Article

Effect of long-term ageing on the rheological properties of rejuvenated asphalt binder

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Abstract

Recycled asphalt products are increasingly being used in asphalt concrete pavements to improve pavement sustainability. Asphalt recycling, while it is undoubtedly an environmentally sustainable practice, includes asphalt binder that is already oxidised. Aged binder is highly brittle and becomes a driving factor for cracking related distresses. As a result, use of recycled materials can have a significant negative impact on pavement performance, specifically when used in increased amounts and cold climatic conditions. In order to improve the performance of asphalt concrete mixtures with recycled materials, rheological properties are changed by adding rejuvenators. In asphalt industry, rejuvenators are either used at an initial virgin state of the binder to reduce mix ageing or blended at a later stage in recycled materials to improve the properties of aged mix. The current study focuses on evaluating the performance of asphalt mixes prepared by blending rejuvenators in already aged binders. Virgin PG 64-22 binder was aged using RTFO and PAV and further mixed with three different kinds of rejuvenators namely Hydrolene 90T, Kendex@ME, and Hydrogreen S at 3%, 6% and 9% by weight of the total binder. To study the behaviour of rejuvenated asphalt binder samples over a long period of time, mixed asphalt samples were then aged for 5, 10, 15, 20, 40 and 60 h in the PAV. Frequency sweep tests were conducted to characterise binder rheology, and parameters such as Glower-Rowe, crossover frequency, and Superpave rutting parameter were calculated. A comparative analysis was carried out to determine the impact of increased ageing and rejuvenator addition in varying amounts on the performance of asphalt mixes. A significant correlation was found out between the types of rejuvenator used in different dosages and the level of ageing in the asphalt binder.

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... sulphur (0 to 9 wt.%), nitrogen (0 to 2 wt.%), and oxygen (0 to 2 wt.%) [1,3,5]. Thus, bitumen consists of many diverse molecular groups, varying in their molecular weights, polarities, and functionalities, making a complete chemical characterisation difficult or nearly impossible [3,6,7]. To determine the complex bitumen structure, the components are generally grouped into four major substance classes called SARA fractions (saturates, aromatics, resins, asphaltenes). ...
... [1]. The SARA classification is a polarity-based separation relying on different solubilities (asphaltenes) and interactions of the different polarities between the phases and the individual fractions of the sample (saturates, aromatics, resins) [1,3,[5][6][7]. ...
Article
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Bitumen is a complex mixture consisting of different hydrocarbons, which can be categorised into substance classes called SARA (saturates, aromatics, resins and asphaltenes) fractions. The saturates, aromatics and resins are further referred to as maltenes or maltene phase. To determine the SARA fractions the asphaltenes were separated from the maltenes in a first step. A standard method to further separate the maltenes is column chromatography (CC). Since column chromatography is a time-consuming and solvent-intensive process, an alternative method for separating maltenes using solid-phase extraction (SPE) was investigated. A total of nine bitumen samples of the same type in different ageing states but from different manufacturers were separated with both methods to determine the mass percentages of the fractions for investigating their comparability. The results show that both methods led to different mass percentages of the fractions. However, with the SPE, separating smaller amounts of maltenes is possible while saving a large amount of material, costs, and workload. Linear regression analyses between the colloidal indices with conventional and rheological parameters revealed that the fractions obtained from SPE led to higher coefficients of determination of the linear regression model. The obtained fractions were further structurally compared with FTIR spectroscopy, whereby the spectra of the SPE fractions and the CC fractions did not show any significant differences. The overall consideration of the results concludes that the SPE can replace the CC.
... Thus, due to the numerous sources from which these materials can be obtained, their chemical composition and physical properties vary greatly, which can have a diverse impact on the rheological and performance-related properties of the final recycled mixtures. For instance, several works have reported a higher efficiency from vegetable oils to reduce the stiffness of the aged RAP binder when compared to petroleum-based rejuvenators [7][8][9][10][11][12]. In addition, researchers have reported better fatigue performance of the aged binder by the addition of vegetable oils, compared to petroleum-based products [7], and that vegetable-based rejuvenators usually require lower doses than petroleum-based materials to provide a similar reduction in the stiffness [7,12]. ...
... In addition, researchers have reported better fatigue performance of the aged binder by the addition of vegetable oils, compared to petroleum-based products [7], and that vegetable-based rejuvenators usually require lower doses than petroleum-based materials to provide a similar reduction in the stiffness [7,12]. Despite the positive rejuvenation effectiveness shown by the addition of vegetable oils, some studies have reported higher long-term ageing susceptibility in the recycled binder blends containing these materials, due to their pre-existing high oxygen content [10,11,13]. Still, the recycled binder blends containing these materials have shown an improved mechanical behaviour as compared to recycled blends with no rejuvenators, as expected. ...
Article
Rejuvenators are agents added during the production of hot mix asphalts with high contents of reclaimed asphalt pavement (RAP) to restore some properties of the aged RAP binder. These materials can be obtained from numerous sources; hence, their chemical composition and physical properties vary greatly, which can have an impact on the final mixtures’ properties. This work assesses key chemical properties of crude palm oil and two of its solid by-products to understand their rejuvenation effect on a blend of a virgin and an aged RAP asphalt binder. The evaluation included thermogravimetry analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and chromatography analysis. Besides, surface free energy measurements (SFE) on the recycled binder blends (i.e., virgin asphalt binder, RAP asphalt binder and rejuvenator) and of two aggregate sources were used to evaluate the impact of the palm oils in the adhesive bonds’ quality and moisture sensitivity of the recycled binder blends-aggregates systems. Results indicate that the palm oil materials have good thermal stability and contain several large molecular size (LMS) compounds that contribute to the rejuvenation effect. Besides, recycled binder blends produced with the palm oil materials developed strong adhesive bonds in dry and wet conditions. Overall, results highlight the potential of palm oil and its solid by-products as rejuvenators for high RAP content asphalt mixtures.
... Maximizing the recycling ratio of RAP is appreciated, but it would deteriorate the mechanical performance of asphalt pavement, particularly the resistance to cracking and moisture damage [3][4][5]. The aging-induced increase in stiffness contributes a lot to the insufficient low-temperature, fatigue, and adhesion performance of RAP binder due to the evaporation and conversion from lightweight molecules (saturate and aromatic) to resin and asphaltene fractions with large polarity and heavy molecular weight [6,7]. ...
