Pressure Aging Vessel Aging Research Articles

Laboratory aging method for simulating the extracted aged asphalt from reclaimed asphalt pavement

This study compared the performance of extracted asphalt and laboratory aged asphalt. The five-year service asphalt mixtures were used for extraction in this study. The laboratory aged asphalt experienced the Rolling thin film oven (RTFO) aging the Pressure aging vessel (PAV) aging with variable duration (5, 10, 15, 20, and 25 hours). By comparing the softening point, viscosity, and rheological properties of both, an aging simulation protocol was established. For laboratory aged asphalt binder, the softening point increases by 3.56 %, 5.68 %, 7.43 %, 8.16 %, and 8.74 % at PAV aging times of 5 h, 10 h, 15 h, 20 h, and 25 h, respectively. The rutting index and viscosity of the aged asphalt gradually increases with the PAV duration. There is a substantial increase in creep recovery rate and a significant decrease in non-recoverable creep compliance for aged asphalt. The rheological aging index demonstrates a linear increasing trend. The sulfoxide (SO) and aromatic (CO) aging indexes of the laboratory-simulated aged asphalt progressively rise with prolonged PAV aging time. The SO and CO aging indexes of the extracted asphalt consistent with RTFO aged asphalt experienced PAV aging 20 and 25 hours. The extracted asphalt can be simulated in the laboratory under standard RTFO conditions and a 22.26 hours PAV duration at a pressure of 2.1 MPa ± 0.1 MPa. This study introduces a methodology for simulating asphalt aging in an authentic service environment by adjusting the laboratory aging test conditions.

Asphalt-Binder Mixtures Evaluated by T1 NMR Relaxometry

Asphalt pavements make up a majority of the essential transportation systems in the US. Asphalt mixtures age and degrade over time, reducing the pavement performance. Pavement performance critically depends on the aging of asphalt binder. The aging of asphalt binder during construction is traditionally modeled by rolling thin film oven (RTFO) testing, while aging during service life is modeled by pressure aging vessel (PAV) testing. Comparing these models to the aging of binders in actual pavements is limited because, to be used for current testing, binders must be separated from the pavement’s aggregate by solvent extraction. Solvent extraction will, at least in part, compromise the structural integrity of asphalt binder samples. Spin-lattice NMR relaxometry has been shown to nondestructively evaluate asphalt properties in situ through the analysis of hydrogen environments. The molecular mobility of hydrogen environments and with it the stiffness of asphalt binder samples can be determined by characteristic T1 relaxation times, indicating the complexity of asphalt-binder aging. In this study, two laboratory-generated asphalt mixtures, a failed field sample, and several laboratory-aged binder samples are compared by NMR relaxometry. NMR relaxometry was found to be able to differentiate between asphalt samples based on their binder percentage. According to the relaxometry findings, the RTFO binder aging compared favorably to the 6% laboratory-mixed sample. The PAV aging, however, did not compare well to the relaxometry results found for the field-aged sample. The amount of aggregate was found to have an influence on the relaxation times of the binder in the mixed samples and an inverse proportionality of the binder content to the primary NMR relaxation time was detected. It is concluded that molecular water present in the pores of the aggregate material gives rise to such a relationship. The findings of this study lay the foundation for nondestructive asphalt performance evaluation by NMR relaxometry.

Effect of reactive fumes suppressant DOPO on the chemical composition and performance of asphalt

9,10-Dihydro-9-oxa-10-phosphorophenanthrene-10-oxide (DOPO), recognized for its role as an efficacious fume suppressant, has been shown to mitigate the emission of noxious vapors emanating from asphalt. However, the comprehensive influence of DOPO on the composition and properties of asphalt had remained unexplored. This study embarked on an in-depth examination of the effects of various DOPO dosages on the chemical composition of asphalt, employing hydrogen nuclear magnetic resonance spectroscopy (1H NMR) alongside an exhaustive analysis of asphalt components. Furthermore, the investigation elucidated the consequences of different DOPO dosages on the physical, rheological properties, and aging resistance of asphalt. The results of 1H NMR and component analysis of asphalt disclosed that DOPO engaged in chemical reactions with the unsaturated groups within the asphalt, catalyzing a metamorphosis of saturates into aromatics and resins. Such chemical transformations were instrumental in augmenting the softening point, viscosity, and rutting propensity of the asphalt while imposing a minimal impact on its penetration and ductility. Post exposure to the thin film oven test (TFOT), pressure aging vessel (PAV), and ultraviolet (UV) aging, the DOPO modified asphalt (DMA) exhibited a diminution in the increment of softening point and viscosity aging index relative to the control asphalt. Furthermore, the DMA showcased enhanced retention rates of penetration and ductility, coupled with substantially reduced shifts in complex modulus and phase angle post-aging, underlining its superior aging resistance. Fourier transform infrared spectroscopy analysis revealed a comparatively slower rate of change in carbonyl and sulfoxide groups in DMA after aging, as opposed to the control asphalt. Notably, DMA exhibited enhanced resistance to UV aging relative to TFOT and PAV aging scenarios, a trait attributable to remarkable UV absorption capabilities of DOPO. Fundamentally, DOPO enhanced the high-temperature performance and aging resistance of asphalt while simultaneously diminishing the emission of noxious fumes.

