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Waste cooking oil (WCO) can be recycled cleanly as the rejuvenating agent for aged asphalt, boosting the utilization of reclaimed asphalt pavement materials in road engineering. However, the sensitivity of asphalt rejuvenated by WCO to secondary aging is unknown, which has an impact on its durability in practical engineering. The objective of this work is to explore the aging behaviors of asphalt binders rejuvenated by different chemical fractions of WCO. The performance of different fractions of WCO before and after aging treatment was evaluated. The sensitivity to aging was discussed for rejuvenated binders with WCO's fractions as rejuvenating agents including the differences in aging resistance between them and the virgin binder. The experimental results indicate that the aging resistance of WCO's fractions depends mainly on their carbon chain length. The sensitivity of rejuvenated asphalt to aging depends strongly on the aging resistance of WCO's fractions. Additionally, it is found that the resistance of rejuvenated binders to aging is better than that of the virgin binder because the WCO's fractions are less volatile than the original light components of the virgin binder. Therefore, substances with strong fluidity and weak volatility in WCO are the optimal candidates for rejuvenating agents of aged asphalt considering both the rejuvenation effect and the resistance to aging. The findings of the research contribute to the sustainability of road engineering. • The aging behaviors of asphalt rejuvenated by waste cooking oil (WCO) were explored. • The performance of different fractions of WCO before and after aging was evaluated. • The aging resistance of rejuvenated asphalt is better than that of the virgin binder. • The sensitivity of WCO rejuvenated asphalt to secondary aging depends strongly on the anti-aging ability of WCO's fractions. [ABSTRACT FROM AUTHOR]

In this study, the efficacy of the extended oven aging procedure outlined in NCHRP 973 for generating laboratory-produced reclaimed asphalt pavement (RAP) was explored. The study also sought to establish a correlation between the results obtained from the aged bitumen extracted from oven-aged asphalt mixture and PAV-aged bitumen. Both aging techniques, with varying durations, were applied, and a series of tests, encompassing penetration, softening point, rotational viscosity, bending beam rheometer, temperature sweep using dynamic shear rheometer, and FTIR, were conducted for comprehensive comparison. The outcomes revealed that the oven aging procedure has limited applicability for simulating the long-term aging of asphalt mixtures. At the temperature of 95°C, an increase in the oven aging duration had minimal impact on the degree of aging, especially beyond five days, as evidenced by various parameters such as penetration, softening point, viscosity, master curves of viscoelastic properties, aging index, and low-, intermediate-, and high-temperature characteristics of the different aged bitumens. Furthermore, a comparative analysis between PAV and bitumen extracted from oven-aged asphalt mixture indicated that bitumen aged for five days in the oven exhibited analogous properties to bitumen subjected to 1 cycle of PAV aging, encompassing chemical, rheological, and physical test results. In conclusion, while some researchers have suggested that performing 2 or 3 cycles of PAV aging may be necessary to simulate long-term aging, the findings indicate that oven aging of asphalt mixture cannot effectively simulate aging characteristics beyond 1 cycle of PAV aging. • Changing the oven aging duration beyond 5 days does not affect asphalt mixture aging. • The PAV aging method, with varying cycles, effectively achieves higher levels of bitumen aging. • A single PAV aging of bitumen yielded results identical to five days of aging the asphalt mixture in an oven. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the changes in adhesion performance between recycled asphalt pavement (RAP) materials and aggregates by the regeneration process. The oil-rich RAP fine aggregate was utilized to assess the adhesion performance and its improvement between recycled asphalt mortar and aggregates. Various testing methods, such as contact angle test, dynamic shear rheometer (DSR), atomic force microscopy (AFM), and water stability tests, were employed to comprehensively analyze and evaluate the adhesion performance of oil-rich RAP fine aggregate in the regeneration process of recycled asphalt mortar at multi-scale. The results show that alkaline aggregate limestone and SBS-modified asphalt exhibit higher adhesion work by surface-free energy theory. The anti-stripping agents XTA2 and LQ20 can improve the adhesion area between recycled asphalt and aggregates. Under the same influencing factors, SBS-modified asphalt, aggregate, and additive type can all improve adhesion performance between recycled asphalt mortar and aggregates. The recycled asphalt mixture prepared from SBS-modified asphalt has a freeze-thaw splitting tensile strength ratio (TSR) increase of 3.5∼10 % compared to matrix asphalt, limestone can increase TSR by 2∼6 % compared to basalt, and TSR increases by 7∼10 % before and after adding anti stripping agents. The mechanism of adhesion performance enhancement in recycled asphalt mortar was analyzed from a micro/nano perspective. That provides a reference for the durability development of RAP recycled asphalt pavement. • The adhesion of aged asphalt in oil-rich RAP fine aggregate increased by 14.7 %. • The water stability performance of mixture is improved by 10 % through the increase of oil-rich RAP fine aggregate adhesion. • The study revealed the adhesion enhancement mechanism of oil-rich RAP fine aggregate recycled asphalt. [ABSTRACT FROM AUTHOR]