Article
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This study investigates the impacts of rejuvenator type/dosage and the aging degree of bitumen on the chemical and rheological properties of rejuvenated bitumen, and propose critical chemo-rheological indicators for evaluating rejuvenation efficiency. Moreover, the potential connections between essential chemical and rheological indices of rejuvenator-aged bitumen blends are explored. Results indicate that chemical indices show linear relationships with rejuvenator dosage and vary depending on the rejuvenator type and aging level of bitumen. All rejuvenators can regenerate certain rheological parameters of aged bitumen to varying degrees, but cannot restore the crossover modulus (Gc). Various rheological indices exhibit different correlations with rejuvenator dosage and sensitivity degrees to the discrepancy in rejuvenator type and aging degree of bitumen. Critical chemical and rheological indicators are proposed based on their sensitivity levels to influence factors, with the aromaticity index (AI), carbonyl index (CI), and sulfoxide index (SI) as effective chemical indices and the complex modulus (G*), crossover frequency (fc), and high-temperature master curve area (AMH) as critical rheological indices for rejuvenation efficiency evaluation. The study finds that the magnitude of rejuvenation efficiency for four rejuvenators is Bio-oil > Engine-oil > Naphthenic-oil > Aromatic-oil, and the linear correlations between the critical chemical and rheological indices, together with their rejuvenation percentages, are significantly affected by the rejuvenator type and aging level of bitumen.
... Aged asphalt can become highly brittle, resulting in reduced penetration and ductility, increased stiffness, and the promotion of viscoelastic property changes during service life, which can cause pavement distress [10][11][12]. Also, after ageing, asphalt rheological parameters such as complex modulus (G*) and creep recovery rate increase, while the non-recoverable creep compliance and phase angle decrease (δ) [13,14]. ...
Article
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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.
... The aging and rejuvenation processes not only affects the shape of the master curves, that is aging decrease the slope of the master curves and rejuvenation increase the slope, but also influences the time-temperature superposition shift factors. Dhasmana et al. [24] found that the aging susceptibility of the recycled binder increased with the increase of rejuvenation percentages. Therefore, understanding the rheological properties of the recycled binder not only requires to consider the dosage effect, but also the aging effect. ...
Article
The recycling of asphalt concrete pavement not only requires to restore the original properties of reclaimed asphalt pavement (RAP) materials, but also consider the properties due to secondary aging simultaneously. Therefore, in order to design recycled asphalt mixtures for construction of sustainable pavement with good performances, it is very important to understand and predicted the viscoelastic behaviors of rejuvenated binders. However, limited studies on the effect of rejuvenator dosage and secondary aging in the rheological behavior of rejuvenated binder are reported. In this study, a novel approach was used to construct the dosage-aging master curves to describe and predict the viscoelastic behaviors of rejuvenated binders considering the effect of reju-venator dosage, aging time and aging temperature. Experimental data of complex modulus and phase angle were used to validate the proposed approach. Rejuvenated binders with rejuvenators at four dosages were aged at various aging temperature and times. Complex shear modulus and phase angle isotherms of each rejuvenated binders for a range of frequencies were constructed simply starting from time-temperature superposed master curves. Two rotations and horizontal shifts procedure were applied to the master curves. Finally, the dosage-aging complex modulus and phase angle master curves were proposed. It was found the twice rotation of master curves of rejuvenated binder process was used to change the shapes of the master curves due to reju-venator dosage and aging based on the dosage-aging rotation factor. The twice horizontally shifted process was used to shift the master curves after twice rotation to the master curves at the reference dosage, aging time and temperature based on the dosage-aging horizontal shift factor. The twice rotation and horizontal shift processes are suitable for rejuvenated binder for using other dosage under other aging conditions, the predicted dosage-aging master curves can be obtained and is good accordance with the measured master curve. Therefore, the complex shear modulus and phase angle values of rejuvenated binders over a range of dosages at any aging time and temperature can be predicted without actual testing.
... Also, RTFOT keeps the modifier agitating during simulation, which avoids the segregation of modifier and asphalt binder. Compared with short-term aging, the aging during the service period is called long-term aging (Dhasmana et al., 2019). Pressurized aging vessel (PAV) is a widely-used and standard method for examining the effects of long-term aging (ASTM, 2013). ...
... Also, RTFOT keeps the modifier agitating during simulation, which avoids the segregation of modifier and asphalt binder. Compared with short-term aging, the aging during the service period is called long-term aging (Dhasmana et al., 2019). Pressurized aging vessel (PAV) is a widely-used and standard method for examining the effects of long-term aging (ASTM, 2013). ...
Article
Full-text available
This work investigated the aging effects on the rheological properties of high viscosity modified asphalt (HVMA). First, the high- and low-temperature rheological properties were measured by a dynamic shear rheometer and a bending beam rheometer, respectively. The aging mechanism was then tested using an Fourier transform infrared spectroscopy and a scanning electron microscope. Besides, a study was performed to compare the aging effects on the rheological properties of HVMA, crumb rubber modified asphalt (CRMA), and neat asphalt (SK-90). The experimental results showed that the effects of the long-term aging on HVMA exceeded those of short-term aging. The complex shear modulus of the HVMA was improved by the aging in the whole frequency range. The complex shear modulus of the HVMA after the long-term aging was larger than after the short-term aging. Thus, the aging improved the high-temperature viscoelastic performance of HVMA. With a decrease in temperature from -12 °C to -24 °C, the low-temperature viscoelastic performance of HVMA decreased since its stiffness modulus and low continuous grading temperature increase. Both of the short- and long-term aging of HVMA were caused by an oxidation reaction, while modifier swelling also happened after long-term aging. Compared to CRMA and SK-90, aging had a limited influence on the high- and low-temperature rheological properties of HVMA.
... However, another rejuvenated binder showed opposite influence trend. Dhasmana et al. [16] evaluated the performance of RAP binders with blended rejuvenators, and found that the aging susceptibility of rejuvenated binders increased with the increasing rejuvenator dosage. Rajib et al. [4] found that the rejuvenators exhibited the significant improvement in restoring the rheological properties of RAP binder, but not that good in terms of durability. ...
