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The aging of bitumen is a major contributor to the failure of asphalt pavements. Realistic and accurate laboratory aging methods can predict bitumen durability and guarantee the use of high-quality components in asphalt pavement. However, current standardized aging methods do not incorporate atmospheric parameters, besides elevated temperatures and...
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... of changes in the chemical composition FTIR spectroscopy was used. The respective bitumen samples were heated up to * 110 °C in a spoon and stirred with a thermometer for homogenization and temperature detection. After reaching the desired temperature small droplets of sample were transferred on a silicone foil. The sample preparation is shown in Fig. 3. For the measurement a Bruker Alpha II with an DTGS detector and an attenuated total reflection (ATR) unit containing a diamond crystal was used. The ATR geometry allows the recording of FTIR spectra in adsorption equivalent mode and the bitumen samples can be applied directly onto the crystal in solid state. All spectra were measured ...
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... In the context of long-term aging, laboratory methods use one or more means to accelerate oxidation such as temperature, pressure, or oxidative environment (Poulikakos et al. 2014;Sreeram et al. 2021;Hofer et al. 2022). Further, previous studies have raised concerns about conducting long-term aging for binders or mixtures at temperatures exceeding 100°C, as that could result in oxidation pathways that may normally not occur in the field (Kim et al. 2018). ...
Developing new and efficient methods to simulate the aging of asphalt binders and mixtures continues to be an important area of research for the asphalt community around the world. Temperatures exceeding pavement service temperatures are typically used to accelerate and simulate long-term aging in laboratory settings. However, it is unclear whether the use of such higher temperatures would have an adverse influence when simulating the aging of typical polymer modified binders. Specifically, the influence of thermal degradation of polymers at elevated temperatures and the resulting deterioration of the aging-related properties of the asphalt binder could be unrealistic when considering polymer degradation in the field. This study explores the use of an oxidative and nonoxidative environment to deconvolute the different aging characteristics of unmodified and styrene butadiene styrene (SBS) modified asphalt binders. Six binders, including two unmodified binders and four SBS-modified binders with two polymer contents (3% and 4.5% binder weight), were aged in two different aging conditions, i.e., under an air blanket and nitrogen blanket, at a temperature of 100°C. The resulting changes in material behavior were investigated using thin film poker-chip testing, dynamic shear rheometer testing, and Fourier transform infrared spectroscopy. Overall, the results from this investigation suggest that long-term aging of asphalt binders or mixtures conducted using temperatures not exceeding 100°C does not result in any significant degradation of polymers in modified asphalt binders.
... Moreover, it is essential to consider the role of Reactive Oxygen Species (ROS) in this process. ROS are known to play a crucial role in the degradation and aging of organic materials, as stated by Hofer et al., (2022) [65]. In the context of iPP, ROS can react with the functional groups present in the material originally or that have arisen due to previous oxidation reactions, leading to the increase in CI, COI, and HI observed. ...
... Moreover, it is essential to consider the role of Reactive Oxygen Species (ROS) in this process. ROS are known to play a crucial role in the degradation and aging of organic materials, as stated by Hofer et al., (2022) [65]. In the context of iPP, ROS can react with the functional groups present in the material originally or that have arisen due to previous oxidation reactions, leading to the increase in CI, COI, and HI observed. ...
... In the context of iPP, ROS can react with the functional groups present in the material originally or that have arisen due to previous oxidation reactions, leading to the increase in CI, COI, and HI observed. Specifically, ROS can react with the hydrocarbons present in polypropylene, leading to the formation of carboxylic compounds and thus increasing CI [65]. ...
