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This study explores different methodologies to select proper doses of three palm-oil-based rejuvenators to restore the properties of the effective binder present in asphalt mixtures with high Reclaimed Asphalt Pavement (RAP) content. Two commercial vegetable-based rejuvenators were also used as reference for comparison. The dose selection methods are based on penetration and softening point in unaged, short- and long-term aged states, and High Temperature Superpave Performance Grade (PGH) verified with Fatigue Low-Temperature Superpave Performance Grade (PGFL). In addition, a novel approach based on the thermodynamic properties of the recycled binder blends (i.e. mix of virgin binder, RAP binder and rejuvenator) quantified through the Surface Free Energy (SFE) measurements was also explored. In all cases, the optimum dose selection was determined by the amount of rejuvenator required to provide equivalent or better properties than the virgin binder in its unaged and aged conditions. The results suggest that the PGH approach verified with PGFL is the most appropriate method to determine the optimum rejuvenator dose. This methodology was initially validated by means of rheological and chemical testing conducted on the recycled binder blends at the selected dose in different ageing states. [ABSTRACT FROM AUTHOR]

Sustainability in road construction can be achieved by integrating recycled materials in the production of new pavement. One such approach is using reclaimed asphalt pavement materials (RAPM) in hot mix asphalt (HMA). Successful implementation of RAPM in HMA can only be achieved by having good comprehension of the essential material characterisation and design process. The main objective of this review is to summarise the literature and provide a keen understanding of the characterisation of materials involved (RAPM and rejuvenators) and mix design, by giving due consideration to the interaction of virgin and recycled materials. Widely used techniques for extraction and recovery of reclaimed asphalt pavement (RAP) binder have been reviewed. The advantages and disadvantages of different characterisation techniques are identified. The effect of various factors on the volumetrics of the recycled mixes is presented. Insight in to the requirements of a rejuvenator by taking into account the changes in binder after ageing is provided. Aspects that need further exploration to normalise and increase the confidence of RAPM in HMA are also highlighted as the future recommendations. [ABSTRACT FROM AUTHOR]

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This study investigates the use of cooking oil waste (COW) and low-viscosity binder (LVB) to improve the performance of reclaimed asphalt pavement (RAP) binders and promote the consumption of by-product materials. The aging resistance capacity of experimentally aged asphalt binders with COW as rejuvenators and recently synthesized high-penetration asphalt binders was evaluated using the Rolling Thin Film Oven Test (RTFOT) and the Pressure Aging Vessel (PAV) tests. The Dynamic Shear Rheometer (DSR) Test, Hamburg Wheel Tracking, and Overlay Tester (OT) were used to evaluate the dynamic shear characteristics and performance of the modified RAP mixture. The test results show that using low-viscosity binder (LVB) positively affected the quality of reclaimed asphalt binder after prolonged aging periods. Additionally, the dynamic shear modulus of the AP1 mixture was 5% less than the reference mixture after the PAV condition, indicating a reduced stiffness effect. Considering the performance of reinforced RAP mixture, all RAP mixtures withstood a load of 20,000 cycles settling under 20 mm after 10,000 cycles. In mix COW1, COW5, and LVB, the final settlement was 3.75 mm, 3 mm, and 2.66 mm. Meanwhile, the load reductions of the above mixes were 73.3%, 74.2%, and 76.4% after 1000 OT cycles. In conclusion, utilizing LVB in RAP binder can produce equivalent benefits as applying a rejuvenator additive, even at a high asphalt content (40%) threshold. This research can offer insights into improving the performance of RAP binders in service and promoting the development of green construction.

In recent years, Reclaimed Asphalt Pavement (RAP) has become very popular in pavement construction due to its benefits to the economy and the environment. The present study investigates the feasibility of employing Waste Cooking Oil (WCO) and Waste Engine Oil (WEO) as rejuvenators blended with reusable asphalt binder through physical and rheological properties at high and intermediate temperatures. Examined conventional properties of WCO-and WEO-modified bitumen include softening point, penetration, ductility and viscosity. In addition to these rheological properties, they also include Amplitude Sweep, Frequency Sweep, Multiple Stress Creep Recovery (MSCR), Linear Amplitude Sweep (LAS) and High-temperature Performance Grading (HTPG) tests carried out by Dynamic Shear Rheometer (DSR). The experimental outcomes revealed that both WCO and WEO could reduce deformation resistance and improve stiffness, workability and viscous behavior of aged bitumen. Moreover, the addition of waste oils improves the fatigue lives of rejuvenated bitumen and enhance fatigue cracking resistance, but at the cost of rutting resistance. Overall, WCO performs better in restoring stiff binder properties than WEO as per rheological testing. [ABSTRACT FROM AUTHOR]

Encapsulated rejuvenating agents for self-healing of bituminous materials have gained significant interest within the road scientific community, turning these enhanced materials into a hot topic. In this study, virgin cooking oil, waste cooking oil, and virgin engine oil were used as encapsulated rejuvenators to restore properties of aged bitumen and their capacity for asphalt self-healing. The alginate-based capsules and their components were characterised by chemical, physical, morphological, thermal stability, and mechanical tests. Self-healing recovery tests of cracked long-term aged bitumen by the effect of oil release were also performed. Main results showed that all rejuvenating oils presented functional groups contributing to the chemical restoration of aged bitumen. Encapsulation of stable O/W emulsions was achieved. Capsules presented uniform size, multicavity microstructure, high encapsulation efficiency, thermal and mechanical stability. Finally, all rejuvenating oils were successfully diffused into an aged bitumen, although virgin cooking oil presented the highest healing capacity. [ABSTRACT FROM AUTHOR]