Thermal Aging Degradation of High-Viscosity Asphalt Based on Rheological Methods.

With the acceleration of the construction of sponge cities in China, porous asphalt pavement (PA) is has been widely used. High-viscosity asphalt (HVA) is the core material in building PA because it has good rheology properties, which can provide good raveling and rutting resistance. However, due to the open-graded structure of PA, HVA was more susceptible to rapid aging, which significantly affects the durability of PA. To investigate the thermal aging effect on the rheological properties of self-modified HVA (SHVA), five types of asphalts were aged using a rolling thin film oven (RTFO) and pressure aging vessel (PAV). Then, rheological tests were adopted, such as temperature sweep test (TS), repeated creep and recovery test (RCR), and bending beam rheometer test (BBR). The results indicate that during the aging process, the oxidation-induced hardening effect of neat asphalt and the degradation-induced softening effect of the modifier changes the rheology properties of HVA significantly. As the aging progresses, the contribution of the modifiers of HVA to anti-aging performance is greatly reduced. At high temperatures, HVA demonstrates better anti-aging performance than conventional styrene-butadiene-styrene (SBS)-modified asphalt (Guo Chuang, GC). The change of the high-temperature rheological indices of the two HVA types (SHVA and TAFPACK-super HVA (TPS)) showed a smaller activation energy index (EAI), a more considerable viscous component of binder creep stiffness (Gv), and more minor accumulated stain (racc), indicating a more significant anti-short-term and long-term aging performance, which is beneficial to the high-temperature performance of asphalts. However, the changes in low-temperature rheological properties do not align with those in high-temperature rheological properties after long-term aging. The BBR test results reveal that TPS exhibits worse low-temperature performance than GC and SHVA. During the thermal aging process, the contribution rate of the modifiers in SHVA against RTFO and PAV aging is higher than that of the modifiers in TPS, which contributes to the superior anti-aging property. Overall, SHVA demonstrates the best anti-aging performance among the five asphalts tested.

Study on accelerated aging rate of asphalt binder under multi-factors coupling conditions

The aging behavior of asphalt binder in service is complex. The accelerated aging methods commonly used in the laboratory are difficult to reproduce the aging behavior of asphalt binder in service. The purpose of this study is to develop a method for predicting the properties of asphalt binder in service. First, a multi-factor accelerating (MFA) aging method was developed to accelerate the aging of asphalt binder. Multi-scale characterization and correlation analysis were conducted on the MFA-aged asphalt binder. Then, the evaluation index of MFA aging was defined, which was used to establish the prediction equation for asphalt binder aging. Finally, the time correlation between field aging, pressure aging vessel (PAV) aging and MFA aging was constructed separately. The results show that accelerated aging of asphalt binder at atmospheric pressure and service temperature can be achieved by the coupled effect of temperature, ultraviolet light and rain. After 5-day MFA aging, the Glover-Rowe (G-R) parameter, an index for evaluating the cracking resistance of asphalt binder, was increased by 308%. The carbonyl index, an index for evaluating the content of chemical functional groups of asphalt binder, was increased by 67%. The correlation between the G-R parameter and the carbonyl index was linear, and the goodness-of-fit was greater than 0.9. The carbonyl index as a key chemical index may reflect the macroscopic properties of asphalt binder. The prediction equation for aging was established based on the carbonyl index of field-aged asphalt binder in Beijing, with reliability greater than 0.98. PAV aging for 20 h was equivalent to 1.35 years of asphalt binder service in Beijing. MFA aging method can better predict the aging time in the field. The prediction accuracy was 97.2%, which was 4.9% higher compared to that of PAV aging. MFA aging for 5 days was equivalent to about 2 years of asphalt binder service in Beijing.

