Effect Of Oxidative Aging Research Articles

The influence of oxidative aging and wax structure on bitumen physical hardening: Insights from model wax compounds

Physical hardening (PH) significantly affects bitumen's low-temperature performance. This paper investigates the effect of oxidative aging and wax structure on PH using 4-mm dynamic shear rheometer (4-mm DSR) and differential scanning calorimetry (DSC) tests. The results show that the wax chain length has a pronounced effect on the PH. Short-chain waxes, such as C18 and C24 affect the PH while longer-chain n-paraffins like C40 or Sasobit have almost no effect. In addition, the physical hardening index (PHI) is not linearly increasing with wax content but shows a maximum at a particular wax percentage. Wax-doped samples that crystallize before reaching the hardening temperatures typically show a reduced PHI compared to those with crystallization temperatures just below the hardening temperature. When crystallization and melting temperatures are not close to the hardening temperatures, the PHIs are typically reduced. Oxidative aging also influenced the PHI and in most cases the hardening decreased after aging. The highest PHI of almost all investigated samples occurs at 0 °C among the four typical temperatures. This investigation provides insights in the mechanism of PH and in the relations between wax contents, the hardening temperature, and the PHI. It also shows that while long-chain waxes used as warm mix additives, will not cause a PH risk, short-chain waxes present in pyrolyzed waste plastic, for example, should be handled with care. In addition, PH is also crucial for the intermediate service temperatures and not exclusively for thermal cracking at low temperatures.

Diosgenin alleviates D-galactose-induced oxidative stress in rats' brain and liver targeting aging and apoptotic marker genes.

The theory of aging is primarily concerned with oxidative stress caused by an imbalance in reactive oxygen species generation and cellular antioxidants. To alleviate the oxidative stress, we investigated the protective effect of diosgenin (DSG) for D-galactose (D-gal) using 20 and 40mg of DSG/kg/day/orally for 42 days. The findings showed that D-gal caused brain and liver oxidative injuries by upregulating aging and oxidative markers. To counteract the oxidative stress caused by D-gal, DSG upregulated glutathione peroxidase-1, superoxide dismutase-1, and glutathione S-transferase-α. DSG also diminished the expression of p53, p21, Bcl-2-associated X protein, caspase-3, and mammalian target of rapamycin in brain and liver, as well as the build-up of β-galactosidase. DSG, in a dose-dependent manner, decreased the oxidative aging effects of D-gal in brain and liver tissues through targeting of aging and apoptotic marker genes. Finally, it should be noted that consuming DSG supplements is a suggesting natural preventative agent that may counteract aging and preserve health through improvement of body antioxidant status and control aging associated inflammation and cellular apoptosis.

Effect of oxidative ageing on stiffness improvement factor for HDPE and PET geogrids

The effect of thermal-oxidative ageing on in-isolation and in-soil stiffness is investigated for two high-density polyethylene (HDPE) and two polyester (PET) geogrids when incubated in an oven at 90°C. It is shown that the in-isolation and in-soil stiffness of three out of the four geogrids decreased during the 4-month ageing time with a faster degradation of the two PET geogrids. In contrast, one of the HDPE geogrids examined with thicker rib showed slower degradation compared to the PET counterparts. It is also shown that a geogrid might have a higher unaged stiffness, but less aged stiffness compared to another geogrid made of the same polymer type. It is suggested that the ageing approach used in this study could be adopted for the selection of geogrids based on their long-term stiffness for structures such as reinforced embankments or mechanically stabilized earth walls that require a long service life. Moreover, results indicate that the stiffness improvement factor for PET geogrids decreases with ageing time. On the contrary, the stiffness improvement factor of the HDPE geogrid increases with time and hypothetically might keep increasing followed by a sudden drop to zero at full degradation of the geogrid.

Double Effects of Oxidative Aging on Carbon Nanotube-Asphalt Nanocomposite Interfaces: Enhancement and Deterioration.