Article
Rejuvenator is commonly used in reclaimed asphalt pavement (RAP) to improve the properties of the blended binder. However, the rejuvenated binder would experience aging again and cause the rejuvenated asphalt mixture prone to durability issues. This study focused on evaluating the impact of oxidative aging on the chemical and rheological properties of rejuvenated binder (RB) by means of Fourier Transform Infrared Spectroscopy and Dynamic Shear Rheometer. First, the aged binders blended with waste engine oil used as the rejuvenator at 0%, 3%, 6%, and 9% by total weight of binder. Then, laboratory oven aging procedures were employed to the RB binders at different aging temperatures and periods. Carbonyl content were determined to understand the effect of temperature and duration on the oxidative aging mechanisms of RB binders. Each RB binder had its specific fast and constant oxidative rates. With the increase of rejuvenator dosage, the temperature sensitivity of RB binders decreased in the constant rate stage and increased in the fast rate stage. The high-temperature true performance grade (HTPG) of RB binders increased with the aging time and temperature, and the effect of rejuvenator dosage on HTPG decreased gradually with aging duration. Based on the master curves of complex modulus and phase angle, the aging time and aging temperature increased the viscoelastic behavior of RB binders, and rejuvenator reduced the viscoelastic behavior, but the effect of rejuvenator lowered gradually during oxidative aging. The crossover frequency, rheological index and Cole-Cole plot demonstrated the aging decreased the viscous components and increased the elastic behavior of the RB binders. As the rejuvenator dosage increased, the viscous component of the aged RB binders increased, and the elastic behavior decreased as well as more transition behavior from viscous to elastic.
... In addition, bio-oils can be improved in blending efficiency with asphalt by reducing its viscosity by the use of plasticizers (Al-Sabaeei et al., 2021;Jiang et al., 2018). Hydrogreen S is commercially available as an alternative to aromatic extracts (Dhasmana et al., 2021). RAPIOL is another commercially available additive consisting of aromatics, resins, and saturates. ...
Article
Full-text available
Prompting high content of reclaimed asphalt pavement (RAP) to be used in road building and maintenance has drawn great attention. The application of rejuvenators is an efficient way to ensure the performance of recycled asphalt mixtures. However, as various types of rejuvenators emerging, limited understanding about rejuvenation poses challenges to put effective ones into use. For precisely evaluating the performance of rejuvenators, plenty of studies were conducted to ascertain the fundamental mechanism of rejuvenating from the microscopic view. This paper provides an overview of studies focusing on the change inside asphalt after adding rejuvenators. Chemical compositions of rejuvenators were collected as basic information. Both laboratorial experiments and molecular dynamic simulations were investigated to not only compare the effectiveness of several rejuvenators but also explain the rejuvenating mechanism. Finally, functional groups of rejuvenator structures were comprehensively examined to provide global understanding about how chemical compositions influence the efficacy of rejuvenators. This review highlights that the essential capacity of a true rejuvenator is to disturb asphaltene agglomerations. Besides, the molecular structures of rejuvenators will not only affect their deagglomerating abilities but also the performances of diffusion and durability. It has been found that gel-permeation chromatography (GPC) analysis is effective in evaluating the performance of rejuvenators, while Fourier transform infrared spectroscopy (FT-IR) and SARA (saturates, aromatics, resins and asphaltenes) analysis are only suitable for assessing asphalt oxidization. In addition, comparing some tests can only detect changes, molecular dynamic simulation can reveal the mechanism both of data and vision. The results of this work can provide comprehensive knowledge for the evaluation and development of rejuvenators.
... To solve this, the rejuvenation of asphalt binders has received increasing attention in recent years, with many studies focused on evaluating suitable techniques to achieve this target [8][9][10]. As a result, many commercial products have been developed that have achieved a great deal of success [11]. Nevertheless, these rejuvenation substances are currently expensive and may be difficult to obtain, especially in developing countries; thus, there is increasing interest in finding a cheap but effective rejuvenating agent [12,13]. ...
Article
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Resource conservation and environmental protection are arguably the primary aims of practically all researchers associated with engineering projects. With this in mind, the present study aims to experimentally and statistically investigate the role of waste engine oil (WEO) as a suitable asphalt rejuvenating agent. For this purpose, three aged asphalt binders were extracted from different reclaimed pavement samples. The test samples were composed of virgin, aged, and WEO-blended binders where dosages of 3, 6, and 9% (by weight of binder) were added after the filtration and heating process. These samples were subjected to various testing methods, including physical, chemical, rheological, and Fourier-transform infrared spectroscopy (FTIR) tests. The addition of WEO was found to efficiently restore the asphalt’s desirable properties depleted by aging, with 9% found to be the optimum content. In addition, each one percent of added WEO restored the values of the asphaltenes, aromatics, resins, and saturates by 4.3, 1.36, 1.31, and 0.5%, respectively. The FTIR analysis revealed a reduction in carbonyl and sulfoxide indices’ values when using WEO agent. This change in chemical composition amendment was reflected by enhanced rheological properties, as the complex shear modulus returned to 84% of its original value when the WEO content reached 9%. Furthermore, the internal colloidal index was also computed and statistically correlated with the rheological parameters. Finally, this study developed models correlating the effect of the rejuvenation process on fatigue and rutting performance.
... The RAP mixtures rejuvenated by WCO (organic) accelerated ageing more than Rapiol and Cyclogen (oil based). Dhasmana et al. [100] assessed the performance of asphalt binder blends with aged asphalt and rejuvenators. Virgin PG 64-22 binder was aged using RTFO and PAV and was further mixed with three rejuvenators: Hydrolene 90T (R1), Kendex@ME (R2), and Hydrogreen S (R3) at 3%, 6%, and 9% by weight of the total binder. ...
Article
Full-text available
Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in hot mix asphalt (HMA) pavements to enhance pavement sustainability. The use of aged asphalt in RAP, which is highly oxidised and has lost its properties due to exposure to traffic loads and climatic conditions throughout its lifespan, can cause asphalt mixtures to stiffen and embrittle, thus negatively affecting the behaviour of asphalt mixtures. This issue may be resolved by including rejuvenating agents that can restore both physical and rheological properties of aged asphalt by increasing maltene fractions and decreasing asphaltene. However, the high restoration capacity of any kind of rejuvenating agent does not assure the durability of restored aged asphalt. This study explored the performance and durability of rejuvenated asphalt mixtures embedded with several types of rejuvenators identified from the extensive literature review. The study serves as a significant reference to predict future challenges in rejuvenating aged asphalt.
... The results of this study are in line with previous investigations on nonmodified RAB blends. Previous studies indicated that both ageing and an increase in recycling rate decreased the crossover frequency(Gómez-Meijide et al., 2018), whereas the opposite effect happened with the addition of rejuvenators(Dhasmana et al., 2019). ...
