Short-term Aging Research Articles

(Invited) Challenges for Accelerating Life Testing of Commercial Lithium-Ion Batteries

Life testing of commercial lithium-ion batteries is critical for predicting lifetime, anticipating failure, and guaranteeing safe operation of real-world battery energy storage systems. The traditional method for conducting life testing is to use accelerated aging experiments, where stress factors such as temperature, charge/discharge rate, or daily charge-throughput are pushed to extremes to drive cell failure, while taking care not to induce degradation mechanisms that do not reflect real-world use. But even ‘accelerated’ aging tests generally require 6 months to several years of testing to reach end-of-life for the current generation of mass-produced lithium-ion batteries. So, many efforts have been made to accelerate ‘accelerated aging’ of commercial cells throughout the battery community. But it is critical to ensure that the results of invasive or novel accelerated life testing experiments match well with not only changes to the electrochemical performance of traditionally aged cells, but also that the impacts of physical or chemical degradation mechanisms are also well characterized.This work compares the results of a 2-year accelerated aging test conducted on 23 commercial large-format NMC-Gr cells with a variety of other accelerated life testing experiments. Coin-cell experiments using both full-cell and symmetric-cell configurations were used to study the microstructural changes and electrochemical behavior of both NMC and graphite electrodes, with the small format allowing for destructive characterization of many test replicates throughout cell lifetime; these experiments can be conducted more quickly than their large-format counterparts, and enable more detailed understanding of the degradation trajectory than the large-format test. However, difficulties in transferring electrochemical trends from the coin-cell format to the large-format cell will be discussed. In addition, cascading failure mechanisms observed in the large-format cells may not occur in coin-cells due to differences in the mechanical and thermal environment of each system. Implications for the design of small-format accelerated life testing using electrodes harvested from commercial batteries will be discussed. Calendar aging was accelerated by monitoring daily self-discharge and quantifying both reversible and irreversible capacity losses; challenges for making quantitative predictions from short-term calendar aging tests will be presented.

Evaluating the Effects of RA on the Rheological Properties and Aging Susceptibility of RAM Asphalt

Recycling agents (RAs) can mitigate the adverse effects of reclaimed asphalt pavement (RAP) on recycled asphalt, which can result in more RAP being added. To explore the effects of four RAs on recycled asphalt, this study used asphalt rheological performance experiments, including the bending beam rheometer (BBR) test, the dynamic shear rheological (DSR) test, and the indirect tensile asphalt cracking test (IDEAL-CT), to study the performance grade (PG), cracking resistance, and cracking susceptibility of recycled asphalt. In addition, an aging model for asphalt was used, and short-term and long-term aging sensitivities were evaluated according to this model. Results showed that US Soybean significantly enhanced the high-temperature and low-temperature performance grade (PGLT) and cracking resistance and reduced cracking sensitivity of the recycled asphalt. In addition, the short-term aging sensitivity was the lowest. It showed the best regeneration effect. However, the recycled asphalt with US Soybean showed the highest long-term aging sensitivity, suggesting that longer aging time results in poorer performance. Ingevity’s PG, cracking resistance, and cracking sensitivity are slightly lower than that of US Soybean, and Ingevity demonstrated the second lowest short-term aging sensitivity. However, its prolonged aging sensitivity was much lower than that of US Soybean. Asphalt and Wax Innovations and Georgia Pacific agents slightly improved recycled asphalt properties. The long-term aging sensitivity of recycled asphalt with four Ras was higher than that of recycled asphalt without Ras. These results indicated that the recycled asphalt’s performance with Ras worsened as aging time increased compared to the original recycled asphalt.