This study looked at the state-of-the-art present knowledge base and trends in the area of using rejuvenators in reclaimed asphalt pavement (RAP) by systemic analysis and visualisation using VOSviewer and Scopus analyser; a total of 1872 studies were mined from the Scopus database for the purpose of this study. This quantitative approach to the review of literature removes author bias. The study was able to identify keywords and their cluster groups making up of core research domains ((1) asphalt binder composition and properties, (2) reclaimed asphalt mixtures (recycling), (3) reclaimed asphalt performance characteristics, (4) reclaimed asphalt sustainability, (5) rejuvenating agents and their performance, and (6) area of application). The study was able to identify the top authors; their document counts and citations; the most influential journals, institutions, and countries leading the way in the research domain; and the link between these authors and keywords within the existing body of literature in the research area. This study will help policymakers in identifying the main research themes and possible area of investments for further research in RAP. This study will also be a valuable compendium to researchers who intend to broaden the scope of the research area. [ABSTRACT FROM AUTHOR]

Growing environmental pollution worldwide is mostly caused by the accumulation of different types of liquid and solid wastes. Therefore, policies in developed countries seek to support the concept of waste recycling due to its significant impact on the environmental footprint. Hot-mix asphalt mixtures (HMA) with reclaimed asphalt pavement (RAP) have shown great performance under rutting. However, incorporating a high percentage of RAP (>25%) is a challenging issue due to the increased stiffness of the resulting mixture. The stiffness problem is resolved by employing different types of commercial and noncommercial rejuvenators. In this study, three types of noncommercial rejuvenators (waste cooking oil (WCO), waste engine oil (WEO), and date seed oil (DSO)) were used, in addition to one type of commercial rejuvenator. Three percentages of RAP (20%, 40%, and 60%) were utilized. Mixing proportions for the noncommercial additives were set as 0–10% for mixtures with 20% RAP, 12.5–17.5% for mixtures with 40% RAP, and 17.5–20% for mixtures with 60% RAP. In addition, mixing proportions for the commercial additive were set as 0.5–1.0% for mixtures with 20% RAP, 1.0–1.5% for mixtures with 40% RAP, and 1.5–2.0% for mixtures with 60% RAP. The rutting performance of the generated mixtures was indicated first by using the rutting index (G*/sin δ) for the combined binders and then evaluated using the Hamburg wheel-track test. The results showed that the rejuvenated mixtures with the commercial additive at 20 and 60% RAP performed well compared to the control mixture, whereas the rejuvenated ones at 40% RAP performed well with noncommercial additives in comparison to the control mixture. Furthermore, the optimum percentages for each type of the used additives were obtained, depending on their respective performance, as 10%, 12.5%, and 17.5% of WCO, 10%, 12.5–17.5%, and 17.5% of WEO, <10%, 12.5%, and 17.5% of DSO, and 0.5–1.0%, 1.0%, and 1.5–2.0% of the commercial rejuvenator, corresponding to the three adopted percentages of RAP. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of two encapsulation methods (i.e., dropping funnel and syringe pump), two concentrations of the alginate-based encapsulating material (2%, and 3%), and three oils as bitumen rejuvenators (virgin sunflower oil, waste cooking oil, and virgin engine oil) on the morphological, physical, chemical, thermal, and mechanical properties of encapsulated rejuvenators for asphalt self-healing purposes. A general factorial design 2 × 2 × 3 was proposed to design 12 different Ca-alginate capsules. Significant differences on the morphological, physical, and mechanical properties of the capsules were analysed by three-way ANOVA and Tukey HSD Post Hoc analyses. The effect of the type of oil on the self-healing capacity of cracked bitumen samples was also evaluated. The main results showed that the design parameters and their interactions significantly affected the morphological, physical, and mechanical properties of the capsules. Capsules synthesised via syringe pump method, with virgin cooking oil and 2% alginate was the most appropriate for asphalt self-healing purposes since its uniform morphology, encapsulation efficiency up to 80%, thermal degradation below 5% wt., and compressive strength above the reference asphalt compaction load of 10 N. Finally, the healing tests showed that virgin cooking oil can be potentially used as a rejuvenator to promote asphalt crack-healing. [ABSTRACT FROM AUTHOR]

The poor low-temperature performance of recycled asphalt is the primary cause of the recycled asphalt disease. However, further strengthening is required to analyze the molecular-level cracking of recycled asphalt. This article presented a comprehensive investigation of the cracking phenomenon of recycled asphalt at both the macro and micro levels. This was achieved through the utilization of experimental tests and molecular dynamics simulations. In this study, pressure-aged asphalt was subjected to 40 h of aging. The aged asphalt was divided into three groups: 30% RAP (reclaimed asphalt pavement) recycled asphalt, 50% RAP recycled asphalt, and 70% RAP recycled asphalt. The three groups were then analyzed in terms of three major indexes. Linear amplitude scanning (linear amplitude sweep, LAS) was conducted on the three groups. The mechanical response law of asphalt was obtained, and it was found that the coefficient of strength of recycled asphalt increased with the increase of RAP dosage. At the same time, the fracture energy density decreased subsequently. Furthermore, the fracture energy density of aged asphalt was 7% lower than base asphalt's. Subsequently, this study examined the four fractions and C=O and S=O functional groups of five types of asphalt and constructed the molecular structures and models of stable base asphalt and aged asphalt. Subsequently, this article constructed a fusion model of new and old asphalt, analyzed the fusion process of new and old asphalt, and studied the factors affecting the blending degree of new and old asphalt. Finally, the factors affecting the cracking performance of rejuvenated asphalt, including the blending degree, the content of the four fractions, and the addition of the rejuvenator, were investigated. The impact of each influencing factor on the cracking performance of recycled asphalt was analyzed from multiple perspectives. In conclusion, the findings of this study provide a valuable guide for interpreting the tensile properties of reclaimed asphalt and the influence of rejuvenators. [ABSTRACT FROM AUTHOR]