Rheological performance of bitumen mixed with laboratory simulated polymerized RAP binders

Researchers have mostly used three artificial aging techniques, namely pressure aging vessel (PAV) binder aging, compacted mix aging (CMA), and loose mix aging (LMA) to simulate recycled asphalt pavement (RAP) binder in the laboratory. RAP binder (RAPB) simulated using different techniques will differ in characteristics and may affect the performance of the base binder differently. Which may affect the parameters used for blending and recycling, such as the selection of base binder, rejuvenator dosage, etc. Therefore, in this study, three RAP binders, namely RAPB-P, RAPB-C, and RAPB-L, were simulated from a polymer modified binder (PMB) with 3.5% SBS content, using PAV aging (100 °C, 20 hrs, 2.1 MPa), CMA (85 °C, 5 days) and LMA (85 °C, 8 days), respectively. These polymerized RAPBs were added to an unmodified binder (AC 30) at three proportions: 15 %, 25 %, and 40 %. These RAPB and AC 30 blends were characterized in terms of their dynamic viscosity, mixing and compaction temperature, and high temperature performance grade (PG). Superpave rutting factor (|G*|/sin δ) and multiple stress creep and recovery (MSCR) test parameters were used to evaluate the rutting performance of the RAPB blended AC 30 binders. Further, resistance to yielding and elastic recovery values were evaluated using the binder yield energy test (BYET). The test results suggested that all three RAP binders affect the performance of the AC 30 binder differently, which was also confirmed by statistical analysis using one-way ANOVA. From MSCR and BYET test results, it may be stated that RAP binder simulated from standard PAV aging may mislead in predicting the high and intermediate temperature performance of AC 30 binder with RAPB. Overall, the present study is helpful for asphalt researchers and practitioners to understand how the selection of different defined aging strategies affects the performance of aged recycled PMB with unmodified base binder.

Evaluation of Asphalt Aging Using Multivariate Analysis Applied to Saturates, Aromatics, Resins, and Asphaltene Determinator Data.

Asphalt is subjected to aging, leading to physical and chemical modifications reducing its performance. Recently, the Western Research Institute developed the SAR-AD method that allowed the separation of asphalt into eight fractions (saturates, aromatics 1, aromatics 2, aromatics 3, resins, asphaltenes 1, asphaltene 2, and asphaltenes 3). In this work, this analytical method was used to study asphalt aging processes in greater detail. Several asphalts of different origins and reconstituted blends were studied. These products were aged during several durations using a PAV (pressure aging vessel) between 0 and 48 h to collect information on the evolution of each SAR-AD fraction. Different evolutions were observed according to the initial asphalt composition and SAR-AD fraction studied. The saturated subfamily seemed to be slightly impacted by aging. The amount of three aromatic subfamilies decreased with a larger decrease of aromatics 3 than aromatics 2, itself larger than aromatics 1. The content of the resin subfamily increased after 48 h of PAV aging. The asphaltene 1 and asphaltene 2 subfamilies exhibited an increasing trend. Moreover, the quantity of asphaltenes 2 created seemed to correlate to the initial asphaltene content. The evolutions of the asphaltene 3 subfamily were not significant. However, a specific behavior was highlighted for the most asphaltenic sample. For this specific sample, the increase of resin content was weaker, the mass of asphaltenes 1 decreased, and the amount of asphaltenes 3 increased during aging. Given the large amount of data generated, an original approach was developed to statistically identify the most affected SAR-AD subfamily and determine correlations among them. Two PCAs (Principal Component Analysis) were conducted on asphalt SAR-AD data. This statistical analysis indicated two generic asphalt aging pathways. The first aging pathway could be the conversion of aromatics 2 into resins, with no evidence that resins could contribute to asphaltene creation. The second aging pathway showed the conversion of aromatics 3 directly into asphaltenes 2. These two aging pathways highlighted that the conversion of molecules in more polar ones during aging could skip SAR-AD subfamilies, meaning that asphaltenes could be created without involving resins.

Effect of Long-Term Aging on Fatigue and Thermal Cracking Performance of Polyphosphoric Acid and Styrene-Butadiene-Styrene-Modified Bio-Blend Bitumen.

