Determining optimum rejuvenator dose for asphalt recycling based on Superpave performance grade specifications

ArticleinConstruction and Building Materials 69:159-166 · July 2014with 1,329 Reads
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  • Article
    Full-text available
    Recycling agents, or rejuvenators, are products with chemical and physical characteristics designed to restore the rheological properties of aged asphalt binders to improve the performance of recycled asphalt mixtures with large quantities of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) that promote economic and environmental benefits. This paper summarizes current knowledge related to the use of recycling agents in the asphalt pavement industry, including properties of recycled and rejuvenated asphalt mixtures. This information is further used to identify current and future challenges that could prevent utilization of recycling agents and production of rejuvenated asphalt mixtures with adequate performance.
  • Conference Paper
    O uso de ligantes asfálticos altamente modificados em camadas intermediarias finas é uma técnica que vem sendo difundida na mitigação do problema de trincamento por reflexão em pavimentos asfálticos. A adição de RAP em misturas asfálticas intermediárias antirreflexão de trincas ainda é pouco usual. O presente trabalho faz uma avaliação, a nível de ligantes asfálticos, sobre o uso de um agente rejuvenescedor junto a um ligante envelhecido, extraído do RAP, quando combinado com um ligante altamente modificado (HiMA), comumente utilizado nesse tipo de mistura asfaltica. O objetivo é verificar as propriedades da combinação de ligantes com variados teores de agente rejuvenescedor. Para tal, as características dos ligantes isolados (HiMA e extraído do RAP) e combinados, com e sem o aditivo rejuvenescedor, foram avaliados. Foram realizados: (i) ensaios de varredura de temperatura e frequência para a obtenção da curva mestra, e (ii) ensaios relacionados à caracterização em termos de trincamento por fadiga, representado pelo ensaio LAS. Os resultados demonstraram que a adição de ligante envelhecido ao HiMA sem o aditivo aumentou a rigidez do ligante novo e diminuiu sua vida de fadiga, ao passo que a adição do agente rejuvenescedor recuperou em parte estas propriedades, mostrando o potencial de utilização do RAP em misturas asfálticas antirreflexão de trincas.
  • Article
    Full-text available
    Economic and environmental demands motivate transportation agencies to increase the amount of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) used in asphalt pavements. These pavements often require a recycling agent to reduce the likelihood of premature cracking. Estimating an optimum recycling agent dosage is critical to maximize its benefit. In this study, three recycling agent dosage selection methods based on the restoration of the performance grade (PG) of the recycled blend (virgin binder, recycled binder, and recycling agent) were explored. Based on the performance of the recycled blends, the method to restore high-temperature PG is recommended to determine the optimum recycling agent dosage.
  • Conference Paper
    Vacuum tower distillation bottom (VTB), is an asphalt material produced through vacuum tower distillation processing in petroleum refineries to increase production of higher economic value lighter components such as gasoline and jet fuel. Due to the loss of saturates from this process, VTB are very stiff and are heavily limited for use in paving. In past binder studies done at Iowa State University, linseed oil based bio-derived materials (BDM) have been shown to improve the low temperature performance of the stiff VTB, as compared to softer paving grade asphalts through rejuvenation. Mix performance must also be examined based on past results. Mix performance of VTB modified with BDM used as rejuvenators (two dosage levels) at low and intermediate temperatures was examined and compared against the performance of a control, and VTB modified with a commercially available rejuvenator (two dosage levels) using the semi-circular bend (SCB) test and the dynamic modulus test at low and intermediate temperatures. Findings show that heat bodied linseed oil (HBO) and partially hydrogenated heat bodied linseed oil (PHBO) combined make for a successful rejuvenator of VTB. 5%HBO and 5%PHBO combined perform equally and better than the commercial rejuvenator and better than the control by lowering stiffness and increasing fracture energy at low temperature, while performing the same at intermediate temperatures.
  • Article
    Full-text available
    Using a rejuvenator to improve the performance of asphalt pavement is an effective and economic way of hot asphalt recycling. This research analyzes the rejuvenating effect on aged asphalt by means of a Mortar Transfer Ratio (MTR) test, which concerns the ratio of asphalt mortar that moves from recycled aggregates (RAP aggregates) to fresh added aggregates when aged asphalt is treated with a regenerating agent and comes into contact with fresh aggregates. The proposed MTR test analyzes the regeneration in terms of the softening degree on aged asphalt when the rejuvenator is applied. The covered area ratio is studied with an image analyzing tool to understand the possibility of mortar transferring from RAP aggregates to fresh aggregates. Additionally, a micro-crack closure test is conducted and observed through a microscope. The repairing ability and diffusion characteristics of micro-cracks can therefore be analyzed. The test results demonstrate that the proposed mortar transfer ratio is a feasible way to evaluate rejuvenator diffusion during hot recycling. The mortar transfer ratio and uncovered area ratio on fresh aggregates are compatible, and can be used to quantify the contribution of the rejuvenator. Within a certain temperature range, the diffusing effect of the rejuvenator is better when the diffusing temperature is higher. The diffusion time of the rejuvenator is optimum when diffusion occurs for 4–8 h. When the rejuvenator is properly applied, the rough and cracking surface can be repaired, resulting in better covered aggregates. The micro-closure analysis visually indicates that rejuvenators can be used to repair the RAP aggregates during hot recycling.
  • Article
    Bio-derived rejuvenating agents have the potential to enhance the rheological properties of the vacuum tower bottoms left over from the crude oil refining process. Enhancement of the rheological properties allows the stiff vacuum tower bottoms to be used as an asphalt binder in hot mix asphalt. This study investigates the use of several experimental bio-derived rejuvenating additives and compares them with a commercially available modifier. The experimental additives include a blend of, heat bodied linseed oil (HBO) and partially hydrogenated heat bodied linseed oil (PHBO). The effect of dosage level and aging influence on rheological properties was studied for the experimental materials and the commercially available additives. The findings show that all the rejuvenators used had similar effects in the reduction of vacuum tower bottom stiffness due to short-term and long-term aging. However, the commercial reju-venator reduced stiffness the most. The results show that the material combination of HBO and PHBO better retain high temperature properties while lowering stiffness at intermediate and low temperatures, thus widening the continuous grade range better than the commercial rejuvenator. To better understand why these effects are taking place in vacuum tower bottoms from both the commercial rejuvenator and the combination of materials HBO and PHBO with aging it is felt that in the future analytical chemistry such as high definition mass spectrometry needs to take place. This will make it possible to understand why these effects are taking place with aging.