The recycling of asphalt pavements requires a good understanding of the material's characteristics. However, the rheological behavior of recycled binder is still not well understood. In this study, a novel method is introduced to construct the master curve of the recycled binders. The concentration of reclaimed asphalt pavement (RAP) binder is used to find the shift factors of the master curve. This master curve is called the concentration master curve (CMC). To verify the applicability of the concept, the CMC was plotted for three different RAP sources procured from two states and the capital of India. The percentage of RAP binder content in the recycled binders was varied (0, 15, 25, 40, 65, 80, and 100%) by weight of the total binder. In all three cases, smooth master curves were obtained. To calculate the allowable RAP, an alternative approach based on the damping energy area (DEA) of recycled binders was proposed. It was found that the allowable RAP content based on the DEA criteria was 40–50% less compared to the conventional high PG temperature (PGH) criterion. An attempt is made to understand the rheological interaction between the RAP binder and RA using the recycled binder compatibility index (RBCI). It was observed that the RAP source is the determining factor behind the compatibility and interaction level between the RAP binder and RA in a recycled binder. [ABSTRACT FROM AUTHOR]

The use of reclaimed asphalt pavement (RAP) is believed to contribute significantly towards overall energy conservation and environmental protection efforts. However, the recycling of aged binder from RAP requires a fundamental understanding of the interaction mechanism between such rejuvenators with recycled and unmodified binders. This study quantitatively investigated the impact of such agents in combination with the aging-rejuvenation process and other binder modifiers (SBS, crumb rubber, and a high viscosity modifier) on the fractional composition, rheology, and colloidal structural stability of asphalt binders. Based on these results, a rejuvenation index (RI) was proposed to quantitatively evaluate the rejuvenation of aged asphalt binder. Aging increased the proportion of resins and asphaltenes of asphalt binders which resulted in the decrease of its rheological properties. After the addition of the rejuvenators, the complex modulus of all aged binders were reduced. Certain rejuvenators transformed up to 5 percentage points of asphaltenes into other fractions. The aromatic oil-based rejuvenator showed the best rejuvenation of unmodified asphalt binder, but theRI was only 0.33. Overall, the results implied that rejuvenation of asphalt binders is a complex topic and further studies should be conducted to correlate the rheological behaviour with rejuvenation mechanisms beyond chemical fractions. [ABSTRACT FROM AUTHOR]

When added to aged bitumen, oil-based rejuvenators are expected to restore its original properties to some degree. The extent of the rejuvenation depends on the composition of the oils. In this study, the effect of individual components of vegetable oils on blends with bitumen was investigated. First, 5% and 10% by weight of two free fatty acids, namely oleic acid and linoleic acid, and one triglyceride, triolein, were blended with bitumen, and thereafter, the blends underwent thermal aging at high temperatures under air in a ventilated oven. The fatty acids and triglyceride are referred to as rejuvenators in this context. Upon thermal aging, the free fatty acids did not produce any effect or were much less effective in decreasing the complex shear modulus (stiffness) of bitumen compared with the triglyceride. One reason for this result may be the favorable chemical changes of the triglyceride at high temperatures compared with the free fatty acids. Above all, this study provides basic knowledge to demonstrate the importance of the chemical composition of vegetable oils that are selected as bitumen rejuvenators, specifically when targeting long-term stability of the blends. [ABSTRACT FROM AUTHOR]

The Sultanate of Oman has experienced rapid development over the last thirty years and has constructed environmentally friendly and sustainable infrastructure while it continues to find economical alternative resources to achieve the goals of the Oman 2040 vision. The primary concerns are preserving natural resources and reducing the impact of carbon dioxide (CO₂) emissions on the environment. This review aims to encourage the sustainable use of reclaimed asphalt pavement (RAP) materials in pavement construction and focuses primarily on employing RAP materials in new pavement projects. Currently, new construction projects utilise a significant percentage of demolished asphalt pavement to save costs and natural resources. The key issue that arises when mixing RAP into new asphalt mixtures is the effects on the mixtures' resistance to permanent disfigurements, such as fatigue cracks, that influence asphalt mixture performance. Numerous studies have assessed the impact of using RAP in asphalt mixtures and found that RAP increases the stiffness of asphalt mixtures, and thus improves rutting resistance at high temperatures. Nevertheless, the findings for thermal and fatigue cracking were found to be contradictory. This review will address the primary concerns regarding the use of RAP in asphalt pavements, and aims to encourage highway agencies and academic researchers in the Gulf countries to develop frameworks for the practical usage of RAP in the construction of sustainable pavement systems. [ABSTRACT FROM AUTHOR]

