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Effect of rejuvenator type and dosage on rheological properties of short-term aged binders
Abstract
Using reclaimed asphalt pavement (RAP) material in pavement construction is typically an environmentally friendly practice. However, the asphalt available in RAP is already oxidized and stiffened due to various environmental processes. To compensate these problems, rejuvenators can be mixed with aged binder with the aim of restoring its original properties. This study investigates the performance of aged binders blended with three different types of rejuvenators. Thin film oven test aged PG 58–28 binder was mixed with raw waste cooking oil (R1), modified waste cooking oil (R2), and Hydrolene H90T (R3) at the concentrations of 3%, 6% and 9% by the weight of the total binder. To enhance rutting resistance, styrene–butadiene–styrene was also blended with rejuvenated binders and tested. Frequency sweep testing at a wide range of temperatures and frequencies was conducted in the Dynamic Shear Rheometer, and time–temperature superposition was used to obtain parameters including Superpave, Glover-Rowe, Shenoy, Crossover frequency and Rheological index parameters. In addition, the Multi Stress Creep Recovery test was performed to gain an in-depth understanding of the rutting performance of the binders. Based on the comparative study of different rejuvenated binders, the binder rejuvenated using a chemically modified waste cooking oil seems to most be effective in improving the overall performance of the binder without compromising its rutting resistance. In addition, the relationship between different cracking parameters indicated that they are not all compatible with each other in terms of ranking binder performance. Finally, the MSCR parameter seems to more effectively capture the influence of rejuvenation and SBS addition to rejuvenated binders more than other parameters.
Supplementary resources (2)
... The Glover-Rowe (G-R) parameter is combination of G* and δ in a black space diagram and is measured from DSR test at frequency of 0.005 rad/s and temperature of 15 • C. As a useful indicator, it has been widely employed by researchers to investigate rejuvenators efficacy in restoration of binder properties at different aging levels (Abdelaziz et al., 2021;Ahmed et al., 2021;Haghshenas et al., 2021). The G-R values for the onset of damage and significant cracking were equal to 180 kPa and 600 kPa, respectively (Anderson et al., 2011;Pournoman et al., 2018). ...
... However, rejuvenators effectiveness decreases with long-term aging, Arámbula-Mercado et al. (2018) stated that increasing a rejuvenator's dosage resulted in a satisfactory restoration of RAP binder properties. Based on G-R results, it was revealed that WCO rejuvenated binder and polymer modified binders were less vulnerable to aging and resulted in higher fatigue cracking resistance (Ahmed et al., 2021;Elkashef, 2017). Fig. 15 depicts the G-R results of various binder blends with the presence of rejuvenators. ...
Incorporating reclaimed asphalt pavement (RAP) increases concern about long-term fatigue and cracking resistance of the resultant mixture due to the presence of an aged binder. Using a rejuvenator is one of the most promising methods to prolong the aging time for initial cracking and allow the inclusion of higher RAP content. Many discrepancies exist in the literature about rejuvenators' effectiveness in improving the fatigue performance of RAP binder and mixture. These ambiguous and contradictory findings are attributed to using different rejuvenator types and dosages, RAP sources and percentages, binders and mixture fatigue testing approaches. This paper comprehensively reviews and investigates the existing literature to fully understand the rejuvenation mechanism and its impact on the fatigue and cracking resistance of RAP binder and mixture using the most available tests and indicators. In addition, a rigorous laboratory study is carried out to determine the sensitivity of indicators to mix composition and variability. It is concluded that the inclusion of rejuvenators into RAP binders and mixtures may not improve their fatigue and cracking performance to the same level as virgin materials. But by utilizing polymer modification, the bonding between materials increases significantly, which results in better fatigue performance of rejuvenated RAP materials. Despite the positive impact of rejuvenators on RAP mixture fatigue performance, a comparison of different tests results does not offer a consistent indicator for determining fatigue resistance. Hence, it is recommended that the future research should be carried out with reasonable test methods, more complicated analytical techniques, service life characterization models, and climate identical test conditions, to clarify the durability index. Also, a complete evaluation of field performance utilizing RAP and rejuvenator is valuable.
... Rejuvenators can be sourced from a variety of materials, including plant oils, waste-derived oils, engineered products, and both traditional and non-traditional refinery base oils [12,13]. It has been proved that the rejuvenation efficiency of different rejuvenators is strongly dependent on various influence factors, such as bitumen source (type) [14], aging level of bitumen [15], rejuvenator type [16] and dosage [17]. Additionally, the bitumen source also affects the aging kinetics and mechanism of bitumen, further influencing the service life and recycling efficiency of asphalt pavement [18,19]. ...
The chemo-mechanical properties of bitumen undergo significant alternations during aging and rejuvenation, posing challenges for accurately evaluating and enhancing rejuvenation efficiency in asphalt recycling. This study investigates how bitumen source, aging degree, rejuvenator type and dosage influence the chemical and rheological performance of rejuvenated bitumen. Comprehensive characterizations are performed using saturate, aromatic, resin, and asphaltene (SARA) fractionation, elemental analysis, gel permeation chromatography (GPC), and dynamic shear rheometer (DSR) tests. To elucidate chemo-rheological correlations, statistical techniques (Pearson correlation, analysis of variance (ANOVA), and Chi-square tests) are combined with artificial neural networks (ANN). Results indicate that the NB bitumen with more colloidal stability and less sulfur content exhibits the highest resistance to long-term aging. FB bitumen with 4.3% sulfur achieves the best high-temperature deformation resistance with rutting failure temperature (RFT) higher than 80°C, and TB bitumen exhibits the longest fatigue life. Rejuvenation using bio-oil is most effective on reducing relaxation time by up to 60% and increasing creep compliance (Jnr3.2) by 1.7-2.5 times, depending on bitumen type. Rejuvenator dosage sensitivity for relaxation stress follows the trend: bio-oil < engine-oil < naphthenic-oil, while aromatic-oil shows variability depending on its source. Among the tested rejuvenators, bio-oil proves most effective, particularly for rejuvenating TB and FB bitumen. The ANN model demonstrates strong predictive performance for rheological properties, achieving R² values between 0.90 and 0.98, with the highest accuracy observed for relaxation indices, followed by fatigue and rutting properties.
... In addition to material characteristics, the fluctuation in rejuvenation effectiveness is also influenced by the arbitrary choice of these chemical and rheological parameters as evaluation criteria in various studies. However, limited research focuses on comparing and determining the critical chemo-rheological parameters for the rejuvenation efficiency evaluation of variable rejuvenator-aged bitumen blends [20,21]. Further standardizing the evaluation criteria is essential to better comprehend the variations in the efficiency of rejuvenators, investigate the underlying mechanisms, and create new rejuvenators with desired characteristics. ...
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.
... According to the National Center for Asphalt Technology [37], the recycling agents (RAs) can be categorized into five main groups: (1) naphthenic oils; (2) paraffinic oils; (3) aromatic extracts; (4) fatty acids and triglycerides; and (5) tall oils. The effectiveness of RAs and their longevity in asphalt binders and mixtures are affected by factors such as type, source and properties of the virgin binder and aged binders, dosage, and blending process of RAs [38][39][40][41][42][43]. RAs can replace missing aromatics that are lost through aging, as demonstrated in this video: https://youtu.be/uwfYjy4PHDU. ...