To scientifically and efficiently utilize reclaimed asphalt pavement (RAP) generated during asphalt pavement maintenance, and to promote resource recycling and sustainable development, this paper developed and evaluated the Fiber-enhanced RAP interlayer for HMA overlay and preservation treatments. In this paper, RAP interlayer was designed based on the Response Surface Methodology (RSM) and the pull-out strength and the shear strength of were tested. Through double-objective optimization and analysis, the recommended proportions were determined as 2.22 kg/m2 of rubber asphalt, 10.57 kg/m2 of aggregate, and 30% RAP content. Subsequently, the effects of different basalt fiber contents on the pull-out strength, shear strength, flexural strength, fatigue life, and permeability coefficient of asphalt mixture with interlayer containing RAP were investigated. The results indicated a significant improvement in these properties with an 80 g/m2 basalt fiber content. The performance of asphalt mixture with Fiber-enhanced RAP interlayer was obviously superior to the asphalt mixture with interlayer without fiber and RAP. According to the test results of Digital Image Correlation (DIC), it was found that basalt fibers effectively reduce stress concentration, delaying the initiation and propagation of cracks. • Fiber- enhanced RAP interlayer is developed. • The RAP content reaches 30%. • Basalt fibers delay the propagation of cracks. [ABSTRACT FROM AUTHOR]

While significant research efforts have been devoted to the rejuvenation of aged bitumen using bio-rejuvenators, a universally recognised approach for dosage optimisation is still yet to be established. Aiming to develop standardised methods to determine the optimal dosages of six types of bio-rejuvenators, this study validated the use of a rheology-based rejuvenation index as a potential universal method. Rheological properties of rejuvenated binders, determined through frequency sweep tests, multiple stress creep and recovery tests, linear amplitude sweep tests, and bending beam rheometer (BBR) tests were carried out with the properties of virgin binder as reference targets. The results indicated that the applied rheology-based rejuvenation index is a feasible approach. This index can ensure improved low- and intermediate-temperature (fatigue) performance of aged bitumen while maintaining high-temperature performance within acceptable limits. Further characterisation of the binders by Fourier Transform Infrared Spectroscopy (FTIR) analysis suggested that the bio-rejuvenation processes will commonly only involve physical softening rather than a chemical reversal of ageing. Therefore, the use of chemistry-based indices is likely not feasible. • Validation of a rheology-based rejuvenation index for bio-rejuvenators. • Rejuvenation index can accurately assess rejuvenator efficiency and predict optimal dosages. • FTIR-based parameters are not feasible for evaluating rejuvenation efficiency. [ABSTRACT FROM AUTHOR]

Hot mix asphalt (HMA) can be formulated with recycled aggregates derived from construction and demolition waste, thereby reducing reliance on natural aggregates. This represents a novel approach to resource management within the construction industry. However, the low-quality coarse recycled concrete aggregates (CRCAs) produced by simple crushing cannot meet the construction technical requirements of asphalt pavement. In this study, two methods, including high-temperature mechanical grinding (HM-CR) and the chemical agent tetraethyl orthosilicate (TEOS) solution infiltration (TS-CR), were used to treat and strengthen the CRCAs. Basic physical indices were tested before and after the treatment, including apparent specific gravity, water absorption, crushing value, mortar adhesion, and asphalt adhesion. Scanning electron microscopy (SEM) and X-ray fluorescence spectrometry (XRF) were employed to analyze the microscopic properties as well as the chemical composition. Results showed that high-temperature mechanical grinding at 400°C with 500 rpm emerged as the most effective physical treatment method, while impregnation with a TEOS mixture with a concentration of 1:6 for 24 hours was recommended as the most effective chemical treatment method. CRCAs treated with the above physical and chemical treatments were incorporated into AC-20 hot mix asphalt at 0 %, 15 %, 30 %, and 45 % by the mass of hot mix asphalt. The hot mix asphalt containing treated recycled concrete aggregates underwent tracking tests through high-temperature wheel tracking, low-temperature trabecular bending, Marshall immersion, freeze-thaw splitting, four-point bending beam fatigue, and IDEAL-CT cracking tests. Results revealed that the addition of CRCAs improved the high-temperature stability of hot mix asphalt to a certain extent. HM-CR improved the low-temperature cracking resistance, water stability, and mechanical properties of hot mix asphalt containing treated recycled concrete aggregates. When the content of CRCAs was controlled below 30 %, the performance of hot mix asphalt met the requirements of the specification. • Physical and chemical methods were employed to enhance the properties of RCAs. • Microscopic observation and chemical analysis were conducted on the treated RCAs. • The replacement proportion 30 % is recommended for asphalt mixtures containing treated RCAs. [ABSTRACT FROM AUTHOR]

The utilization of Reclaimed Asphalt Pavement (RAP) in pavement construction has gained prominence as a sustainable approach to reduce material costs and environmental effect. However, a significant challenge associated with increased RAP incorporation lies in the potential fracture distress caused by the aged binder. The purpose of this study is to assess the cracking performance of asphalt mixtures incorporating three levels of recycled materials (30% RAP, 50% RAP, and 30% RAP along with 5% Reclaimed Asphalt Shingles (RAS)). Three softening oils were employed to improve the cracking performances at two aging levels. Performance evaluations, including cracking performance assessments at intermediate and low temperatures, were carried out and compared with control mixtures. The findings of this study reveal that the incorporation of softening oils, as investigated herein, offers a viable means of producing asphalt mixtures featuring high RAP content while preserving performance comparable to that of a virgin mix. From a binder perspective, the Glover–Rowe (G–R) parameter and fatigue life at 10% strain level emerge as robust indicators for evaluating cracking resistance under conditions pertaining to intermediate and low temperatures. • Bio-Oils exhibited superior performance in restoring binder and mixture properties across various aging conditions with high RAP/RAS content. • Fatigue life at a 10% strain level and the G-R parameter exhibited strong correlations with the CT index. • Carbonyl and sulfoxide indices of FTIR test can reflect the aging rate of asphalt binders with recycling agents but cannot evaluate the cracking resistance. [ABSTRACT FROM AUTHOR]