Reclaimed asphalt pavement (RAP) is the deteriorated pavement material, containing aged binder and aggregates. A rejuvenator is normally added to the mixture to reduce its stiffness, by blending with the aged binder and changing the properties of the mixture. Therefore, it is necessary to have an insight into the microstructure of the RAP and rejuvenated RAP. In this study, waste engine oil (WEO), waste vegetable oil (WVO) and waste grease (WG) are used as rejuvenators, at different dosages. The interaction between the rejuvenator and RAP is evaluated through microscopic analysis, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. The microscopic analysis has provided the orientation and distribution of the aggregate, depicting the significant increase in coating of aged binder on the RAP with the increase in the rejuvenator dosage. The FTIR and XRD results have shown that rejuvenator has restored the asphaltenes and maltenes ratio and fluidity of the RAP. WG has comprehensively enhanced the asphaltenes and maltenes ratio, compared to the WEO and WVO. However, microscopic analysis suggests that the WG has high agglomeration. Overall, it is concluded that 6% WVO is a perfect dosage to enhance fluidity of the RAP. [ABSTRACT FROM AUTHOR]

This research aims to deliver a new promising asphalt binder rejuvenator developed from food waste to mitigate the effects of aging on the asphalt. The research relied on three different binders: two unmodified PG 64–22 binders and a Polymer Modified (PMA) PG 76–22 binder. Moreover, a field-extracted RAP binder is utilized in evaluating the rejuvenator's efficiency. For this study, the proposed food waste bio-oil (FWBO) is compared against two market-available rejuvenators. The experimental program relied on aging control binder samples for each asphalt type with no rejuvenation using the Rolling Thin Film Oven (RTFO) test, followed by the Pressure Aging Vessel (PAV) test for 20 hours to create an Artificial RAP (ARAP) binder. Then, ARAP and RAP binders were blended with 5% by their weight with one of the two on-market rejuvenators (#1, #2) or the proposed FWBO rejuvenator. Testing results reveal that low-temperature relaxation was significantly improved for all the investigated samples after an additional PAV aging cycle, as Delta Tc values increased compared to the control binders. Further, samples' master curves were used to calculate the Glover–Rowe (G-R) parameter, crossover frequency, and modulus (ωc, Gc*). The results clearly showed the ability of the FWBO to reduce the aging rate and improve the rheological properties of RAP binders. Further, the Fourier Transform Infrared Spectroscopy (FTIR) test showed that the new FWBO rejuvenator reduces the oxidation levels of the aged RAP binders, as suggested by the carbonyl index. [ABSTRACT FROM AUTHOR]

Growing environmental pollution worldwide is mostly caused by the accumulation of different types of liquid and solid wastes. Therefore, policies in developed countries seek to support the concept of waste recycling due to its significant impact on the environmental footprint. Hot-mix asphalt mixtures (HMA) with reclaimed asphalt pavement (RAP) have shown great performance under rutting. However, incorporating a high percentage of RAP (>25%) is a challenging issue due to the increased stiffness of the resulting mixture. The stiffness problem is resolved by employing different types of commercial and noncommercial rejuvenators. In this study, three types of noncommercial rejuvenators (waste cooking oil (WCO), waste engine oil (WEO), and date seed oil (DSO)) were used, in addition to one type of commercial rejuvenator. Three percentages of RAP (20%, 40%, and 60%) were utilized. Mixing proportions for the noncommercial additives were set as 0–10% for mixtures with 20% RAP, 12.5–17.5% for mixtures with 40% RAP, and 17.5–20% for mixtures with 60% RAP. In addition, mixing proportions for the commercial additive were set as 0.5–1.0% for mixtures with 20% RAP, 1.0–1.5% for mixtures with 40% RAP, and 1.5–2.0% for mixtures with 60% RAP. The rutting performance of the generated mixtures was indicated first by using the rutting index (G*/sin δ) for the combined binders and then evaluated using the Hamburg wheel-track test. The results showed that the rejuvenated mixtures with the commercial additive at 20 and 60% RAP performed well compared to the control mixture, whereas the rejuvenated ones at 40% RAP performed well with noncommercial additives in comparison to the control mixture. Furthermore, the optimum percentages for each type of the used additives were obtained, depending on their respective performance, as 10%, 12.5%, and 17.5% of WCO, 10%, 12.5–17.5%, and 17.5% of WEO,

This study evaluated the effect of two encapsulation methods (i.e., dropping funnel and syringe pump), two concentrations of the alginate-based encapsulating material (2%, and 3%), and three oils as bitumen rejuvenators (virgin sunflower oil, waste cooking oil, and virgin engine oil) on the morphological, physical, chemical, thermal, and mechanical properties of encapsulated rejuvenators for asphalt self-healing purposes. A general factorial design 2 × 2 × 3 was proposed to design 12 different Ca-alginate capsules. Significant differences on the morphological, physical, and mechanical properties of the capsules were analysed by three-way ANOVA and Tukey HSD Post Hoc analyses. The effect of the type of oil on the self-healing capacity of cracked bitumen samples was also evaluated. The main results showed that the design parameters and their interactions significantly affected the morphological, physical, and mechanical properties of the capsules. Capsules synthesised via syringe pump method, with virgin cooking oil and 2% alginate was the most appropriate for asphalt self-healing purposes since its uniform morphology, encapsulation efficiency up to 80%, thermal degradation below 5% wt., and compressive strength above the reference asphalt compaction load of 10 N. Finally, the healing tests showed that virgin cooking oil can be potentially used as a rejuvenator to promote asphalt crack-healing.

