaluate the fatigue performance of bitumen over the course of its lifetime. This study comparatively evaluated the fatigue performance of six aged bitumen samples using various commonly employed time sweep testing-based approaches, including conventional methods (50% reduction in complex modulus and peak in phase angle) and newer methods (peak in S × N and two dissipated-energy-based approaches). The statistical analysis of the results illustrated that although the trends of fatigue life versus ageing levels were similar, different methods had significantly varying results. It was generally seen that ageing increased stiffness and the calculated fatigue life of bituminous binders improved when commonly applied strain levels of 5% and 7.5% were used. This result demonstrates the need to develop more robust methods to fully capture the true fatigue related deterioration of aged binders in the future. Among all the methods, the peak in S × N approach was found to be the most efficient based on the criteria used in the study and was the recommended approach considering current limitations. It showed no apparent defects and had the best correlations with other methods when the applied strains were 5% and 7.5%.

Analysis of the Degree of Blending (DoB) of recycled asphalt mixtures with variation in mixing temperature, type, and RAP content

Presently, there is a significant increase in studies dedicated to the reuse of Reclaimed Asphalt Pavement (RAP) material obtained from the recycling of asphalt coatings. This procedure aims to reduce production costs and minimize environmental impacts. To carry out the reuse of this material, it is crucial to understand the interaction mechanisms between the aged binder of the RAP and the new binder. These mechanisms can be assessed through the Degree of Binder Activity (DoA) and the Degree of Blending (DoB). DoA represents the quantity of aged binder available for the new mixture, being an intrinsic property of each RAP. On the other hand, DoB indicates the degree of blending between the aged and new binders, being influenced by external factors such as mixing parameters, thus presenting a challenge in quantification. This study sought to establish a predictive model to quantify DoB based on Dynamic Modulus and Fourier-Transform Infrared Spectroscopy (FTIR) tests. These tests were conducted on mixtures containing four different RAPs, varying in different content levels and mixing temperatures. In each RAP, DoA was quantified, and a statistical analysis was performed to verify the significance of independent variables in dynamic modulus results. After this step, four modeling attempts were made, choosing the one that not only presented significant independent variables but also obtained the highest predicted R² value. The chosen model was validated and demonstrated small variations compared to DoB obtained by the generated equation. Thus, it is concluded that the DoB modeling conducted in this study highlights that mixing temperatures and RAP content influence factors such as DoA, dynamic modulus, FTIR, and consequently, DoB. Additionally, the practicality of the model was emphasized, as it successfully predicted DoB using a single mechanical and chemical test.

Molecular Dynamics Simulation and the Regeneration and Diffusion Effects of Waste Engine Oil in Aged Asphalt Binder.

In recent years, the potential of waste engine oil (WEO) as a rejuvenator for aged asphalt binders has gained significant attention. Despite this interest, understanding WEO's regeneration mechanism within aged asphalt binders, particularly its diffusion behavior when mixed with both aged and virgin asphalt binders, remains limited. This study adopts a molecular dynamics approach to constructing models of virgin, aged, and rejuvenated asphalt binders with different WEO contents (3%, 6%, 9%, and 12%). Key properties such as the density, glass transition temperature, cohesive energy density, solubility parameter, viscosity, surface free energy, fractional free volume, and diffusion coefficient are simulated. Additionally, models of rejuvenated asphalt binder are combined with those of aged asphalt binder to investigate mutual diffusion, focusing on the impact of WEO on the relative concentration and binding energy. The findings reveal that WEO notably decreased the density, viscosity, and glass transition temperature of aged asphalt binders. It also improved the molecular binding within the asphalt binder, enhancing crack resistance. Specifically, a 9% WEO content can restore the diffusion coefficient to 93.17% of that found in virgin asphalt binder. Increasing the WEO content facilitates diffusion toward virgin asphalt binders, strengthens molecular attraction, and promotes the blending of virgin and aged asphalt binders.