Article
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Incorporating reclaimed asphalt (RA) in surface layer mixtures is still limited due to performance concerns, and it becomes even more challenging when combining aged polymer-modified bitumen (PMB) with virgin PMB. This study aims to evaluate, from a binder perspective, the feasibility of incorporating reclaimed polymer-modified binder (RPMB) in new surface layer mixtures. To address this challenge, blends of RPMB and virgin PMB were investigated at three replacement rates (20%, 40% and 60%) with and without a tall oil-based rejuvenator. First, the viscoelastic behaviour of the blends was assessed using a dynamic shear rheometer. Moreover, physicochemical changes were tracked using infrared spectroscopy and fluorescence microscopy. The experimental investigation revealed that, due to polymer degradation of the RMPB, only the blends with 20% RMPB exhibited polymer activity. Finally, the use of the rejuvenator compensated for the rheological properties of the aged RPMB and reduced the susceptibility to non-load-associated cracking.
Article
This study evaluated the aging resistance of asphalt mixtures containing various percentages of reclaimed asphalt pavement (RAP) and rejuvenators after short-term (ST) and long-term (LT) aging. To this end, rubberized waste oils (i.e., waste engine and cooking oils) and pure waste oils were used as rejuvenators in asphalt mixtures including different percentages of RAP materials (i.e., 25%, 50%, and 75% by the weight of mixtures). The rejuvenated RAP mixtures underwent ST and LT aging processes separately. Afterward, the dynamic modulus (DM) test, semicircular bending (SCB) test, and moisture sensitivity (MS) test were conducted to evaluate the mechanical properties of different samples. The outcome results showed that before exposing samples to LT aging, the efficiency of all rejuvenated mixtures’ stiffness and also their cracking resistance were close together. After applying LT aging, the mechanical properties of RAP mixtures including rubberized rejuvenators were much better than pure rejuvenators. This issue indicated that rubberized rejuvenators and, consequently, RAP mixtures containing these rejuvenators, are more aging resistant and have a superior LT performance. Additionally, there was no concern observed regarding the moisture susceptibility of rejuvenated RAP mixtures before and after applying the aging process.
Article
Reusing bitumen and asphalt is an approved practice, but the efficiency highly depends on adding virgin bitumen. Rejuvenators have gained increased importance in reaching independence from crude oil and exploring possibilities of multiple reuses. However, rejuvenators are often tested and evaluated exclusively on artificially aged bitumen samples. Therefore, the main objective of this publication is to investigate the rejuvenation of Reclaimed Asphalt Pavement (RAP) binders using three RAP samples and three rejuvenators. Rheological material properties, chemical effects of rejuvenation processes and the ageing behaviour after rejuvenation are examined. The results are further compared to rejuvenated artificially aged bitumen. It has been found that the rejuvenators reveal varying degrees of impact on RAP binders and artificially aged bitumen samples, as artificially aged bitumen samples tend to show fewer ageing changes than the RAP binders. Moreover, also the ageing behaviour of the pure rejuvenator influences the success of reuse.
Article
Single reuse of asphalt is an approved practice, but its success highly depends on restoring the properties of the aged binder. Rejuvenators have become increasingly important for softening the binder because they make it possible to increase the amount of reclaimed asphalt pavement (RAP) while reducing the dependence on virgin bitumen. The vital questions to be investigated are how the rejuvenators affect the ageing properties of bitumen and if rejuvenators offer the possibility of cyclic bitumen reuse. The main objective of this publication is to present the current state of the art regarding the effects of rejuvenators on bitumen ageing. The results of laboratory life cycle simulations indicate that repetitive ageing and rejuvenation processes are possible, but reuse mainly depends on the rejuvenator type and its interaction with the respective bitumen sample. There are rejuvenators that have good rejuvenating properties but accelerate subsequent ageing, which is essential to consider when evaluating a rejuvenator. Bitumen rejuvenated with petroleum-based products, such as aromatic extracts, performs slightly better after subsequent ageing than when rejuvenated with bio-based products. As there are a limited number of studies simulating cyclic bitumen reuse, more studies are necessary to evaluate the general limits of bitumen reuse.
Article
The high-quality regeneration of aged SBS modified asphalt could promote to achieve the objective of low-carbon development. In this study, to reconstruct the structure of aged SBS, two kinds of reactive flexible rejuvenator (RFRs) named T-PEG and T-HTPB were synthesized from 2,4-toluylene di-isocyanate, polyethylene glycol and hydroxyl terminated polybutadiene. The ordinary regenerated SBS modified asphalt (RSBSMA) and reactive RSBSMA were prepared by using aromatic hydrocarbon oil (AO) and (T-PEG/T-HTPB + AO) respectively. Afterwards, the chemical structures and physio-rheological performance of RSBSMAs after short-term and long-term thermal-oxidative aging were explored. The results of Fourier transform infrared spectra showed that the butadiene and ether bond indices of reactive RSBSMA decreased significantly after aging, indicating that T-HTPB regenerated SBS mainly suffered the breaking of carbon-carbon double bonds, while the degradation of segments with ether bonds appeared in SBS restored by T-PEG. The carbonyl and sulfoxide indices of reactive RSBSMA were lower than those of ordinary RSBSMA, revealing that the effect of thermal-oxidative aging on asphalt was prevented by the restoration of aged SBS structure. The changing amplitude of physical and rheological properties of reactive RSBSMA after aging was less than that of ordinary RSBSMA, which confirmed that the aging resistance of reactive RSBSMA was stronger than that of ordinary RSBSMA due to the repair of aged SBS structure. Different RFRs could offer diverse anti-aging abilities on reactive RSBSMA. The research results suggested that T-PEG rather than T-HTPB was a better choice as a reactive rejuvenator of aged SBS modified asphalt.
Conference Paper
Reclaimed Asphalt Pavement (RAP) continues to be the most recycled product in America. In 2018, the National Asphalt Pavement Association (NAPA) determined that 82.2 million tons of RAP was reused in new Hot Mix Asphalt (HMA). The average RAP content was 21 percent, which is similar to estimates in Canada where 15 to 20 percent of RAP is typically reused. However, the same survey highlighted that in 2018 approximately 110 million tons of RAP was left unused in stockpiles, which is problematic from a sustainability perspective. Properly engineered asphalt mixtures incorporating RAP have been shown to perform as well as virgin HMA. Rejuvenating agents such as organic compounds generated from petroleum processing have been utilized to achieve the desired quality while ongoing evaluation of newer recycling agents such as waste or vegetable oil derivatives shows considerable promise. The focus of this paper is to provide a better understanding of how to engineer and produce mixtures containing various proportions of RAP (and potentially Reclaimed Asphalt Shingles, RAS) while improving cracking performance. The development of a potential framework for the use of rejuvenating agents is presented along with a discussion on the proper design and production of durable quality mixtures using RAP.