Environmental, economic, and social benefits are encouraging the incorporation of reclaimed asphalt pavement (RAP) in stone matrix asphalt (SMA) mixtures. However, RAP-incorporating mixtures have higher stiffness, which leads to fracture failure. This research used semicircular bending (SCB) tests to evaluate the fracture characteristics, i.e., maximum tensile strength (TS), fracture energy (FE), and flexibility index (FI), of RAP-incorporating SMA mixtures with different rejuvenators. Four RAP contents (10%, 20%, 30%, and 40% by weight of the aggregate) and four different rejuvenators [waste vegetable oil (WVO), waste engine oil (WEO), waste grease (WG), and palm oil sludge (POS)] with four rejuvenator dosages (0%, 3%, 6%, and 9% by weight of binder) were used to prepare SMA mixtures. Fracture characteristics were analyzed using 100-mm-diameter Marshall specimens. Rejuvenated mixtures had about a 10% increase in the TS compared with nonrejuvenated mixtures. The WVO and WEO substantially increased the TS, FE, and FI values other two rejuvenators, whereas WG and POS provided no improvement. The incorporation of rejuvenator improved the fracture resistance and allowed up to 40% RAP content. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses were performed to examine the rejuvenators' effectiveness at the microlevel. SEM images measured the level of activation of aged binder and the lubrication effect of different rejuvenators. In terms of fracture characterization, 30% RAP content along with 6% WVO was the best performing SMA mixture. [ABSTRACT FROM AUTHOR]

The use of high amounts of reclaimed asphalt pavement (RAP) in asphalt pavements has many economic and environmental benefits; however, there are concerns about brittleness and potential cracking of asphalt mixtures. One of the solutions to address this concern is through the inclusion of recycling agents (rejuvenators). The purpose of this study was to explore the effect of different types of recycling agents (biooils, vegetable oils, tall oil, aromatic extract, and paraffinic oil) on the rheological, microstructural, nanomechanical, and chemical properties of asphalt binder blends with high RAP content. Rheological properties were assessed using a dynamic shear rheometer. Atomic force microscopy was used to determine the microstructural characteristics and nanomechanical properties of the asphalt binder blends. A wavelet packet transform approach was proposed to quantify surface roughness characteristics. Fourier transform infrared spectroscopy was used to evaluate the chemical properties based on carbonyl and sulfoxide indices. Results indicated a correlation between the phases observed in the microstructure and rheological performance. Biooil recycling agents were the most effective in improving the microscopic distribution and rheological properties of binder blends, followed by vegetable oils. However, chemical analysis suggested that the addition of recycling agents did not reverse oxidative aging. Finally, the study recommended a rejuvenation index (RI) that quantified the effectiveness of recycling agents in improving blending and reducing stiffness and aging susceptibility. The RI signified that tall oil was the most susceptible to aging, followed by aromatic extract and paraffinic oil, whereas biooils and vegetable oils were the least susceptible to aging. [ABSTRACT FROM AUTHOR]

The article describes the effiency of polymer-modified road bitumen regeneration with two types of rejuvenators. Two alternative rejuvenators have been selected aromatic oil Nygen 910 and soft road bitumen V12000. PMB 45/80-55 bitumen, which is used in the upper and lower layers of asphalt pavement, was investigated. During the life time of the asphalt pvement, due to the effects of solar UV radiation, temperature and oxygen, of all the layers of the structure asphalt top layer reaches the highest degree of aging. Short-term and long-term aging were performed to simulate the aging of the bitmen under laboratory conditions. To determine the optimal amount of rejuvenator experiments were performed with 8%, 10% ir 14% rejuvenator by bitumen mass. The effect of rejuvenators were evaluated by studying the main physical properties of bitumen: penetration and softening temperature. Ina n experimental study, aromatic oil was found to be more than 2.5 times more effective than soft bitumen. Article in Lithuanian. Atnaujinančiųjų medžiagų poveikis pasendinto polimerais modifikuoto kelių bitumo penetracijai ir minkštėjimo temperatūrai Santrauka Straipsnyje aprašomas polimeru modifikuoto kelių bitumo regeneravimo dviejų rūšių atnaujinančiosiomis medžiagomis efektyvumas. Pasirinktos dvi alternatyvios atnaujinančiosios medžiagos – aromatinė alyva Nygen 910 ir minkštasis kelių bitumas V12000. Tirtas PMB 45/80-55 bitumas, kuris naudojamas asfalto dangos viršutiniuose ir apatiniuose sluoksniuose. Asfalto dangos eksploatacijos metu dėl saulės UV radiacijos, temperatūros ir aplinkos deguonies poveikio asfalto viršutinis sluoksnis pasiekia didžiausią senėjimo laipsnį iš visų konstrukcijos sluoksnių. Bitumo senėjimui laboratorijos sąlygomis imituoti atliktas trumpalaikis ir pagreitintas ilgalaikis sendinimas. Siekiant nustatyti optimalų atnaujinančiosios medžiagos kiekį eksperimentai atlikti su 8 %, 10 % ir 14 % atnaujinančiosios medžiagos nuo bitumo masės. Atnaujinančiųjų medžiagų poveikis vertintas tiriant pagrindines bitumo fizikines savybes: penetraciją ir minkštėjimo temperatūrą. Eksperimentinio tyrimo metu nustatyta, kad aromatinė alyva yra daugiau nei 2,5 karto efektyvesnė nei minkštas bitumas. Reikšminiai žodžiai: asfalto mišinys, atnaujinančiosios medžiagos, bitumas, fizikinės savybės, Nygen 910, regeneravimas, V12000.