Asphalt aging and its anti-aging mechanism based on quantum chemistry

To study asphalt aging and its anti-aging mechanism, the Frontier Orbital theory, Fukui Function, and Density Functional Theory are applied.The data reveals that 65 nm UV light can dissociate O2 into O radicals during UV aging. Among the resin components, sulfur (S) exhibits the highest radical attack index (f0) of 0.131. Resin molecules absorb UV light at 344 nm and 311 nm, leading to π electron transitions in S with a 28% probability. This result aligns with f0, indicating that f0 adequately reflects chemical reactivity. Resin molecules with electron transitions in S can form sulfoxide by creating a new delocalized π bond with unpaired electrons from oxygen radicals. Thermal oxidative aging at a temperature of 241 K has the potential to form carbonyl, hydroxyl, and peroxide bridge bonds. Ageing-resistant agents with a high f0 value on their outer layer compete with resin molecules in radical reactions, thereby exhibiting anti-aging effects. Calculation results indicate a slight increase in the number of carbonyl and peroxide bridge bonds after short-term aging, which becomes more prominent under pressure aging. UV aging is expected to result in a significant increase in sulfoxide, carbonyl, and ether bonds. The combination of experimental and calculated findings suggests that using quantum chemistry for qualitative analysis of aging mechanisms is a feasible approach. This method aids the investigation of asphalt anti-aging measures and enhances the efficiency of optimizing asphalt anti-aging agents.

Short-term and long-term aging effect of the rejuvenation on RAP binder and mixes for sustainable pavement construction

• Physical and rheological properties of rejuvenated RAP and virgin binder compared. • Determination of optimum dosage range of the rejuvenator. • Performance evaluation rejuvenated RAP mixes. This investigation analyzes the usefulness of Mahua oil (M-oil) in reclaimed asphalt pavement (RAP) binder which simulates the short-term and long-term aging behavior of asphalt. As the inclusion of a higher amount of the RAP in the bituminous mix is susceptible to fatigue and thermal cracking, the use of a rejuvenator is a suitable option that can reinstitute the properties of the virgin binder. Different percentages of M-oil such as 1%, 2%, 3%, 4%, 5%, and 6% added to the short-term and long-term aged binder. Blended rejuvenated binders were evaluated through various physical properties. It was noticed that the inclusion of a rejuvenator increases the penetration, ductility, and flash point and reduces the softening point, and viscosity. Rheological properties conclude that rejuvenating short-term and long-term aged binder is feasible and can be considered an effective way to recycle the RAP binder. Further, rejuvenated (5% and 6% M-oil by weight of aged binder which is the optimum dosage) mixes were prepared with RAP mixture for short-term and long-term aging conditions to study the mechanical properties, i.e., moisture sensitivity and rutting. Finally, it was concluded that 5% M-oil successfully rejuvenated the RAP mixes in long-term aging conditions.

Effect of Sasobit/Waste Cooking Oil Composite on the Physical, Rheological, and Aging Properties of Styrene–Butadiene Rubber (SBR)-Modified Bitumen Binders

The modifying effects of polymer on bitumen low-temperature performance are substantially compromised by the thermal breakdown of styrene–butadiene rubber (SBR) polymer during bitumen mixture production operations. The efficacy of the utilization of Sasobit/waste cooking oil (Sasobit/WCO) as a warm-mix additive has been demonstrated in mitigating the adverse consequences of thermal aging on SBR-modified bitumen binder (SB) while preserving the binder’s original performance characteristics. However, few studies have been conducted to further investigate the rheological properties and aging resistance of SB modified with Sasobit/WCO compounds. In this work, three additives—Sasobit, WCO, and Sasobit/WCO composite—were selected, and their effects on the physical and rheological characteristics of SB as well as the temperatures at which the mixtures were prepared were assessed. In addition, by using dynamic shear rheometers (DSR) and bending beam rheometers (BBR), the effects of this innovative warm-mix addition on the performance grade (PG) and aging resistances of SB were evaluated. According to the results, Sasobit/WCO composites outperform Sasobit and WCO in lowering the mixture preparation temperature. Sasobit/WCO also improves both the high- and low-temperature performance of SB simultaneously. Compared to hot-mix asphalt mixtures, the addition of Sasobit/WCO reduces the preparation temperature of the bitumen mixtures by 19 °C, which in turn helps to minimize the negative effects of temperature aging on the functioning of the SB. Additionally, the Sasobit/WCO composite addition can improve the SB mixture’s resistance to thermal cracking. After the introduction of Sasobit/WCO, the high-temperature PG of SB was raised by two levels, regardless of whether the warm-mix impact was taken into account. With the addition of Sasobit/WCO, SB’s resilience to short-term aging was enhanced.