Polyphosphoric acid (PPA) and styrene-butadiene-styrene (SBS) were adopted to produce PPA-SBS-modified bio-blend bitumen, which achieved excellent mechanical performance. However, its long-range performance, such as the fatigue and thermal cracking behavior under long-term thermal oxidation, is not well understood. Therefore, a pressure aging vessel (PAV) system was applied to simulate the aging behavior of the bitumen under the action of thermal oxidation. Then, a linear amplitude sweep (LAS) test combined with a viscoelastic continuum damage (VECD) model was applied to investigate the fatigue properties of the bitumen. Moreover, a bending beam rheometer (BBR) test was conducted to evaluate the thermal cracking resistance of the bitumen before and after PAV aging. Meanwhile, an atomic force microscope (AFM) was applied to observe the microscopic topography. The results show that the original compound-modified bitumen can bear more fatigue damage than that of the control bitumen at the failure point, and it also has excellent fatigue resistance at 2.5%, 5%, 7.5%, and 10% applied strain. Moreover, the VECD model can accurately predict the fatigue life of the bitumen under different applied strains. The variation ratio of stiffness modulus for the compound-modified bitumen is below that of the control bitumen after PAV aging, so it shows a better anti-aging performance. Finally, the AFM test shows that PPA and bio-bitumen decrease the heterogeneity of the bitumen, reducing the difference between phases.

Use of Accelerated Natural Aging to Simulate Long-Term Asphalt Binder Aging in Pavements

Asphalt binder is prone to aging in usage conditions. Although aging an asphalt binder using a pressure aging vessel (PAV) is a popular method to simulate the long-term aging of the binder, questions have been raised about the accuracy of this method. This research is focused on (i) examining the detailed physicochemical aging processes of asphalt binders aged in a relatively natural condition, (ii) evaluating the effects of supporting medium on asphalt binder aging, (iii) comparing aging trends of binders from different crude sources, (iv) modeling and forecasting the long-term aging behaviors of asphalt binders. Seven types of neat asphalt binders were studied, and two types of supporting media were used. The natural aging condition was set to be 60°C in a dark environment, and the thickness of the asphalt film was reduced to about 0.8 mm. The longest natural aging treatment duration was 75 days. Samples were periodically taken to test their physicochemical properties. The binders were also subjected to PAV treatments for comparison purposes. It is found that most physicochemical properties of the naturally aged binders exhibit a fast change stage followed by a relatively slow change stage. At the slow change stage, commonly used properties can be predicted well through linear models. In general, PAV aging does not reflect well the aging trends and characteristics of binders treated in the more natural conditions. Therefore, it is proposed to consider using natural aging to simulate asphalt binder aging for road pavements with high expectations on durability.

Effect of chemical warm-mix additives on asphalt binder rheological and chemical properties in the context of aging

Warm-Mix Asphalt (WMA) has achieved gradually increasing popularity among researchers and agencies because of the environmental and economic benefits associated with lower production temperatures. An ongoing research study sponsored by the Oklahoma Department of Transportation (ODOT) is focusing on evaluating how different chemical WMA additives and the associated lower production temperatures impact asphalt binder and mixture properties and exploring potential relationships between asphalt rheology and chemistry in the context of chemical WMA and various aging conditions. This manuscript presents partial findings from this study that involved testing of two binder types (modified and unmodified binder) and four different WMA additives (chemical additives). Different aging conditions were simulated by changing the Rolling Thin Film Oven (RTFO) temperature, and by subjecting the binder to different cycles of Pressure Aging Vessel (PAV) aging. Frequency and Temperature Sweep tests by a Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests were performed for rheological characterization, while Fourier Transform Infrared Spectrometer (FTIR) test was conducted for chemical characterization. Analysis of the test results indicated that while all the WMA additives can improve the rheological and chemical properties of control binders at original and RTFO conditions, two additives cause inferior properties after 20 h, 40 h, and 60 h of PAV aging, indicating possible higher aging susceptibility and long-term performance concerns. Good correlations (R2 greater than 0.8) observed between binder rheological parameters and chemical indices indicate the existence of fundamental relationships between asphalt binder’s engineering properties and chemical make-up, which also supports the possibility of using FTIR as a quick screen or fingerprint tool for binder selection and comparison. Two new rheological parameters have been proposed for evaluation of the polymer-modified binder in this study. This was important to address the presence of multi-transition behavior in modified binders. These two parameters show consistent trends with increasing aging conditions.