  • Article
    Full-text available
    Este trabalho avalia o uso de um resíduo de óleo vegetal como agente rejuvenescedor de ligantes asfálticos. Para tal, características de um ligante nos estados virgem, envelhecido e rejuvenescido são avaliadas com base em resultados de viscosidade, módulo de cisalhamento dinâmico e ângulo de fase. Adicionalmente, ensaios de caracterização de morfologia superficial são realizados em um microscópio de força atômica para identificar alterações microscópicas nas diferentes fra-ções constituintes do ligante. Um procedimento de quantificação destes constituintes é apresentado e empregado no trabalho. Espera-se que os resultados do estudo sirvam para promover práticas de engenharia sustentáveis a partir do uso de resíduos que possibilitem o rejuvenescimento de ligantes asfálticos envelhecidos, além de incentivar o desenvolvimento de técnicas avançadas de caracterização dos comportamentos destes materiais em diferentes escalas e de identificação de correlações entre eles.
  • Article
    Full-text available
    Dramatically rising asphalt binder cost, dwindling budgets, growing traffic loads, and the desire to find more sustainable paving practices are forcing agencies to seek ways for maximizing the re-use of Reclaimed Asphalt Pavement (RAP). While most of the academic and industrial institutions have been focused on the development of procedures to recycle hot asphalt mixes with up to 40% RAP content, a few industry innovators have refined 100% recycling technologies over the past four decades to a level where routine production of 100% recycled mixes is in clear sight. The main hindrance in the widespread use of 100% recycling is the unproven performance of 100% RAP pavements and lack of a unified and rational system for selection of materials and mix design. The objective of this research was, therefore, to critically investigate the concept of 100% recycling, determine whether such mixtures can perform as well as conventional asphalt mixes and if yes, develop a mixture design method for 100% recycled asphalt. This article presents a summary of the research, demonstrating that with adequate mixture design 100% recycled asphalt mixtures can perform equally to conventional asphalt. The available production technologies are also shortly summarized. Finally an environmental effect and cost calculation is performed demonstrating reduction of emission by 35% while reducing the costs of materials by half.
  • Article
    Full-text available
    The quality of asphalt binder recycling is largely dependent on molecular diffusion between virgin asphalt binder, aged asphalt binder, and rejuvenator. In this study, molecular dynamics (MD) simulations were used to study diffusion and interaction mechanism of rejuvenating agent in recycled asphalt binder. The diffusion process of rejuvenator into virgin and aged asphalt binder was studied using a three-layered model. A mixture model of virgin and aged asphalt binder was built to evaluate the effect of rejuvenator on the molecular structure of asphalt binder, such as nanoaggregate behaviour and translational mobility. The simulation results of the layered model suggest that rejuvenator may improve blending efficiency of virgin and aged asphalt binder depending on temperature. The calculated inter-diffusion coefficients indicate that the rejuvenator diffuses faster into virgin asphalt binder than aged asphalt binder. The radial distribution functions of asphaltene, resin, and aromatic pairs show that rejuvenator causes the molecular structures of virgin and aged asphalt binder more similar to that of virgin asphalt binder. The rejuvenator reduces the self-association trends of asphaltene molecules, but saturates from local aggregation inside the rejuvenated asphalt binder. On the other hand, rejuvenator increases translational mobility of saturate, aromatic, resin and asphaltene fractions.
  • Article
    Full-text available
    Waste cooking oil (WCO), in many cases, can rejuvenate aged asphalt and restore its properties. However, the influence of WCO qualities on rejuvenation behaviors of aged asphalt has not been investigated in detail. The objective of this paper was to evaluate the effects of WCO viscosity and acid value on the basic, rheological, and chemical properties of a typical rejuvenated asphalt. Penetration, ring and ball (R and B) softening point, and ductility were tested to evaluate the influence of WCO qualities on basic properties of rejuvenated asphalts. Then, the rheological properties of rejuvenated asphalt were characterized based on rotational viscometer (RV), dynamic shear rheometer (DSR), and bending beam rheometer (BBR) test results. Further, SARA (saturates, aromatics, resins, and asphaltenes) fraction analysis and Fourier transform infrared spectroscopy (FTIR) tests were performed to investigate the effects of WCO qualities on asphalt chemical composition. Finally, grey correlation coefficients were calculated and the relationships between WCO qualities and rejuvenated asphalt properties were quantitatively evaluated. The experimental results indicated that WCO qualities influence the rejuvenation behaviors of aged asphalt significantly, and the WCO with higher qualities (low acid value and viscosity, as defined in this research) tends to achieve better rejuvenation effects. Based on the results of grey correlation analyses, the acid value is, relatively, a better indicator than viscosity in predicting the rejuvenation efficiency of WCO. The rejuvenation thresholds of WCO are varied with the categories of properties of rejuvenated asphalts, and WCO with an acid value of 0.4-0.7 mg KOH/g, or a viscosity of 140-540 mm²/s, can meet all of the performance requirements for asphalt rejuvenation used in this research.