Combination of High Yield Strength and Improved Ductility of 21Cr Lean Duplex Stainless Steel by Tailoring Cold Deformation and Low-Temperature Short-Term Aging

Combination of High Yield Strength and Improved Ductility of 21Cr Lean Duplex Stainless Steel by Tailoring Cold Deformation and Low-Temperature Short-Term Aging

Improvement of Properties of Gelatinization and Retrogradation of Adzuki Bean Starch by Adding Glycolipid

To improve the storage quality of adzuki bean paste from starch aging, the effects of glycolipid addition on the properties of gelatinization and retrogradation properties of adzuki flour obtained by the retrogradation inside adzuki bean during storage and transportation are investigated. The results indicate the significant differences in the gelatinization and the distribution of starch granules for different varieties of beans. The higher gelatinization temperature of adzuki flour results in the lower enthalpy of gelatinization with an undulating tendency of the retrogradation due to the short-term aging of amylose and long-term aging of amylopectin within adzuki flour. In the early stage of aging, the coexistence of protein, fat, and starch inside adzuki flour hinder the aging of starch. An Avrami equation is introduced to characterize the aging process of the starch–protein–fat–water system of different varieties of adzuki flours. The nucleation mode of the crystal nucleus has a significant effect on the aging rate of different varieties of adzuki flour. The fat in the system fails to demonstrate a significant effect on the nucleation mode of starch retrogradation. The addition of glycolipids increases the gelatinization enthalpy of adzuki flour. Glycolipids can reduce the aging degree of adzuki flour, and the inhibition effect on the retrogradation of sucrose monoester is greater than that of maltose monoester. The research results provide the valuable guidance for the high-quality processing and storage of adzuki bean paste from starch aging.

Simulation of the Time Needed for Long-Term Asphalt Ageing in the Rolling Thin Film Oven Relative to That of the Pressure Ageing Vessel.

Rheological test standards require asphalt samples, both original and under ageing conditions. The most common laboratory equipment in specifications for short-term and long-term ageing simulation tests are the rolling thin film oven (RTFO) and the pressure ageing vessel (PAV). However, the cost of acquiring PAV and the duration of long-term ageing tests can be a limiting factor. This work aimed to establish the equivalent time of the long-term ageing test in the RTFO that corresponds to the PAV. For this, the Brazilian asphalt PEN 50/70, specified by penetration, was aged at different times (85, 170, 255, and 340 min) in the RTFO at the standard temperature (163 °C). For each time, using a dynamic shear rheometer (DSR), tests such as Multiple Stress Creep Recovery (MSCR) and Linear Amplitude Sweep (LAS) were performed, and the rheological properties (complex modulus (G*) and phase angle (δ)) were measured. The same tests were conducted on the samples aged in the long term and in the PAV. The test parameters obtained from applying different times while using the RTFO were compared with the PAV results, and the equivalent time was settled through linear regression, resulting in 300 min. In order to confirm the equivalent time, samples aged in the RTFO for 300 min were assessed using the same rheological tests, and the parameters were compared to those obtained after PAV ageing. At the equivalent time, the difference between RTFO and the PAV for the rutting parameter (G*/sinδ, 58 °C) was 6%, while for the fatigue parameter (G*.sinδ, 19 °C), the difference was 1.0%. The MSCR non-recoverable creep compliance parameter differences, considering stress levels of 0.1 kPa and 3.2 kPa, were 9.7% and 11.7%, respectively. For the fatigue life obtained in the LAS test at strain levels of 1.25% and 2.5%, the difference between RTFO and PAV, at the equivalent time, was 7.6% and 7.8%, respectively. For the Brazilian unmodified asphalt PEN 50/70 and parameters evaluated in this work, 300 min is the equivalent time that simulates long-term ageing in the RTFO.