This study evaluates the environmental and economic benefits of recycled asphalt (RA), recycled asphalt pavement (RAP), warm mix asphalt technology (WMA), wood fly ash (WFA), crumb rubber (CR) from end-of-life tires and kraft lignin in individual pavement courses and in a full-depth flexible pavement. The study performs LCA and LCCA for 19 individual mixtures (cradle-to-site) and six pavement scenarios (cradle-to-cradle). Four impact categories are considered: quantities of materials used, global warming potential (GWP), cumulative energy demand (CED) and road owner costs. Of all the materials and technologies considered, RA and RAP have the most positive effect on boosting more sustainable road construction and maintenance. The results of pavement scenarios show that combining materials and technologies evaluated in the study in a single pavement reduces GWP by 30.7%, CED by 25.0%, and costs by 17.9% compared to a pavement with virgin aggregates and asphalt manufacturing at hot mix asphalt temperatures. The need for raw materials in road pavement for all life cycle is significantly reduced by 45.8% for aggregates, 41.9% for bitumen, 100% for mineral filler, 50% for cement, and 100% for bitumen modifier. A total of 1446.6 tons of WFA, 20.5 tons of tire rubber, and 5.7 tons of kraft lignin can be incorporated into a 1 km section over the entire life cycle. [Display omitted] • Recycled asphalt has the most impact on reducing GHG, energy consumption, and costs. • Using kraft lignin to replace bitumen reduces GHG, yet increases energy demand and costs. • Chemical warm mix asphalt technology reduces GHG, energy demand, and costs. • Using fly ash in pavement base to replace cement is a more sustainable than use in asphalt to replace mineral filler. • Using tire rubber in the modification of asphalt increases GHG, energy demand, and costs. [ABSTRACT FROM AUTHOR]

Presently, there is a significant increase in studies dedicated to the reuse of Reclaimed Asphalt Pavement (RAP) material obtained from the recycling of asphalt coatings. This procedure aims to reduce production costs and minimize environmental impacts. To carry out the reuse of this material, it is crucial to understand the interaction mechanisms between the aged binder of the RAP and the new binder. These mechanisms can be assessed through the Degree of Binder Activity (DoA) and the Degree of Blending (DoB). DoA represents the quantity of aged binder available for the new mixture, being an intrinsic property of each RAP. On the other hand, DoB indicates the degree of blending between the aged and new binders, being influenced by external factors such as mixing parameters, thus presenting a challenge in quantification. This study sought to establish a predictive model to quantify DoB based on Dynamic Modulus and Fourier-Transform Infrared Spectroscopy (FTIR) tests. These tests were conducted on mixtures containing four different RAPs, varying in different content levels and mixing temperatures. In each RAP, DoA was quantified, and a statistical analysis was performed to verify the significance of independent variables in dynamic modulus results. After this step, four modeling attempts were made, choosing the one that not only presented significant independent variables but also obtained the highest predicted R² value. The chosen model was validated and demonstrated small variations compared to DoB obtained by the generated equation. Thus, it is concluded that the DoB modeling conducted in this study highlights that mixing temperatures and RAP content influence factors such as DoA, dynamic modulus, FTIR, and consequently, DoB. Additionally, the practicality of the model was emphasized, as it successfully predicted DoB using a single mechanical and chemical test. • Predictive Model Redefines Asphalt Blending. • Sustainable Pavement: DoB Breakthrough. • Innovative Model Enhances Recycling Impact. [ABSTRACT FROM AUTHOR]