The aim of this study was to investigate, in addition to degradation processes, the rheological, crystalline, and molecular dynamics changes in isotactic polypropylene microplastics with average sizes of 0.5 and 2 mm, aged in a photothermal oxidation chamber for 166 days. In addition to commonly used techniques in microplastics research, time-domain nuclear magnetic resonance (TD-NMR) in fast field cycling and fixed field modes, was employed for the first time in the study of these materials, providing non-destructive information that supports other results. Concurrently with X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), rheometry, Fourier-transform infrared spectroscopy (FTIR), surface wettability, and scanning electron microscopy (SEM) techniques, two antagonistic phenomena were observed over the aging period. One associated with the surface degradation of microplastics and increased molecular mobility, and the other related to morphological changes in the internal layers, leading to increased rigidity. These phenomena occur slightly differently depending on the average particle size. Through multivariate data analysis with principal component analysis (PCA) and hierarchical cluster analysis (HCA), it was possible to determine that the degradation process intensifies after 62 days of simultaneous exposure to ultraviolet radiation, temperature, and oxidizing atmosphere. The obtained data highlight that even synthetic polymers with long degradation periods can undergo, in the form of microplastics, initial morphological changes in just 15 days and degradation processes within a few months of exposure to weathering conditions.
... Such processes are also known for other natural bulk products, such as lignocellulosics, and oxidized functions, such as carbonyls and carboxyls, are used as markers to follow oxidative changes [16,17]. In the investigations of Mirwald et al. and Hofer et al.,O 3 and NO 2 concentrations were changed systematically at elevated temperatures in a special ageing device [18,19]. The experiments showed that ROS had significant oxidational impact, and that the combination of NO 2 with molecular oxygen led to disproportionally pronounced ageing. ...
... This study puts special focus on the less discussed features in the FTIR spectra of SARA fractions. An analysis on the formation and distribution of the most prominent oxidation products, ketones and sulfoxides, can be found elsewhere [14,19,20,38,42,[44][45][46][47][48][49]. First, a qualitative assessment of the regions 3700-3000 cm − 1 , 1800-1350 cm − 1 and the range below 1350 cm − 1 is provided. ...
Bitumen is an important construction material applied as sealing material in roofing membranes and as binding material in roads. Due to its organic nature, it is prone to environmentally induced changes on the molecular up to the macroscopic-mechanical level, resulting in a limited service life. Various individual spectroscopic and chromatographic methods have been applied to elucidate specific aspects of the ongoing chemical processes. However, a general view and systematic chemoanalytical approaches are still missing. In this study, the impact of ageing during construction and paving and after 5-years on a test field was analyzed by looking at the chemical changes within bitumen and its polarity-based fractions. Elemental analysis showed doubling of the oxygen content on the binder level and molecular exchange of nitrogen-, oxygen-, and sulfur-containing structures between the fractions. The combined use of two-dimensional nuclear magnetic resonance (NMR) and fluorescence spectroscopy indicated the increase in size of aromatic systems by aromatization and/or dehydrogenative polymerization reactions. Fluorescence and infrared spectroscopy demonstrated the ageing sensitivity of nitrogen-containing structures, such as amides and porphyrins. Finally, in-depth analysis of the specific nature and fate of hydroxyl groups with 31 P NMR spectroscopy after derivatization revealed increasing amounts of aliphatic carboxylic acids and alcohols with ageing. The outcome of this study aims at improving the understanding of ageing processes in bitumen and at showing new ways to use and combine analytical approaches for proper assessment of bitumen ageing.
... Secondly, the binder was short-term aged by storing it for 75 min at 163°C in a ventilated oven ('Pre'VBA). A detailed description of this method can be obtained from (Hofer et al., 2022). Afterwards, an adapted version of the VBA setup was used for LTA, which will be described in-depth below. ...
... The reason for choosing this aging atmosphere is the high oxidation potential of NO 2 in air for bitumen. A significant increase in stiffness and content of sulphoxides and carbonylic structures has been observed in the past when exposing bitumen samples to air + 600 ppm NO 2 (Hofer et al., 2022). The mixture of NO 2 and air was provided in gas bottles, which were directly attached to the inlet of the aging cell. ...