Computational modelling for predicting rheological properties of composite modified asphalt binders

The complicated viscoelastic characteristics of asphalt binders make it a challenging task to precisely predict their rheological behavior. This study aims to investigate and compare the suitability of response surface methodology (RSM) and machine learning (ML) modeling approaches in predicting the complex modulus (G*), phase angle (δ), and rutting parameter (G*/sinδ) of Nano Silica (NS) and/or waste denim fiber (WDF) modified asphalt binders before and after short-term aging. To achieve this, an experimental scheme was designed for RSM and ML modeling with three variables including NS contents (0–6%), WDF contents (0–6%), and testing temperature (40–76 °C) as the inputs, and provided the G*, δ and G*/sinδ before and after short-term aging as the outputs. A wide range of ML algorithms was evaluated to determine the optimum ML model that can be used to accurately predict the rheological properties of NS/WDF-modified asphalt binders. RSM analysis results indicated that the G*, δ, and G*/sinδ of NS/WDF composite asphalt are significantly affected by the %NS, %WDF, and test temperatures. The RSM-developed models showed coefficient of determination (R2) values exceeding 0.97 for all responses, indicating adequate agreement between experimental results and models developed by RSM. From ML algorithms optimization and among all evaluated ML models, it was found that Gaussian process regression (GPR) exhibited the highest R2 with a value of (0.99) and the lowest Root Mean Square Error (RMSE) with a value of approximately 1%. The performance evaluation of the GPR model for predicting all responses showed a very small difference between the predicted and experimental results, highlighting the prediction accuracy of the developed ML models.

Modern two-component modifiers inhibiting the aging process of road bitumen

The bitumen physicochemical properties of are constantly changing during both the production of asphalt mixtures and the service of road pavements. These changes involve bitumen hardening which consequently cause formation of defects and cracks in road pavements. Therefore, in recent years, prolonging road pavement life by inhibiting the bitumen aging process is a key trend in road engineering, bringing many economic, environmental and social benefits. In line with these trends, the main objective of this research was inhibition of short-term bitumen aging by two-component chitosan-based polymer composites containing ligands with different chemical structures, i.e. polyaniline, methacrylamide and 2-acrylamido-2-methylpropanesulfonic acid. This paper presents their effect on the TFOT aging process, as well as physicochemical and structural changes. Studies show that the strongest anti-aging properties are demonstrated by the chitosan:polyaniline composite. Its use at 2 % w/w allows it to maintain 90 % of the primary penetration value, increase the softening point by only 2°C and increase dynamic viscosity by 17% in comparison to non-aged modified bitumen. In addition, the use of the composite makes it possible to reduce the degree of bitumen components oxidation, which is seen from the reduction of carbonyl and sulfoxide indices by more than 33 % and 47 %, respectively.

Impact of aging protocols on asphalt binder behavior: A laboratory and field study

In this study, the focus was on the analysis of asphalt binder aging, a complex process that induces physical, chemical, and rheological changes in these materials, affecting the performance of asphalt mixtures over time. While thermal-oxidative aging is well-documented, the aspects of photo-oxidative aging and the influence of moisture are frequently overlooked. The investigation assessed 50/70 asphalt binder that underwent short-term and long-term aging in both laboratory and field climatic conditions in Brazil. Initially, these binders underwent short-term aging using the Rolling Thin-Film Oven (RTFO) method. Subsequently, the binders were subjected to prolonged aging, exposing them to heat, oxygen, UV radiation, and moisture. The chemical results unveiled distinct reaction mechanisms during thermal and photochemical aging processes. Greater oxidation was observed when binders were exposed to UV radiation, while the oven protocol resulted in increased binder stiffness. Following prolonged aging, a noticeable increase in binder stiffness was observed, particularly when exposed to a temperature of 85 °C. Concurrently, a decrease in fatigue resistance at high strains and a reduction in permanent deformations were identified after aging. The effects of UV radiation were less pronounced than anticipated, mainly due to the lower chamber temperature (60 °C). Nevertheless, the applied stimuli expedited the aging process, underscoring the significance of including UV radiation and moisture in laboratory aging studies. Additionally, it was observed that the aging protocol at 85 °C yielded results analogous to those observed under field conditions over a six-month period in the northeastern region of Brazil.