The Sultanate of Oman has experienced rapid development over the last thirty years and has constructed environmentally friendly and sustainable infrastructure while it continues to find economical alternative resources to achieve the goals of the Oman 2040 vision. The primary concerns are preserving natural resources and reducing the impact of carbon dioxide (CO₂) emissions on the environment. This review aims to encourage the sustainable use of reclaimed asphalt pavement (RAP) materials in pavement construction and focuses primarily on employing RAP materials in new pavement projects. Currently, new construction projects utilise a significant percentage of demolished asphalt pavement to save costs and natural resources. The key issue that arises when mixing RAP into new asphalt mixtures is the effects on the mixtures’ resistance to permanent disfigurements, such as fatigue cracks, that influence asphalt mixture performance. Numerous studies have assessed the impact of using RAP in asphalt mixtures and found that RAP increases the stiffness of asphalt mixtures, and thus improves rutting resistance at high temperatures. Nevertheless, the findings for thermal and fatigue cracking were found to be contradictory. This review will address the primary concerns regarding the use of RAP in asphalt pavements, and aims to encourage highway agencies and academic researchers in the Gulf countries to develop frameworks for the practical usage of RAP in the construction of sustainable pavement systems.

The article describes the effiency of polymer-modified road bitumen regeneration with two types of rejuvenators. Two alternative rejuvenators have been selected aromatic oil Nygen 910 and soft road bitumen V12000. PMB 45/80-55 bitumen, which is used in the upper and lower layers of asphalt pavement, was investigated. During the life time of the asphalt pvement, due to the effects of solar UV radiation, temperature and oxygen, of all the layers of the structure asphalt top layer reaches the highest degree of aging. Short-term and long-term aging were performed to simulate the aging of the bitmen under laboratory conditions. To determine the optimal amount of rejuvenator experiments were performed with 8%, 10% ir 14% rejuvenator by bitumen mass. The effect of rejuvenators were evaluated by studying the main physical properties of bitumen: penetration and softening temperature. Ina n experimental study, aromatic oil was found to be more than 2.5 times more effective than soft bitumen. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

[Display omitted] • The molecular structure of functional rejuvenators have been designed. • The diffusion rates of the primary and enhanced structures were investigated. • Two rejuvenation methods for rejuvenators were proposed. • The chain alkanes exhibit the best performance recovery effect. In hot in-place recycling (HIR) technology, there are many shortcomings and challenges such as low mixing temperature, short mixing time and less virgin asphalt binder, demanding multifunctional rejuvenators with higher diffusion rates. Therefore, there is an urgent need to develop a rejuvenator that balances diffusion rate and performance recovery. In this study, molecular dynamics (MD) simulation was employed to establish the basic structure of oil fractions, including chain alkanes, cycloalkanes and aromatic hydrocarbons. To improve the diffusion rate of rejuvenators, functional groups in penetrants and surfactants, such as hydroxyl, carboxyl, amide, ether, and ester groups, were incorporated into the basic structure for artificial design and enhancement. The diffusion rates of the primary and enhanced structures were investigated, and the internal factors for diffusion were analyzed. Furthermore, two rejuvenation methods for rejuvenators were proposed based on the changes in non-bond interaction energy in different asphalt binder systems. Moreover, the performance recovery of different rejuvenators were investigated. The results show that the diffusion rate of chain alkanes in the basic structure is the fastest, while that of aromatic hydrocarbons is the slowest. When ether and ester groups are used as enhanced structures, the diffusion rates of chain alkanes increase by 34.7% and 61.1%, respectively. Regarding performance recovery, chain alkanes exhibit the best performance recovery effect, which is further enhanced when ether and ester groups are employed as enhanced structures. [ABSTRACT FROM AUTHOR]

Highlights • Summary of current knowledge on recycling agents (rejuvenators) and their application. • Identification of current and future challenges that prevent utilization of recycling agents. • Evaluation of recycling agents effectiveness in binder blends and asphalt mixtures. • Characterization of rejuvenated binder blends and rejuvenated asphalt mixtures. • Cost-effectiveness associated with the use of recycling agents. Abstract 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. [ABSTRACT FROM AUTHOR]

Reclaimed Asphalt Pavement (RAP) is a widely used recycled material in pavement construction. Whereas the integration of RAP into asphalt mixtures is a complex subject and need to understand every aspect that entailed in the mix design. The aim of this review paper is to provide comprehensive knowledge about the developments and challenges of the RAP in the asphalt mixtures, along with the mechanisms involved. The blending process and rejuvenator are two key factors that govern RAP content, and this can even surge up to 100% in the asphalt mixtures. The blending between the RAP and the virgin materials is very crucial in the context of performance and durability of RAP mixtures. While rejuvenator is an additive which may act as a catalyst and enhance the aged RAP binder properties. A detailed description of distinct types of the rejuvenators and their performances are discussed in this paper. Several aspects of the RAP mixtures including mix design, constituent materials, performance, RAP with polymer modified asphalt binder, as well as environmental benefits are highlighted. This study gives information to the researchers, engineers, and designers about the RAP technology. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Rejuvenator addition on RAP conveyor belt, dryer outlet or in mixer is recommended. • Early rejuvenator addition might be advantageous for mixture performance. • Rejuvenator addition before and after RAP dryer produce the same emissions. Abstract Rejuvenator is an oil that can be added during asphalt production to restore Reclaimed Asphalt Pavement (RAP) binder. Ten potential locations for rejuvenator addition in asphalt plant were ranked in terms of pavement performance, plant operation, and environmental safety. A full scale production was performed to compare rejuvenator addition to cold RAP on conveyor belt versus addition to hot RAP in mixer (video https://youtu.be/LYBq93e8BG0). Mixture test results indicated that spraying of rejuvenator onto cold RAP facilitates rejuvenator diffusion in RAP binder resulting in improved asphalt fatigue and crack propagation resistance. Both addition locations generated equal organic carbon emissions from asphalt plant. [ABSTRACT FROM AUTHOR]