  • Article
    Full-text available
    Performance-based mixture tests were used to design 100% recycled mixtures while verifying the potential to use the test methods for routine design of highly recycled asphalt mixtures. Two different gradations of recycled mixtures were prepared, each with two different binder contents and a polymer modified bitumen for one of the mixtures. A bio-based rejuvenator was always applied to ensure the targeted binder grade. The results demonstrated that it is possible to design a 100% mixture with rutting resistance, fracture toughness, and stiffness performance at the level of a conventional AC8 mixture. However semi-circular bend fracture toughness test at 0°C was not sensitive enough to changes in binder content and its properties therefore it is not recommended for using in mixture design optimisation of highly recycled asphalt. © 2019
  • Article
    Full-text available
    An important concern that limits the RAP content in asphalt mixtures is the fact that the aged binder that is present in the RAP can cause premature cracking. Rejuvenators are frequently added to high RAP mixtures to enhance the properties of the binder. There is no existing method to predict the longevity of a rejuvenated asphalt. This study investigated the aging of rejuvenated binders and compared their durability with that of virgin asphalt. Various samples with different types and proportions of RAP, virgin binder, and rejuvenator were aged by RTFO and three cycles of PAV. DSR and BBR tests were conducted to examine the high-temperature and low-temperature rheological properties of binders. Results indicated that the type and dosage of the rejuvenator have a great influence on the aging rate and durability of the binder. Some rejuvenators make the binder age slower, while others accelerate aging. These observations confirm the importance of evaluating the long-term aging of recycled binders. For this purpose, critical PAV time was proposed as a measure of binder’s longevity.
  • Article
    Extensive researches have been conducted on using reclaimed asphalt pavement (RAP) material in production of recycled hot mix asphalt. According to literature, the aged binder is the main obstacle to incorporate high amount of RAP into asphalt pavement which causes premature distresses such as fatigue failure and low temperature cracking in pavement structure. To overcome this problem, rejuvenating agent or rejuvenator is usually used to restore the RAP binder properties to a condition that resembles that of fresh asphalt binder. Different types of rejuvenators have been used previously. This study provides an overview on utilizing RAP, and the use of rejuvenators, type and dosage, in production of asphalt pavement.
  • Article
    Full-text available
    As the cost and demand for bitumen and aggregate resources increase, it is vital to implement more sustainable practices in asphalt pavement construction. Recycled asphalt pavement (RAP) technology involves the use of recycled asphalt material in the construction of new pavement surfaces which presents significant economic and environmental savings. In order to facilitate the further development of RAP technology, mix performance issues attributed to the use of high quantities of RAP need to be addressed. The present study investigated the use of RAP and the effect of binder rejuvenation on performance properties of hot-mix asphalt (HMA) mixes, with the aim of establishing RAP pavements as a standard practice in the asphalt paving industry in Australia and New Zealand.
  • Article
    Full-text available
    Recycling of highway materials is an effort to preserve the natural environment, reduce waste and provide a cost-effective way for construction of highways. The reclaimed asphalt pavement (RAP) contains stiffened binder caused by loss of volatile materials and oxidation. Hence, the addition of high amount of the RAP to asphalt mix may make it prone to fatigue failure. Due to this reason, addition of RAP to asphalt mixture in substantial amount has been a challenge so far. Therefore, ‘rejuvenators’ which are supposed to restore chemical and physical properties of the aged asphalts are used effectively in asphalt mixture. In this study, two locally available oils, i.e. pongamia oil (locally known as Karanja oil) derived from the seeds of Pongamia pinnata and a composite rejuvenator made of castor oil and coke oven gas condensate have been explored for rejuvenating the aged binder. The rheological properties of aged binder and rejuvenated binders were studied using a dynamic shear rheometer. From the various rheological tests conducted, it was found that certain proportion of pongamia oil as well as composite castor oil was able to impart desirable rutting as well as fatigue performance for the rejuvenated binder samples. The thermal analysis carried out using thermogravimetric analysis ensured adequate thermal stability for the binder specimens treated with these oils. In terms of binder performances, it was found that these oils could be considered as suitable rejuvenators for effectively restoring properties of the aged binder. Performance studies on RAP mixes may be extended for recommending these two oils as rejuvenators for hot mix pavement recycling.
  • Article
    Full-text available
    The world is on the run looking for new energy resources, improvements and conservation on current energy resources while at the same time trying to keep the environment safe and clean, keeping in mind the economic constraints of all the above. Recycling and minimization of waste produced from the above activities are among top priorities for policy makers. Oil shale is on the rise as an additional source of energy. This sector of the industry has not yet reached maturity and still under development. One application of oil shale is the direct combustion, where fine oil shale is produced as a waste and considered an environmental hazard. This investigation proposed the incorporation of such filler size oil shale into hot mix asphalt (HMA). The study used Superpave design method. The study included resilient modulus, creep and fatigue measurements. The results showed a mixed performance where, depending on the HMA formulation, the inclusion of oil shale filler produced better performance than the control limestone filler whereas other formulations showed the contrary.
  • Asphalt binders produced at refineries are becoming stiffer due to an ever-increasing demand for more expensive lighter and heavier fraction products such as gasoline, jet fuel, and lube oils. To increase output of lighter fractions and heavy gas oils, refineries have gone through upgrades producing higher amounts of stiffer asphalt binders such as Vacuum Distillation (VD) tower, Solvent De-Asphalting (SDA), and Residuum Oil Super critical Extraction (ROSE) unit bottoms. Materials used to soften/repair stiff asphalt binders are known as fluxes. Through recent work at Iowa State University, great potential was seen for epoxidized plant oil materials as fluxes/rejuvenators. Within this work two epoxidized plant oil products derived from soybeans, EBS and EMS were manufactured and used for modifying three stiff asphalt binders produced from VD tower, SDA and ROSE units. A full Superpave binder investigation found that improvement in low temperature performance was greater than improvement in high temperature performance for the SD and ROSE unit bottoms using when using either EBS or EMS. It was also found that substantial decreases in costs, fuel usage, and emissions could be gained through the use EBS and EMS in the production of asphalt mix. RÉSUMÉ Abstracts provided in English will be translated to French and vice versa.