To predict the performance of bituminous products during their service life, an accurate simulation of the aging behaviour is required. Several laboratory methods are available, yet the correlation to field aging is mostly missing. In this study, an unmodified bitumen was exposed to laboratory aging with the Pressure Aging Vessel (PAV) using one to five aging cycles and the Viennese Binder Aging (VBA) method, followed by a comparison to a field sample of the same base binder. Measurements with the dynamic shear rheometer (DSR) and Fourier-transform-infrared (FTIR) spectroscopy showed that the field aging level could not be reached neither with VBA nor with multiple PAV cycles, but a better approximation compared to the standard aging procedure was achieved. The FTIR spectra displayed a high degree of correlation between the VBA and field aged sample, especially regarding carbonyl formation in the aromatic fraction and the intensity of the sulphoxide band in the resin and asphaltene fractions. Additionally, the VBA sample showed more similarities to the field sample regarding fluorescence excitation–emission maps. Although both laboratory aging methods are an improvement to the standard procedure, the VBA method allowed for a better qualitative simulation of the chemical properties of the investigated field sample.
... However, whatever the process used to simulate aging of asphalt binders or mixtures, the results show that the stiffness modulus, the carbonyl and sulfoxides indexes and the asphaltene content increase with aging (Airey, 2003;Braham et al., 2009;Bressi et al., 2016;Hofko et al., 2017;Huang et al., 2022;Kambham et al., 2019;Kim et al., 2013;Liu et al., 2020;Petersen, 2009;Rad et al., 2017). Recently, some correlations between the ageing index (AI) and the shear modulus |G * | at 46 • C, 1.592 Hz on three different bitumens aged according to the Pre Viennese binder aging method (Pre-VBA) in different atmospheres (NO in N 2 , NO 2 in N 2 , NO 2 in air, O 3 in Ar + O 2 ) have been addressed (Hofer et al., 2022). Similar work was previously addressed by Rad et al. (2017) and some correlations were proposed. ...
The effects of short and long-term thermo-oxidative aging on stripping resistance, rut depth, stiffness modulus, fracture and fatigue resistances of asphalt concretes have been assessed. A modified RILEM thermo-oxidative aging procedure on loose asphalt mixtures has been used to evaluate the gradual evolution of these properties with the aging duration. Two short-term aging durations (4 and 8 hours at 135∘C) and three long-term thermo-oxidative aging durations (3, 6 and 9 days at 85∘C) and a reference mixture (0 day aging) have been considered to this end. The impact of long-term thermo-oxidative aging on the chemo-rheological properties of recovered asphalt binders have been investigated. At the binder scale, the results show an increase in the Fraass temperature, the softening point, the shear modulus |G∗|, the aging index (AI=IS0 + IC0) and a decrease in the penetration grade with the aging duration. Some correlations between the viscoelastic transition parameters (TVET, GVET and ωVET) of the recovered asphalt binders and the aging index have been established. At the mixture scale, the results show that the stiffness modulus (|E∗|) increases with the aging duration, while the index of fracture resistance (IFR), the stripping resistance (CW/CD), the rut depth (P) and the fatigue deformation (ε6) decrease with the aging duration. Finally, some correlations between the aging index and the rheological and the mechanical properties of binders and concretes (|G∗|, |E∗|, P, IFR, ε6) have been proposed.
... Volatilization happens when light components of asphalt evaporate during mixing the binder with aggregates in a hot drum. On the other hand, when the oxygen in the air reacts with the asphalt binder, oxidation occurs accordingly (Zhang et al. 2011b, Mirwald et al. 2020, Hofer et al. 2022, Mirwald et al. 2022. Current Superpave binder specification usually employs rolling thin-film oven (RTFO) and pressure aging vessel (PAV) aging tests to simulate these two types of aging in the laboratory, respectively. ...
In order to understand the contribution of asphalt components to thermoreversible aging, the extended bending beam rheometer (Ex-BBR) test, SARA fractions separation, and thermal analysis were performed on a series of asphalt binders from different sources. The results indicated that thermoreversible aging is not an inherent characteristic of asphalt, and some binders were not affected by thermoreversible aging. Grade loss caused by thermoreversible aging showed a high correlation with wax content in asphalt but had no apparent relationship with asphaltenes content and colloidal structure index used. Moreover, the thermal analysis results well explained the degree of thermoreversible aging in the asphalt binder. Finally, the endothermic peak and crystallites formed in asphalt binder could have resulted from the long side chains in naphthene aromatic molecules.
