Aged Binder Research Articles

Effects of waste engine oil and crumb rubber rejuvenator on the performance of 100% RAP binder

It is frequently essential to add rejuvenators to recycled mixtures comprising reclaimed asphalt pavement (RAP) to increase their performance. In this research, CR was desulfurized using WEO to produce a compound rejuvenator. The asphalt mixes containing 100% RAP binder were modified and rejuvenated with 0%, 3%, 6%, 9%, and 12% WEO-CR. The performance of the HMA samples were assessed using the Marshall stability-flow test, indirect tensile strength (ITS) test, and wheel-tracking device. The results showed that using a 9% WEO-CR rejuvenator restores the physical properties of the aged binder. In addition, the findings revealed that adding 100% RAP binder to the asphalt mixtures increased the tested properties of HMA samples; however, for the long-term performance of HMA, the aged binder may adversely affect the performance of the HMA mixture. Therefore, the addition of the WEO-CR rejuvenator was found to improve the overall performance of the mixture which improved the physical and chemical properties of the asphalt binder and enhanced the mechanical performance of HMA compared to the control mixture.

Chemical and rheological characterisation of in-situ SBS modified asphalt pavement considering the effect of aging gradient

ABSTRACT Clarifying the evolution of in-service asphalt pavement aging is critical to the project-level strategy decision of pavement maintenance. However, the environmental-induced differences in field aging evolution are still unclear. To address this problem, this research aims to first characterise field aging in terms of both chemistry and rheology, and then to investigate the factors controlling the aging gradient of asphalt pavement from both the environment and the mixture itself. Field cores were collected from 14 sections of 10 highways with different in-service times, climatic conditions, and mixture types. Field-aged binder was extracted from wearing course with different depths. Laboratory-aged binder after different cycles of Pressure Aging Vessel (PAV) were also evaluated as a benchmark for field-aged binders. The rheological and chemical properties of both the field-based and lab-based aged binders were measured using dynamic shear rheometer (DSR) and Fourier transform infrared (FTIR) spectrometer, respectively. Moreover, the mortar film thickness index (Tm ) of mixture from 4 sections was characterised through image processing techniques. The changing rate of the pavement in 0–2 cm characterised by carbonyl index was closely correlated with environmental factors. Higher solar radiation, lower annual days >30°C, and thicker mortar film thickness lead to a greater aging gradient.

Blending efficiency of reclaimed asphalt rubber pavement mixture and its correlation with cracking resistance

Despite significant number of studies on recycling of conventional reclaimed asphalt pavement (RAP) mixtures into new asphalt mixture construction, research on recycling reclaimed asphalt rubber pavement (RARP) is still quite limited. The special multiphase system of asphalt rubber (AR) binder may cause a more complicated blending condition during the recycling of RARP due to the existence of rubber particles, and the blending efficiency of RARP and virgin AR mixtures is still unclear. The main objective of this study is to investigate the mobilization tendency of aged AR binder during the recycling of RARP mixture considering both the potential mobilizations of bitumen phase and rubber particles, as well as their correlation with the cracking resistance of the RARP mixture. AR mixtures containing 40% RARP were prepared at three different mixing temperatures and one warm mix case with the inclusion of a foam-based additive. A special gradation design was used to track the mobilization of aged AR binder from RARP to virgin coarse aggregates. Mobilization indexes of bitumen and rubber were established based on Fourier transform infrared spectroscopy and thermal gravimetric analysis tests, while the cracking resistance of the RARP mixture was evaluated by the semi-circular bending test. The mobilization indexes indicated that rubber and bitumen were simultaneously mobilized, and a higher mixing temperature led to stronger mobilization tendencies. In addition, a positive correlation was found between both mobilization indexes and the cracking resistance of the RARP mixture. The foam-based WMA additive markedly improved the blending efficiency but compromised the cracking resistance of the RARP.