Highlights • EAF, RAP, foundry sand and rejuvenators have been used to design alternative mixtures. • The mixes were aged according the SHRP to the long-term oven aging (LTOA) method. • The mixes aged with alternative materials were treated to be used as RAP in new mixes. • The results obtained demonstrate the recyclability of experimental asphalt mixes. • Fatigue performance evaluation of the recycled asphalt mixes is recommended. Abstract The aim of this study was the evaluation and validation of the recyclability potential of asphalt mixtures that incorporate high proportions of by-products (electric arc furnace slag and foundry sand) and reclaimed asphalt pavement in their composition. In a first stage, the performance of these asphalt mixes was assessed using mechanical tests such as Marshall, water sensitivity, wheel tracking, stiffness and resistance to fatigue. Then, the samples underwent thermal aging treatment in order to be used as RAP in the manufacturing of new samples. Two rejuvenators were studied to check their effectiveness for the purpose of achieving this aim. Finally, the mechanical performance of these new mixes was evaluated. The results demonstrated a suitable technical performance and a good recyclability of the asphalt mixes used to replace practically all conventional aggregates. However, appropriate design and evaluation of the mixes is required, assessing the binder properties and the mechanical performance of the asphalt mix as well as evaluating its fatigue performance. [ABSTRACT FROM AUTHOR]

The present paper focuses on the behavior of Stone Mastic Asphalt (SMA) mixes incorporating rejuvenated Reclaimed Asphalt Pav ement (RAP) materials. The RAP materials were tested for its physical properties and later were rejuvenated using various rejuvenators such as waste cooking oil, waste engine oil and shredded plastics. The rejuvenated RAP materials were incorporated in the SMA mixes at various replacement lev els i.e. 0%, 30%, 50% and 70% (by weight). Various binder properties such as viscosity, rheological properties and chemical composition were evaluated for the aged and rejuvenated material. The rejuvenators were incorporated at different dosage levels i.e. 2%, 4% and 6% (by weight of binder). The optimal rejuvenation dosage for each type of rejuvenator was identified and mix design for the SMA was optimized for evaluating its physical and mechanical proper ties. Based on the results, the optimum rejuvenator dosage was identified at 6% for waste cooking oil and waste engine oil, while 2% for shredded plastics. It was observed that the addition of rejuvenators improved the performance of RAP based SMA mixes. [ABSTRACT FROM AUTHOR]

Highlights • Three soybean-derived rejuvenators were added to a neat binder. • The thermal properties of the rejuvenators were studied using DSC and TGA. • The thermal properties of the rejuvenators can be related to the rheological changes in the binder. • The rejuvenators behaved differently even though they were derived from same source. Abstract Rejuvenators are widely used to improve the properties of asphalt binders particularly low temperature and fatigue cracking behavior. Rejuvenators vary significantly in terms of their physical properties and chemical composition. The nature of the interaction between the rejuvenators and the base asphalt binders is very complex and an extensive study into the chemical and thermal properties of the rejuvenators and how they impact the rheological properties of rejuvenated binders is of paramount importance. In this research, a neat PG58-28 binder is rejuvenated with three different materials produced from soybean oil at a dosage of 6% by total weight of binder. The rheological properties of the control and rejuvenated binders are assessed using performance grades showing a drop in both the critical low and high temperature grades with rejuvenation. The oxidative stability of the rejuvenators as well as the rejuvenated binders is studied using thermogravimetric analysis (TGA). The crystallization and melting points of the rejuvenators are observed using differential scanning calorimetry (DSC). DSC is also used to examine the glass transition temperatures of the control and rejuvenated binders. The TGA results showed one of the rejuvenators to be susceptible to oxidation which agreed with the rolling thin film oven (RTFO) mass loss results. The glass transition temperature of the rejuvenated binders decreased denoting improved low temperature cracking properties in line with the performance grade results. [ABSTRACT FROM AUTHOR]

• IGMH method was used for the first time to investigate the weak interaction characteristics between various rejuvenators and asphaltene molecules. • The molecular mechanisms responsible for deagglomeration effect of rejuvenators on asphaltene dimer was revealed by DFT method. • New form electrostatic and dispersion-attraction between rejuvenators and asphaltene staking disturbed π-π effect over the aromatic region of asphaltene. • Bio-rejuvenators showed a significant enhancement of the deagglomeration efficiency in asphaltene dimers compared to petroleum-based rejuvenators. In this work, a high quantum level of density functional theory (DFT-D) approach and fourier transform infrared spectrum (FTIR) at a micro-level were used to understand one phenomenon: the specific molecular mechanisms responsible for the deagglomeration effect of 10 kinds of representative molecules of bio- and petroleum-based rejuvenators on asphaltene aggregations found in the aged asphalt. The DFT results indicated that the action site of rejuvenators in sulfoxide group (S = O) position was bound stronger than those in carbonyl (C = O) and pyridine nitrogen. Compared with petroleum-based rejuvenators, bio-rejuvenators were responsible for significant contribution to the deagglomeration process when they were adequately inserted into the oxidized asphaltene dimer. Especially, 2-methoxyphenol (phenolic compounds) showed significantly higher efficiency than either of them. The deagglomeration behavior was mainly attributed to a new interaction (hydrogen-bonds of O-H··O/N-H··O and dispersion-attraction) of a series of competing factors between the rejuvenators and the asphaltenes. This polarized the charge distribution throughout the aromatic region of the asphaltene dimer and built up a multi-centered electron density (such as a three-center four-electron H-bond), thus destroying eventual interactions between asphaltene stacks and reducing the extent of clustering of asphaltene units that were intensified during oxidative aging. The FTIR data painted a preliminary picture of the hybrid rejuvenator-asphaltene as aromatic cores with shorter aliphatic side chains and more carbonyl and hydroxyl side groups, and showed the absence of chemical bonding interaction between the rejuvenators and asphaltene nanoclusters. [ABSTRACT FROM AUTHOR]