Homogeneity Enhancement of Mixtures Containing Epoxy Polymer and 100% Reclaimed Asphalt Pavement.

The utilization of reclaimed asphalt pavement (RAP) could reduce the cost of pavements containing epoxy polymer (EP) materials. This study was aimed at improving the homogeneity of an EP-reclaimed asphalt mixtures (ERAMs) at both the micro- and meso-scale to provide a reference for an ERAM production process. At the microscale, nanoindentation tests were conducted to characterize the diffusion between the EP and aged asphalt mastic. At the mesoscale, computerized tomography (CT) X-ray scanning and MATLAB analysis were employed to investigate the distribution of the aggregate within the ERAM. The results revealed that mixing temperature played a significant role in the diffusion and distribution between the EP and the aged asphalt mastic, thus impacting the mechanical properties of the material. Heating at 180 °C (the recommended mixing temperature of EP) resulted in a wider blending zone between the EP and the aged asphalt mastic compared to heating at 160 °C (the usual mixing temperature of ordinary reclaimed asphalt mixtures). The overall dispersion of the aggregate in the ERAM exhibited greater homogeneity in the vertical direction than in the horizontal direction. Adjusting the gradation of the RAP was found to be effective in reducing horizontal variability in the distribution of the coarse aggregate, fine aggregate, and air voids in the ERAM. Adjusting the RAP gradation further enhanced the vertical homogeneity in the distribution of the fine aggregate, while its impact on the vertical distribution of the coarse aggregate was minimal. Short-term aging led to increased variability in the distribution of the coarse aggregate, fine aggregate, and air voids within the ERAM. However, adjusting the gradation was effective in mitigating the adverse effects of short-term aging on both horizontal and vertical homogeneity in the aggregate distribution.

Estimating tensile strength ratio of asphalt mixtures using Surface Free Energy (SFE) and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR)

Moisture damage often leads to pavement failure, particularly as pavements age. The widely adopted AASHTO T283 test evaluates asphalt mixtures’ susceptibility to moisture damage but has shortcomings, time-consuming procedures, and lack of representation of realistic aging effects. Given the adoption of AASHTO T283 by state agencies, this study aimed to establish correlations with reliable and practical tests, especially Surface Free Energy (SFE)’s work of cohesion (Wc) and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) tests’ carbonyl and sulfoxide indices, to estimate AASHTO T283′s Tensile Strength Ratio (TSR%). Three asphalt binders (PG 52–34, PG 64–22, and PG 76–22) were assessed at oxidation levels (original, short-term, and long-term). Analysis of Variance (ANOVA) and linear regression analysis were conducted to assess the relationship between SFE and FTIR-ATR with TSR%. Results showed PG 52–34 mixtures had the highest TSR%, while PG 76–22 mixtures had the lowest, decreasing with higher oxidation. PG 52–34 had higher Wc values than PG 76–22, reducing with higher oxidation. FTIR-ATR measured higher carbonyl and sulfoxide index values for PG 52–34 and lower values for PG 76–22. ANOVA and linear regression analysis highlighted correlations between TSR%, SFE, and FTIR-ATR, with the combined effects of Wc, carbonyl, and sulfoxide indices showing the strongest relationship. The findings demonstrate that SFE and FTIR-ATR measurements showed potential in predicted TSR% for the asphalt mixtures. Particularly, predicted TSR% values differed the highest from actual TSR% for PG 52–34 without aging and at short-term aging but achieved accurate predictions with small absolute differences under long-term aging conditions.