Understanding the mechanisms of oxidative aging effects on the carbon nanotube (CNT)-asphalt nanocomposite interface has long been a challenge, as there are two opposing effects: enhancement and deterioration. In this study, a multiscale coupling method is proposed to analyze the dual effect of oxidative aging on the CNT-asphalt nanocomposite. The method is based on density functional theory (DFT) and molecular dynamics (MD) simulations, supported by microscopic interface observation and macroscopic property testing with a focus on the composite interface. The results show that oxidative aging has a resetting effect on benzene ring stacking at the interface and enhances the binding energy of CNT-asphalt. Meanwhile, oxidative aging enhanced the interfacial charge transfer, but no chemical reaction occurred between CNT-aged asphalt. This is also verified by Fourier Transform Infrared Spectroscopy (FTIR). Enhancement and degeneration effects of oxidative aging occur via distinct mechanisms. Oxidative aging enhanced the interfacial shear barrier by approximately 5% and the energy barrier by 44.87%, which increased the high-temperature deformation resistance of the CNT-asphalt nanocomposites. However, molecular oxidation was not responsible for the decline in the fatigue resistance. According to scanning electron microscopy (SEM) and atomic force microscopy (AFM) results, oxidative aging elevates the content of polar molecules, leading to an increase in the solid properties of asphalt and a 39.6% decrease in surface adhesion. This disrupts the three-dimensional network of the CNT and ultimately leads to a reduction in crack resistance. This study clarifies the mechanism underlying the dual effect of oxidative aging and provides fundamental support for understanding asphalt aging behavior and the interfacial behavior of composites.

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

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

Effects of Oxidative Aging on Dielectric Strength of Natural Ester Oil Under DC Voltage Stresses

The developments in the research and design of HVDC transmission equipment prompted this investigation into determining the electrical strength of insulating oil under DC voltage stresses. The manufacturers of oil-filled high-voltage equipment are continually tasked with developing novel insulating liquids with high dielectric strength, efficient heat transfer, and low environmental effect. As new energy sources are developed, these materials must function on direct current (DC). To ensure the long-term reliability of power equipment, it is essential to understand the degradation characteristics of insulating oil in long-term operations. Due to the limited literature on the behaviour of aged insulating oil in direct voltage stresses, breakdown tests are conducted on a typical electrode arrangement in fresh and oxidatively aged mineral oil and natural ester oil (FR3) in an effort to provide additional understanding on the DC breakdown voltage (DCBDV) of these oils. In this paper the statistical behaviour of DCBDV experimental results is analyzed by using normal, two and three parameter Weibull distributions by subjecting the oils to thermal stresses at elongated ageing hours of 90, 200 and 500 hours. The Anderson-Darling test and goodness of fit is applied to verify the experimentally obtained DCBDV data to a specific statistical distribution. Results show that breakdown strength of FR3 under DCBDV is higher than that of MO in both polarities after oxidative ageing. However, with the increase in ageing duration, the breakdown strength reduces for both the oil samples. It is observed that the majority of data also confirm to normal and Weibull distributions.

Deterioration Effects of Oxidative Aging on Graphene-Asphalt Nanocomposite Interfaces: Multiscale Modeling.

The purpose of this study is to explore the mechanism of interfacial degradation of graphene-asphalt nanocomposites by oxidative aging and to explain the principle of reduced cracking resistance. In this study, density functional theory (DFT), molecular dynamics (MD) simulation, atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, and linear amplitude scanning test (LAS) were used to quantify the effect of oxidative aging on the interfacial degradation of graphene-asphalt nanocomposites with different scales, and the coupling mechanism between scales was systematically analyzed. The results show that interfacial degradation is a complex multiscale coupling behavior. Oxidative aging reduced the fatigue life (Nf) of graphene-asphalt nanocomposites by 8.6% due to a 63.9% reduction in shear barriers and a 14.2% reduction in energy barriers at the molecular interface. Furthermore, oxidative aging enhanced the intermolecular interactions and compatibility of the graphene-asphalt molecules. The interfacial interaction of aged graphene-asphalt nanocomposites is mainly van der Waals force. Graphene-aged aromatics and graphene-aged saturates were the most compatible interfaces, and there was typical benzene ring stacking between graphene and aged aromatic 2. Aged aromatics and aged saturates are the main promoters of interfacial strength and stress transfer, while aged asphaltenes and aged resins sometimes play a weakening role, as verified by the AFM. In addition, DFT calculations show that there is no chemical reaction between graphene and aged asphalt molecules, which is consistent with the FTIR results. This study provides a theoretical basis for the development of targeted antiaging and anticracking technologies for asphalt-based materials.