... Studies have also shown the presence of such gases in urban spaces near pavement surfaces at low concentrations [14]. Oxidative gases such as ozone and nitrogen oxides are capable of reacting to asphalt binders and can significantly increase its rate of oxidation when used in higher concentrations than naturally occurring near pavement surfaces [15]. Previous studies have shown the significant possibility of accelerating the aging of loose mixtures using such oxidative gases [16]. ...
The simulation of field aging using laboratory techniques is an essential prerequisite in the design of high-quality asphalt mixtures. Previous studies in this area have indicated the potential to use an accelerated method for aging loose mixtures using highly oxidative gases, namely ozone and other reactive oxygen species (ROS). Based on that, the present work was concerned with the investigation of the accelerated aging mechanisms in effect and upscaling of the experimental setup to accommodate larger quantity of mixes. Firstly, the chemical transformations and real time oxidation products formed under an ozone rich environment were compared to an air-based environment for three binders using a Vocus proton transfer reaction (PTR-TOF) time-of-flight mass spectrometer. It was observed that the formation of oxygenated species was significantly higher under an ozone rich environment, indicating higher levels of oxidation. The high-resolution level characterization of the oxidation series of several different molecules provided definitive evidence to support the previous hypothesis of using ozone and ROS to fast-track the oxidation of asphalt mixtures. Following this, an experimental method was developed to age up to nine kilograms (kg) of loose mixtures obtained from a mixing plant using ozone and ROS, in a duration of 22 h. After aging, different properties of the mixtures were compared to analogous mixtures aged as per a benchmark method of loose mixture aging at 95 °C for 5 days in a laboratory oven. The various results obtained from the IDEAL-CT tests, rheological and chemical property analyses of extracted binders clearly illustrated the effectiveness of the oxidative gas based aging method for the accelerated aging of loose mixtures, providing comparable levels of aging as traditional methods. Overall, the work conducted in this study provides comprehensive results regarding critical aspects of the developed method and alludes to the opportunity for wide scale applicability.
In this study, Dynamic Shear Rheometer (DSR) and Fourier Transform Infrared (FTIR) spectroscopy tests were performed on 35-50 and 70-100 penetration-graded asphalts. Both tests were performed on specimens at three different ageing states: unaged, short-term aged using the standard rolling thin film oven (RTFO) device, and long term aged by placing RTFO residue in the pressure aging vessel (PAV) apparatus. The tests were accomplished to quantify how ageing affects the results of both tests, namely the complex shear modulus for the DSR test and the carbonyl, sulfoxide, and ageing indices for the FTIR spectroscopy test. Both sets of measurements confirm that the harder asphalt stays harder than the softer asphalt after undergoing ageing, but the rate of hardness is higher for the softer asphalt. For instance, on average, PAV ageing was found to increase the amplitude of the shear complex modulus, from the unaged state, by 4.3 times and by 6.2 times for the 35-50 and 70-100 asphalts, respectively. It was also found that ageing decreases the phase angle for asphalt and the decrease is more pronounced for the softer asphalt (70-100) than the harder one (35-50). This was attributed to more maltenes content in the softer asphalt that transform into asphaltenes during ageing. Correlation coefficient between FTIR signals from the same samples revealed that FTIR spectroscopy as used in this research has an excellent repeatability. The repeatability was also confirmed using measures of dispersion such as the coefficient of variation, which was found not to exceed the 1.2%. The 35-50 asphalt was found to have more C=O and S=O links than the 70-100 asphalt since it showed more absorbance in the carbonyl and sulfoxide bands. These links are thought to make the asphalt physically harder. An analysis of variance study revealed that ageing is a statistically significant factor as measured using ageing indices calculated from FTIR spectroscopy data with the index AIFTIR being the most sensitive to ageing among all considered indices. Empirical power equations with high coefficient of determination values were established to predict DSR results from FTIR index values, which was possible since both types of measurements show the same trend with ageing.