This research aims to use a balanced mix design (BMD) approach to investigate the effect of recycling agents (RAs) and an anti-stripping agent on the mechanical properties of warm-mix asphalt (WMA) containing different levels of reclaimed asphalt pavement (RAP). The BMD used three RAs (aromatic extract, triglycerides and fatty acids, and tall oil), an amidoamine WMA additive (PAWMA®), and an anti-stripping agent (Zycotherm®). The Dynamic Creep (DC), Indirect Tensile Strength (ITS), and Semi-Circular Bending (SCB) fracture tests were respectively used to evaluate the rutting, moisture susceptibility, and cracking resistance of mixtures. In addition, two-dimensional and three-dimensional (2-D and 3-D) performance interaction diagrams were developed as typical approaches for the BMD of asphalt mixtures. For mixtures with RAP, the results indicated that the aromatic extract and tall oil RAs decreased the moisture susceptibility, while triglycerides and fatty acids increased the moisture susceptibility. In addition, the RAs generally decreased the rutting resistance of mixtures while they increased the cracking resistance. This effect was more noticeable in the mixtures treated with triglycerides and fatty acids. The results also showed that introducing PAWMA® and Zycotherm® to the mixtures improved their resistance to moisture damage, cracking, and rutting.
... Table 4 lists the technical requirements of the hot-mixed asphalt binder [30]. The rejuvenator types were distinguished based on a difference in the 60 °C-viscosity, mass change, and viscosity ratio after short-term aging [31]. With the increase of 60 °C-viscosity, the sequence of six rejuvenator groups was R1, R5, R25, R75, R250, and R500. ...
This study aims to comprehensively investigate the rejuvenation efficiency of various self-developed compound rejuvenators on the physical, mechanical, and aging properties of aged bitumen, asphalt mortar, and mixture. The results revealed that the restoration capacity of vacuum distilled-oil rejuvenators on high-and-low temperature performance-grade of aged bitumen is more significant. In contrast, an aromatic-oil based rejuvenator is good at enhancing low-temperature grade and aging resistance. Moreover, the temperature and time of the curing conditions for mixing recycling of asphalt mixture were optimized as 150 °C and 120 min. Furthermore, the sufficient anti-rutting, structural stability, and moisture resistance of recycled asphalt mixture affirmed the rejuvenation efficiency of compound rejuvenators.
... They're all on par with VA in terms of performance (64.2 dmm). Several studies have found that increasing the rejuvenator percentage causes binder stripping [55] and harms the physical and chemical compositions [56]. With this respect, Zaumanis et al. [57] have proposed that the percentage of rejuvenating agents that restore the penetration of binder containing RAP can correspondingly fulfill the Superpave criterion for rejuvenator content. ...
Due to the poor cracking performance of aged binders, the use of reclaimed asphalt pavement (RAP) in road pavements is limited. When applying a greater RAP percentage, the use of a rejuvenator is necessary. The re-juvenator's unfavourable softening impact, on the other hand, causes the pavement to be vulnerable to rutting. As a result, RAP binders with optimized rutting and fatigue cracking properties are required. Therefore, this study was carried out to evaluate the simultaneous effects of 70% waste engine oil (WEO) and 30% SBS copolymer as a compound rejuvenator (WS-rejuvenator) on the performance of asphalt binders and mixtures containing RAP binders of 30% and 50%. The physical, chemical and rheological properties of asphalt binders were evaluated using the conventional tests, SARA (Saturate, Aromatic, Resin, and Asphaltene) analysis, FTIR test, thermal gravimetric analysis (TGA), DSR, and BBR. The mechanical properties of mixtures were examined using the Marshall, indirect tensile strength, moisture damage, rutting, and aggregate coating tests. The findings showed that WS-rejuvenator at 5% and 10% recovered the physical characteristics of asphalt binders containing 30% and 50% RAP, respectively. Furthermore, WS-rejuvenator was able to compensate for the light components of the RAP binder that were lost over time. As a consequence, the behavior of the RAP binder at high, moderate, and low temperatures was recovered to that of the virgin binder. By mixing the RAP binder with the compound rejuvenator, the oxygenation indices were effectively reduced. The TGA revealed that the thermal stability of regenerated binders was equivalent to that of the virgin binders. In addition, the mechanical properties of regenerated mixes were enhanced in comparison to the control mixture. In summary, the adoption of RAP and WEO-SBS rejuvenator in asphalt mixtures show promising outcomes to enhance greener pavement materials application in the future.
... Nonetheless, several studies have shown that excess rejuvenator content leads to binder stripping [64]. Also, it has a detrimental influence on rheological characteristics [65]. In this regard, Zaumanis et al. [66] suggested that the amount of rejuvenator that recovers the penetration of aged binder may also meet the criteria of SHRP, which is an optimal rejuvenator content. ...
Rejuvenators have been utilized to restore the physical and rheological properties of aged asphalt binders found in the reclaimed asphalt pavement (RAP). Also, the rejuvenators are utilized to enhance the cracking resistance of asphalt containing RAP. In addition, polymers have been efficiently applied to enhance the rutting performance of rejuvenated mixtures. The purpose of this study was to assess the influence of combining SBS copolymers and aromatic oil (AO) at the same time as a hybrid rejuvenator (HR) on the performance of high RAP asphalt binders and mixtures. HR is a mixture of 25% SBS and 75% AO. The properties of the rejuvenated binders were assessed by SARA (Saturates, Asphaltene, Resin, and Aromatics) fractions analysis, Fourier Transform Infrared Spectrum (FTIR), physical tests, high-temperature storage stability test, Dynamic Shear Rheometer (DSR) test, and Bending Beam Rheological (BBR) test. In addition, the mechanical behaviour of the rejuvenated mixtures was assessed using the Indirect Tensile Strength (ITS) test, moisture susceptibility test, resilient modulus test, and wheel tracking rutting test. The results showed that appropriate adjustment of the SARA fractions and SBS copolymer could improve the overall performance of mixtures and binders with high RAP content. However, it is asserted that a field investigation of this compound rejuvenator should be done to further analyze its influence on the long-term field behavior of high RAP mixtures.
... In this case, the hydrocarbon asphalt binder becomes more brittle due to oxidative and volatilization effects [7]. 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]. ...
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.
... To this end, researchers have suggested to use recycling agents (RAs) as an appropriate way for lowering the stiffness of mixture in order to increase the percentage of RAP materials in asphalt mixture. Based on the previous studies [53][54][55][56], the effectiveness of RAs is dominantly controlled by their origins. Therefore, RAs with two different origins (i.e., aromatic extracts and triglycerides/fatty acids) were employed in this research to consider their effect on the cracking performance of RAP mixtures. ...