Thermal and Oxidative Aging Effects of Polyamide-11 Powder Used in Multi-Jet Fusion.

The transition of additive manufacturing (AM) from a technique for rapid prototyping to one for manufacturing of near net or net components has been led by the development of methods that can repeatedly fabricate quality parts. High-speed laser sintering and the recently developed multi-jet fusion (MJF) processes have seen quick adoption from industry due to their ability to produce high-quality components relatively quickly. However, the recommended refresh ratios of new powder led to notable amounts of used powder being discarded. In this research, polyamide-11 powder, typically used in AM, was thermally aged to investigate its properties at extreme levels of reuse. The powder was exposed to 180 °C in air for up to 168 h and its chemical, morphological, thermal, rheological, and mechanical properties were examined. To decouple the thermo-oxidative aging phenomena from AM process related effects, such as porosity, rheological and mechanical properties characterisation was performed on compression-moulded specimens. It was found that exposure notably affected the properties of both the powder and the derived compression-moulded specimens within the first 24 h of exposure; however, consecutive exposure did not have a significant effect.

Influencing Factors and Evaluation of the Self-Healing Behavior of Asphalt Binder Using Molecular Dynamics Simulation Method

In order to investigate the self-healing behavior of asphalt binder at the molecule scale, the self-healing models of neat and aged asphalt binder with different damage degrees were established by introducing a vacuum pad between two layers filled with asphalt molecules. With this model, the self-healing process was simulated at various healing conditions to reveal the effects of oxidative aging, damage degree and healing temperature on the self-healing property. In addition, self-healing efficiency was evaluated using the indexes representative of the characteristics of different self-healing stages. Our results show that the oxidative aging weakened the stacked structure of the asphalt binder and increased the healing activation energy barrier. The increasing damage degree extended the distance for particles to travel, thus prolonging the time required for the crack interfaces contacting with each other. The elevated temperature improved the molecular mobility by supplying more energy to the molecular system. Furthermore, the self-healing process was evaluated quantitatively by the density variation at the crack closing stage and the diffusion coefficient at the intrinsic healing stage. The duration of each stage was influenced by the oxidative aging, damage degree and healing temperature. The findings in this paper are helpful to reveal and evaluate the self-healing property of asphalt binder.

Investigation of the Effect of Oxidative Aging and Temperature Sensitivity on the Illinois Flexibility Index and Disc-Shaped Compact Tension Tests

This study investigated the sensitivity of the Illinois flexibility index test (I-FIT) and the disc-shaped compact tension [DC(T)] test with respect to oxidative aging and testing temperature. For this purpose, five plant-produced surface course asphalt mixtures covering a wide range of performance-graded asphalt cement (PGAC) were utilized. As for oxidative aging sensitivity, two methods of forced-draft oven aging, at 85°C for 120 h and at 95°C for 72 h, were utilized. Furthermore, to measure the temperature sensitivity, the I-FIT test was conducted at 23°C, 24°C, 25°C and PGAC intermediate temperatures, while the DC(T) test was conducted at −18°C, −24°C, and −30°C. In this study, the analysis of the I-FIT test results from oxidative aging showed that both methods of aging caused a reduction in flexibility index values of asphalt mixtures, and the flexibility index values after two methods of aging were statistically comparable. Moreover, even though oxidative aging caused a reduction in DC(T) fracture energies of asphalt mixtures containing hard PGAC, the fracture energies before and after the two methods of aging were statistically similar for asphalt mixtures. The analysis of the I-FIT test results from testing temperature sensitivity showed that the flexibility index values of asphalt mixtures containing hard PGAC at 23°C were statistically dissimilar to those at 25°C when the testing temperature dropped from 25°C to 23°C. Consequently, regarding the I-FIT test, the comparable flexibility index values from the two methods of oxidative aging suggested utilization of forced-draft oven aging at 95°C for 72 h as a less time-consuming method compared to forced-draft oven aging at 85°C for 120 h to evaluate the effect of oxidative aging. In addition, the variability in flexibility index values due to the drop in testing temperature suggested exercising caution when conducting the test on asphalt mixtures containing hard PGAC.