Development of a model for the estimation of indirect tensile strength of RAP speciments using machine learning methods

A model for prediction of Indirect Tensile Strength (ITS) of Reclaimed Asphalt Pavement (RAP) specimens is developed in this study using Machine Learning (ML) technique. Principal Component Analysis (PCA) was used to transform grading curves of RAP and obtain reduced amount of data for further analysis. Different Multivariate Polynomial Regression (MPR) models were developed considering properties of RAP (aged binder content and its penetration, grading curves before and after extraction (black and white curves)), manufacturing process (preheating temperature) and properties of testing samples (air void content). Analysis showed that PCA can be adequately used to reduce the number of variables required to describe grading curves (74% of variance was described with first two principal components). Additionally, it was concluded that the simplest (Linear) MPR Model was the most precise overall - coefficient of the determination was 0.59, which can be considered as quite high for such a data set (more than 40 RAPs from different sources were analyzed).

Fatigue Behavior and Healing Properties of Aged Asphalt Binders

This study aims to investigate the fatigue behavior and healing properties of aged asphalt binders. Both 70# and SBS-modified asphalt binders were aged using a rolling thin-film oven test (RTFOT), and their physical properties were analyzed. Their fatigue behavior and healing properties were investigated using a dynamic-shear-rheometer time-sweep test. The influence of healing on fatigue behavior was evaluated in terms of the fatigue life ratio (FLR), and a new index was defined (accumulated dissipation-energy ratio, ADER) to evaluate the healing properties of aged asphalt binders. Aging reduced the penetration and ductility of both the asphalt binders, and large aging degrees increased their softening points. Small aging degrees slightly decreased the softening point of the SBS-modified asphalt binder but increased that of 70# asphalt binder. The former had a better thermal-oxidative aging resistance than the latter. Aging increased the complex shear modulus of the binders, resulting in a longer fatigue life under controlled-stress conditions. The fatigue life of aging asphalt binders obeyed a good (R2>0.90) double-logarithmic linear relationship with the stress level. Healing recovers the asphalt complex shear modulus and extends its fatigue life. Additionally, the FLR and ADER increased with a decrease in aging degree and an increase in the healing period.

UV-Excited Fluorescence as a Basis for the In-Situ Identification of Natural Binders in Historical Painting: A Critical Study on Model Samples

The fluorescence emission by aged organic binders used in painting is a well-known phenomenon. Several literature studies were devoted to its investigation, both on pure binders and on their mixtures with some pigments. Nevertheless, a systematic study about the real possibility of exploiting such a phenomenon for the non-invasive identification of binders in ancient paintings is still lacking. In the present work, a prototype portable fluorimeter was used to analyze a significant number of model painting samples containing different binders (drying oils, egg yolk, milk, animal glue, and gum Arabic) mixed with various pigments having different hues. The model samples were naturally aged in a period ranging from fifteen to one year. The effects on the spectral pattern due to the different binders, the recipes used to prepare them, and the pigments mixed with them were examined. The fluorescence spectra were corrected for the absorption of the emitted radiation due to the pigments. Finally, the corrected spectra were treated by principal component analysis to determine if the possibility of distinguishing at least the most fluorescent and common binders, i.e., drying oils and egg, existed. It was shown that, even if the technique cannot be effectively applied in the case of mixed or superimposed binders, it allows to put forward at least a preliminary hypothesis when pure binders are used.

Performance Evaluation and Characterization of Extracted Recycled Asphalt Binder With Rejuvenators