This paper aims to evaluate the influence of two recycling agents (RAs) on the cracking behavior of warm mix asphalt (WMA) containing up to 50% reclaimed asphalt pavement (RAP). Two chemically different types of recycling agents, namely aromatic extracts and triglycerides/fatty acids, together with a WMA additive (Sasobit®) were introduced to the mixture. A hot mix asphalt (HMA) mixture (as control mixture) and seven WMA mixtures containing three different dosages of RAP (0, 25, and 50%) and modified by two RAs were prepared. The fracture toughness and energy of the above-mentioned asphalt mixtures were evaluated under pure modes of I and II and mixed mode I/II using the semi-circular bending (SCB) test at mid and subzero temperatures. The results indicated that the cracking resistance of the WMA mixtures without RAP is better than the HMA mixtures under different modes of fracture regardless of the temperature (-15 C and 25 C). In addition, at -15 °C, the presence of RAP in the WMA mixtures reduced the fracture toughness and energy while at 25 °C, it results in an increase in fracture toughness and energy. Moreover, the addition of RAs to the WMA mixtures containing RAP increased the fracture toughness and energy at -15°C. Although RAs decreased the fracture toughness and energy of the RAP blended WMA mixtures at mid-temperature, the performance of these mixtures was better than the HMA mixture.
It is important to fully restore the performance of aged styrene–butadiene–styrene (SBS) modified bitumen (SMB) and reduce its construction temperatures in high-value recycling the waste SMB mixtures. This study aims to assess the performances regeneration and warm-mixing effects on aged SMB by using a compound rejuvenator, i.e. reactive warm-mix rejuvenator (RWR), which consisted of rubber oil, epoxy-terminated polybutadiene ether, cardanol (CA), modified polyethylene (PE) wax and antiaging agent. Two commercial rejuvenators were employed to compare with the RWR. The rejuvenating effects were evaluated through frequency sweep test, multiple stress creep test, cracking temperature test, linear amplitude sweep test, and chemical and morphological structure analyses. The warm-mixing effect was explored by the rotational plate viscosity test. Results indicate that RWR can react with oxygen-containing functional groups on broken molecular chains of SBS polymer with the catalysis of triethanolamine, which enables fractured crosslinking network structure to be repaired successfully. Meanwhile, light components supplied by RWR is able to restore the bitumen matrix of aged SMB to a similar level of original SMB. The RWR is able to effectively restore the viscoelasticity and plateau region of phase angle of aged SMB to the level that is mostly close to that of original SMB, while those two commercial rejuvenators are barely satisfactory. When the RWR content is 12%, the rejuvenated SMB exhibits the satisfactory high- and low-temperature performances, and the better fatigue resistance ability by comparing with original SMB. The modified PE wax in RWR has a lubrication effect on the interaction between macromolecular polymer chains, which gives rise to significant reduction in construction temperatures of rejuvenated SMB incorporating the RWR.
This study investigates the effects of reclaimed asphalt pavement (RAP) and crumb rubber-modified asphalt (CRMA) on the viscoelastoplastic properties of asphalt mixtures under a range of aging conditions. Six asphalt mixtures, with varying RAP contents (0 %, 30 %, and 50 %) and CRMA modifications, were evaluated through dynamic modulus (|E*|) and flow number (FN) analyses. The specimens were subjected to authentic field-aging
conditions for periods of 0, 3, 6, and 9 months. The results reveal that increasing RAP content enhances volumetric properties, Marshall stability, and rutting resistance. CRMA significantly improves fatigue performance and further bolsters rutting resistance, although some detrimental effects are observed at lower temperatures. Aging has a pronounced impact on the mixtures’ performance, particularly on |E*|, Prony series coefficients, viscoelastic strain (εve), and viscoplastic strain (εvp). Newly proposed aging indices, the dynamic modulus aging index (DMAI) and viscoplastic aging index (VPAI), effectively capture the changes in viscoelastoplastic behavior under different aging durations. These findings underscore the potential of RAP and CRMA to enhance pavement durability, prolong service life, and contribute to the development of sustainable and resilient infrastructure. The research offers valuable insights into the performance of asphalt mixtures incorporating RAP and CRMA under real-world conditions.
The utilization of Reclaimed Asphalt Pavement (RAP) in asphalt pavement has obtained global popularity because of its cost-efficiency, technical advantages, and positive environmental influence. However, incorporating RAP requires careful consideration of cracking resistance because of the existence of age hardening of bitumen in RAP. For the mixtures containing high RAP contents, rejuvenators are often applied to enhance the performances of aged bitumen and the cracking of mixtures. This research aims to evaluate the effects of different rejuvenators on the rheological properties of bitumen and the cracking resistance of the mixture under short and long-term aging conditions. To achieve this goal, three rejuvenators - namely, RA1 (petroleum-based), RA2 (waste vegetable oil-based), and RA3 (modified soybean oil-based) were evaluated at contents of 0%, 4%, 12%, and 20%, respectively. The dynamic shear rheometer (DSR) test results show that, under unaged and rolling thin-film oven (RTFO) aging conditions, blended bitumen with RA1 and RA3 have higher G*/sinδ than RA2. Conversely, under pressure aging vessel (PAV) aging conditions, blended bitumen with RA1 and RA3 has lower G*sinδ than that with RA2. Regarding the cracking resistance, the indirect tension asphalt cracking test results show that, under short-term oven aging (STOA) conditions, the mixture using RA2 and RA3 has a higher cracking tolerance index (CT Index ) than the one with RA1. However, under long-term oven aging (LTOA) conditions, the mixture using RA1 has the highest CT Index value. In addition, the high correlations between G*sinδ with CT Index and post-peak slope (|m 75 |) and between the CT Index and |m 75 | are observed.
Determination of optimum rejuvenator dosage is critical to the performance of 100% hot recycled asphalt mixtures. Further, at the optimum dosage, the rejuvenated binder is expected to have chemical and mechanical properties similar to the targeted virgin/control binder. The present study used waste engine oil (WEO) and tall oil (TO) to rejuvenate recycled asphalt pavement (RAP) binders obtained from two different sources. The optimum dosages of the rejuvenators were evaluated using different test procedures. The chemical, morphological, and performance characteristics of the RAP binders rejuvenated at the optimum dosages were studied. True fail temperature was identified as the most suitable parameter for estimating the optimum rejuvenator dosage. The optimum rejuvenator dosages of WEO were found to be 19% and 18%, respectively, for the two RAP sources considered in this study. The corresponding dosages for TO were estimated as 17% and 14%, respectively. Saturates-aromatics-resins-asphaltenes (SARA) analysis indicated that the rejuvenators were able to restore the chemical properties of the RAP binders, the degree of restoration being a function of the rejuvenator type and stiffness of the RAP binder. Results from atomic force microscopy (AFM) analysis confirmed that the rejuvenated binders showed the formation of new structures that were unique for different combinations of RAP binder and rejuvenator. Rutting and fatigue characteristics, evaluated using multiple stress creep and recovery (MSCR) and linear amplitude sweep (LAS) tests, respectively, improved after rejuvenating the RAP binders. In terms of rejuvenation and performance characteristics, TO showed better results in comparison to WEO.