  • Article
    Full-text available
    Rejuvenators can restore the reclaimed asphalt pavement (RAP) binder for another service period. To achieve this, homogeneous distribution of rejuvenator and good diffusion into reclaimed asphalt binder film has to be ensured. Ten potential rejuvenator addition locations are summarised, and two most promising are compared in full-scale study: spraying of rejuvenator on cold reclaimed asphalt on the feeding belt before heating versus addition of rejuvenator to hot reclaimed asphalt in mixer. RAP samples were collected at various places in the production line to evaluate the effect of rejuvenator addition location on softening point, penetration, rheology and chemical composition of extracted binder. The results revealed that passing through the extreme temperatures in the RAP heating drum does not sacrifice mechanical performance or increase chemical ageing of the rejuvenated binder. A benefit of early rejuvenator addition is that it provides a longer residing time of rejuvenator on the binder and thus potentially may allow higher binder activation and better blending of RAP binder with rejuvenator and virgin binder. This has to be evaluated through mixture tests.
  • Article
    Full-text available
    Recycled asphalt mixtures with high amounts of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) can be excessively stiff, brittle, and prone to cracking. The use of recycling agents, or rejuvenators, can significantly reduce mixture stiffness and improve performance, specifically cracking resistance. In this study, the performance of recycled and rejuvenated asphalt mixtures from several field projects, located in different environmental zones across the United States, was evaluated considering various recycling agent dosages determined by the contractors. Field core test results and the visual distress surveys of the field projects demonstrated that using the field recycling agent dosages yielded poor mixture performance. Laboratory test results demonstrated that adding the recycling agent at the dosage to match the continuous high-temperature performance grade (PGH) of the rejuvenated binder blend (virgin/base binder, recycled binder, and recycling agent) to that of the target binder PGH specified based on climate and traffic requirements yielded improved mixture performance. The rejuvenated mixtures at this recycling agent dosage showed significant reduction in stiffness and improved cracking resistance, and facilitated the use of higher quantities of recycled materials, regardless of aging level, while maintaining rutting resistance after short-term aging.
  • Article
    Full-text available
    In this study, the aged asphalt binder and mixture were laboratory prepared through short-term ageing testing and long-term ageing testing. Firstly, the effect of rejuvenator on physical properties of aged asphalt binders was investigated. In addition, a series of laboratory tests were performed to evaluate the influence of ageing and rejuvenator content on the mechanical properties, durability and dynamic characteristics of asphalt mixtures. Physical test results of asphalt binder testified that rejuvenator used can efficiently recover the aged asphalt binder. However, the effect of ageing and rejuvenator content exhibits different trends depending on the physical property tests conducted. Moreover, artificially aged asphalt mixture with rejuvenator has better ability to resist moisture damage and ravelling. In addition, the ITSR value is more suitable to evaluate the moisture susceptibility for asphalt recycling. Although rejuvenator improves the thermal cracking resistance and fatigue property of aged asphalt mixture, rejuvenated mixture shows greater modulus and inferior ability to resist reflective cracking than the unaged mixture. Moreover, rejuvenated mixture shows less dependence on frequency at high temperature regions and stronger dependence at low temperature regions compared to unaged and long-term aged mixtures.
  • Article
    The long-term effects of SBS-modified binders and rejuvenators on the properties of high-RAP mixtures, especially the cracking resistance, have not been resolved. Therefore, this paper evaluates the cracking resistance of polymer-modified asphalt binders, mastics, fine aggregate matrices (FAMs) and mixtures containing RAP material and a rejuvenator. A series of laboratory tests is performed on different asphalt material scales, including a frequency sweep test; a BBR test for asphalt binders, mastics and FAM mixes; and a dynamic modulus test and the Illinois flexibility index test for asphalt mixtures. Short-term ageing and long-term ageing are also considered for different asphalt material scales. The results show that the asphalt binders and mixes containing RAP materials have similar Glover-Rowe (G-R) values and flexibility index (FI) values to those of the virgin binders and mixtures that are only subjected to short-term ageing. These results indicate that a rejuvenator can partially decrease the stiffness of the RAP material before long-term ageing; however, the cracking resistance of asphalt materials obviously decreases after long-term ageing. Asphalt materials containing RAP are more susceptible than virgin asphalt material to thermal cracking, and the rejuvenator does not improve the long-term cracking resistance of high-RAP material. The correlations between different laboratory ageing conditions for the asphalt binder, mastic, FAM and mixture are analysed. Binders subjected to PAV 20 h ageing present rheological properties equivalent to those of mixes subjected to the long-term oven ageing (LTOA) protocol for 5 d at 85°C. Binders subjected to PAV 40 h ageing present rheological properties equivalent to those of loose mixtures subjected to the LTOA protocol for 12 h at 135°C. The cracking resistance parameters of the binders, mastics and FAMs are also compared with the cracking resistance parameters of the mixture, and the results illustrate that the G-R parameters of asphalt binder, mastic and FAM are well correlated with the G-R parameter and FI parameter of the mixture. Moreover, the G-R parameter can predict the cracking performance of the asphalt mixture.
  • Thesis
    The effects of using recycling agents (RAs) on hot mixture asphalt (HMA) have recently acquired special attention in the academic community due to the fact that recycled mixtures typically have high stiffness as a result of long periods of oxidative aging, mainly driven by environmental conditions (e.g., sunlight, temperature, and oxygen). In addition, the use of RAs in HMA aims at restoring the rheological and physicochemical properties of the aged binder contained in the reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) to provide the HMA mixtures with adequate performance, similar or superior to that of virgin HMA (i.e., without RAP, RAS, or RA). Subsequently, the objective of this thesis is to study the rheological and ageing characteristics of asphalt binder blends fabricated with RAP, RAS, and recycling agents using high recycled binder ratios (RBRs). The materials were retrieved from a recent field project constructed in Texas that incorporated high percentages of RAP/RAS materials with recycling agents and warm mixture asphalt additives in five highway sections. The laboratory characterization included: (1) blending charts, dosage estimations, and master curves from dynamic shear rheometer, (2) the Glover-Rowe (GR) parameter in Black Space diagrams, and (3) Fourier transform infrared spectroscopy (FTIR). The results indicated that the use of the T1 recycling agent allowed for restoring the rheology (i.e., G* and phase angle) in all the combinations studied. Furthermore, validation of the regional linear blending concept allowed for calculating dosages of RA. The G-R parameter in Black Space diagrams showed that more than 40 pressure aging vessel (PAV) hours of artificial aging produce high stiff blends with high cracking susceptibility (i.e., damage zone between 180 kPa and 450 kPa). Furthermore, FTIR data showed a tendency of increase in the carbonyl area when using the T1 RA. Results include a suggested set of laboratory tools for characterizing binder blends, and a proposed methodology for determination of optimum dosages of RA in recycled mixtures with high RBR to be used in future research.