The use of rejuvenators in asphalt concrete (AC) have been receiving greater attention recently due to their effect on improving the performance of AC mixes to control the impact of the increasing use of recycled asphalt. This study evaluates the effectiveness of a rejuvenator to reduce AC’s cracking susceptibility utilizing the Illinois Flexibility Index Test (I-FIT). The AC’s rutting potential was assessed using the Hamburg Wheel Track Test. Samples were prepared on unaged and short-term aged conditions to identify the effect of service time on AC mixes. This study found that increasing rejuvenator content on AC mixes may reduce cracking susceptibility, but possibly increase rutting. Both 2-D and 3-D balanced mix design interaction plots show that designing a durable AC mix with recycled material can be achieved by controlling rejuvenator content with and without aging. Contractors and agencies alike may use interaction plots to develop AC mixes with optimal balanced performance. [ABSTRACT FROM AUTHOR]

Reclaimed asphalt pavement (RAP) is stiffer than the virgin material due to aging, thus it is expected to have worse cracking resistance. By adding bio-based rejuvenators, RAP binder mechanical performances at low temperatures improve: fracture toughness temperature of RAP decreases after the addition of rejuvenators to a level similar to the virgin binder. Furthermore, work to fracture of RAP binder increases after the addition of rejuvenators. Addition of rejuvenators to RAP binder can restore both mechanical properties and toughness at low temperature. However, despite the rejuvenators’ addition, physio-chemical oxidation did not reverse as mechanical changes were not caused by chemical changes at functional groups level. Results confirmed how considering the effect of aging is crucial when studying how rejuvenators affect the RAP binder chemically and mechanically. [ABSTRACT FROM AUTHOR]

Several reports exist on the use of natural-oil-based materials as rejuvenators to restore the properties of aged binders—more specifically, regarding their ability to enhance the binders’ low-temperature properties and to reduce their stiffness. Rejuvenators are typically made of low molecular weight constituents which could easily volatilize and thus render the rejuvenated binder thermally unstable. Hence, the study of the thermal stability of rejuvenated binders is of paramount importance. In this research, a binder with a performance grade (PG) of PG58-28 modified with a soybean-derived rejuvenator at 12% by mass is added to an extracted reclaimed asphalt pavement (RAP) binder at a ratio of 1:5 resulting in a rejuvenator dosage rate of 2% by total mass of binder. The PG of the rejuvenated RAP binder is determined using both dynamic shear rheometer and bending beam rheometer. The thermal stability of the rejuvenator and the binders is verified using thermogravimetric analysis (TG). The rejuvenator shows good thermal stability up to a temperature of 302 °C. The RAP binder containing the rejuvenator shows similar thermal stability to the unrejuvenated RAP binder. The evolved gases from the TG analysis are analyzed using Fourier transform infrared (FTIR) to chemically characterize the rejuvenator and the binders. The FTIR spectrum of the rejuvenator reveals characteristic peaks. The intensity of these peaks serves as an indication of the rate of mass loss of the rejuvenator within the rejuvenated RAP binder. [ABSTRACT FROM AUTHOR]

• RAP mixtures with any rejuvenator type outperformed the cold patching mixture. • 100% Hot RAP mixtures behaved similar to virgin Superpave Hot Mix Asphalt. • RAP mixtures with petroleum-based rejuvenator performed better than bio-based ones. • Impact of RAP source was insignificant in most test types compared to RAP gradation. • RAP patching of the potholes could cost 22 times less than cold patching mixture. Fixing the potholes using bituminous patching mixtures is a critical and costly pavement maintenance activity. The patching mixture's quality significantly affects patch durability and performance; always using the best material available is advisable. This study investigated the feasibility of using 100% hot recycled asphalt pavements (RAP) as a possible patching material by comparing the performance results with cold patching mixtures (CPM) as well as Superpave hot mix asphalt (SHMA) mixtures. Four different RAP mixtures, two fine-graded and two coarse-graded, from two distinct sources, are obtained. RAP mixtures were handled in a laboratory environment to obtain the hot recycled patching materials. Three different rejuvenators were incorporated into hot-recycled pavement material (HRPM) at manufacturer-recommended dosages to determine the best rejuvenator type. Performances of the mixtures are evaluated in terms of linear viscoelastic characterization, permanent deformation, and low-temperature thermal cracking potentials using dynamic modulus, flow number, and indirect tensile strength tests, respectively. The results show that RAP mixtures with any RAP source, gradation, and rejuvenator type outperformed CPM in performance tests and behaved similarly to SHMA mixtures. [ABSTRACT FROM AUTHOR]