Rejuvenators are used in the asphalt industry to improve the performance and durability of aged binders and facilitate the use of recycled asphalt materials. The purpose of this study was to evaluate the impact of rejuvenator type and dose on the laboratory performance of asphalt binders. For this study, recycled asphalt pavement (RAP) and extracted RAP binder were obtained from an airfield reconstruction project located in Atlantic City, NJ. One petroleum-based (aromatic extract) and three organic-based (corn oil, tall oil, and modified vegetable oil) rejuvenators were evaluated in this study. Each rejuvenator was used at two different rejuvenator doses (6% and 12% by total RAP binder weight) and was aged at three different levels. Performance grade testing, frequency sweep tests, critical temperature differential (ΔTc ), and Fourier transform infrared spectroscopy (FTIR) tests were conducted. Results showed that the use of rejuvenators lowered the high and low performance grade of extracted RAP binders, in particular organic-based rejuvenators had a greater impact on the performance grade. ΔT c was also improved through the use of rejuvenators. In fact, the extracted RAP binder exceeded the high severity ΔTc threshold (−5°C), whereas the rejuvenated RAP binders improved ΔT c to values greater than the low severity threshold (−2.5°C). Similar findings were observed from the Glover-Rowe parameter as well, in which rejuvenated RAP binders improved the cracking resistance of the extracted RAP binder. When assessing the aging susceptibility, modified vegetable oil and corn oil rejuvenators showed the smallest change in performance between aging levels.

Effect of Chemical Warm Mix Additive on the Properties and Mechanical Performance of Recycled Asphalt Mixtures

Newer technologies such as warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) have gained international approval and have been considered as appropriate solutions that support the sustainability goals of the highway sector. However, both technologies present some shortcomings. The lower mixing and compaction temperatures of WMA reduce the binder aging and the bond between the aggregates and the coating binder, thus resulting in less rutting resistance and higher moisture susceptibility. On the other hand, RAP mixes tend to be stiffer and more brittle than conventional hot mix asphalt (HMA) due to the effect of aged binder. This tends to increase the crack propagation distresses. In an attempt to overcome their individual shortcomings, this study investigated the new concept of a combined WMA-RAP technology. The chemical WMA additive Rediset LQ1102CE was utilized with mixtures incorporating low (15%), medium (25%), and high (45%) RAP contents. Dynamic modulus (DM) and flow number (FN) tests were conducted to investigate the effect of Rediset on the behavior of RAP mixtures. The dynamic modulus |E*| mastercurves were developed using the sigmoidal model and Franken model was used to fit the accumulated permanent deformation curve. The results of this study showed that Rediset addition improved the cracking resistance of RAP mixtures. However, the rutting resistance was reduced but kept within the acceptable range except for mixtures containing low RAP content.

Bitumen as a Binder in Flexible Pavement Through New Additives and in Situ Polymerization

Bitumen is a black non-crystalline thermoplastic viscous substance used for millennia as an adhesive, sealant and water proofing agent. Bitumen is modified with a number of additives and broadly classified polymeric and other chemical modifiers. Heavy loads, greater tyre pressure and increasing traffic are stressing roadways, triggering early breakdowns. Severe climate and an increasing focus on safety have motivated research into roadway paving materials. To solve these issues highway engineers and researchers have sorted to bespoke pavement materials. It has been shown that polymer modifiers may enhance the binder's ageing properties, delaying the detrimental effects of the process, which results in an improved pavement. Our findings suggest that waste PET- derived (polyethylene terephthalate) compounds, antistripping characteristics are on par with those of commercially available antistripping chemicals. A huge environmental pollution issue may be alleviated as a result of the latest research into the recycling of waste PET (polyethylene terephthalate) in bituminous concrete.

Research on the Ability of Bio-rejuvenators to Disaggregate Oxidized Asphaltene Nanoclusters in Aged Asphalt.

A real rejuvenator must have the ability to disaggregate oxidized asphaltene nanoclusters. However, few studies pay attention to the topic, and there is a lack of comparison of the disaggregation ability of different rejuvenators. Thus, the disaggregation ability and regeneration mechanism of three bio-rejuvenators (waste cooking oil (WCO), waste wood oil (WWO), and straw liquefied residue oil (SLRO)) on oxidized asphaltene nanoclusters were studied in this paper. Laboratory tests and molecular dynamics (MD) simulation were used to compare the effectiveness of the three bio-rejuvenators and reveal its corresponding mechanism. It is found that these bio-rejuvenators have a softening effect on aged asphalt binder, but not all of them can disaggregate oxidized asphaltene nanoclusters. The introduction of WWO and WCO can effectively disturb the nanoclusters caused by the increase of polar functional groups during the oxidation process. The effect of WWO is more significant, but neither of them can restore the asphaltene dispersion to the virgin asphalt binder. SLRO has an adverse effect on the disaggregation of oxidized asphaltene nanoclusters. WCO, WWO, and SLRO showed different disaggregation mechanisms, including ″pull-out, intercalation, and compression″, respectively. WCO and WWO can increase the activation energy reduced by aging in a short aging time, and SLRO makes the activation energy lower. Such findings can help enterprises screen more reasonable rejuvenators to facilitate the recycling of reclaimed asphalt pavement (RAP) materials and promote the sustainable development of the construction industry.