Evaluation of physical hardening and oxidative aging effects on Delta Tc of asphalt binders

The Delta T c ( Δ T c ) is a rheological parameter for asphalt binders, which has been adopted in the past years by many highway agencies in North America for asphalt binder selection. In this study, the effects of the low-temperature physical hardening and oxidative aging on Δ T c are experimentally investigated and analysed. The experimental study is performed on both plain and polymer-modified binders. The results show that both physical hardening and oxidative aging have strong effects on decreasing Δ T c . An approximate linear relationship is identified between Δ T c and rheological parameters, such as the creep stiffness (S) and the m-value. The linear relationship is theoretically explained by analytical derivation. Based on the linear relationship, a graphical method is proposed for interpreting Δ T c using the log(S)-m diagram. By this method, it is found that polymer modification increases the susceptibility of Δ T c to oxidative aging, while it does not significantly affect the susceptibility of Δ T c to physical hardening.

Atomic insight into the nano-cracking behaviour of bitumen: considering oxidative aging effects

Experimental understanding of the nanoscale cracking mechanism in bitumen is challenging. This paper adopts molecular dynamics simulation to study the loading-induced cracking behaviour from four aspects: (1) stress-displacement states; (2) morphology evolution; (3) energy contribution; and (4) the relationship with chemical compositions. Simulation results indicated that the nano-cracking process can be divided into the following stages: increase of free volume (stage I), formation of nanovoids, (stage II), nucleation and propagation (stage III), filamentation (stage IV) and separation (stage V). The density drop was observed in the area where saturates agglomerated, which potentially caused the formation of nanovoids. Energy analysis indicated that the cracking behaviour was related to the non-bond interaction, especially van der Waals interaction. Oxidative aging increased the intermolecular bonding and reduced the molecular mobility, which resulted in larger tensile strength but lower ductility. In addition, the effects of temperature on the nano-cracking behaviour were also presented.

Rejuvenating Agents vs. Fluxing Agents: Their Respective Mechanisms of Action on Bitumen Subjected to Multiple Aging Cycles

During the service life of road pavements, the asphalt, more specifically the surface layer, is susceptible to aging due to the oxidation phenomenon and the loss of the volatile compounds of bitumen, which functions as the binder in the asphalt conglomerate. Road pavements that undergo a significant level of oxidation become rigid and susceptible to cracking, and new paving operations will need to be carried out in order to make the road ideal for continued use. However, due to recent eco-friendly initiatives that have been put in place to promote a circular economy and also mitigate the problem of environmental pollution, the asphalt industry is currently devising means of safeguarding the environment while also minimizing the cost of the production of road pavements without compromising their quality. As a general solution to this issue, old asphalt pavements are removed and recycled as reclaimed asphalt (RA), with the aim of restoring the original properties of the binder in such a way that RA can be re-used in combination with virgin materials to produce new road pavements. In this research study, virgin bitumen is subjected to a cycle of aging, after which two recycling agents are used to modify the aged bitumen samples. These samples containing the different recycling agents were subjected to a second aging cycle, a second recycling agent treatment, and then again subjected to a final aging cycle. The two recycling agents have different compositions, and each one of them could be either a rejuvenating agent or a fluxing agent. This study investigates the effect of these recycling agents on aged bitumen, and how the addition of these recycling agents influences the changes observed between virgin, aged and recycled bitumen. This would enable an understanding of rejuvenation and fluxing mechanisms, which will help in the classification of the asphalt recycling agents as either rejuvenating or fluxing agents. Dynamic shear rheology, atomic force microscopy, and light microscopy to determine asphaltene melting point were the techniques used in this investigation. The results obtained demonstrate that rejuvenating agents are more effective in reversing the effects of oxidative aging on the bitumen binder than fluxing agents.