Waste cooking oil (WCO) as a rejuvenator is gaining attention in the pavement industry to incorporate higher reclaimed asphalt (RA) in asphalt mixture. This review article provides a comprehensive review on the current state and the feasibility of turning WCO and RA into cleaner and sustainable asphalt pavement material. Considering the advancements in research related to the utilization of WCO in RA mixture, it was necessary to critically review the past and recent studies to provide a methodological scope for future research. The review discusses a plethora of characteristics focusing on chemical, rheological, simulation, environmental, and economical findings related to the utilization of WCO in RA mixtures. Based on the review, WCO can be adjudged as a potential material to rejuvenate asphalt mixtures with higher recycled asphalt content. Furthermore, although WCO enhances low-to-intermediate temperature performance, studies indicated that moisture damage and higher temperature properties are compromised. Future research scope exists in understanding the rejuvenation capabilities of different WCOs and blends of different types of WCO, optimizing the transesterification process of WCO to improve its quality, molecular dynamic simulations focusing on transesterified WCO, quantification of environmental and economic benefits of recycled asphalt mixtures with WCO, and field performance studies.
Hot recycling of reclaimed asphalt pavement (RAP) into new hot-mix asphalt (HMA) is a complex process that must be precisely calibrated in the asphalt plants. In particular, temperature is a key parameter that, if inadequately set, can affect the final mix performance as it influences the RAP binder mobilization rate and the severity of bitumen short-term aging. The present paper aims at evaluating the effect of HMA production temperature on the behavior of mixtures including 50% of RAP and two types of rejuvenating agents. In particular, volumetric, mechanical, chemical, and rheological properties of the mixes and binder-aggregate adhesion have been investigated on the HMA produced in the laboratory at 140 °C or 170 °C. The results showed that the adoption of a lower production temperature did not significantly influence the air voids content in the mix, but determined a less stiff, brittle and cracking-prone behavior. Moreover, the decrease of the HMA production temperature was profitable for the increase of bitumen-aggregate adhesion.
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.
Pavement preservation treatments applied before significant deterioration and cracking has occurred can extend the service life of a pavement and reduce future maintenance costs. Rejuvenating materials can help to increase the performance of these preservation treatments. Soybean derived additives have been found to greatly reduce the stiffness of aged and brittle asphalt binders. This study proposes the use of these bio-based additives to be used in a fog seal emulsion and as a bio-cutback treatment. The use of functionalized soybean oil in asphalt pavement treatments can greatly reduce the environmental concerns related to other petroleum-derived materials while providing an economical benefit to local agriculture economy. A small field study was conducted to measure the effectiveness of these biomaterials. No significant effect was observed in the extracted asphalt properties, or the low-temperature fracture energy measured by disk-shaped compact tension test (DCT); however, a decrease in the dynamic modulus at higher frequencies and a large decrease in permeability was observed. The treatments were successful in sealing the asphalt pavement, but a higher application rate is needed to show more significant differences in the rheology.
The current practice of recycled waste oil mainly includes waste cooking oil (WCO) and waste engine oil (WEO), etc. This paper provides a comprehensive and in-depth review of the current state and the feasibility of turning these oils into cleaner asphalt pavement materials. The latest types and sources of WCO and WEO in recent years were summarized and analyzed. Furthermore, two kinds of rejuvenated asphalt were sampled, after which they were used to analyze and evaluate the basic properties, rheological properties, microscopic morphology and the mechanism of aged asphalt rejuvenation. Subsequent results revealed that both WCO and WEO could restore the basic performance of aged asphalt, returning it to its original state. In addition, rejuvenated asphalt containing WCO or WEO showed excellent low temperature performance. Though the high-temperature performance of the aged asphalt could be restored with optimum oil content, the recovery was unsatisfactory. Moreover, it was observed that the high quantity of light components presents in the WCO and WEO was the key factor responsible for aged asphalt rejuvenation. Additional research is needed to fully understand the effects of the various waste oils on the performance of aged asphalt. Based on the current situation of single rejuvenator with either WCO or WEO, a compound rejuvenator with WCO and WEO is proposed to better recover waste oils, produce cleaner asphalt rejuvenators, and more effectively reduce environmental pressure. Further study is also needed to improve the compatibility between the compound rejuvenator and aged asphalt. Ultimately, the capability of recycling waste oils into aged asphalt would help minimize water and land pollution, reduce dependence on nonrenewable resources, and diversify asphalt pavement recycling options.
Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges. In the past 10 years, the pavement infrastructure strongly supports the rapid development of the global social economy. New theories, new methods, new technologies and new materials related to pavement engineering are emerging. Deterioration of pavement infrastructure is a typical multi-physics problem. Because of actual coupled behaviors of traffic and environmental conditions, predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis. In order to summarize the current and determine the future research of pavement engineering, Journal of Traffic and Transportation Engineering (English Edition) has launched a review paper on the topic of “New innovations in pavement materials and engineering: A review on pavement engineering research 2021”. Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering, this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world. The content includes asphalt binder performance and modeling, mixture performance and modeling of pavement materials, multi-scale mechanics, green and sustainable pavement, and intelligent pavement. Overall, this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.
One of the most important concerns in using different additives for improving fatigue and low-temperature cracking resistance is the diminishing rutting resistance of pavement. In this research, saturates, aromatics, resins, and asphaltenes (SARA)-separation, dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR) tests were conducted to study the interaction between chemical components and rheological behavior of binders with 25, 50, and 100 percentages of reclaimed asphalt pavement (RAP) binder modified with a softer binder and rejuvenator. The results show that the use of general guidelines for RAP content that do not consider the specific properties of all component materials in use has major limitations. The parameters obtained from rheological tests correlate positively with the asphaltene content. Using just asphaltene content as an index is more reliable than using Gastel and Asphaltene indices for investigating the effect of aging or adding an aged binder because its correlation with MSCR parameters is stronger. In this research, it also discovered that 100% of RAP content could be replaced in the case of an oil rejuvenator addition.
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.
Fatigue resistance is an important factor in high quality Hot Mix Asphalt (HMA). Asphalt cements containing higher concentrations of polymer are known to be more strain tolerant, which can provide improved fatigue resistance in HMA. Polymer modified asphalt is a proven way to improve fatigue performance.
Many municipalities and the Ontario Ministry of Transportation have implemented the Double Edge Notched Tension (DENT) Test with the intention of improving the fatigue performance of the asphalt cement and the corresponding HMA. The DENT is performed at an intermediate temperature that should correspond with fatigue performance. The Multiple Stress Creep Recovery (MSCR) Test is an environmental temperature test that measures the compliance and elastic response of an asphalt binder. The MSCR is conducted at the high-performance grade temperature based on the local 7-day maximum temperature.
This paper will provide the results of a study, which has evaluated asphalt cements containing increasing concentrations of polymer. The results from this research have shown that there is no clear relationship between polymer modification and DENT performance. On the other hand, the percent recovery showed a very good correlation with polymer modification and performance. Based on the information presented in this paper, the MSCR is ultimately expected to be validated by HMA fatigue testing while the DENT is not.
With the rapid economy growth and continuously increased consumption, a large amount of glass waste
materials is generated. This study attends to study the performance of asphalt concrete mix, where some of
fractional fine aggregate is substituted with different percentages of crashed glass materials of 5%, 10%, 15%
and 20 %. The Marshall design was used to examine the influence of the Optimum Asphalt Content (O.A.C.)
at different fine glass percentages and the resistance against water. Asphalt-concrete mix properties can be
improved by using a hydrated lime admixture and other mixtures. It is expected that the recycling and use of
waste glass in asphalt mixes is feasible. Subsequently, by obtaining low price and economic mixes that will
reduce the O.A.C., increase the stability and the durability of the mix, in addition to increasing the skid
resistance of the road surface, this will reduce accidents and save a lot of money. By crushing and sieving,
waste glass materials can be used as fine aggregates in asphalt concrete, where this is called glassphalt.