Investigation of Oxidation Homogeneity in Asphalt Puck after Simulation of Long-Term Aging (Pressure Aging Vessel).

For decades, it has been known that the creation of oxygenated functional groups, especially carbonyl and sulfoxide, is among the main causes of chemical aging and degradation of asphalt. However, is the oxidation of a bitumen homogeneous? The focus of this paper was to follow the oxidation phenomena through an asphalt puck during a pressure aging vessel (PAV) test. According to the literature, the asphalt oxidation process that leads to the creation of oxygenated functions can be divided into the following successive main steps: the absorption of oxygen in asphalt at the air/asphalt interface, diffusion into the matrix, and reaction with asphalt molecules. To study the PAV oxidation process, the creation of carbonyl and sulfoxide functional groups in three asphalts were investigated after various aging protocols by Fourier transform infrared spectroscopy (FTIR). From these experiments performed on different layers of asphalt puck, it was observed that PAV aging resulted in a nonhomogeneous oxidation level inside the entire matrix. Compared to the upper surface, the lower section exhibited carbonyl and sulfoxide indices 70% and 33% lower, respectively. Moreover, the difference in the oxidation level between the top and bottom surfaces increased when the thickness and viscosity of the asphalt sample increased.

Impact of Laboratory Long-Term Aging Procedures on Intermediate-Temperature Behavior of Asphalt Binders in Asphalt Fine Aggregate Matrix Mixtures

The durability of asphalt mixtures and flexible pavements are closely related to the properties of the asphalt fine aggregate matrix (FAM) with aging. However, there are still no uniform aging procedures specified for laboratory-prepared FAM. In this study, the intermediate-temperature behavior of FAM under various accelerated aging procedures was investigated at the binder scale to reveal the influence of the FAM aging. Three different long-term aging procedures were considered, including loose mixes aging (95°C and 135°C) and pressure aging vessel (PAV) protocols. Frequency sweep test and linear amplitude sweep (LAS) test were carried out on binders extracted from aged FAMs. Rheological tests were also performed on corresponding binders with standard PAV procedure to show the impact of FAM during the aging process. Moreover, an aging kinetics model was put forward to qualify the linear rheological property evolutions for fast and constant aging reaction stages under various aging conditions. The results show that 135°C loose FAM mixes aging significantly reduces the fatigue performance of styrene-butadiene-styrene (SBS) modified binder, and employing 95°C loose mixes aging and PAV aging procedures can avoid this adverse effect. Moreover, to match the aging degree of asphalt and FAM, an aging duration more than 40 h is recommended.

Recycling potential of used crumb rubber for second-round asphalt modification

Crumb rubber (CR) has been widely applied to advance sustainable pavement technology. Two major industrialization processes (dry and wet) are dominant in the practice. With the increased maintenance needs of CR modified asphalt mixture , there is a salient engineering issue that if the aged CR can function as a “tea bag” for reusing purpose in the recycling of pavement material . To cope with this issue, this study innovatively focuses on two perspectives: property investigation of the asphalt binder modified by the aged CR, and further modification effect evaluation of the aged CR utilizing the liquid phase of the modified binder . Specifically, aged CR agents are prepared by two approaches that simulate the long-term aging of CR after the dry or wet process, respectively. Pen60/70 and five types of asphalt binder samples with the addition of processed CR are prepared to test, evaluate, and compare. The liquid phase samples of the asphalt binder incorporating different CR agents are prepared for further modification effect evaluation. Conventional engineering properties tests and rheological tests are also conducted. Test results show that compared to pressure aging vessel (PAV) aging, ultraviolet (UV) aging has less impact on CR. The coupling effect of the initial modification and PAV aging can significantly undermine binder's engineering performance. The rheological test results and modification efficiency analysis demonstrate that initial modification or the aging process limits the potential of the further utilization of aged CR. The results of this study can prompt the understanding of aged CR and benefit its industrial application. • The rubberized asphalt samples modified with aged CR were prepared and evaluated. • The modification effect of aged CR was further evaluated by the liquid phases. • The aged CR generated by UV aging or PAV aging can still be an effective modifier. • The aged CR recycled from PAV aged CRMA is not suitable for re-modification.