Evaluation of waste engine oil rejuvenation for highly short term aged asphalt binder

Evaluation of waste engine oil rejuvenation for highly short term aged asphalt binder

Reclaimed Asphalt Pavement Binder Extraction and Recovery Evaluation and Their Effects on the Recycling Agent Assessment

The use of reclaimed asphalt pavement (RAP) has proved to be an advantageous alternative for the restoration and construction of new roads, with regard to the economical and environmental performance of the recycled material. However, one of the concerns about the use of RAP in the production of new asphalt mixtures is related to its inherent variability, manifested mainly in the asphalt binder. Some procedures to recover the aged binder are commonly used, such as extraction with solvents and recovery applying distillation techniques. These methods might change the intrinsic properties of the asphalt binder (e.g., rheological and chemical characteristics), which may lead to flaws in the dose of the recycling agent. The present study evaluated the variability of the techniques of asphalt binder extraction-recovery from a RAP source, and its effects on the final assessment of binder blend between RAP binder and a softer binder for recycled hot mix asphalt. The results show that automated extraction provided statistically satisfactory values for determination of the RAP binder content. The recovery method conditions, however, were not efficient with regard to solvent removal for 40% of the analyzed RAP samples. Pearson’s coefficients indicated a weak correlation between RAP binder aging indices and its rheological behavior, probably because of the presence of solvent. Tetrachlorethylene (TCE) spectrum band at wavelengths of 903 to 915 cm−1 tends to affect binder stiffness more than wavelengths of 771 to 783 cm−1, underestimating high temperature continuous performance grade ([Formula: see text]) and consequently the binder blend results.

Changes in the nanoscale asphaltene particles and relaxation spectra of asphalt binders during aging and rejuvenation

Asphalt binder is a widely used engineering material. It is essentially a nanomaterial with colloidal particles suspended in an oily medium. As asphalt binder ages, the colloidal particles are subject to fundamental physicochemical changes such as agglomeration, which is translated into dramatic engineering property changes of the asphalt binder. In engineering practices, organic rejuvenators are often added to the aged asphalt binder, with the hope of breaking down the nanoparticles and restoring its original engineering properties. However, how the nanoparticles evolve during the aging and rejuvenation of asphalt binder remains hypothetical. This study revealed the fundamental changes of the colloidal particles in asphalt binder during aging and rejuvenation. Moreover, changes in the morphology of colloidal particles are connected to the relaxation spectrum of the asphalt binder. As a result, practitioners do not have to rely on complicated methods and equipment to observe asphalt binders at the microscopic level. Instead, they can employ commonly used engineering tests with a dynamic shear rheometer (DSR) to decipher what occurs at the nanoscale during asphalt binder aging and rejuvenation. This would greatly assist practitioners in material selection and design.