Satisfactory performance of upper asphalt pavement layers can be achieved by adding glass waste with 10%
of the mix.
It is important to understand rutting susceptibility of asphalt binders at laboratory scale to ensure a long lasting pavement. Researchers have reported applicability of four rheological parameters: (1) Superpave parameter—G*/sinδ (2) Shenoy’s parameter—G*/(1−(1/tanδsin)), (3) non-recoverable creep compliance—Jnr, measured from multiple stress creep recovery test and (4) zero shear viscosity (ZSV) to evaluate rutting resistance of binders. However, comparison of these rutting parameters for warm mix additives (WMA) modified asphalt binders have not been reported in open literature. Thus, this study was undertaken to evaluate rutting performance of a SBS co-polymer modified binder (PMB40) containing three WMA additives using four rheological parameters listed above. Three different WMA additives: wax based (Sasobit®), water based (Advera®) and surfactant based (Rediset®) were selected in this study. Based on three parameters (Superpave, Shenoy and Jnr), it was found that addition of Sasobit® and Advera® help to improve rut resistance of PMB40 binder while Rediset® decreases rut resistance of the binder. The ZSV showed rut resistance improvement for all the additives, which is contrary to the results obtained from other three parameters. Both the Superpave and Shenoy parameters showed a similar trend in rutting resistance of the binder. The optimum dosage of Advera® and Sasobit® was determined based on the Superpave, Shenoy and Jnr parameters. Since, the addition of Rediset® resulted in decrease in rutting behavior, optimum dosage of Rediset® could not be ascertained. A good correlation was found between the Superpave rutting parameter (G*/sinδ) and other three parameters (G*/(1 − (1/tanδsinδ)), ZSV, and Jnr). The outcome of this study showed that, Jnr may be considered as a reliable rut parameter due to realistic test conditions associated with it. The Superpave parameter is more conservative compared to Shenoy parameter, and thus it may still be considered as an important rutting parameter in the absence of Jnr. The ZSV needs further validation to comment on its applicability.
Traditionally, various forms of shift factors such as Arrhenius, Williams-Landel-Ferry (WLF), and polynomials have been used with asphalt materials. Shift factors have also been estimated with binder viscosity parameters. Successful extrapolation of viscoelastic functions requires a robust form of shift factor-temperature relationship. This form is important for performing calculations at the extremes of temperature found in practice. A preliminary analysis of complex modulus E* data of mixtures obtained from the Mechanistic-Empirical Pavement Design Guide (MEPDG) database demonstrated that the Kaelble form of shift factor could describe the functional form of the shift factor more accurately than the Arrhenius, WLF, or polynomial-fitting functions. However, the Kaelble shift function as originally described uses the same temperature as a reference temperature and as an inflection temperature. This factor creates a problem when attempts are made to implement the function in a design method or when materials are compared at a given temperature. Since 2008, additional work has investigated the use of this shift function to describe the properties of asphalt materials, particularly mixes and materials that require a wide range of property description (both above and below the glass transition or some other defining point). A modified form of the Kaelble function has been implemented in analysis software and thus makes multiple calculations more rapid. Additional analysis working with MEPDG E* database materials has shown that shifting works best with the Kaelble modification of the WLF equation. The same method has been applied to other asphalt materials.
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.
This paper examines effects of a new biobased modifier, "biobinder," on low-temperature properties of asphalt binder and compares the results with those of conventional modifiers: crumb rubber, Gilsonite, styrene-butadiene-styrene (SBS), and polyphosphoric acid (PPA). Low-temperature characteristics of modified and nonmodified asphalts were studied using experimental and modeling approaches. A three-point bending beam rheometer was used to measure the stress-strain response of each specimen. A theoretical approach was used to determine stiffness and stress release rate; in addition, the Burgers model was implemented to predict the stored and dissipated energy ratio and quantity of derivation of creep compliance in each of modified and nonmodified asphalt specimens. Effects of various modifications were compared based on both the calculated stored and dissipated energy ratio and quantity of derivation of creep compliance. The proposed biobinder is produced from the thermochemical conversion of biomass (including animal waste, switch grass, and woody biomass). Biobinder is then blended with virgin binder to produce biomodified binder (BMB). This paper argues that the improved low-temperature rheological properties in biomodified binder is reflected in the enhancement in energy dissipation ratio and quantity of derivation of creep compliance.
The Superpave specification parameter |G*|/sind for high temperature performance grading of paving asphalts has not been found to be adequate in rating various binders, especially some polymer-modified ones, for their rutting resistance. This has led researchers to seek other possible parameters that may better relate to rutting resistance and also to search for ways to improve the existing parameter |G*|/sind so that it is more sensitive to pavement performance. Some researchers have suggested the repeated creep and recovery test, while others have used a semi-empirical approach as a means to refine the existing Superpave specification parameter.
The present work revisits the proposed refinements of the Superpave specification parameter and shows that the semi-empirical approach involving curve-fitting of experimental data is not necessary if the derivations are based on fundamental concepts. The final equations obtained through a theoretical development are verified using part of the same experimental data that were used by the earlier researchers.
Since the realization that the Superpave specification parameter |G*|/sind is not adequate in rating polymer-modified binders for high temperature performance grading of paving asphalts, researchers have been seeking ways to refine this parameter to make it more sensitive to pavement performance and also find other possible parameters that may better relate to rutting resistance. Most of these efforts have led to positive results in the right direction, but each has its own set of limitations that is preventing immediate implementation of the suggested ideas.
From amongst the various suggestions, the one that has the highest merit for possible use is the refinement of the Superpave specification parameter, namely, the term |G*|/(1-(1/tandsind)) that evolved through a theoretical derivation based on fundamental concepts (Shenoy, 2001). This performance-based specification term was shown to be more sensitive to the variations in the phase angle d than the original Superpave specification parameter and thus described the unrecovered strain in the binders more accurately. Though this refinement led to better discrimination between rutting resistance of various asphalts, not all asphalts with the same performance-grade based on the new parameter (Shenoy, 2001) behaved identically in their rutting performance in laboratory mixture test evaluations.
By model-fitting the master curve formed from |G*|/(1-(1/tandsind)) versus frequency data at various temperatures for each binder, a rut-controlling term was extracted that correctly graded the binders in terms of the mixture performance (Shenoy, 2002). However, this approach is not appropriate for routine use as it requires large sets of data generation at various temperatures to form the master curve before determination of the model parameters for the rut-controlling term.
The present work proposes an alternative method of using the term |G*|/(1-(1/tandsind)) such that it can be easily adopted as a high temperature performance grading specification for asphalts and evaluates its efficacy through actual field performance data.