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Although the use of high reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) contents in asphalt mixtures is desirable for environmental and economic reasons, these mixtures are prone to cracking, ravelling, and other durability-related pavement distresses mainly due to the heavily aged recycled binders. Highway agencies and the asphalt paving industry have been exploring the use of recycling agents (RA) in order to produce these mixtures with desirable performance. This study focused on characterising the long-term rejuvenating effectiveness of RA on asphalt blends and mixtures with high RAP and RAS contents. Materials from two field projects were used to prepare a number of asphalt blends and mixtures with various combinations of base binder, recycled material, and RA. These blends and mixtures were subject to various aging protocols prior to being characterised for their oxidation kinetics, rheological properties, and cracking resistance. The test results indicated that the RA evaluated in this study were effective in partially restoring the properties of recycled materials, but their rejuvenating effectiveness diminished with aging. Nevertheless, the recycled blends and mixtures with RA achieved equivalent or even better rheological properties and cracking resistance than those with an allowable amount of recycled materials per agency specifications but without RA. In addition, adding RA had no significant effect on the oxidation kinetics of the recycled blends, but increased their susceptibility to physical hardening in response to oxidation. Finally, the correlation between laboratory aging protocols for asphalt blends and mixtures were determined; the laboratory long-term oven aging protocols of 5 days at 85°C on compacted specimens and 1 day at 135°C on loose mix yielded binders with equivalent rheological properties to those subjected to rolling thin film oven (RTFO) plus approximately 10 and 40 h of pressure aging vessel (PAV), respectively.
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This paper presents the results from a laboratory investigation on the effects of aging on the properties of two binders recovered from two different sources of Reclaimed Asphalt (RA) and additivated with a biorejuvenator derived from pine trees. It has been already proven that the rejuvenators are able to restore some of the properties of the aged binder present in the RA, but nowadays their effects into the long-term period are not well known. In this regard, the rejuvenated asphalt binders and a virgin binder, defined as a target, have been aged artificially to simulate short- and long-term aging. All binders have been studied conducting physical, chemical, rheological, and performance-related tests at three different aging levels. Results show that physical and rheological properties can be fully restored by the addition of the proper dose of rejuvenator, while the chemical composition should be investigated in more detail. Rejuvenated binders exhibit great long-term performance especially at high and low temperatures, but also show significant resistance against fatigue at intermediate temperatures.
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Countermeasures to the aging of bituminous asphalt binders is a highly important topic for service-life extension of asphalt in the field and for recycling old pavements into new structures with similar functional requirements as the original structure. Countermeasures are usually achieved by applying additives that restore the adhesive and mechanical properties of the original bituminous binder. The additives are commonly termed (asphalt) rejuvenators. This study examined the performance of two very distinct rejuvenating agents. The effectiveness of rejuvenators is usually measured by comparing the penetration and softening point of the rejuvenator-aged bitumen blend with reference values of the virgin binder. The study used a dynamic shear rheometer to evaluate the rejuvenating capabilities of the two additives. The microstructures of the virgin binder and the rejuvenated blends were obtained by atomic force microscopy. Subsequently, the rheological results were related to the microstructure morphologies. From the rheological experiments, both rejuvenators exhibited the desired softening and property-restoring performance. However, there was a strong difference in the amount of rejuvenator needed to achieve complete rejuvenation. By correlating rheology to the microstructural observations, the effects of the rejuvenators were found to be distinct at microscopic length scales: rejuvenation was achieved by distinct chemophysical mechanisms. One of the rejuvenators restored the virgin microstructure, whereas the other rejuvenator generated a new morphology. Thus, the study demonstrated that by combining rheological and microstructural techniques, the mechanism and performance of rejuvenation can be understood. This finding may help guide future designs and optimization of asphalt-rejuvenating agents.
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The objective of this study was to examine if asphalt rejuvenators can offset the stiffness attributed by the hardened binder from reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) in mixtures that incorporate high RAP and RAS content without adverse impact on the performance of the mixtures. Also, to assess, if rejuvenators can help the hardened binder from the RAP/RAS comingle with the virgin binder. Overall, the results showed that asphalt rejuvenators can mitigate the stiffness of the resultant binder. The cracking characteristics of the mixture improved by the addition of the rejuvenators, however, the rutting and moisture susceptibility were adversely impacted at the dosage and the testing conditions used. Also, the tests results at 4°C generally showed that there was blending of the rejuvenated and virgin binder, however, no conclusion could be made at the higher temperatures.
Article
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Because of aged binder, high reclaimed asphalt pavement (RAP) content mixes are susceptible to cracking failures and are less workable than virgin mixtures. The potential of six differently originated recycling agents was evaluated in this study to restore the desired binder properties using conventional binder test methods and the results were compared with performance-related test results of 100 % RAP mixture. Binder test results showed that application of organic products require much lower dose to provide the same softening effect as petroleum products. The workability of binder and mixture was improved compared to RAP, but remained lower than that of reference virgin mixture. All rejuvenated mixtures proved to be very rut resistant. Low temperature performance of RAP, measured by creep compliance at -10 °C, was improved with the application of all recycling agents and RAP mixes rejuvenated with waste vegetable products even performed equal or better than virgin mixture. Organic oil and both waste vegetable products provided the best performance in binder and mixture fatigue resistance tests as measured by linear amplitude sweep and fracture work density respectively. Overall, the organic products outperformed the petroleum based additives in most tests, which partly can be attributed to un-optimized recycling agent dose. It was observed that penetration test may be a good indicator for initial selection of optimum dose since the results provide indication of rut resistance as well as fatigue performance of mixture and can be easily predicted using an exponential relationship that was developed in the research.
Article
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This paper describes the use of Black diagrams of complex modulus versus phase angle to detect the occurrence of inconsistencies in rheological data caused by testing irregularities and distinctive material properties. In general, conventional penetration grade bitumens can be classified as “thermo-rheologically simple” materials with their rheological properties being temperature and time equivalent provided that they are determined within the binder's linear viscoelastic region and by suitable testing procedures. In the paper, Black diagrams have been successfully used to identify compliance (testing) errors in rheological data associated with the inappropriate use of various dynamic shear rheometer spindle geometries. The results indicate that using a 25 mm diameter testing geometry at complex modulus values greater than 105 Pa leads to an overestimation of elastic response and an underestimation of binder stiffness. As Black diagrams do not require any manipulation of rheological data prior to data presentation, they provide a convenient means of assessing the effect of polymer modification and oxidative ageing on the rheological properties of bituminous binders. In general, semi-crystalline EVA PMBs tend to show unique rheological characteristics at intermediate temperatures due to the occurrence of different crystalline structures at different temperatures. Elastomeric SBS PMBs tend to produce a distinctive elastic response at high temperatures/low frequencies as a result of their dominant polymer network. Finally, Black diagrams have been used to identify discrepancies in rheological data due to non-linear effects before attempts are made to shift the data to produce smooth, continuous master curves.