  • Article
    As the amount of reclaimed asphalt pavement (RAP) material used in asphalt mixtures has increased recently, it is vital to address problems regarding aged binder incorporated in RAP. Asphalt binder hardens during its production process as well as during service life of pavements. External influences such as oxygen and ultraviolet radiation affect greatly bitumen characteristics. Thanks to adding rejuvenating agents, the original binder properties should be recovered and resulting asphalt binder parameters should become equal to those measured upon the reference material. In this study, four different rejuvenator agents and one neat soft binder were employed to rejuvenate the artificially aged binder by a complete blending between both constituents. Thereafter, empirical as well as performance based binder properties were examined with a dynamic shear rheometer (DSR) and with a bending beam rheometer (BBR). Three different dosages of each rejuvenator were added to evaluate the required amount for the original binder properties to be restored. Moreover, the softening efficiency of each agent was assessed by means of the Ring and Ball test. Finally, the optimum amount of each rejuvenator needed for the blend to achieve the target specification was determined. It can be concluded that the rejuvenators affect binder properties greatly, and mainly in a positive way. However, the data also indicate significant discrepancies between the types of the rejuvenator.
  • Article
    Full-text available
    Recycling of an asphalt pavement reduces construction cost as well as the environmental degradation. Adding the bitumen emulsion as a rejuvenator in aged and oxidised asphalt binder improves its viscosity and stiffness without significantly decreasing the carbonyl index. This results in a high aging rate of such asphalt materials. This study proposes Cereclor as an alternate rejuvenator in the replacement of conventional bitumen-based emulsion. The main objectives of this study were to investigate the effect of Cereclor on aged asphalt binder’s characteristics, aging resistance and on the durability of Reclaimed Asphalt Pavement (RAP) modified asphalt mixtures. Carbonyl index was calculated from IR spectra of samples before and after laboratory aging to evaluate the aging resistance. It was observed that a 9% by weight of Cereclor rejuvenates 40/50 pen grade aged asphalt binder to the level of 60/70 pen grade bitumen. For durability assessment of RAP and rejuvenated mixes, fatigue, rutting and moisture susceptibility tests were performed. Four-point beam fatigue test showed that a 9% dose of Cereclor has increased the fatigue life of RAP by almost two times as compared to emulsion. Rut depth for all samples was in the range of 3–4 mm satisfying the rutting failure criteria. Overall, this study revealed that Cereclor has higher rejuvenation potential as compared to bitumen-based emulsion and thus it can potentially be used in pavement recycling.
  • Article
    The overall objective of this study was to evaluate the influence of selected recycling agents (RAs) and recycled materials on the development of cracking potential with respect to oxidative aging. Given the complex nature of varying base asphalt binders, recycled materials, whether recycled asphalt pavement (RAP), reclaimed asphalt shingles (RAS), or both, and the complexity of their combined interactions with recycling agents, standard evaluation protocols for binder grading and evaluation may be insufficient. The binder blend aging predictions or oxidation modeling evaluation was introduced as a means to evaluate the combined influence of both binder oxidation kinetics and resulting rheological changes on the measured cracking potential of the various binder blends—that is, Glover–Rowe (G-R) parameter—driven by temperature estimation modeling over simulated in-service durations at example geographic locations. This evaluation has demonstrated the importance of adequate characterization of the specific materials being used in conjunction with selection of the correct dose of the appropriate recycling agent to ensure sufficient resistance to cracking and embrittlement of proposed material combinations. The combined influence of all the interested components did not always add up to the sum of the individual parts, nor are the measured interactions consistent with increased levels of oxidation. Therefore, the prevailing conclusion of the study as a whole indicated that material-specific evaluations are needed to identify the complex interactions taking place within the material combinations of interest, but also multiple levels of aging at appropriate intervals may be necessary for comprehensive characterization.
  • Chapter
    Pavement rehabilitation will become the main activity in the road engineering sector in the majority of developed countries. Thus, large quantities of reclaimed asphalt pavements (RAP) will be generated and their reuse in asphalt mixtures would provide considerable economic and environmental benefits. To overcome the problems caused by using an excessive amount of RAP in asphalt mixtures, the use of rejuvenators will play a key role. Recent years have seen the emergence of many types of asphalt rejuvenators. The main objective of this study is to characterize the effect of different rejuvenators (varying in nature) on the rheological properties of aged asphalts binders. For this purpose, an aged binder extracted from RAP was blended with four rejuvenators at different dosages. Their rheological properties were then evaluated using frequency sweep tests and several rheological parameters that assess the brittleness of aged binders (“G*·sin δ”; R-value and crossover frequency; G-R parameter). The results indicate that the rejuvenator based on oleyldiamine ethoxylate showed the best performance. However, similar results can also be achieved using bio-rejuvenators from plant-based ester resins.
  • Article
    Full-text available
    The Maine Department of Transportation (DOT) currently allows 20% reclaimed asphalt pavement (RAP) in base and intermediate courses. To help the Maine DOT decide whether RAP could be increased to 50%, this study evaluated the critical laboratory properties of hot-mix asphalt with 50% RAP materials and rejuvenator. The scope of work consisted of preparing 20% and 50% RAP mixes with and without rejuvenators and testing compacted specimens for their volumetric properties, moduli, indirect tensile strength, moisture susceptibility, and low-and intermediate-temperature cracking potential. Two rejuvenators were used: (a) generic waste vegetable oil and (b) proprietary, commercially available rejuvenator. Virgin binder, extracted RAP binder, and extracted binder from recycled mixes were tested for continuous performance grading. The results showed that rejuvenators improved the properties of high RAP mixes, and the performance of rejuvenated 50% RAP mixes was equal to that of the currently allowed 20% RAP mixes. Results from semicircular bending tests were used to evaluate and quantify the effect of rejuvenators on mixes with high RAP content. Field trials of 50% RAP mixes were recommended as a result of the study.