Effect of aging level on the healing properties of an induction-heated ultra-thin wearing course and its mechanism

Electromagnetic induction heating can accelerate crack self-healing in asphalt concrete and extend its service life. In the maintenance project of existing pavements, induction heating and ultra-thin wearing course can be combined by paving functional induction heating wearing course. However, the ultra-thin wearing course is directly affected by the environment and loading, and undergoes aging in the service process. Thermo-oxidative aging is an irreversible and important mechanism that seriously affect the rheological and healing properties of asphalt. Therefore, the purpose of this work is to examine the impact of thermo-oxidative aging on the induction heating-healing of an ultra-thin wearing course mixture. Firstly, the AC-5 induction heated ultra-thin wearing course (IHUC) containing 1 % steel wool fiber by aggregate mass was prepared. Subsequently, the IHUC was aged to six different levels. Then, the induction heating and healing properties of the aged IHUC were evaluated. Simultaneously, the aged asphalt binder was extracted and its rheological characteristics and chemical alterations were studied. The outcomes showed that the heating rate of IHUC decreased, but the temperature gradient effect reduced at higher aging level. The optimal healing temperature of IHUC shifted to a higher temperature region and the healing rate decreased. Both heating cycles and thermo-oxidative aging reduce healing effectiveness, but the impact of heating cycles is less compared to aging. Rheology and chemical structure test results of extracted asphalt binder showed that the transformation of the molecular structure caused the fluidity and self-healing properties of asphalt were decreased. This ultimately decreased the healing rate of IHUC.

Experimental measurement and molecular dynamics simulation analysis of thermal aging performance in composite solid propellants

As a complex mixed system, the aging mechanism of high-energy composite materials involves the aging of each component itself, interactions between components, and transformation of microstructural and thermodynamic properties. The study of a single component or performance parameter has great limitations for elaborating the cognitive complexity of aging processes, making it difficult to reveal the underlying principles of physicochemical property transformation. Thus, it can only be applied as an empirical summary. In view of this, this study comprehensively utilized numerical analysis and experimental detection to explore the evolution of micromolecular conformation and changes in macro aging performance from four aspects of composite systems, including binder aging, plasticizer migration, bond interface debonding, and mechanical property transformation. There was good consistency observed between molecular simulation and thermal aging experiments, indicating that there was basically no post curing process for HTPB propellants using TDI as the curing agent. In the early stage of aging, scission chain was the main process and, in the later stage of aging, oxidation crosslinking the main process. Oxidative crosslinking increased the mean square radius of gyration and glass transition temperature of the binder system, reduced the peak value of radial distribution function, and revealed the reason for the change of propellant hardness and CC and CO double bond content. However, chain degradation increased the number of polar groups, enhanced intermolecular polarity, reduced the solubility parameter, and increased the free volume fraction of the mixed system and the dioctyl sebacate diffusion coefficient. This resulted in an increase in the tangent value of the HTPB propellant loss angle from 0.43 to 0.44° and a decrease in the glass transition temperature from 203.3 to 202.0 K. The binding energy at the interfaces of AP/HTPB and Al/HTPB increased first and then decreased, which was consistent with SEM images of bonding interfaces. The joint effect of binding energy and mechanical properties of the binder system promoted the transformation of the stress-strain curve of aging propellant.