Article
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The use of bitumen as a construction material dates back to antiquity. The materials in use then were mostly naturally occurring in contrast to modern bitumens which have become highly technical artificial materials. This article reviews the current understanding of bitumen structure and the consequences in terms of properties, with a strong emphasis on the rheological properties. The links between chemistry, structure and mechanical properties are highlighted in the framework of an updated colloidal picture of bitumen. It shows that a simple solvation parameter allows quantifying the effect of the asphaltenes on the rheological properties of bitumen. This appears as a promising approach in order to understand more complex phenomena such as bitumen ageing or the diffusion of rejuvenating oils into an older bitumen. From this structural modelling, the effect of several modifiers, such as polymers, acids or mineral fillers, is explained using fundamental results from the mechanics of colloidal suspensions and multiphase materials through the Palierne model. Thus, relevant parameters describing polymer-bitumen or mineral fillers-bitumen interactions can be extracted, as detailed from literature data. In the case of mineral filler, volume fraction is the key parameter but particle size comes also into play when fine fillers are considered. In the case of polymer-modified bitumens, the swelling extent of the polymer controls all other parameters of importance: volume fraction of dispersed phase and mechanical properties of both dispersed and continuous phases. In addition, interesting rheological features due to droplet shape relaxations are described in polymer-modified bitumens. Although a general picture of bitumen structure is shown to emerge, the many fundamental points that remain to be addressed are discussed throughout the paper.
Article
This paper presents a study that uses gel permeation chromatography (GPC) to characterize the aging process of blends of aged crumb rubber–modified (CRM) binders containing rejuvenating agents. Two aging processes proposed by SHRP binder specifications—rolling thin-film oven (RTFO) and RTFO + pressure-aging vessel (PAV)—were used for the aging of the blends. The GPC profiles—namely, the molecular size distributions—of the blends of aged binders and rejuvenating agents were measured by GPC, and different molecular sizes of these blends were calculated. Three aged CRM binders and two aged control binders of PG76-22 (3% styrene–butadiene–styrene–modified binders) were mixed with several percentages of either a rejuvenator or a softer binder to produce the blends. In addition, performance properties of these blends at three different aging states—that is, no aging, RTFO aging, and PAV aging—were tested and correlated with the larger molecular sizes of the GPC results. It was concluded that compositional changes of these blends due to the RTFO and RTFO+PAV aging processes were well reflected by GPC results. In addition, correlations between the large molecular size and the performance properties of the blends are rather good.
Article
During ageing the chemical composition of bitumen changes, which is reflected by the change in the distribution of bitumen fractions. By measuring the spectrum of fractions, and by correlating fractional changes during ageing within bitumen with the corresponding spectra, a connection between bitumen’s age and the fluorescence spectrum can be drawn. While the age of bitumen increases, its fluorescence emission intensity decreases. Therefore non-aged, laboratory aged (rolling thin film oven test (RTFOT) and RTFOT + pressure ageing vessel) bitumen and bitumen extracted from asphalt slabs from a test field after different time periods were investigated. The test field confirmed the connection between intensity and ageing time, further the development of an oxidation gradient over the vertical cross section of the asphalt slabs could be observed. A modified RTFOT was conducted to study the effects of different temperatures and operating times on the fluorescence emission spectrum, as well as the influence of air (containing traces of atmospheric radicals) by conducting the test with nitrogen. Even under nitrogen atmosphere the intensity decreased, which is assigned to internal reactions.
Article
Preventive maintenance of asphalt concrete can often extend the pavement life for a number of years at relatively low costs. The types of preventive maintenance discussed in this report include rejuvenators, slurry seals, surface treatments, and crack sealing. the report's emphasis is directed toward the use of asphalt rejuvenators. The maintenance procedure should be selected for a specific project to be maintained, and the treatment should be designed for the project. Random selection of maintenance procedures may be ineffective, resulting in loss in performance and additional life-cycle costs. This report provides some guidance into the selection process for maintenance procedures, problem areas to consider, and expected performance of various procedures.
Conference Paper
This study was conducted to investigate if rheological plots of the shear modulus (G*) and the phase angle, commonly known as a Black Space Diagram, and binder rheological parameters derived from master curves using the Christensen-Anderson model can be used to evaluate the binder in high Reclaimed Asphalt Pavement (RAP) mixtures in terms of aging and performance. Additionally, these diagrams were utilized to analyze the binder from the same mixtures with the incorporation of Warm Mix Asphalt (WMA) technologies. Finally, mixture performance test were conducted to validate the results obtained from the binder plots. A Superpave mixture incorporating all virgin materials (no RAP) and a PG64-28 binder was designed. The same mixture was then designed with the incorporation of 15%, 25%, 35% and 50% RAP with the same PG64-28 binder. A PG52-34 softer binder and the PG64-28 with WMA were also used for the 35% and 50% RAP mixtures. The results from the rheological space diagrams were compared to mixture test results for rutting, moisture damage susceptibility and fatigue cracking to determine if they correlate. The rheological space diagrams indicated that increased RAP content led to a binder in the mixture that was more aged than the binder in the virgin material control mixture. The use of the softer PG52-34 binder or a WMA technology decreased the degree of aging with the softer binder being more effective than the WMA technologies. These results generally agreed with the mixture tests.
Article
This paper presents a study in which the changes in properties of a virgin AC-20 (ASTM designated) due to aging are characterized by means of the high pressure-gel permeation chromatography (HP-GPC). Furthermore, molecular size distribution analysis was used to characterize Mobilsol-30 (a recycling agent) and to determine the proper amount required to restore salvaged binders to an AC-20 specification range. In addition, the changes in properties due to aging of the weathered binder that had been restored to an AC-20 specification range were also characterized by means of the HP-GPC. It was concluded that the weathering actions (simulated in the laboratory) would cause increases in large molecular size (LMS) and decreases in medium molecular size (MMS) and small molecular size (SMS). These changes may be detrimental to asphalt characteristics because they result in drastic changes in asphalt consistency. A greater amount of a specific recycling agents is required to restore a more age-hardened binder to its original consistency; hence, the more the molecular size distribution moves away from the original balance.