  • Article
    Full-text available
    Aging is the accumulation process of diverse detrimental changes in molecular structures with advancing age. Resistance to aging is termed durability. Complex molecular systems such as asphalt binder need to be protected against aging. In this paper, a state-of-the-art review of anti-aging technologies used to prohibit or to rejuvenate the aged asphaltic materials is provided. The kinetics of molecular structures during aging and the group of molecules affected mainly are discussed. The latest developments on antioxidation and rejuvenation technologies are given as well showing the impact of antiaging technologies for the asphalt binder.
  • Article
    The excellent comprehensive performance of SBS modified bitumen (SMB), during a long-term thermo- and photo-oxidative exposure, will fail to satisfy the pavement requirement. In this paper, the synergistic effect of 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol diglycidyl ether (BUDGE) on the molecular weight of aged SBS was firstly studied, through a simulation, to confirm whether a new polymer structure can be obtained. Then, the reactive rejuvenating system containing MDI, BUDGE and bituminous composition returning agent (MDI-BUDGEs) was applied in the rejuvenation of aged SMB. The results show that the rebuilt molecular structure of aged SBS can be obtained with the combination of MDI and BUDGE. Meanwhile, MDI-BUDGEs can improve the low-temperature ductility and inhibit the sharp fall of the softening point of aged SMB, while decrease the viscosity-temperature response at 120–165 °C. Also, MDI-BUDGEs can contribute for increasing the viscous component, improving the fatigue resistance and remaining the high-temperature performance grade of aged SMB, and moreover, decrease the limited elastic modulus and the elastic-plasticity transition rate to avoid the occurrence of the brittle failure within a small strain range.
  • Article
    This paper investigated the effects of concurrent recycling of fine reclaimed asphalt pavement (RAP) and coarse steel slag aggregate (SSA) on fracture resistance of asphalt mixes. To this end, a set of 576 Semi- circular bending (SCB) specimens with different ratios of these two marginal materials with and without warm mix asphalt (WMA) additive were prepared in two aging levels and underwent up to five freeze and thaw (FT) cycles. Following, specimens were tested at 25 �C in three-point bending configuration and their critical strain energy release rate (Jc) and flexibility index (FI) were determined and statistically compared to each other. Results disclosed that FT cycles, long-term (LT) aging and the inclusion of RAP decrease the fracture resistance, while the inclusion of SSA increases it. Moreover, incorporation of RAP improves the moisture susceptibility of asphalt mixes, while incorporation of SSA increases this sus- ceptibility. Overall, concurrent incorporation of SSA and RAP was found to be beneficial in improving the fracture resistance and moisture susceptibility of conventional asphalt mixes.
  • Article
    Results of a study conducted by the New Hampshire Department of Transportation (NHDOT) in cooperation with three local paving contractors are presented. Plant-produced hot-mix asphalt (HMA) mixtures containing reclaimed asphalt pavement (RAP) percentages from 0% to 25% were obtained from seven different batch plants. Twenty-eight mixtures were sampled and sent to the binder testing laboratories at NHDOT and Pike Industries, Inc. The virgin binders were also sampled and sent for binder testing. Binders were extracted and recovered from all of the mixtures and were tested to determine the performance grade (PG) binder grade and critical cracking temperature. The effect of the RAP at various percentages on binder properties was evaluated. High-end PGs were found to remain the same or increase only one grade for the mixtures tested. Low-end PGs also remained the same or bumped only one grade, and the critical cracking temperatures changed by only a few degrees for the mixtures examined in this study. Results of this study led to a change in the implementation of the new NHDOT specification in regard to the use of recycled asphalt binder in HMA.
  • Improved mix design, evaluation, and materials management practices for hot mix asphalt with high Reclaimed Asphalt Pavement content
    • R West
    • J R Willis
    • M Marasteanu
    West R, Willis JR, Marasteanu M. Improved mix design, evaluation, and materials management practices for hot mix asphalt with high Reclaimed Asphalt Pavement content. NCHRP Report; 2013 Jan.
  • Prediction of effect of bio-based and refined waste oil modifiers on rheological properties of asphalt binders
    • Z Lei
    • A Golalipour
    • H A Tabatabaee
    • H U Bahia
    Lei Z, Golalipour A, Tabatabaee HA, Bahia HU. Prediction of effect of bio-based and refined waste oil modifiers on rheological properties of asphalt binders. In: Transportation research board 93rd annual meeting, Washington, D.C.; 2014.
  • Standard Method of Test for Determining the Fracture Properties of Asphalt Binder in Direct Tension (DT) American Association of State Highway and Transportation Officials
    • Aashto T
    AASHTO T314. Standard Method of Test for Determining the Fracture Properties of Asphalt Binder in Direct Tension (DT). American Association of State Highway and Transportation Officials; 2010.
  • The shell bitumen handbook
    • J Read
    • D Whiteoak
    Read J, Whiteoak D. The shell bitumen handbook. 5th ed. London: Thomas Telford Publishing; 2003.
  • Impact of high RAP contents on structural and performance properties of asphalt mixtures. IL: Illinois Center for Transportation
    • Al-Qadi Il
    • Q Aurangzeb
    • Carpenter
    • Sh
    • Pine Wj
    • Trepaner
    Al-Qadi IL, Aurangzeb Q, Carpenter SH, Pine WJ, Trepaner J. Impact of high RAP contents on structural and performance properties of asphalt mixtures. IL: Illinois Center for Transportation, Springfield; 2012.
  • Standard Specification for Performance-Graded Asphalt Binder. American Association of State Highway and Transportation Officials
    • Aashto M
    AASHTO M320. Standard Specification for Performance-Graded Asphalt Binder. American Association of State Highway and Transportation Officials; 2005.