Continuous spectrum approach to evaluate the effect of binder modification and aging

ABSTRACT The present work proposes a novel mathematical approach to directly obtain the continuous spectrum of asphalt binder from frequency domain data. Using the asymmetric sigmoidal function to obtain continuous spectrum offers advantages of flexibility and improvement in describing the spectrum well. Initially, complex modulus, storage modulus, and storage compliance master curves were constructed using experimental data. In the next stage, the continuous relaxation and retardation spectrum were constructed directly from the storage modulus and storage compliance master curves, respectively. Statistical indicators like mean, variance, and skewness were used to describe the shape of these finalised continuous spectra. To check the efficacy of the proposed approach, asphalt binders altered with modifiers (at different dosages) were aged under laboratory conditions. Critical evaluation of the results indicated that the underlying changes could be captured using the continuous spectra (which were not obvious with respective master curves or black space diagrams). Continuous spectra of binders constructed (with different dosages of modifier and under different aging conditions) were compared using the statistical indicators. Thus, the spectral shape parameters could capture the effect of aging and modifier dosage. These changes can be attributed to molecular changes, chemical reactions occurring with the addition of modifiers and aging.

Influence of selected reactive oxygen species on the long-term aging of bitumen

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 molecular oxygen. Crucial chemical components like reactive oxygen species (ROS), e.g. nitrogen oxides (NOx) or ozone (O3), are completely neglected. This study focusses particularly on the reactivity of individual ROS, such as nitrogen monoxide (NO), nitrogen dioxide (NO2) and O3, in regards to the long-term aging (LTA) of three unmodified bitumen. For LTA an adapted version of the Viennese Binder Aging method was used and the aged bitumen samples were analyzed with the dynamic shear rheometer and Fourier-Transform-Infrared spectroscopy, respectively. The results show that NO as a single component does not induce significant aging, whereas NO2 leads to severe bitumen deterioration, which is even more accelerated when a second oxygen source is present. In comparison, the reactivity of O3 is rather mild and it did not cause additional aging for two of the investigated binders. This study provides evidence, that ROS play a crucial role in bitumen aging and should thus not be neglected when addressing realistic aging conditions in the laboratory.

Asphalt Binder "Skincare"? Aging Evaluation of an Asphalt Binder Modified by Nano-TiO2.

Aging by oxidation of asphalt roadway material promotes changes in its physical, chemical, and rheological properties, affecting its hardening and accelerating the degradation of its corresponding asphalt mixture. Titanium dioxide (TiO2) has been applied in engineering investigations to promote anti-aging and photocatalytic properties. In this study, a commercial binder was modified with nano-TiO2 (using contents of 0.1, 0.25, 0.5, 1, 2, 3, and 6%). It was evaluated by physicochemical and rheological tests (penetration, softening point, mass loss, dynamic viscosity, rheology, and Fourier transform infrared spectroscopy—FTIR) before and after aging by rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV). The results indicated that incorporating nano-TiO2 mitigates binder aging, pointing out 0.25% as an optimum modification content for the investigated asphalt binder.

The Combined Effect of Ultraviolet Irradiation and Temperature on Hot Mix Asphalt Mixture Aging

Reliable accelerated simulation of asphalt aging is of significant interest to asphalt researchers and pavement practitioners alike. However, current laboratory aging protocols are either based on binder aging rather than mixture aging or use dry ovens to heat asphalt mixtures, omitting the important effects of UV radiation. Binder aging cannot take into account the interactions between the binder and aggregate phases during aging, while the omission of UV radiation ignores an important catalyst in the aging process. In this study, a comparison of the effect of conventional thermal oven aging to the combined effect of heat and ultraviolet irradiation on the resilient modulus and surface texture of dense-graded asphalt field cores and gyratory-compacted samples was undertaken. Significantly higher rates of modulus increase with aging time were measured for the samples aged by both heat and ultraviolet irradiation. The gyratory-compacted samples showed more realistic results in terms of surface texture compared to the field cores, likely due to the extraction of field cores from a small area of pavement that was subjected to concentrated pneumatic tyre rolling, which was not representative of typical asphalt construction. It was concluded that using aging indices, calculated as the ratio of the aged value to the initial value, is recommended for asphalt aging investigations. The findings of this study highlight the significance and importance of developing aging protocols that combine heat, ultraviolet irradiation, and any other environmental factors that may affect the aging behaviour of asphalt mixtures.