This study investigates the chemical characteristics of rejuvenators and the effect of different rejuvenators on the morphology and fundamental behavior of rejuvenated asphalt binders. Gas chromatography-mass spectroscopy (GC-MS) and atomic force microscopy (AFM) were conducted to determine the chemical composition of rejuvenators and asphalt surfaces' morphology. Also, surface free energy (SFE) measurements were performed to quantify the cohesive bond energy of rejuvenated binders. The thin film oven test (TFOT)-aged performance graded (PG) 58-28 binder was rejuvenated with waste cooking oil (UT), chemically modified waste cooking oil (TR), and Hydrolene H90T (HL) at concentrations of 3%, 6%, and 9% by weight of the total binder. To understand the compatibility, styrene-butadiene-styrene (SBS) was also blended with rejuvenated binders. The experimental study found the variability of free fatty acid compositions in rejuvenators, which is hypothesized to affect pavement performance. Results showed that rejuvenation alters the surface microstructure of binders, which provides insights into the overall performance of the binder. Also, rejuvenation improves the moisture damage resistance of binders significantly. This experimental study found a good correlation between the chemical, morphological, and fundamental behavior of the rejuvenated binders, which is expected to help quantify the performance of rejuvenated asphalt mixes.
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.
With the ever-increasing awareness for sustainability, the utilization of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt paving has become more and more popular in recent years. To restore the rheological and other properties of aged binders, rejuvenators are commonly used during the asphalt mixtures production containing RAP and/or RAS. The conventional rejuvenation incorporation method is to blend the rejuvenators with virgin binder first, followed by mixing with other recycled materials. This paper presents a laboratory study on asphalt binder with a different rejuvenator application procedure, which blends the rejuvenators with the recycled materials first and then incorporates the blends with the virgin binder afterwards. Rheological and aging properties of asphalt binders blended with different procedures were analyzed through the dynamic shear rheometer (DSR) test and gel permeation chromatography (GPC) tests. Compared to the conventional method, it was revealed that the method by blending the rejuvenators with the recycled materials first significantly improved the workability of the binder blends during mixing. The new method resulted in a different rheological property and caused less aging effect for the asphalt binder blends in the short-term aging. However, for the long-term aging, the two incorporation methods exhibited similar aging effects on the binder blends.
In Canada, over 90% of the paved roads are asphalt pavements. Most of these pavements were built decades ago, which are currently exhibiting a significant amount of surface distresses. These distresses includes potholes, rutting (deformation in the wheel path), and cracking. To repair these distressed pavements, the road agencies spend millions of dollars every year, of which a significant portion goes to acquiring new natural aggregates and asphalt. To reduce the rehabilitation cost, road agencies use up to 100% reclaimed asphalt pavements (RAP) in new construction. However, the asphalt available in recycled pavements is oxidized and stiffened due to various environmental processes which are susceptible to thermal and fatigue cracking. To soften and to decrease the viscosity of the RAP materials, various rejuvenators are being in practice. The rejuvenators are able to reactivate and restore the original properties of this long-term aged asphalt binder. Using Waste Cooking Oil (WCO) is one of the eco-friendly solutions which contains the similar lighter oil components of asphalt and can be used as an acceptable rejuvenator. Recent studies showed that WCO has an excellent potential to be used as a good rejuvenator in the hot mix asphalt (HMA) industry. This review article summarizes the performance and adverse effects of WCO as a rejuvenator.
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.
This study investigated the effects of aging on the micromechanics, chemical functional groups, and rheological properties of SBS-modified asphalt, with the help of atomic force microscopy, Fourier transform infrared spectroscopy, and dynamic shear rheometry, respectively. Aging has a significant effect on the micromechanics of asphalt and its distribution, especially in the pressure aging–vessel aging process. The micromechanics are affected by the chemical functional groups directly, and the resulting changes are the outcome of the synergistic effect of the aging of base asphalt and the degradation of the SBS modifier. The micromechanics were quantitatively consistent with the rheological properties, thus indicating that the micromechanics of the asphalt surface contribute to the macro-mechanical behavior. Such a systematic approach for the characterization of the aging process of SBS-modified asphalt could provide a scientific method for improving the properties and recycling of SBS-modified asphalt.
Bio-binder is a renewable material which can be derived from natural resources. Applications of bio-binder in enhancing asphalt’s properties have gained profound progresses in past several years. However, limitation still exists in our knowledge on adhesion property of asphalt blended with bio-binder. This study aims to characterize adhesion behavior of bio-binder modified asphalt using sessile drop device (SDD) and atomic force microscopy (AFM). Relationship between the two test results is also investigated. It is shown that addition of bio-binder would introduce different impacts on surface properties for different base asphalts (Pen30 and Pen70 asphalts in this paper), which may be attributed to distinct compatibilities between bio-binder and different asphalts. And the work of adhesion data demonstrates that the bio-binder enhances the interaction between basalt and bio-binder modified Pen70 asphalt binders while depress the interaction between basalt and bio-binder modified Pen30 asphalt binders. It is also found that AFM adhesive force is tip-dependent which may be interpreted using different contact mechanics. In this paper, the high coefficient of variation in soft tip’s data may result from the capillary force and contamination during scanning. Interestingly, dispersive surface free energy and AFM results show some reasonable agreements for modified Pen70 asphalts, though there is still a gap between these two methods’ results. It is speculated that the variations between surface free energy method and AFM measurement can be attributed to the differences in probe substance, test scale and measured components. Findings in this paper not only promote the development of bio-binder modified asphalt, but also shed lights of the application of AFM in characterization of asphalt’s adhesion property.
Terminal Blend (TB) rubberized asphalt is a promising technology in producing crumb rubber asphalt as it overcomes the shortcomings such as lack of storage stability and workability. However, the limitation of TB asphalt is that the high temperature property is drastically reduced compared to conventional rubberized asphalt binders due to the degradation of crumb rubber. Currently, the studies regarding to modification to improve its high temperature property is not adequate. The objective of this paper is to investigate the optimum modification formula of asphalt binders using styrene-butadienestyrene (SBS) and polyphosphoric acid (PPA) and explore their mechanism of modification. Firstly, dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test were conducted to evaluate the rheological properties at both high and low temperatures. Furthermore, Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) test were conducted to detect the chemical changes of TB modified asphalt binders. Finally, the high temperature stability and fatigue property of TB modified asphalt mixtures were applied to verify the performance properties. Results indicates that 20T3S (20 wt% crumb rubber and 3 wt% SBS) used to produce the modified binders was the best modification formula considering both high and low temperature rheological properties. The modification mechanism was that SBS formed 3D cross-linking network structure in TB binder, which played an important role in enhancing high temperature properties of TB binders. Additionally, 20T3S asphalt mixture had better high temperature stability and fatigue performance comparing to 4.5S (4.5 wt% SBS) modified asphalt mixture.
Fatigue cracking is a common form of pavement failure and is strongly tied to the properties of the asphalt binder used in the mix. The Superpave grading procedure is currently used in the United States and in other parts of the world to classify and select asphalt binders for the design of asphalt mixtures. The parameter,
, in the Superpave grading system is used to control the quality of the binder at intermediate temperatures. It is also used by many as a metric to measure the inherent fatigue cracking resistance of an asphalt binder. It is widely recognised that while this parameter was a significant improvement over previous binder grading and selection methods, it does not accurately measure the inherent fatigue damage resistance of asphalt binders. This paper provides a review of several studies that have attempted to develop methods to measure the fatigue damage resistance of asphalt binders during the last two decades. The studies reviewed in this paper have been classified into four main categories based on the type of test method employed. The four categories include: time sweep performed using the Dynamic Shear Rheometer (DSR), amplitude sweep using the DSR or its variations, ductility-based test methods and strength-based tests. This paper focuses primarily on tests developed in the United States with an emphasis to improve the existing Superpave criteria along with relevant research from other parts of the world.