  • Standard Test Methods for Quantitative Extraction of Bitumen From Bituminous Paving Mixtures
    ASTM D2172. Standard Test Methods for Quantitative Extraction of Bitumen From Bituminous Paving Mixtures. American Society for Testing and Materials; 2011.
  • Standard Test Method for Penetration of Bituminous Materials
    ASTM D5. Standard Test Method for Penetration of Bituminous Materials. American Society for Testing and Materials; 2006.
  • Impact of high RAP contents on structural and performance properties of asphalt mixtures
    • Al-Qadi Il Aurangzeb
    • Q Carpenter
    • S H Pine
    • W J Trepaner
    Al-Qadi IL, Aurangzeb Q, Carpenter SH, Pine WJ, Trepaner J. Impact of high RAP contents on structural and performance properties of asphalt mixtures. IL: Illinois Center for Transportation, Springfield; 2012.
  • 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
    This paper compiles work carried out to study the process of mixing old and new (rejuvenator) binders by diffusion during asphalt recycling, as well as studies of structural stability of recycled binders. FTIR-ATR (Fourier Transform Infrared Spectroscopy by Attenuated Total Reflectance) was employed to monitor rejuvenator diffusion. Generally, diffusion rates are influenced by temperature, size and shape of the diffusing molecules and the viscosity of the medium in which the diffusion takes place. Since bitumen ageing normally leads to a considerable increase in viscosity, it was decided to investigate its influence on the diffusion process. The results presented in this study imply that it is the maltene phase viscosity that governs the diffusion rate, rather than the viscosity of the bitumen as a whole, and that bitumen ageing does not have a significant effect on the diffusion process. Diffusion was also monitored using rheological detection, which correlated fairly well with the rates of diffusion observed chemically using FTIR-ATR. Structural stability of mixtures of old and new bituminous binders were studied using three-dimensional turbidimetric titration, where the three dimensions are a visualisation of the Hansens solubility parameters have dispersive, polar and hydrogen bonding components. The study was initiated to investigate the possible negative consequences of mixing old and new binders during asphalt recycling. The results regarding mixtures of old and new binders indicated that structural stability is not a limiting factor in asphalt recycling, provided that the old and new binders are compatible.
  • Article
    Today's sustainability-driven systems require a product or process to be environmentally beneficial as well as cost-effective. This study used life-cycle cost analysis (LCCA) and life-cycle assessment (LCA) to consider the economic and environmental feasibility of using a high content of reclaimed asphalt pavement (RAP) in asphalt mixtures. The LCCA conducted in the study incorporated agency cost as well as the costs incurred by the user in the construction work zone. Initial construction as well as future maintenance and rehabilitation activities were considered in the analysis. The hybrid LCA took into account the material, construction, and maintenance and rehabilitation phases of the pavement life cycle. The results showed savings in terms of costs and energy use and reduction in greenhouse gas emissions with an increase in RAP content. On the basis of the LCCA and LCA performed under various performance scenarios, break-even performance levels were identified for mixtures with up to 50% RAP content. Break-even performance levels underscored the importance of achieving field performance for recycled mixtures equivalent to that for control virgin mixtures.
  • Standard Practice for Recovery of Asphalt from Solution Using the Rotary Evaporator
    • Astm D
    ASTM D5404. Standard Practice for Recovery of Asphalt from Solution Using the Rotary Evaporator. American Society for Testing and Materials; 2012.
  • Article
    Full-text available
    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
    Full-text available
    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
    Full-text available
    This paper presents research evaluating the effectiveness of rejuvenators for production of very high (40% to 100%) reclaimed asphalt pavement (RAP) content mixtures. Nine differently originated softening agents were tested; these included plant oils, waste-derived oils, engineered products, and traditional and nontraditional refinery base oils. Two different dosages of the agents were added to binder extracted from RAP to evaluate their softening potential through testing of kinematic viscosity and penetration at two different temperatures. At 258C the softening efficiency varied by a factor of 12 between the most and least effective rejuvenators. Consistency results at different temperatures were used to express temperature susceptibility by means of penetration index (PI), penetration–viscosity number, and bitumen test data chart of the softened binders. The PI results varied measurably depending on the rejuvenator and supported the low-temperature mixture test results, showing that PI may be a good and simple measure of rejuvenation effectiveness. Low-temperature mixture embrittlement was evaluated at 2108C through determination of the indirect tensile strength and creep compliance for rejuvenated 100% RAP mixture samples. It can be concluded that four of the nine tested rejuvenators reduced extracted binder consistency to the necessary level and reduced susceptibility of RAP mixtures to low-temperature embrittlement. Of the four, two engineered products tested had notably different performance but neither was superior to similar generic oils.
  • Article
    Full-text available
    Asphalt is the most recycled material in the USA at a re-use rate of 99%. However, by average only 10–20% reclaimed asphalt pavement (RAP) is used in a given mix design and large part of the RAP is degraded for use in lower value applications. The amount of RAP in asphalt mixtures can be significantly increased with the application of good RAP management practice, readily available modern production technologies and advanced knowledge of mix design. This paper summarizes the state-of-the-art approaches for increasing the amount of RAP in asphalt mixtures above 40%. The production challenges and common pavement distresses of very high RAP content mixtures are identified and methods to optimise the mix design as well as production technology in order to allow manufacturing of such sustainable mixtures are described. The best practices for RAP management and economic benefits of high RAP use are also discussed.