Quantifying Weathering-Aging Test Parameters of High Viscosity–Modified Asphalt by Establishing a Conversion Relationship with Standard PAV Aging

The purpose of this study was to quantify the weathering-aging degree by establishing a conversion relationship with standard pressure-aging vessel (PAV) aging, thus guiding the selection of environmental parameters in the weathering-aging test. First, the orthogonal test was used to determine the most severe weathering-aging combination. Then the rheological property and chemical composition of high viscosity–modified asphalt (HVMA) after weathering-aging and standard PAV aging were investigated by dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC) tests. Afterward, the radar figure was used to establish the conversion relationship between weathering aging and standard PAV aging. The results show that the most severe weathering-aging condition combination is 70°C, 1,000 W/m2, and 70% relative humidity (RH). The molecules from the polymer, asphaltene, and maltene phase exhibit dynamic migration processes of molecular weight during aging, thus leading to the transition from a viscous component to an elastic component in HVMA. Compared with PAV aging, HVMA has more significant chemical changes during weathering aging due to the coupling effect of solar radiation and heat. Most of the performance changes of HVMA are similar in weathering aging and standard PAV aging except for functional groups and R3.2. The 4 days of weathering aging at 70°C, 1,000 W/m2, and 70% RH shows the best accordance to the standard PAV aging.

Effect of High Content of Waste Tire Rubber and Sulfur on the Aging Behavior of Bitumen

High content rubber modified bitumen (HCRMB) prepared from the high content of waste tire rubber and bitumen has good performance while allowing greater use of the waste tires. However, HCRMB is subject to aging during use, which can affect its performance. The purpose of this paper was to investigate the effect of high content of waste tire rubber and sulfur on the aging behavior of bitumen. The properties of all bitumen were tested using rolling thin film oven aging (RTFOT) test, pressure aging vessel (PAV) test, frequency sweep tests, temperature sweep (TS) test, multiple stress creep recovery (MSCR) test, and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) test. Test results show that the addition of sulfur to HCRMB leads to an improvement in the elasticity of HCRMB. The elasticity of HCRMB with different amounts of sulfur increases with aging. In addition, the increase in the amount of sulfur can improve the RTFOT aging resistance and the PAV aging resistance of HCRMB. Sulfur cannot reduce the degree of oxidation of HCRMB after aging, but can inhibit the degree of desulfurization of HCRMB. Furthermore, the aging process of HCRMB with different amounts of sulfur is dominated by the degradation of polybutadiene.

Effects of aging on rheological, chemical, and micromechanical properties of waterborne epoxy resin modified bitumen emulsion

ABSTRACT Bitumen emulsion, which is widely used for surface treatment and cold recycling in pavement engineering, has the advantage of not requiring heating during construction. But it has the disadvantage of low mechanical strength, especially at higher temperatures. Various studies have proved that waterborne epoxy can effectively improve the mechanical properties of bitumen emulsion. However, how aging affects the performance of waterborne epoxy resin-modified bitumen emulsion is still unclear. This study aims to fill this knowledge gap through combined rheological and microscopic characterisation. Fourier transform infra-red spectroscopy (FTIR) was first applied to characterise the oxidative reaction during the pressure aging vessel (PAV) test. The rheological behaviours before and after PAV aging were evaluated through dynamic shear rheometer (DSR) tests. The peak force tapping quantitative nanomechanical (PFT QNM) test was further conducted to measure the micromechanical performance of the waterborne epoxy bitumen emulsion residues. The results indicated that waterborne epoxy resin could improve the resistance to oxidative aging of the emulsion residues. In addition, it was found that the complex moduli generally increased while the phase angle decreased after PAV aging, and the aging process would lead to higher micromechanical modulus and lower adhesion.

Rheology, Chemical Composition, and Microstructure of the Asphalt Binder in Fine Aggregate Matrix after Different Long-Term Laboratory Aging Procedures

This study investigated the common aging protocols for binders and asphalt mixtures on fine aggregate matrix (FAM). Currently, no unified aging protocols are specified for laboratory-prepared FAM. The majority of FAM-related aging research used asphalt binders and mixture aging specifications. However, the practicality of employing these methods on FAM was not extensively examined. The rheological properties, chemical composition, and microstructure of aged binders extracted from FAM were extensively evaluated. For comparison, pressure aging vessel (PAV) aged binders and aged binders extracted from asphalt mixtures were similarly tested. Statistical analysis was performed on aging indices derived from test findings. Matching the aging level of FAM, aged binders, and asphalt mixtures required shortening the aging time for FAM under PAV aging or prolonging the aging time of loose mixes aging at 95°C during the early stages of aging. FAM’s aging level was not statistically different from that of binders and mixtures under severe aging circumstances. The findings of this paper will be valuable in multiscale testing of asphaltic materials.