Article
Long-term pavement performance (LTPP) projects with hot mix asphalt were evaluated using three proposed indicators for low temperature cracking resistance. The primary objectives were to compare ways to combine stiffness and relaxation properties to correlate with cracking, assess data collection schemes in the LTPP relating to the analysis methods, and provide agencies with information to develop approaches for cataloging binders and performance. The Superpave low-temperature specification was compared with the recently developed Glover-Rowe parameter to relate laboratory-measured properties to field cracking. Complex modulus and phase-angle master curves were constructed to plot binder properties in Black Space. Results show the Superpave specification and Glover-Rowe parameter were able to capture one significantly cracked section which had test data obtained within a reasonable amount of time from field measurement. However, the available LTPP data was not ideal for Glover-Rowe analysis, where frequency sweeps at several temperatures are desired. The information presented is particularly relevant as tighter budgets delay maintenance and rehabilitation, exposing pavements to extensive aging.
Article
Rejuvenators have been used as recycling agents to restore some performance properties of oxidized Reclaimed Asphalt Pavement (RAP) binders for cold in-place recycling and as surface treatments to preserve weathered asphalt pavements. However, they have not been widely used in Hot Mix Asphalt (HMA) containing high recycled asphalt contents because of the uncertain effect of rejuvenators, concern about the lack of adequate mixing of the old binder and the rejuvenator, and the required reaction time on performance properties of the recycled binders and asphalt mixtures. The objective of the study presented in this paper is to evaluate the effect of using a rejuvenator pre-blended with a virgin asphalt binder on performance properties of HMA with a high RAP content. The study consisted of the determination of optimum content for rejuvenator, mix design, and conducting binder and mixture tests to assess the performance characteristics (moisture susceptibility, mixture stiffness, top-down cracking, low- Temperature cracking, and rutting) of two recycled asphalt mixtures-50% RAP mix and 50% RAP mix with rejuvenator-relative to those of a virgin mixture. The use of rejuvenator in the recycled mixture improved its cracking resistance without adversely affecting its resistance to moisture damage and permanent deformation.
Article
The ability to recycle large amounts of asphalt pavement hinges on the capability of restoring the properties of the aged asphalt binder contained within the old pavement to that of virgin binder. Common practice in asphalt pavement recycling is to blend reclaimed asphalt pavements (RAP) with a recycling agent to chemically restore the aged asphalt binder. Waste engine oil from automobiles has been shown to improve asphalt binder when applied in small quantities, with the added advantage of being a waste product itself. Using waste engine oil as a chemical additive to restore the properties of RAP uses one waste material to increase the recyclability of another, which is environmentally and socially desirable.In this study, a PG 58-28 neat, virgin binder was blended with reclaimed asphalt binder (RAB) and waste engine oil. The blends were then tested to study the interactions between RAB and waste engine oil. Using Fourier-Transform Infrared Spectroscopy (FT-IR), the differences in the samples were compared using the structural indices associated with asphalt binder aging. This testing revealed a decrease in the two aging indices of the blended asphalt binder, indicating that waste engine oil has the ability to chemically restore aged asphalt binder.Asphalt mixture testing was then performed with mixtures of virgin asphalt, virgin binder, RAP and waste engine oil, in quantities similar to the binder testing, to see if the rejuvenation shown in FT-IR led to an improvement in the performance of the pavement specimens. After specimens were created, testing for freeze thaw durability, and rutting susceptibility was conducted. The results of the mixture testing failed to show an improvement of the freeze thaw durability or rutting susceptibility of specimens created with RAP and waste engine oil when compared to mixtures containing only new materials.
Article
Awareness that natural, financial, and energy resources are scarce goods has increased. Thus demand is growing for infrastructure that is not only of high quality but also efficient. Efficiency, in this case, aims to optimize cost and energy consumption over the complete life cycle of a structure. The objective is to build long-lasting infrastructure with low maintenance demands and with high recycling potential after it has reached the end of its service life. For bituminous bound materials, the aging of asphalt binder has a crucial impact on durability and recyclability. Because asphalt binder is organic by nature, the thermal and oxidative aging processes affected by chemical and structural changes occur when asphalt mixes first are produced and applied and continue over the course of their service life. Increasing stiffness and brittleness of the binder make pavement more prone to thermal and fatigue cracking. The interdisciplinary research project reported here worked toward a better understanding of the physicochemical fundamentals of asphalt binder aging, as well as of the impact of binder aging on the mechanical properties of asphalt binder and asphalt mixes. Through extensive chemical and mechanical analyses, a new model was developed to explain the aging process comprehensively (i.e., on the physicochemical and mechanical levels). Aging can be determined mathematically by micromechanical modeling. With the model presented in this paper, changes in asphalt binder as a result of aging (i.e., increasing brittleness and stiffness) can be explained.
Article
It is no secret that all levels of government face unprecedented levels of deficits. While revenues drop, the costs to maintain infrastructure grow with its age. The question of sustainability takes center stage. Can the United States afford to keep its highway assets, all 3 million miles of its paved roads? The study reported in this paper examined hot in-place pavement recycling (HIPR) as a way to reduce the cost of pavement rehabilitation. The Florida Department of Transportation built a test section in 2002 and a control section in 2003 to compare the cost and performance of HIPR with conventional milling and resurfacing. After 8 years, in-service data were used to draw some conclusions. The test and control road sections performed well. The HIPR section was built at less than half the cost of the conventional section. Projections showed that HIPR was cost-effective and would save 40% more than the conventional method of pavement rehabilitation. These cost savings, taken together with derived environmental benefits, make pavement in-place recycling an option that should not be ignored.
Article
For environmental protection and to reduce costs, asphalt concrete manufacture incorporates reclaimed materials from the deconstruction of road surfaces under renovation in a process designed specifically to reduce the use of virgin materials (bitumen and aggregates). When the recycling rate is high (over 30% of reclaimed asphalt pavement -Rap-), it is essential to control the properties of the final binder -RacB- (mixture of reclaimed asphalt pavement binder -RapB- and virgin binder-VB-) to guarantee the mechanical performances of the reclaimed asphalt concrete. The aim of the present study was to consider the rheological characteristics of the virgin binder and the type of rejuvenating agent it contained and their effect on the conventional and rheological characteristics of the final binder; the reclaimed asphalt pavement binder used in all these tests was first defined in terms of its rheology and consistency. All the final binders were obtained using a methodology which ensured a common controlled consistency, whichever virgin binder was used. The effect of aging on these final binders in the course of manufacture and during the lifetime of the asphalt concrete on the road was simulated experimentally by the RTFOT (Rolling Thin Film Oven Test) and the PAV (Pressure Aging Vessel) procedure. A rheological study of all the binders was then carried out using traditional standard tests, and in addition a specifically adapted experimental procedure was used to assess the behaviour of the product at different operational temperatures.