Impacts of Field and Laboratory Long-Term Aging on Asphalt Binders

Asphalt binder aging accelerates cracking of flexible pavement. Quantifying the extent of binder aging allows the formulation and selection of appropriate binders for flexible pavement applications. Asphalt binder aging depends on climatic exposure, asphalt concrete field-surface density, and binder chemistry. The aim of this work was to select a laboratory-aging protocol to represent realistic field aging in Illinois. Binders were extracted from field cores aged from eight to 31 years. Extracted binders were tested for rheology and chemical characteristics. Small- and large-strain rheological parameters were determined. In addition, chemical functional groups and molecular weight distribution of extracted binders were evaluated. Effects of aging across pavement depth were also investigated. Double pressure-aging vessel (PAV) was identified as a suitable laboratory long-term aging protocol to represent eight to 12 years of aging for flexible pavements in Illinois. Thresholds were proposed for selected small- and large-strain rheological parameters representing realistic field aging. These thresholds may be used for binder selection and procurement to ensure the binder’s long-term performance. Furthermore, chemical analysis on extracted binders showed that only specific carbonyl functional groups are affected by field aging.

Thermal, chemical and rheological properties of asphalt binders extracted from field cores

The intermediate-temperature performance of extracted asphalt binders (EABs) is altered when recycled asphalt shingles (RAS) and/or reclaimed asphalt pavement (RAP) are included in asphalt mixes. This happened as a result of the RAP’s aged asphalt binder and the RAS’s oxidized air-blown asphalt. Thus, the rheological properties of EABs from field cores were examined at intermediate temperatures. The fatigue life and the Superpave fatigue cracking parameter were among the rheological properties. Thermogravimetric analysis and Fourier transform infrared were used to analyze EABs’ thermal and chemical characteristics, respectively. The relationships between EABs’ fatigue cracking resistance, thermal, and chemical characteristics were scrutinized. Ages of mixes, percentages of RAP and/or RAS, and intermediate performance grade (PG) temperatures of virgin asphalt binders (VABs) controlled the resistance of EABs to fatigue cracking. Considering VABs with the same intermediate PG temperatures, EABs from older mixes with higher RAS percentages had higher resistance to fatigue cracking than those from younger mixes with lower RAP percentages. When RAP percentages in asphalt mixes were increased, EABs’ resistance to fatigue cracking deteriorated. Thermal and chemical analyses along with rheological characteristics are suggested as indicators of EABs’ intermediate-temperature performance.

Surface Characteristics of Ageing Asphalt Binder Coupling Thermal Oxidation and Ultraviolet Radiation

In this study, styrene-butadiene-styrene (SBS) modified asphalt binder was aged by thermal oxidation coupled with ultraviolet (UV) radiation. Fluorescence microscopy (FM), scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) detector, surface free energy, optical technology, Fourier transform infrared spectroscopy, and dynamic shear rheometer were used to explore the surface characteristics and trace the chemo-rheological evolution of the asphalt binder at various durations of aging. Both FM and SEM could observe two phases of degradation of the polymer under thermo-oxidation. The surface of UV-aged asphalt binder produced more cracks, observed by FM and SEM, and bulged along these cracks and some fragmented blocks appeared. EDX results indicated that the oxygen content of the surface of the asphalt binder increased with increasing aging duration, leading to more oxygen-containing compounds, more carbonyl and sulfoxide groups, increasing polarity, and decreasing contact angle of water droplets on the surface of the asphalt binder. Coupled aging increased the reflectance in all regions from 200 nm to 2,500 nm, while thermo-oxidative aging alone increased the reflectance from 200 to 400 nm and produced the opposite result in the other region. With increased aging duration, UV-aged asphalt binder becomes brighter and thermo-oxidative aged asphalt binder becomes darker. The asphalt binder samples did not discolor much with varying aging duration, and the color difference was more similar than opposite. The results of testing chemo-rheological properties indicated that the addition of UV radiation significantly increased the stiffness and elasticity and produced more obvious effects on the surface characteristics of variously aged binders.