The development of the well-known Christensen–Anderson (CA) rheological model grew out of attempts to model the relaxation spectra of asphalt binders using a skewed logistic distribution function. For this reason, there exist very strong relationships between the CA model parameters and the characteristics of relaxation spectra for asphalt binders. This paper presents a recently developed equation that allows direct and accurate calculation of the relaxation spectra from CA model parameters, demonstrating the nature of this relationship. Of the CA model/spectrum parameters, the most important in terms of describing overall behaviour and potential performance is the R-value, which describes the shape and skewness of the spectrum. This parameter and other similar rheological parameters have been linked to various important aspects of asphalt binder behaviour, including fatigue resistance, chemical composition and degree of oxidative ageing. This makes the parameter R a potentially useful parameter for inclusion in asphalt binder specifications, although care must be taken in how it is determined to ensure that it is accurate, repeatable and reflects the performance characteristics of interest.
The present study was undertaken to evaluate the effects of two types of reclaimed asphalt pavement (RAP) binders on rheological properties and Superpave performance grade (PG) of a styrene-butadiene-styrene (SBS) co-polymer modified binder (PMB). Two RAP materials: one from urban highway (RAP-A) and other from rural highway (RAP-S) were collected in the study. The asphalt binder extracted from RAP-A and RAP-S had different viscosity, rheological and chemical characteristics. The asphalt binder extracted from RAP-A was found to be stiffer compared to the binder obtained from RAP-S. The PMB was blended with different proportions (i.e., 0, 15, 25 and 40% by weight of binder) of RAP-A and RAP-S binders. Different physical tests, namely penetration, softening point, viscosity, ductility and elastic recovery were conducted on PMB blended with the RAP binders. In addition, high and low temperature Superpave PG of PMB with RAP blended binders were determined based on dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, respectively. The results from physical properties of asphalt binders showed that addition of RAP binders adversely affected performance of PMB. Both type of the RAP binders had difference influence on physical properties of PMB. Addition of 15% of RAP bumped PG of PMB by one grade interval (i.e., from PG76 to PG82). The maximum grade bump for high temperature PG was found to be one grade interval even after addition of 40% RAP. The low PG grade did not change with addition of the RAP binders. Statistical analyses were conducted to compare effects of two types of RAP binders on properties of PMB. Overall the results showed that type of the RAP binder can have different influence on consistency and Superpave PG of PMB, thus caution should be taken during selection of grade of a base binder.
The performance of asphalt binder modified with waste cooking oil (WCO) is affected by the quality of the WCO itself because of the degradation process during frying activity. The quality of WCO can be determined by conducting an acid value test, wherein an increased acid value has caused the decreasing of rheological performance. Therefore, untreated WCO with a high acid value is chemically modified and pre-treated with alkaline catalysts to undergo transesterification. The transesterification of WCO is performed as a pre-treatment to reduce high free fatty acid (FFA) content, which is equivalent to the acid value. The treated WCO sample undergoes a chemical test (acid value), physical test (penetration and softening test), and rheological test through a dynamic shear rheometer (DSR). The rheological performance of rutting, which is analyzed using DSR, is compared between the untreated and treated WCO to determine any improvement in rutting resistance after chemical modification. Results show that the acid value reduces from 1.65 mL/g to 0.54 mL/g after the chemical treatment of WCO. The decrease in acid value affects the improvement of penetration, softening point test, and rheological performance test, wherein increased failure temperature is achieved at 70 °C for treated WCO compared with the untreated WCO at 64 °C.
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.
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.
Non-load related cracking of asphalt pavements is cracking that is associated with the development of thermal stresses – usually manifesting itself as transverse and block cracking. Transverse cracking is generally referred to as low temperature cracking since it is associated with cracking that develops as the asphalt pavement is subjected to low temperatures that approach the limiting stiffness of the asphalt binder. Block cracking, however, is usually associated with cracking that may happen as the asphalt pavement ages and loses durability.
As part of a research project involving airfield asphalt pavements, a laboratory study was conducted to evaluate if there was any potential relationship between asphalt binder properties and non-load related cracking. The objective of the research was to identify one or more parameters that could be easily determined by testing that would allow an airport manager to monitor the loss of durability experienced with aging and to use the information to assess when the airfield asphalt pavement would need preventative maintenance to minimize the effects of non-load associated cracking.
In the laboratory study, three asphalt binders were selected representing different expected aging characteristics. Testing was conducted on asphalt binders in their unaged condition, as well as on asphalt binders that had undergone long-term aging in the Pressure Aging Vessel (PAV) at 100°C and 2.1 MPa pressure for 20, 40, and 80 hours. The purpose of the longer PAV aging times was not to correlate with any expected service life, but simply to create a more highly-aged sample.
Past research indicated some relationship between ductility (conducted at an intermediate temperature) and the durability of an asphalt pavement. Using ductility as the hypothesized property related to flexibility, two parameters were identified that related well to ductility and the expected loss of flexibility with aging. The first is a parameter suggested by other researchers – G′/(η′/G′) – as determined using the Dynamic Shear Rheometer (DSR). The second is a parameter that quantifies the difference in continuous grade temperature for stiffness and relaxation properties – referred to in the paper as ΔTc. In both cases, the parameters appear to quantify the loss of relaxation properties as an asphalt binder ages.
Limited field testing from three general aviation airports generally validated the findings from the lab study, with the newer pavements having values of G′/(η′/G′) and ΔTc that indicated less aging and more flexibility than the older pavements. Based on the study findings, values were identified for both parameters that could provide an indication of a loss of durability that could lead to an increased risk of non-load associated cracking.
The aim of this contribution is to investigate the possibility of using microcapsules containing waste cooking oil (microWCOs) in situ rejuvenating aged bitumen. MicroWCOs had been successfully fabricated by in situ polymerization using prepolymer of methanol melamine formaldehyde (MMF) as shell material. The properties of morphology, size, shell thickness and mechanical properties had been adjusted by the emulsion speed and core/shell ratios. It was found that MicroWCOs had thermal stability in melting bitumen and survived during repeated temperature changes. Moreover, WCO can easily penetrate into age bitumen as a rejuvenator. The aged bitumen had a trance to recovery its virgin properties after rejuvenated including penetration value, softing point value, and viscosity value.