  • Article
    The recycling of reclaimed asphalt pavement (RAP) helps road authorities to achieve their goal of a sustainable road transport system by reducing waste production and resources consumption. The environmental and economic benefits of using RAP in hot mix asphalt (HMA) applications could be pushed up to the limit, by producing totally recycled HMAs (100% RAP), but the performance of this alternative must be satisfactory. In fact, these mixtures could possibly present problems of workability and durability, higher binder aging and low fatigue cracking resistance. Thus, the objective of this study is to determine if totally recycled HMA mixtures could be a good solution for road paving, by evaluating the merit of some rejuvenator agents (commercial product; used engine oil) in improving the aged binders’ properties and the recycled mixture performance. Several binder samples were prepared with the mentioned rejuvenators and characterized (Pen, R&B and dynamic viscosity), in order to select the best rejuvenator contents. The production temperatures of the corresponding recycled mixtures were evaluated based on their workability. Totally recycled HMAs were produced with the best previously observed combinations, and their performance (water sensitivity, rutting resistance, stiffness, fatigue resistance, binder aging) was assessed. The main conclusion of this study is that totally recycled HMAs can be a good alternative for road paving, especially if rejuvenator agents are used to reduce their production temperature and to improve their performance.
  • 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.
  • Conference Paper
    Full-text available
    In order to sustain the needs of the 21 st century civil infrastructure, we need a paradigm shift in recycling – from current 20-40% to 100% (zero waste). The main hindrance to successful recycling of high Reclaimed Asphalt Pavement (RAP) content mixes is the lack of confidence which stems from a lack of under-standing of the rejuvenation and diffusion process that is supposed to occur when a recycling agent is added to an aged asphalt mix. This research presents finite element simulation of rejuvenator diffusion into an aged asphalt binder film. Five different rejuvenators and aged RAP binder were tested to obtain the required input data for simulation – viscosity at different temperatures and molecular weight. The simulation was run assuming 100% RAP mixture and three different temperatures were simulated for three rejuvenator dosages. The final viscosity for complete diffusion and the required time to reach this state was determined. The results show significant differences in the softening potential of different rejuvena-tors and helps in the estimation of temperature range to reach homogeneous rejuvenator concentration within the binder film before the production process is completed. The simulation results are compared with mechanical tests of binder penetration and mixture creep compliance to confirm the softening effect.
  • Article
    Nowadays, the main problem pertaining to the use of the recycled asphalt pavement (RAP) material in hot mix asphalt (HMA) is the ageing of bitumen, which limits the percentage of applied RAP in the HMA. In this respect, rejuvenation of bitumen binder is the major but the most costly part of recycling. This paper investigates the novelty of using waste cooking oil (WCO), which is frequently found as a polluting waste material in landfills and rivers from the food industry, to rejuvenate the bituminous binder. The physical properties of the original bitumen, aged bitumen and rejuvenated bitumen were measured and compared by the conventional bitumen binder tests including softening point, penetration and Brookfield viscosity, and statistical analyses were used to assess the results. In general, the results showed that the aged bitumen was rejuvenated by the WCO due to a change in its physical properties, which resemble the physical properties of original bitumen (80/100). The optimum percentage of waste cooking oil for the rejuvenated aged bitumen group of 50/60, 40/50, and 30/40 was recognised by adding 1%, 3–4%, and 4–5% WCO, respectively. The statistical analyses also confirm that there was no significant difference between the original bitumen and rejuvenated bitumen.
  • 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
    Full-text available
    Rejuvenator is not a commonly used softening agent to be used in recycling of reclaimed asphalt pavement RAP. In this study, Superpave mixtures containing RAP were designed using rejuvenating agents, including a rejuvenator and a softer binder, and subsequently evaluated in terms of the volumetric results, obtained the indirect tensile strength ITS of samples as well as evaluating the mixtures for rutting using the asphalt pavement analyzer APA. The content of the rejuvenator used for those mixtures containing the rejuvenator was determined from the blending charts of RAP binders containing the rejuvenator. A total of 12 Superpave mixtures including 10 containing RAP and two virgin were designed. The results indicated, for the mixtures tested for this project, that: 1 properties of the recycled mixtures using the rejuvenator, such as ITS and APA, were better than those containing the softer binder; 2 10% more RAP could be incorporated in the Superpave mixtures by using the rejuvenator than using the softer binder; and 3 the blending charts established under the Superpave binder specifications can be used to determine the content of the rejuvenator for the recycling.
  • Article
    The objective of this research was to show a way to conduct rejuvenation of aged polymer modified asphalt binder (PMB) successfully. To fully evaluate and understand the rejuvenation of aged PMB, the Penetration grade tests including penetration, soften point, ductility and elastic recovery and Superpave™ PG grade tests including DSR, BBR and DDT were conducted. The rejuvenation effect of aged PMB by utilizing a fluid recycling agent in common use for binder rejuvenation was evaluated. And then the compound rejuvenation effect of aged PMB by utilizing the recycling agent with a new modifying additive for binder modification was evaluated. The experimental results indicated that the recycling agent in common use currently does not apply to polymer modified asphalt binder rejuvenation. But the recycling agent together with the modifying additive can restore the characteristics of aged polymer modified binder very well. Therefore, compound rejuvenation of polymer modified asphalt binder is recommended. Key wordspolymer modified asphalt binder-penetration grade test-superpave™ PG grade test-recycling agent-modifying additive-compound rejuvenation
  • Article
    This paper aims to study the effect of adding different ratios (from 10 to 40%) of three recycling agents (RAs), including RA-25, RA-75 and RA-250, to the reclaimed asphalt binder (RAB) with a viscosity of 42800 poises and also to the reclaimed asphalt concrete (RAC) according to the Marshall mix design method. The study includes a variety of tests designed to determine the difference between the three RAs in terms of penetration, viscosity, softening point, ductility, toughness of the asphalt binder, as well as indirect tensile strength, and stability value of Marshall specimens. The results show that adding the RA increased the cohesiveness of RAB and thus improved the applicability of RAB. Of the three RAs in this study, RA-25 offered the best performance when added to asphalt binder. This study proposes a recycling model to predict the changes in RAB viscosity when adding RAs. The results of this model show a close fit with experimental data from laboratory tests. This model allows highway engineers to estimate the amount of RA added to aged binder. Marshall tests show that the RA-75 specimen had higher indirect tensile strength and stability value than the RA-25 and RA-250 specimens. Based on overall performance and cost comparisons among the three RAs, this study regards RA-75 as the RA of choice. KeywordsRecycling agent–Viscosity–RAB–RAP–Recycling model
  • 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.