Aging Resistance Evaluation of an Asphalt Mixture Modified with Zinc Oxide

The phenomenon of the oxidation and aging of asphalt binders affects the strength and durability of asphalt mixtures in pavements. Several studies are trying to improve the resistance to this phenomenon by modifying the properties of the binders with nano-particles. One material that shows promise in this field is zinc oxide (ZnO), especially in improving ultraviolet (UV) aging resistance. Few studies have evaluated the effect of these nano-particles on the thermo-oxidative resistance of asphalt binders, and, on hot-mix asphalt (HMA), studies are even more scarce and limited. Therefore, in the present study, the resistance to thermo-oxidative aging of an HMA manufactured with an asphalt binder modified with ZnO was evaluated. An asphalt cement (AC 60–70) was initially modified with 0, 1, 3, 5, 7.5, and 10% ZnO (percentage by weight of asphalt binder; ZnO/AC in wt%), and then exposed to aging in Rolling Thin-Film Oven tests (RTFOT) and a Pressure Aging Vessel (PAV). Penetration, viscosity, and softening point tests were performed on these binders, and aging indices were calculated and evaluated. Samples of HMAs were then manufactured using these binders and designed by the Marshall method, determining the optimum asphalt binder content (OAC) and the optimum ZnO/AC ratio. Control (unmodified) and modified HMA were subjected to short-term oven aging (STOA) and long-term oven aging (LTOA) procedures. Marshall, Indirect Tensile Strength (ITS), and resilient modulus (RM) tests were performed on these mixtures. LTOA/STOA results of the parameters measured in these tests were used as aging indices. In this study, ZnO was shown to increase the thermo-oxidative aging resistance of the asphalt binder and HMA. It also contributed to an increase in the resistance under monotonic loading in the Marshall and ITS tests, and under repeated loading in RM test. Likewise, it contributed to a slightly increasing resistance to moisture damage. The best performance is achieved using ZnO/AC = 5 wt%.

Preparation and Performance Evaluation of Castor Oil-Based Asphalt Regeneration Agent.

Regeneration agents play a critical role in modifying the mechanical properties and durability of RAP asphalt mixtures. This paper aimed to develop a castor oil-based asphalt regeneration agent. The effects of this regeneration agent on the pavement performance of laboratory-aged asphalt and an RAP asphalt mixture were comparatively studied by a series of laboratory tests. For the developed castor oil-based asphalt regeneration agent, the weight ratio of the castor oil to dibutyl phthalate was determined as 1:4. Moreover, the regeneration effectiveness of the castor oil-based regeneration agent was tested on three laboratory-aged asphalt binders and an RAP asphalt binder; the penetration, softening point and ductility of the RAP asphalt binder recovered to 83 dmm, 50.3 °C, and more than 100 cm, respectively. The optimum content of the regeneration agent was 5% by the weight of the aged asphalt binder. Furthermore, the castor oil-based regeneration agent could effectively restore the pavement performance of an RAP asphalt mixture. In this study, the RAP percentage can reach up to 60% by the weight of the HMA mixture using the castor oil-based asphalt regeneration agent according to the Chinese specification.

Regeneration Effect of a New Bio-Based Warm-Mix Rejuvenator on Performance and Micro-Morphology of Aged Asphalt.

The use of warm-mix recycling technology can reduce the mixing temperature and the secondary aging of binders in reclaimed asphalt pavement (RAP), which is one of the effective ways to recycle high-content RAP. In this study, the penetration, softening point, ductility, and viscosity were used to characterize the conventional physical properties of aged asphalt after regenerating, while a dynamic shear rheometer (DSR), force ductility tester (FDT), and atomic force microscope (AFM) were used to evaluate the rheological performance and micro-morphology of aged asphalt incorporating a new bio-based warm-mix rejuvenator (BWR) and a commercial warm-mix rejuvenator (ZJ-WR). The regeneration mechanism of warm-mix rejuvenators on aged asphalt was analyzed by Fourier transform infrared spectroscopy (FTIR). The results show that the new bio-based warm-mix rejuvenator can restore the conventional physical properties, low-temperature performance, and micro-morphology of aged asphalt with an appropriate dosage, but it has a negative effect on high-temperature performance. In comparison with 2D area parameters, 3D roughness parameters were more accurate in evaluating the variation in micro-morphology of aged asphalt after regeneration. The FTIR analysis results indicate that both the new bio-based warm-mix rejuvenator and the commercial warm-mix rejuvenator regenerate aged asphalt by physical action, and AS=O and AC-H values are more reasonable than the AC=O value for the restoration evaluation of aged asphalt. And the new bio-based warm-mix rejuvenator has a better regeneration effect on the performance and micro-morphology of aged asphalt than the commercial warm-mix rejuvenator.