This paper presents the production, modification, and characterization of biobinder from swine manure. A hydrothermal process was used to convert swine manure to a bio-oil. The bio-oil was fractionated to extract water, solid residue, and some of the organic compounds. The sticky residue after fractionation was used as a replacement for asphalt binder. This paper presents production and chemical and rheological characterization of the biobinder as compared with petroleum-asphalt binder. Biobinder from swine manure was found to be a promising candidate for partial replacement for petroleum-asphalt binder. Considering the limitations imposed on growth of swine farms by manure management practices and environmental regulations and the increasing demand for asphalt binder for infrastructure rehabilitation, this sustainable development will result in major improvements in environmental and economical impacts in both the agricultural and construction sectors. Hence, this study offers a unique approach that simultaneously addresses the increased depletion of petroleum resources the growing swine manure pollution and released greenhouse gases and the development of sustainable alternative for petroleum-asphalt binder. The use of biobinder will improve petroleum-asphalt binder's low temperature properties while reducing asphalt pavement construction costs; the cost of biobinder production is estimated to be 0.54/gal.) and that of asphalt binder is 2/gal). DOI: 10.1061/(ASCE)MT.1943-5533.0000237. (C) 2011 American Society of Civil Engineers.
Rejuvenators are products designed to restore original properties to aged (oxidized) asphalt binders by restoring the original ratio of asphaltenes to maltenes. These products are used to retard the loss of surface fines and to reduce the formation of additional cracks; however, for a rejuvenator to be successful, it must penetrate the pavement surface. Besides, application of a rejuvenator will also reduce the skid resistance of the pavement, which may be significant for runways or other areas where high aircraft speeds are likely to occur. To solve this, in [1], these rejuvenators were encapsulated and mixed in asphalt concrete. The idea is that once the stress in the capsules reaches a certain threshold, the particles break and the rejuvenator is released. This research focuses on the properties of these capsules. Four different types of rejuvenators will be encapsulated and their effect on the properties of the capsules investigated. Besides, the release mechanisms of the capsules will be unravelled. Finally, the capsules will be mixed in a porous asphalt mixture, and their aspect examined under the microscope once the asphalt sample is broken under indirect tensile tests.
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.
Reclaimed asphalt pavement (RAP) mixtures have shown good resistance to rutting for hot-mix asphalt (HMA) pavement. Mixtures with polymer-modified binders such as styrene-butadiene-styrene (SBS) have also shown good performance against rutting and cracking. This paper presents the laboratory evaluations used to determine the rutting and cracking performance of the RAP mixtures with SBS polymer-modified binders as virgin binders. The asphalt pavement analyzer (APA) test and indirect tensile (IDT) test were conducted for the laboratory evaluation. The properties of SBS polymer-modified binders blended with recovered RAP binders were also investigated. The binder tests included G*/sin delta as the rutting parameter and G*sin delta as the cracking parameter of the Superpave(R) PG grade system. The multiple stress creep and recovery test, which has recently received attention as an indicator of the rutting potential of polymer-modified asphalt binders, was also performed. RAP mixtures with SBS polymer-modified binders were fabricated containing different amounts of RAP materials: 0%, 15%, 25%, and 35%. From the APA and Superpave IDT tests, RAP mixtures with modified binders showed good performance regardless of the amounts of RAP materials in HMA. Even though the parameters, G*/sin delta and G*sin delta, and the percentage of recovery indicated the different amounts of RAP binders in polymer-modified binders, the relationship between these parameters and mixture performance was not clearly identified.
The styrene-butadiene-styrene (SBS) triblock copolymer was used to modify the asphalt binder. The morphology and engineering properties of the binders were investigated using transmission electron microscopy (TEM), rotational viscometer, and dynamic shear rheometer. The morphology of polymer-modified asphalt was described by the SBS concentration and the presence of microstructure of the copolymer. When the SBS concentration increased, the copolymer gradually became the dominant phase, and the transition was followed by a change in engineering properties of SBS-modified asphalt. Results from TEM showed that depending on the asphalt and copolymer source, a variety of morphology can be found. The SBS-modified binders might show a continuous asphalt phase with dispersed SBS particles, a continuous polymer phase with dispersed asphalt globules, or two interlocked continuous phases. The optimum SBS content was determined based on the formation of the critical network between asphalt and polymer. Because of this network formation, the binders showed a large increase in the complex modulus that indicates resistance to rutting. At low SBS concentrations, the Kerner model was found to be appropriate to estimate the theological properties of SBS-modified asphalt. An adapted Kerner equation was proposed in this study to predict the complex modulus of modified asphalt at high SBS concentrations.
Asphalt cements are often regarded as a colloidal system containing several hydrocarbon constituents: asphaltenes, resins, and oils. The high molecular weight asphaltene particles are considered to be covered in a sheath of resins and dispersed in the lower molecular weight oily medium [Whiteoak (1990) The Shell Bitumen Handbook (Shell Bitumen UK, Riversdell House, Surrey, UK)]. However, the exact arrangement of the asphaltene particles within the oily phase will vary depending on the relative amounts of resin, asphaltene, and oils. It is this arrangement and the degree of association between asphaltene particles that govern the rheological properties of the cement [Simpson et al. (1961) J. Chem. Eng. Data 6:426–429; Whiteoak (1990)]. Here we report for the first time the observation of a three-dimensional network of asphaltene strands within straight, polymer-modified, and aged asphalt cements. While the existence of a asphaltene/resin micelle network has been proposed in previous studies [Whiteoak (1990)], direct observation has not been reported. The network is expected to greatly influence the rheological properties of the asphalt binder and ultimately the properties of asphalt concretes. In situ fracture studies of asphalt cement/aggregate composites indicate a possible correlation between the network structure and adhesion between the cement binder and aggregate. Microsc. Res. Tech. 38:529–543, 1997. © 1997 Wiley-Liss, Inc.
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.
In this study, the characteristics and performance of three commonly used catalysts used for alkaline-catalyzed transesterification i.e. sodium hydroxide, potassium hydroxide and sodium methoxide, were evaluated using edible Canola oil and used frying oil. The fuel properties of biodiesel produced from these catalysts, such as ester content, kinematic viscosity and acid value, were measured and compared. With intermediate catalytic activity and a much lower cost sodium hydroxide was found to be more superior than the other two catalysts. The process variables that influence the transesterification of triglycerides, such as catalyst concentration, molar ratio of methanol to raw oil, reaction time, reaction temperature, and free fatty acids content of raw oil in the reaction system, were investigated and optimized. This paper also studied the influence of the physical and chemical properties of the feedstock oils on the alkaline-catalyzed transesterification process and determined the optimal transesterification reaction conditions that produce the maximum ester content and yield.
Every year, there is a demand of more than 110 million metric tons of asphalt all around the world. This represents a huge amount of money and energy, from which a good part is for the preservation and renovation of the existing pavements. The problem of asphalt is that it oxidizes with time and therefore its beneficial properties disappear. Traditionally, rejuvenators spread in the road surface, are used to restore the original properties of the pavement. The problem is that, for a rejuvenator to be successful, it must penetrate the pavement surface. Furthermore, application of a rejuvenator will reduce the skid resistance of the pavement and, besides, rejuvenators have many aromatic compounds that can be harmful for the environment. To solve these problems this paper introduces a new concept in road construction: encapsulated rejuvenators. The basic principle is that when the stress in capsules embedded in the asphalt reaches a certain threshold value, the capsules break and some rejuvenator is released, restoring the original properties of the pavement. This paper will show how to prepare such capsules and how to determine their characteristics. This is one of the first steps towards intelligent pavements.
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