The warm mix recycling technology of asphalt pavement can improve the utilization rate of solid waste in highway construction industry on a large scale, and reduce the emission of harmful gases (NO X , CO 2 , benzopyrene, etc.) in the process of road construction. It is one of the effective ways to realize carbon neutrality in highway construction industry. The main purpose of this study is to systematically analyze the fatigue characteristics of warm mix recycled asphalt (WMRA) from the perspective of quantitative research, and to provide scientific basis for the popularization and application of this technology. Therefore, this study mainly evaluated the anti-fatigue characteristics of WMRA under different conditions based on the linear amplitude sweeping test (LAS test). Based on the calculation and analysis of the commonly used fatigue judgment indexes (stress-strain curve, phase angle-strain curve, S×N curve (S is the ratio of the instantaneous modulus to the initial modulus of the material, which is often replaced by the virtual modulus in the LAS test, and N is the number of cyclic loadings.), virtual strain storage energy-strain curve), the peak strain of virtual strain storage energy is recommended as the fatigue judgment standard from the perspective of reliability and accuracy, and the peak strain of damage factor is proposed as one of the new fatigue judgment standards. In this paper, the nucleation of microcracks and the coalescence of microcracks are distinguished in the process of fatigue damage evolution, and the peak strain of virtual strain energy storage and the peak strain of damage factor are used as the judging indexes respectively. Finally, based on the theory of continuum damage mechanics, the loss modulus of WMRA is selected as the representative value of material properties to calculate the virtual modulus and damage factor, and the fatigue damage evolution model of WMRA based on the viscoelastic continuum damage model (VECD model) was constructed. Based on this model, the anti-fatigue characteristics of WMRA with the reclaimed asphalt pavement (RAP) content were analyzed. [Display omitted] • The peak strain of virtual strain storage energy is reliable and accurate to evaluate WMRA. • The virtual strain storage energy corresponds to the microcrack nucleation of WMRA. • The peak strain of the damage factor was proposed as a new fatigue failure criterion. • The peak strain of the damage factor corresponds to the microcrack coalescence of WMRA. [ABSTRACT FROM AUTHOR]

Pothole repairing is routine and substantial maintenance work for public work agencies to improve road conditions and traffic safety. This study developed sustainable and cost-effective pothole patching materials by circular uses of three recyclable materials, including reclaimed asphalt pavement (RAP), waste cooking oil (WCO), and plastic. The biobinder was synthesized via the polymerization of WCO with co-crosslinker Maleic Anhydride (MA). The low-density polyethylene (LDPE) plastic was used to modify a biobinder to enhance its elasticity. Results showed the RAP-biobinder mixtures and RAP-biobinder-plastic mixtures had higher indirect tensile strength and improved rutting resistance compared to the RAP-WCO mixtures. The designed patching mixtures exhibited superior mechanical performance compared with the commercial cold patch mixtures. Field pothole patching tests were also conducted to assess the workability and patching performance of the developed patching mixtures. The RAP-WCO mixture demonstrated sufficient workability and effective patching performance based on one-year monitoring. • Waste cooking oil (WCO) was polymerized using Maleic Anhydride to synthesize biobinder. • Low-density polyethylene (LDPE) plastic was used to modify a biobinder to enhance its elasticity. • WCO, biobinder, and plastic was used to mix with 100% reclaimed asphalt pavement to produce pothole patching mixtures. [ABSTRACT FROM AUTHOR]

The granular sub-ballast layer commonly used in the construction of modern railway tracks, but its use involves a significant consumption of natural aggregates, which, moreover, must meet certain requirements that are sometimes unavailable. Therefore, the possibility of using recycled aggregates arises to promote sustainable development. In this context, this research focuses on assessing the feasibility of using RAP (Reclaimed Asphalt Pavement) as a sub-ballast layer in railway tracks, these recycled materials can contribute to increased load-bearing capacity and waterproofing of the lower layers due to the presence of adhered bitumen, studying the optimal application process to achieve a layer with high mechanical performance. It presents a laboratory investigation on the influence of different design factors on the mechanical performance of the layer, evaluating the effects of RAP characteristics, and the impact of the compaction procedure. Although these recycled materials primarily presented challenges in terms of size, particle distribution, and strength, which differ from the aggregates commonly used in similar high-demand layers, laboratory tests simulating expected service conditions for these materials in railway tracks have shown the viability and suitability of using recycled asphalt materials to achieve more sustainable railway tracks. Under compaction conditions at temperatures commonly achieved in construction (above 40 ºC) and considering its particle size distribution, it is possible to create a layer with high performance in terms of strength and durability. • RAP was studied to be used as granular subballast for railway track. • Influence of RAP type, compaction temperature and particle size were evaluated. • Full-scale track box tests were conducted to simulate real conditions scenario. • RAP showed appropriate behavior for application as sub-ballast in railway tracks. [ABSTRACT FROM AUTHOR]

Given the growing demand for sustainable road construction materials, this research aims to evaluate the synergistic effects of incorporating recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) in asphalt mixtures. Induction heating was also utilized to enhance the self-healing ability of asphalt mixtures, with the intention of prolonging their lifespan and mitigating environmental impacts. This research assessed the pavement performance of recycled asphalt mixtures (RAM) with different RCA and RAP dosages. The induction heating performance, cooling performance, and effective heating depth of RAM were tested. Lastly, the cumulative healing efficiency of the RAM was evaluated under multiple "fracture-healing" conditions. Findings indicated that the inclusion of RCA and RAP negatively influenced the water stability, high-temperature deformation resistance, and crack resistance at low temperatures of the RAM. However, when the RCA content was 20 % and the RAP content did not exceed 20 %, the road performance of the RAM met the requirements. The contents of the RCA and RAP had no discernible effect on the RAM's induction heating capability. Moreover, when the RCA content was 20 % and the RAP content did not exceed 10 %, the effective heating depth of the RAM could reach 50 mm. Using fracture energy recovery rate as the healing index, after three cycles of "fracture-healing", the RAM with 20 % RCA achieved the highest cumulative healing efficiency of 291 %. The cumulative healing efficiency of recycled asphalt mixtures with 20 % RCA and 10 % RAP was close to that of normal asphalt mixtures. This research contributes to reducing the consumption of non-renewable resources, minimizing environmental impact, and maintaining or even improving the performance of asphalt pavements by optimizing the use of RCA and RAP. [Display omitted] • The synergistic use of RCA and RAP in asphalt mixtures for sustainable road construction was examined. • The optimal RCA and RAP contents for maintaining road performance were identified. • Induction heating was utilized to enhance the self-healing of recycled asphalt mixtures. • Using 20 % RCA and no more than 10 % RAP improves the cumulative healing efficiency of asphalt mixtures. [ABSTRACT FROM AUTHOR]