Effect of oxidative aging of biochar on relative distribution of competitive adsorption mechanism of Cd2+ and Pb2+

In this study, aged biochar (CCB350 and CCB650) were obtained from pyrolysis of corn stalk biochar (CB350 and CB650) at the degree of 350 °C and 650 °C by artificial oxidation with hydrogen peroxide (H2O2). Also, the mechanism of Pb2+ and Cd2+ on fresh and aged biochars was analyzed qualitatively and quantitatively by batch adsorption experiments combined with characterization. The adsorption isotherm results showed that aging treatment decreased the adsorption capacity of Pb2+ and Cd2+ and inhibited the competitive adsorption behavior of heavy metals. In the single-metal system, precipitation and cation exchange were considered as the main adsorption mechanisms for CB350 and CB650, with a ratio of 40.07–48.23% and 38.04–57.19%, respectively. Competition between Pb2+ and Cd2+ increased the relative contribution of mineral precipitation, but decreased the contribution of cation exchange mechanism. Aging resulted in the rise of the contribution of surface complexation to the adsorption of Pb2+ and Cd2+ on biochars, especially in low-temperature biochars, but weakened the contribution of mineral precipitation to the adsorption. Further, the contribution of other adsorption mechanisms was significantly enhanced for high-temperature aged biochars. These results are important to evaluate its long-term application prospects in the natural environment.

Molecule Dynamics Simulation of the Effect of Oxidative Aging on Properties of Nitrile Rubber.

The effects of oxidative aging on the static and dynamic properties of nitrile rubber at the molecular scale were investigated by molecular dynamics simulation. The aged nitrile rubber models were constructed by introducing hydroxyl groups and carbonyl groups into rubber molecular chains to mimic oxidative aging. The static and dynamic properties of the unaged and aged nitrile rubber under different conditions were evaluated by mean square displacement, self-diffusion coefficients, hydrogen bond, fractional free volume, radial distribution function, cohesive energy density and solubility parameter. The results show that the elevated temperature intensified significantly the mobility of rubber molecular chains and fractional free volume, while the compressive strain displayed the opposite effect resulting in packing and rearrangement of rubber chains. The introduction of hydroxyl groups and carbonyl groups enhanced the polarity, intermolecular interactions, the volume and rigidity of molecular chains, implying weaker mobility of molecular chains as compared to unaged models. The compressive strain and oxidative aging both decreased the fractional free volume, which inhibited gaseous and liquid diffusion into the rubber materials, and slowed down the oxidative aging rate. This study provides insights to better understand the effect of molecular changes due to oxidative aging on the structural and dynamic properties of rubber materials at the molecular level.

Thermal and Oxidative Aging Effects of Polyamide-11 Powder Used in Additive Manufacturing

Thermal and Oxidative Aging Effects of Polyamide-11 Powder Used in Additive Manufacturing

Antioxidant Effect of Lactobacillus fermentum CQPC04-Fermented Soy Milk on D-Galactose-Induced Oxidative Aging Mice.

The aim of this study is to evaluate the changes in soy isoflavones and peptides in soy milk after lactic acid bacterial fermentation, and explore the positive effects of fermented soy milk on an oxidative aging mouse model induced with D-galactose. We found that free soybean isoflavones and peptides increased after soy milk was fermented by Lactobacillus fermentum CQPC04. The in vivo results indicated that L. fermentum CQPC04-fermented soy milk enhanced the organ index of the liver and spleen, and improved the pathological morphology of the liver, spleen, and skin. L. fermentum CQPC04-fermented soy milk increased the enzymatic activity of glutathione peroxidase (GSH-Px), total superoxide dismutase (T-SOD), and catalase (CAT), increased glutathione (GSH), but decreased the levels of nitric oxide (NO) and malondialdehyde (MDA) in serum, liver, and brain tissues of oxidative aging mice. The above mentioned fermented soy milk also increased the levels of collagen I (Col I), hyaluronic acid (HA), and collagen III (Col III), and decreased the levels of advanced glycation End products (AGEs) and hydrogen peroxide (H2O2). The RT-qPCR results showed that L. fermentum CQPC04-fermented soy milk upregulated the mRNA expression of nuclear factor erythroid 2?related factor (Nrf2), heme oxygenase-1 (HMOX1), quinone oxido-reductase 1 (Nqo1), neuronal nitric oxide synthase (NOS1), endothelial nitric oxide synthase (NOS3), Cu/Zn–superoxide dismutase (Cu/Zn-SOD), Mn–superoxide dismutase (Mn-SOD), and CAT, but downregulated the expression of inducible nitric oxide synthase (NOS2) and glutamate cysteine ligase modifier subunit (Gclm) in liver and spleen tissues. Lastly, the fermented soy milk also increased the gene expression of Cu/Zn-SOD, Mn-SOD, CAT, GSH-Px, matrix metalloproteinases 1 (TIMP1), and matrix metalloproteinases 2 (TIMP2), and decreased the expression of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) in skin tissue. In conclusion, L. fermentum CQPC04-fermented soy milk was able to satisfactorily delay oxidative aging effects, and its mechanism may be related to the increase in free soy isoflavones and peptides.