The Influence of a New Food Waste Bio-Oil (FWBO) Rejuvenating Agent on Cracking Susceptibility of Aged Binder and RAP

This research aims to deliver a new promising asphalt binder rejuvenator developed from food waste to mitigate the effects of aging on the asphalt. The research relied on three different binders: two unmodified PG 64–22 binders and a Polymer Modified (PMA) PG 76–22 binder. Moreover, a field-extracted RAP binder is utilized in evaluating the rejuvenator’s efficiency. For this study, the proposed food waste bio-oil (FWBO) is compared against two market-available rejuvenators. The experimental program relied on aging control binder samples for each asphalt type with no rejuvenation using the Rolling Thin Film Oven (RTFO) test, followed by the Pressure Aging Vessel (PAV) test for 20 hours to create an Artificial RAP (ARAP) binder. Then, ARAP and RAP binders were blended with 5% by their weight with one of the two on-market rejuvenators (#1, #2) or the proposed FWBO rejuvenator. Testing results reveal that low-temperature relaxation was significantly improved for all the investigated samples after an additional PAV aging cycle, as Delta Tc values increased compared to the control binders. Further, samples’ master curves were used to calculate the Glover–Rowe (G-R) parameter, crossover frequency, and modulus (ωc, Gc*). The results clearly showed the ability of the FWBO to reduce the aging rate and improve the rheological properties of RAP binders. Further, the Fourier Transform Infrared Spectroscopy (FTIR) test showed that the new FWBO rejuvenator reduces the oxidation levels of the aged RAP binders, as suggested by the carbonyl index.

Aging Characteristics of Rubber Modified Bitumen Mixed with Sulfur after Terminal Blend Process

The influence of sulfur on the chemical, rheological, and aging resistance of terminal blend rubberized bitumen (TBRB) was studied. TB hybrid bitumen (TBHB) was prepared from with different sulfur contents (0.1, 0.2, 0.3, 0.4 wt%) and TBRB prepared with neat bitumen and crumb rubbers at 20% content. TBHB binders were aged by rolling thin film oven test (RTFOT) and pressure aging vessel (PAV), respectively. The chemical composition of TBHB binders was monitored by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). Rheological properties of all TBHB samples were tested. Chemical composition results show that TBHB can inhibit the degradation of polybutadiene compared with TBRB in the RTFOT stage, and the polybutadiene degradation is the main process of TBHB in the RTFOT stage, while the TBHB is mainly desulfurized after PAV aging. Meanwhile, the increase in sulfur content in the TBHB can improve the desulfurization degree of the TBHB binder after PAV. TBRB containing sulfur can improve the mechanical properties and elasticity and reduce the hardening degree during aging. Moreover, blending sulfur into the TBRB caused a lower complex modulus aging index after aging, which indicates that TBHB has superior aging resistance.

Chemical, Physical, and Rheological Evaluation of Aging Behaviors of Terminal Blend Rubberized Asphalt Binder

Terminal blend rubberized asphalt (TBRA) is widely used as binder of asphalt mixtures due to its technical characteristics of storage stability. However, its road performance deteriorates due to the aging process of TBRA. The purpose of this study is to evaluate the aging characteristics of TBRA binders containing 0%, 5%, 10%, 15%, and 20% content of crumb rubber (CR) by weight of the neat binder. All the binders were treated with rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV), respectively. The chemical compositional changes were monitored by attenuated total reflection (ATR)-Fourier transform infrared spectroscopy (FTIR), and physical and rheological properties were tested on neat asphalt and TBRA binders. FTIR test results show that TBRA binders offer greater long-term aging resistance than the neat asphalt binder, and E10TB (10% by weight CR) exhibits the highest long-term aging resistance. With the increase of CR, the temperature sensitivity property of the TBRA binders increases, whereas their high-temperature stability decreases. After PAV aging, blending CRs into neat asphalt causes a higher phase angle aging index and Jnr aging index, and lower critical temperature aging index, complex modulus aging index, softening point increment, and rutting factor aging index, indicating their superior long-term aging resistance. Moreover, based on the correlation analysis, the critical temperature aging index (CTAI) has a good linear relationship with the physical aging index (SPI) and chemical aging index (ΔICA).