The plant-mixed cold recycling technology of emulsified asphalt (CRTE) is widely applied in road engineering due to its environmental and economic advantages. The composition of raw materials directly affects the road performances of the mixtures, and then affects the serving quality of the asphalt pavement. Therefore, an in-depth interpretation of various raw materials and factors affecting the performances is crucial for enhancing the design and production of cold recycled asphalt mixtures of emulsified asphalt (CRME). The present paper provides a review of the state-of-the-art studies in the area of the composition of raw materials and performances influencing factors of CRME. Firstly, the roles of reclaimed asphalt pavement (RAP) materials and virgin aggregates in CRME are briefly introduced. Secondly, the strength formation mechanism of five additives and emulsified asphalt is introduced in detail. Afterwards, critical factors affecting the road performances of the mixtures are described in detail. Finally, some challenges in the current research are discussed, and the corresponding recommendations are proposed for future exploration. • Introduce the composition of raw materials in CRME. • Summarize the strength formation mechanism of various raw materials. • Describe the critical factors affecting the road performances of the CRME. • Provide technical challenges and future recommendations for CRTE. [ABSTRACT FROM AUTHOR]

To increase the content of reclaimed asphalt pavement (RAP) materials in reconstructed asphalt pavements, this study introduced an enhanced graded recycling (EGR) method, supplemented by the addition of a bio-rejuvenator and basalt fibers to further enhance the performance of recycled asphalt mixtures. The performance of composite recycled asphalt binder was investigated using chemical composition tests, multiple stress creep and recovery tests, and bending beam rheometer (BBR) tests. The morphological characteristics and crushing tests of recycled aggregates were carried out to determine the material proportions of new and waste aggregates. Asphalt mixtures with varying RAP contents (20 %, 40 %, 60 %) were prepared using the EGR method and subjected to low-temperature, high-temperature and water stability tests. It was found that the chemical fractions and rheological properties of aged asphalt binders could be effectively restored using a rejuvenator. The high-temperature and low-temperature performance of the composite recycled binders could be improved by the incorporation of basalt fibers. The mechanical properties and morphological characteristics of recycled aggregates were close to those of new aggregates. The mass ratio of 1:1 between new and recycled aggregates was recommended. The low-temperature performance and water stability of the recycled asphalt mixture prepared using the EGR method could be improved without compromising the high-temperature performance. • Introduced a method for producing recycled asphalt mixtures and evaluated its effectiveness. • The performance of recycled aggregate is comparable to new aggregate. • The performance of recycled asphalt mixtures prepared using this method surpasses the traditional method. [ABSTRACT FROM AUTHOR]

The research presents the strength characteristics and theoretical mix design of full-depth reclamation (FDR) with cement for road maintenance and rehabilitation. The reclaimed aggregates used in the study were pulverized and blended on the investigation site by the recycler machine. The FDR mix design covered the reclaimed asphalt pavement (RAP), reclaimed base, and reclaimed subbase courses. The unconfined compressive strength (UCS) was tested on the FDR with cement under different mix proportions, cement content, moisture content, and curing time. Two factors that affect the UCS of FDR, viz., moisture-induced packing density and moisture for cement hydration, were observed. The mix proportion with 40 % RAP required at least 6 % cement to stabilize the FDR for use as a bound base course as per the standard, while the effective limit of cement content for FDR was 9 %. The strength prediction model of FDR with cement was presented theoretically based on the modified soil-moisture/cement ratio concept. The verification of the proposed strength model was performed using 7 and 28-day UCS from another investigation site. The design recommendations for FDR with cement were summarized. This discovery could offer a cost-effective and precise method for the mix design of FDR with cement. • Reclaimed materials in FDR were blended and stabilized with cement. • Strength of FDR with cement can be normalized by a modified soil-moisture/cement ratio. • Strength prediction model was adopted for FDR with cement. • Case study for verification of the strength prediction model was conducted. • Step-by-step mix design of FDR with cement was summarized. [ABSTRACT FROM AUTHOR]