Laboratory evaluation of different bio-oil recycled aged asphalts: Conventional performances and microscopic characteristics

The performance of diverse types of bio-oils varies greatly from each other, which makes it arduous to apply different bio-oils directly in engineering practice. This study is based on physical and microscopic properties, studying different types of bio-oil recycled asphalt and analyzing their differences. Five bio-oils (castor oil, straw oil, soybean oil, gutter oil, and vegetable oil) were used to regenerate asphalts after short-term and long-term aging to prepare recycled asphalts. The physical performances of recycled asphalts with different bio-oils were assessed, including penetration, softening point, and ductility tests. In addition, scanning electron microscopy was utilized to investigate the microscopic morphologies of recycled asphalts. Simultaneous thermogravimetry and differential scanning calorimetry were applied to determine the thermal stabilities of recycled asphalts. Finally, Gel permeation chromatography was employed to analyze the asphalt's relative molecular masses. The results revealed that vegetable and gutter oil have apparent adverse effects on temperature sensitivity and high-temperature performance of aged asphalt. In contrast, they have positive effects on low-temperature performance. All five bio-oils can repair cracks on the surface of aged asphalt. However, the surface wrinkles of vegetable oil-recycled asphalt and castor oil-recycled asphalt are relatively less and have an outstanding recycling effect. The slight thermal weight loss of recycled asphalts corresponding to castor oil, straw oil, and soybean oil at high temperatures positively impacted the high-temperature stability of aged asphalt. The castor oil and soybean oil recycled asphalts have significantly larger relative molecular masses and have advantages in high-temperature performance. This paper reveals the impact of different bio-oils on asphalt regeneration, which contributes a theoretical basis for promoting the practical implementation of bio-oil in road projects, with obvious economic and social benefits.

Multi-scale study of compound modified asphalt materials by waste cooking oil and organic montmorillonite on high temperature performance

Asphalt binder as a by-product of petroleum is a finite resource. Hence, finding an alternative material for asphalt binder is a potential topic in the road engineering. Performance of compound-modified asphalt material at high temperatures, by waste cooking oil (WCO) and organic montmorillonite (OMMT) was investigated in this study, and the multi-scale correlation evaluation was conducted. The findings revealed that the bio-oil significantly reduces the barrier to rutting of asphalt materials within multi-scales, and rutting resistance was reduced with increased content. High-temperature performance can be regained or even better than that of base asphalt materials when WCO Bio-oil: OMMT is 1:1, and OMMT can compensate for the loss of high-temperature performance. Besides, the multi-scale correlation analysis shows that the Jnr3.2 index of OMMT composite modified bio-asphalt mastic, asphalt mixtures' resistance to rutting at high temperatures can be predicted using their short-term aging condition.

Run-Time Resource Management in CMPs Handling Multiple Aging Mechanisms

Run-time resource management is fundamental for efficient execution of workloads on Chip Multiprocessors. Application- and system-level requirements (e.g. on performance vs. power vs. lifetime reliability) are generally conflicting each other, and any decision on resource assignment, such as core allocation or frequency tuning, may positively affect some of them while penalizing some others. Resource assignment decisions can be perceived in few instants of time on performance and power consumption, but not on lifetime reliability. In fact, this latter changes very slowly based on the accumulation of effects of various decisions over a long time horizon. Moreover, aging mechanisms are various and have different causes; most of them, such as Electromigration (EM), are subject to temperature levels, while Thermal Cycling (TC) is caused mainly by temperature variations (both amplitude and frequency). Mitigating only EM may negatively affect TC and vice versa. We propose a resource orchestration strategy to balance the performance and power consumption constraints in the short-term and EM and TC aging in the long-term. Experimental results show that the proposed approach improves the average Mean Time To Failure at least by 17% and 20% w.r.t. EM and TC, respectively, while providing same performance level of the nominal counterpart and guaranteeing the power budget.