Article
Effect of ageing on bitumen chemistry and rheology was studied. Seven bitumens were aged according to the thin film oven test (TFOT) and the rolling thin film oven test (RTFOT). The binders were characterised using infrared spectroscopy, chromatography and dynamic mechanical analysis. Statistical correlation between different chemical parameters, as well as between chemical and rheological parameters, was examined. The relationship between TFOT and RTFOT was also investigated. It was observed that ageing influenced bitumen chemistry and rheology significantly. However, chemical and rheological changes were generally not consistent, and consequently, ageing susceptibility of bitumens may be ranked differently when different evaluation methods are used. Regardless of the type of the parameters measured, a strong correlation was observed between TFOT and RTFOT, and the two ageing procedures show similar severity.
Article
Rejuvenator content needed for recycling reclaimed asphalt pavement (RAP) is now mostly determined by considering the penetration or viscosity criterion of the blend of aged asphalt with added rejuvenator. In the study, a comprehensive approach stressing the performance-related properties of the blend, is attempted for determining the rejuvenator content according to strategic highway research program (SHRP) binder specifications. To this end, a series of dynamic shear rheometer and bending beam rheometer tests were carried out on the blends in three states and different temperatures of different aged asphalts with various rejuvenator contents. It is clearly indicated that the performance-related properties of the blends at three different temperatures specified by SHRP binder specifications were effectively changed with rejuvenator content, and the relationships between the properties and rejuvenator content were quite linear. Rejuvenator content needed for recycling RAP is thus able to be reasonably determined when all the requirements specified by SHRP binder system at the three temperatures are satisfied.
Article
Current knowledge on material-related aspects of asphalt recycling with focus on findings from fundamental studies is summarized. By way of introduction, a general description of different types of asphalt recycling methods is given, after which a more detailed compilation of material-related knowledge is presented. Special attention is given to the binder rejuvenation process at asphalt recycling, that is the restoration of reclaimed binder properties. Studies concerning properties of recycled mixtures are also summarized.
Article
This paper presents a study that uses gel permeation chromatography (GPC) to characterize the aging process of blends of aged crumb rubber-modified (CRM) binders containing rejuvenating agents. Two aging processes proposed by SHRP binder specifications - rolling thin-film oven (RTFO) and RTFO + pressure-aging vessel (PAY) - were used for the aging of the blends. The GPC profiles-namely, the molecular size distributions-of the blends of aged binders and rejuvenating agents were measured by GPC, and different molecular sizes of these blends were calculated. Three aged CRM binders and two aged control binders of PG76-22 (3% styrene-butadiene-styrene-modified binders) were mixed with several percentages of either a rejuvenator or a softer binder to produce the blends. In addition, performance properties of these blends at three different aging states - that is, no aging, RTFO aging, and PAY aging-were tested and correlated with the larger molecular sizes of the GPC results. It was concluded that compositional changes of these blends due to the RTFO and RTFO+PAV aging processes were well reflected by GPC results. In addition, correlations between the large molecular size and the performance properties of the blends are rather good.
Article
Rheological techniques are used to investigate the rejuvenation of aged bitumen. The thermal transition associated with the collapse of the compact structure constituted by asphaltene is determined by Dynamic Mechanical Thermal Analysis. For aged bitumen, this transition shifts to a higher temperature but when rejuvenating agents are added, the transition returns to its original value. The “rutting factor,” G*/sin δ allows to define the maximum temperature the binder can reach without permanent deformation. The employed rejuvenating agents are suitable because permanent deformation is postponed. Viscosity results reveal that aged bitumen needs a high mixing temperature (>200C) to behave like a fluid material able to wet, adhere, and envelop aggregates. The addition of rejuvenating agents considerably reduces mixing and compaction temperatures. The mixture of 80% aged bitumen—20% recycled motor oil, obtained exclusively from waste materials is an apt binder that can compete satisfactorily with new 60/70 bitumen.
Article
Firstly, the performance-based properties of rejuvenated aged asphalt binders, i.e., the blends of aged binders containing a rejuvenator at various percentages, were investigated under high, intermediate and low temperatures. The tests were conducted on the blends at three stages as follows: no aging, rolling thin film oven (RTFO) residuals and as well RTFO + pressure aging vessel (PAV) residuals through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. Optimum concentrations of the rejuvenator needed for the blends to reach a target PG grade were obtained from the blending charts of the rejuvenated aged binders in terms of performance properties. The rejuvenator is a soft binder containing a low asphaltene content of 2 wt%. Secondly, selected performance-based properties were conducted on hot mix asphalt (HMA) using the rejuvenated aged binder and a virgin HMA as a control mixture. Results showed that the rejuvenator affected significantly the performance-based properties of both the rejuvenated aged binders and the mixtures containing the rejuvenated aged binders. It was possible to get optimum concentrations of the rejuvenator using the blending charts so that the rejuvenated binders reach a target PG grade. The mean value of the concentrations was proved to be more reliable through the performance-based properties of the mixtures if it is used for a design value for recycling. The properties of the asphalt paving mixtures with the rejuvenated binders were even improved or in the same level as the properties of the virgin mixtures.
Asphalt rejuvenators: "fact, or fable
  • R E Boyer
Boyer, R. E. (2000). Asphalt rejuvenators: "fact, or fable". Presented at the Transportation Systems 2000 (TS2K) Workshop 28 February-3 March, San Antonio, Texas.
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Bitutech RAP and PER: High RAP and warm-mix asphalt solutions
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Turning back time: Rheological and microstructural assessment of rejuvenated bitumen
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Nahar, S., Qiu, J., Schmets, A., Schlangen, E., Shiraaz, M., van de Ven, M., & Scarpas, A. (2014). Turning back time: Rheological and microstructural assessment of rejuvenated bitumen. Presented at the 93rd annual Meeting of the Transportation Research Board, Washington DC.
Evaluation of the relationship between asphalt binder properties and non-load related cracking
  • G Rowe
Rowe, G. (2011). Evaluation of the relationship between asphalt binder properties and non-load related cracking. Journal of Association of Asphalt Paving Technologists, 80, 649-662.
Interrelationships in rheology for asphalt binder specifications
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Rowe, G. (2014, November). Interrelationships in rheology for asphalt binder specifications. Proceedings of the 59th Annual Conference of the Canadian Technical Asphalt Association, Winnipeg, Manitoba.
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AASHTO, T240-09. (2009). Standard method of test for effect of heat and air on a moving film of asphalt (rolling thin-film oven test).
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