The agglomeration of reclaimed asphalt pavements (RAP) affects the low-temperature performance and water stability of hot-recycled asphalt mixtures (HAM). To address this problem, a surface-active regeneration agent which named polyacrylamide (PAM) was employed. The effects of the coarse-grained RAP agglomeration rate, the alterations in the aged asphalt before and after the addition of PAM, and the degree of diffusion and fusion between old and new asphalt on HAM performance were investigated using macroscopic experiments, molecular dynamics simulations, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The findings revealed that the water stability of HAM first decreased and then slightly increased as the RAP agglomeration rate increased. Notably, at a 60% coarse-grained RAP agglomeration rate, the water stability of the mixture was at its poorest, accompanied by a declining low-temperature stability. Utilizing Fick's diffusion principle, in conjunction with molecular dynamics simulations, FTIR, and SEM analyses, it was observed that PAM effectively diffused and fused with the aged asphalt. This resulted in enhanced diffusion coefficients for both old and new asphalt, consequently mitigating aging effects on the aged asphalt. Furthermore, the regeneration agent facilitated the diffusion and fusion process between old and new asphalt, thereby improving HAM performance and reducing the adverse impact of coarse-grained RAP agglomeration on the road performance of thermally recycled mixtures. • The agglomeration of recycle asphalt pavement material was characterized. • Molecular dynamics simulation was applied. • Analysis of the diffusion fusion characteristics of new and aged asphalt based on the Fick's diffusion principles • The effects of regeneration agent on enhancing the road performance of hot recycled asphalt mixtures was studied. [ABSTRACT FROM AUTHOR]

Using reclaimed asphalt pavement (RAP) in asphalt concrete (AC) reduces the need for nonrenewable resources. However, excessive RAP can cause premature cracking in pavements due to its stiff and aged nature. To address this issue, studies propose the incorporation of recycling agents (RA) in RAP recycled mixtures. Nevertheless, incorporating RA may reduce mixture's rutting and moisture resistance. Alternatively, incorporating waste plastic in AC can positively balance the RA negative effects. Therefore, this study explores the simultaneous use of polypropylene (PP) waste plastics and soybean oil RA to improve the overall performance of high-RAP mixtures. Due to its high melting point, PP can have different roles in the asphalt mixture depending on the mixing temperature used. To explore that, three different methods of incorporating PP into a high-RAP mixture were attempted. Five different mixtures were developed varying the binder (virgin and modified with RA), and the PP mixing procedure. Then, the mixtures were subjected to performance-based testing procedures (SCB IFIT and HWTT) as well as to boiling test to verify binder-aggregate adhesion. It was confirmed that the use of soybean oil enhances the cracking performance of the high-RAP mixtures, but the rutting and moisture performances were compromised. However, incorporating PP made the mixture more resistant to moisture and rutting in different instances. It was found that pre-heating the aggregates at higher than PP melting point allows a better coating of aggregates by PP, and results in improved binder-aggregate adhesion, leading to better cracking, rutting, and moisture performance of high-RAP mixtures. • This research investigates the use of waste plastics in high-RAP mixtures produced with recycling additives. • Three different mixing methods were evaluated to incorporate polypropylene waste plastic (PP) into high-RAP mixtures. • PP inclusion improved moisture and rutting resistance in specific instances, particularly when aggregates were pre-heated above PP's melting point. [ABSTRACT FROM AUTHOR]

The use of high percentages of reclaimed asphalt pavement (RAP) in asphalt mixtures offers economic and environmental advantages. However, state agencies place limits on RAP usage to avoid its indiscriminate use without a full understanding of its long-term performance implications. To achieve a more informed and rational use of higher RAP contents, it is essential to quantify recycled binder availability (RBA) and incorporate it into asphalt mixture design. The current design methods often assume complete RBA, leading to less durable mixtures. Standardized mixture design methods fail to rigorously account for the effects of RBA on the volumetric composition of asphalt mixture. Recently, the availability adjusted mixture design (AAMD) method was developed to address these issues by explicitly considering partial RBA in the interpretation of mixture volumetric properties and accounting for the role of RAP agglomerations on aggregate structure. This study tests the hypothesis that the AAMD method can mitigate the adverse performance consequences of RAP through the control of 'available' volumetric and effective binder properties. This was achieved by comparing virgin and RAP mixtures designed with similar 'available' volumetric properties according to the AAMD method. Additionally, control mixtures with RAP contents ranging from 20 to 35 percent were compared to AAMD mixtures with similar 'available' volumetric properties designed with the same RAP content and with 50 percent RAP. The collective results demonstrate that the AAMD method effectively mitigates negative performance consequences of RAP by controlling the 'available' volumetric and effective binder properties. • The Availability Adjusted Mixture Design (AAMD) method is able to mitigate adverse effects of RAP through the control of 'available' volumetric and effective binder properties. • Asphalt mixtures designed through the AAMD method present improved cracking performance as compared to mixtures designed through Superpave method for the same intended volumetric properties. • Mixtures with increased RAP content – up to 50 percent – designed with AAMD method presented a better cracking performance than Superpave designed mixture with lower RAP content. • AAMD method is a rational approach to interpret the impact of recycled asphalt materials in asphalt mixtures and can be used to design RAM mixtures accurately to obtain the desired performance. [ABSTRACT FROM AUTHOR]