Laboratory and Field Performance Evaluation of Cracking of Airfield Warm Mix Asphalt with Reclaimed Asphalt Pavement at the National Airport Pavement and Materials Research Center

The U.S. Federal Aviation Administration is exploring initiatives to decrease transportation greenhouse gas emissions by developing carbon reduction strategies, including using low-embodied carbon materials, such as reclaimed asphalt pavement (RAP), in airport pavement construction. However, verifying RAP’s viability for airfield pavements with laboratory and field performance measures is essential. This study compared the cracking susceptibility of a P-401 hot mix asphalt and warm mix asphalt (WMA)+RAP airfield mixes using laboratory performance tests and conducted a preliminary evaluation of pavement responses from accelerated pavement testing (APT) fatigue tests. The observations and outcomes presented in this paper found that adding 20% of recycled materials with WMA additives had a decreasing impact in mix performance but did not overly affect the asphalt mix properties, as cracking properties from the different test procedures were found with comparable outcomes. Additional observations from strain gauges and temperature probes in the National Airport Pavement and Materials Research Center test cycle 2 APT fatigue test sections showed that the maximum tensile strains in the WMA surface lane 5 south section were consistently higher than those in the WMA+RAP lane 6 south section, which may be because of the higher load level that it was exposed. Additionally, the hardened or aged RAP binder in the entire lane 6 south section may have increased its stiffness, resulting in lower strain levels than in the lane 5 south section. Notably, both sections showed an increase in tensile strains with an increase in asphalt concrete temperature, which confirmed the temperature dependency behavior of asphalt concrete.

Assessment and mechanism of antioxidant activity of phenols as asphalt antioxidants

ABSTRACT The interest in the antioxidant properties of phenolic compounds in asphalt has grown significantly. This study primarily focuses on the comprehensive assessment and elucidation of the antioxidant activity mechanisms of various phenolic compounds as asphalt antioxidants. The suitability of different antioxidant indices for evaluating the effectiveness of phenolic anti-aging agents in base and SBS modified asphalt is assessed by experimental outcomes. Through this analysis, the anti-aging mechanism of phenolic antioxidants in asphalt is unveiled. Phenolic antioxidants were observed to diminish the G* value of aged asphalt, elevate the δ values of aged asphalt binder, augment the non-recoverable creep compliance of aged asphalt binder, decrease the percent recovery of aged asphalt binder, enhance the fatigue performance of aged asphalt binder, and lower the Ic = o and Ic = c of aged asphalt binder. This indicates that phenolic antioxidants improve the aging and fatigue resistance of asphalt binders, with antioxidant activities in the following order: p-Coumaric acid < resveratrol < tea polyphenol. Moreover, incorporating phenolic antioxidants into SBS modified asphalt not only restrains asphalt oxidation but also mitigates SBS degradation.

Physical and Chemical Methods to Assess Performance of TPO-Modified Asphalt Binder

The demand for effective asphalt additives is growing as road infrastructure ages and more sustainable pavement solutions are needed. Tire pyrolysis oil (TPO) is an example material that has been gaining attention as a potential asphalt additive. While physical performance grade (PG) temperatures are the predominant performance requirements for asphalt binders, chemical properties are also significant in the evaluation of asphalt performance. There is a need to chemically characterize the aging of asphalt binders modified with TPO and link chemical changes in binder components to binder performance. This study compares 2%, 4%, and 8% TPO and asphalt binder blends via dynamic shear rheometry (DSR), Fourier-transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) relaxometry. The variability in the modified blends was seen by both physical and chemical testing during four different blending times (1, 60, 120, and 240 min). After blending, high and intermediate PGs were determined by physical testing. The 8% TPO blend reduced the high PG of the binder from 64 °C to 58 °C. This effect was confirmed by chemical testing through changes in carbonyl indices and NMR relaxation times. With more oil present in the binder matrix, the binder’s resistance to rutting was reduced. While the high PG was hindered, the intermediate PG remained unchanged for all TPO blends. This physical similarity was mirrored in chemical testing. The chemical and physical variability along with the hindrance of the high PG temperature indicate that more treatment may be needed before TPO can be effectively applied to asphalt binders. This study suggests a correlation between physical performance and key chemical indicators.