Thermo-oxidative aging and thermal cycling of PETI-340M composites

Polyimide composites (PETI-340M) were fabricated and subjected to high-temperature aging and thermal cycling to evaluate resistance to degradation. Mechanical-degradation mechanisms and kinetics depended on aging temperature. Aging at 232°C resulted in strength loss due to polymer degradation, while intra-tow cracking was the dominant mechanism during aging at 288°C. Composite panels subjected to thermal-cycling fatigue (−54°C to 232°C) retained mechanical properties without microcracking. However, in regions containing pre-existing fabrication-induced defects (primarily voids), intra-tow microcracks were observed after thermal cycling. Unlike some polyimide composites (PMR-15), oxidative aging effects during thermal cycling were negligible. The thermo-oxidative stability and the retention of mechanical performance after thermal cycling indicates potential for long-term, high-temperature structural applications.

Stabilization Effects of Natural Compounds and Polyhedral Oligomeric Silsesquioxane Nanoparticles on the Accelerated Degradation of Ethylene-Propylene-Diene Monomer.

In this work the analysis on the stabilization activities of some natural antioxidants (rosemary extract, capsaicin, quercetin or oleanolic acid) is presented. A similar contribution of an inorganic structure—polyhedral oligomeric silsesquioxane (POSS) nanoparticles—is also evaluated. The stabilization effects on the oxidation protection were investigated for several formulations based on ethylene-propylene-diene-terpolymer (EPDM). The samples were examined in pristine state or after γ-irradiation, when the accelerated degradation scission of polymer macromolecules followed by the mitigation of oxidation. Three evaluation procedures: chemiluminescence, FTIR spectroscopy and thermal analysis were applied for the characterization of stability efficiency. The delaying effect of oxidative aging in EPDM matrix is illustrated by the values of activation energy, which are correlated with the type and concentration of embedded compounds. The durability of studied EPDM formulations is discussed for the assessment of material life. The improved behavior of structured hybrids useful for the optimization application regimes is essentially based on the antioxidant properties of polyphenolic components in the cases of natural antioxidants or on the penetration of free radical intermediates into the free volumes of POSS.

Variable-temperature Fourier-transform infrared spectroscopy study of asphalt binders from the SHRP Materials Reference Library

A wide range of asphalt binders were studied by variable-temperature Fourier-transform infrared spectroscopy (VT-FTIR) to understand how peak position and intensity are affected by temperature. Conditioning times of 20 and 60 hours were selected in the pressure aging vessel (PAV) to provide two levels of oxidative aging. Spectral intensity consistently increased at lower temperatures, but the magnitude of change varied a great deal depending on binder source. Peak positions within the 2,919–2,856 cm−1 range were found to shift to lower wavenumbers at lower temperatures. In contrast, peak positions within the 1,456–1,465 cm−1 range shifted higher. Shifts were found to both weaken or enhance by oxidation. The wax precipitation temperature (WPT) was generally found to experience a decrease after mild oxidation but increase after more extensive aging. No clear trends were found for the effect of oxidative aging on solid wax content as measured by VT-FTIR. These results provide new and important insights on how binder structure changes at cold temperatures.