This study examines the effect of reclaimed asphalt pavement (RAP) material dosage and incorporation method on the mechanical characteristics of Cold Asphalt Mix (CAM). The RAP materials were fractionated into fine and coarse in addition to the unfractionated method. Four levels of RAP dosage (25, 50, 75, and 100%) were considered for each category. The mix design parameters, such as total fluid and emulsion content, were evaluated using the Indirect Tensile Strength (ITS) test. Overall, 455 specimens were prepared for mix design. The Optimum Emulsion Content (OEC) is the design emulsion content determined at peak value of ITS test. ITS, Indirect Tensile Stiffness Modulus (ITSM), and moisture susceptibility tests were conducted. Incorporating RAP in CAM increased the average tensile strength predominantly by 34% in coarse mixes, 28% in unfractionated, and < 10% in fine mixes. The average ITSM of the mixture increased by 30%, 60%, and 80% for fine, coarse, and unfractionated RAP. Further, emulsion demand was reduced by 53%, 43%, and 79% for fine, coarse, and unfractionated RAP, which showed that the RAP incorporation method profoundly influenced OEC. However, regardless of fractionation, CAM mixes showed lower cracking resistance and higher moisture susceptibility with increased RAP dosage. Two different conditioning protocols were used to capture the variation in moisture susceptibility for all 13 mix combinations. Coarse and unfractionated RAP mixes significantly differed in ITS, moisture susceptibility, cracking tolerance index, and ITSM. VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) approach was selected to rank the outperforming combination. The overall ranking of RAP incorporation showed that the coarse RAP mixes outperformed fine and unfractionated RAP mix characteristics. The study recommends restricting RAP usage by up to 75% to ensure the required performance of CAM mixtures. • Effect of RAP fractionation and dosage on emulsion demand in cold asphalt mix (CAM). • Assessment of RAP fractionation in moisture susceptibility of CAM. • Cracking potential of CAM with RAP incorporation methods and dosage. • Use of VIKOR approach for selection of better mix characteristics. [ABSTRACT FROM AUTHOR]

Reclaimed asphalt pavement (RAP) is widely utilized as a green base/subbase material. Still, this material can only be used in small amounts in asphalt concrete mixtures. Many studies have shown that a large amount of RAP replacement could make asphalt pavements less effective. The goal of this study is to evaluate the mechanical properties of asphalt concrete made with 100% RAP aggregate and crushed polyethylene terephthalate (PET) bottles. The effect of adding PET to RAP aggregate was investigated with PET contents ranging from 0% to 1.0% by weight of RAP aggregate. The improved static and dynamic performances of the RAP asphalt concrete were assessed via the Marshall stability, the strength index (SI), the indirect tensile strength (ITS), the indirect tensile fatigue (ITF), the indirect tensile resilient modulus (IT MR), and the resistance to rutting tests. The optimum PET content of 0.6% provided the best performance across all experimental testing, resulting in a 25% improvement in Marshall stability, 19% in SI, 69% in ITS, 11% in IT MR , 270% in ITF, and 80% in rutting resistance compared to 0% PET content. Furthermore, it has been determined that an increase in ITS results in a corresponding increase in IT MR , exhibiting a linear correlation. After carefully analyzing the cyclic test data, a model for fatigue distress was suggested. This study's results will aid in developing sustainable pavement options, including RAP and PET, from both an economic and environmental standpoint. • PET is used as a polymer additive for RAP asphalt concretes. • The influence of PET content on mechanical properties is discussed. • The distress model for PET modified RAP asphalt concretes is proposed. • PET increased the adhesion among aggregate and asphalt cement and also the stifness. [ABSTRACT FROM AUTHOR]

In this study, a warm mix additive (composed of diamine and fatty acid amine) and a rejuvenator (consisting of styrene-butadiene-styrene and aromatic elements) were synthesized to facilitate the incorporation of 50% recycled asphalt pavement (RAP) in warm mix asphalt for the surface layer and 100% RAP in cold asphalt mixtures for the base layer. The effect of WMA and rejuvenator-modified asphalt binder was performed through rotation viscosity, dynamic shear rheometer, and bending beam rheometer. Simultaneously, the performances of RAP-modified asphalt mixtures were assessed using dynamic modulus, overlay test, and flow number test. Constructing two testbed roads provided a real-world evaluation of two surface mixtures and two base mixtures. The results indicated that modifying asphalt binder PG 64–22 with 2.0% warm mix additive (WMA) and 5.0% rejuvenator upgraded the performance grade to PG 76–22, significantly improving rutting resistance, and reducing 40% creep stiffness. The asphalt mixture with 50% RAP, modified with WMA and rejuvenator, demonstrated a better resistance to rutting and low-temperature cracking compared to the original mixture. Both surface and base mixtures met field application specifications, exhibiting excellent performance after a year of service, as confirmed by pavement condition surveys, and falling weight deflectometer tests, thus highlighting the potential for sustainable and high-performance recycled asphalt solutions in road construction. • New warm mix additive and rejuvenator enhance RAP use by up to 50% at lower temperatures (145℃ mixing, 120℃ compaction). • Synthesized additives modified binder improved resistance to rutting and reduced susceptibility to low-temperature cracking. • Asphalt mix with developed additive exhibits superior tensile & indirect strength in testbed. • Base mixture with cement and acrylic polymer emulsion, exhibits good workability and reduced deflection. [ABSTRACT FROM AUTHOR]