CHARACTERIZATION OF ASPHALT MODIFICATION USING GROUND RUBBER AND REACTIVE RUBBER NR-g-MA AS COMPATIBILIZER

This study aims to improve the quality of asphalt by adding ground tyre rubber (GR) and reactive rubber (NR-g-MA) as compatibilizers of asphalt-rubber mixability. The use of GR has been widely used to improve the performance of asphalt and extend the service life of asphalt. The NR-g-MA used was the product of the copolymerization of SIR-20 rubber grafts with maleic anhydrous (MA) through a melting process in an internal mixer. Mixing of GR in asphalt was carried out in an external mixer with composition of asphalt/GR 95/5 phr at the temperature of 180oC for 90 minutes. The performance of asphalts were measured based on conventional test of penetration and softening point. The rheological properties of asphalt were measured using a Dynamic Shear Rheometer (DSR). Important parameters of the rheological properties measured are complex shear modulus (G*) and phase angle (d). Asphalt resistance to the permanent deformation (rutting) were determined on asphalt that has undergone a short-term aging process in a rolling thin film oven (RTFO) and measured at high temperatures (58-82OC). Fatigue crack resistance was tested on asphalt that has undergone a long-term aging process using the method of pressure aging vessel (PAV) and measured at low temperatures (25-31OC). Asphalt-GR mixtures' chemical, thermal and morphological properties were studied using ATR-FTIR, DSC/TGA, and SEM respectively. The results showed that adding used ground rubber (GR) decreased the penetration value by 9.93 – 18.87% and increased the softening point of asphalt from 5.57 – 11.40%. Rheological analysis showed that the addition of GR and compatibilizer NR-g-MA increase the value of complex shear modulus (G*) and decrease the phase angle (d) of the asphalt. The addition of ground rubber and reactive rubber of NR-g-MA to asphalt improve the performance of asphalt because it has rutting resistance at high temperatures as well as improves asphalt cracking resistance at low-temperature measurements. The addition of NR-g-MA reactive rubber to modified asphalt ground rubber can increase the mixability of asphalt-rubber used tires.

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.

New insight: Nitrosation of n-phenyl-β-naphthylamine in the early stage of nitroplasticizer aging

Antioxidants are additives and used for inhibiting oxidative degradation of many polymeric materials. Likewise, to maintain long-term stability of nitroplasticizer (NP) used in the formulation of a polymer-bonded energetic material, 0.1 wt.% of an arylamine antioxidant, n-phenyl-β-naphthylamine (PBNA) was added. Recently, the detection of PBNA nitration has brought forth the mechanistic complexity of antioxidant chemistry and created a path to understand how NP naturally degrades over time. Through a short-term aging experiment and with optimized LC-QTOF analysis, a reaction between PBNA and nitrous acid (HONO) that precedes the nitration event has been found, known as nitrosation. The identification of nitroso-PBNA has solidified the HONO elimination mechanism in NP degradation and provided new insight on the role of this arylamine antioxidant. It also shows how stabilizer reactions with key intermediate degradation species can be a contributing process in polymer degradation.

Properties of recycled facemask fiber modified asphalt binder: Comparative analysis of surface modification and composite modification method

Polymer-modified asphalt binders had been developed as a novel strategy for road and building materials. People generally use disposable facemasks to reduce the risk of respiratory diseases during travel and commuting. These discarded masks will become a serious environmental problem. Recycled facemask has great potential application in the modified asphalt, but its modification effect of modified asphalt needs to be studied. In this work, different kinds of fibers and their modified asphalts had been successfully prepared and comparatively analyzed after the surface of fibers treated by butyl acrylate (BA) and further modified by copper oxalate (CO) nanoparticles. From the test results, the activation energies of polypropylene fiber extracted from recycled facemask (RPF) modified asphalt (RPA), treated RPF (MRP) modified asphalt (MRPA), and MRP further decorated with CO (MRPCO) modified asphalt (MRPCOA) were 64.08 kJ/mol, 59.09 kJ/mol, and 62.32 kJ/mol, respectively. MRP and MRPCO were better dispersed in asphalt than RPF. MRPA performed a lower value of the viscoelastic than RPFA, but MRPCOA performed the higher value of viscoelastic than MRPA. Compared with RPA, the short-term aging factors of MRPA and MRPCOA decreased by 31.73% and 53.18%, while long-term aging factors of MRPA and MRPCOA decreased by 11.34% and 12.31%. From the nanoindentation data, the maximum depth of MRPA increased by 5.23% and the hardness decreased by 2.55% than RPA. The maximum depth of MRPCOA also decreased by 6.68% and its hardness also decreased by 4.45% than MRPA. These results indicated composite modification of RPF performed better than only surface modification based on the viscoelastic and aging properties of modified asphalts. It provided a meaningful study for the potential applications of various recycled polymeric fibers in modified asphalt binder in the future.