The use of unclassified reclaimed asphalt pavement (RAP) is limited due to concerns about raw material variability, impacting RAP mixture performance consistency. Space constraints lead to aggregating recycled materials from various projects into "unclassified RAP," hindering its potential benefits. The evaluation of uncertainties, particularly in dynamic modulus |E*|, is crucial for assessing performance and reliability in asphalt mixtures containing unclassified RAP. In this research, A systematic approach for calculating the coarse and fine RAP ratios based on unclassified RAP content, along with regulated processing and fractionation meeting standards was implemented. Then, a probabilistic model was established, utilizing the sigmoidal function, to analyze the uncertainty in |E*| as a function of the reduced frequency for asphalt mixtures with varying unclassified RAP contents (0%, 15%, 25%, and 45%). The findings revealed that |E*| uncertainty was minimal at low temperatures, reasonable at service temperatures, and critical (COV > 30%) at high temperatures for standard and RAP mixtures. Importantly, increasing unclassified RAP content doesn't worsen |E*| uncertainty. Mixes with high unclassified RAP content showed similar or lower COV values across analyzed frequencies. The proposed approach can reduce COV values in high unclassified RAP content mixes, offering a practical solution to leverage these materials' benefits. • Mixtures containing unclassified fractionated RAP were evaluated • A reliable probabilistic model for recycled asphalt mixtures is developed, enhancing future pavement design analysis • The uncertainty in dynamic modulus |E*| varies with temperature and RAP content. • Revealed nominal, moderate, and critical uncertainties in |E*| at low, service, and high temperatures, respectively. • More unclassified RAP doesn't significantly increase uncertainty, challenging concerns and promoting sustainable practices. [ABSTRACT FROM AUTHOR]

SBS modified asphalt (SBSMA) pavements have gained popularity worldwide due to their prominent performance. However, its maintenance and reconstruction projects will produce a large amount of reclaimed asphalt pavement (RAP) during the long-term service of asphalt pavement. Adding rejuvenators products is a common method to recycling RAP. However, conventional rejuvenators are typical component regulators applicable to recycling unmodified asphalt, while there is a poor regeneration effect for the aged SBS modified asphalt (A-SBSMA), because it cannot repair the degraded SBS polymer. Fortunately, reactive rejuvenator (RR) has achieved this breakthrough based on the research findings in recent years. It contains special compounds that have the ability to repair the degraded SBS. The vital questions to be investigated in the present review are how the four current systems of RR (epoxy system, isocyanate system, compound system and polymer system) affect A-SBSMA's properties and how well does its regeneration effect. Existing research indicated that RRs are favorable for the regeneration of A-SBSMA and have their respective characteristics. This review summaries various RR different regeneration mechanism, and analyzed its effects on physical properties, rheological properties, high and low temperature properties, and microscopic characteristics of A-SBSMA. Although research on RR is still in its infancy with a limited number of relevant studies, they show an excellent regeneration effect for A-SBSMA and hold a promising prospect. Overall, this review provides information on the feasibility of using RR as a sustainable SBSMA rejuvenator to promote conserving resources and reusing RAP. [Display omitted] • Traditional regenerant is not completely suitable for A-SBSMA regeneration. • RR can realize the re-crosslinking of SBS polymer fragments. • RR can comprehensively regenerate A-SBSMA performance. • RR has a unique regeneration mechanism for A-SBSMA. [ABSTRACT FROM AUTHOR]

Currently, the utilization rate of fine reclaimed asphalt pavement (FRAP) in hot recycled asphalt mixtures is low. Therefore, this study focuses on the development and performance optimization of recycled gussasphalt (RGA) with a FRAP content of 38.5%. The total content of reclaimed asphalt pavement (RAP) is 50%. The impact of various factors on the pavement performance of RGA, including modifier dosage, asphalt content, type of asphalt, rejuvenating agent, mixing time, and RAP preheating temperature was analyzed. The results show that RGA has good workability and fatigue resistance. Its high- and low-temperature performance meets the requirements of the Chinese specification for gussasphalt, but it is still slightly inferior to gussasphalt made from virgin materials. Increasing the preheating temperature of RAP and extending the mixing time of RGA can enhance the performance of RGA. But excessive increases will cause asphalt aging, which negatively affects RGA's low-temperature performance and fluidity. More attention should be given to improving the low-temperature performance of RGA, which can be improved by selecting asphalt with better resistance to aging or by incorporating a rejuvenating agent. RGA offers significant economic benefits, with a cost reduction of approximately 27% compared to GA. • Recycled gussasphalt (RGA) containing 50% RAP was developed. • This RGA exhibits satisfactory workability, fatigue resistance, and economic benefits. • Choosing suitable asphalt or reinforcing modifiers is important for improving the high-temperature performance of RGA. • The impact of mixing time and preheating temperature of RAP on the performance of RGA was investigated. • Adding rejuvenating agents is the optimal strategy to improve the low-temperature performance of RGA. [ABSTRACT FROM AUTHOR]

Because of the widespread use of reclaimed asphalt pavement (RAP), various recycling agents (RAs) are developed and used in pavement engineering nowadays to restore the properties of RAP in asphalt mixes. Whereas there are many RA products available, it remains unclear on the fundamental rejuvenation mechanisms behind different RAs and the selection method of proper RA product to restore these recycled materials properties. In addition, there are important questions on hold in terms of RAP repeated recycling and the continuity of restoration capacity from these RAs. Therefore, this study is designed to track the properties changes of the asphalt binders in the context of multiple aging and rejuvenating cycles (MARC). Three different types of RA products are selected and evaluated using rheological characterization and chromatography (molecular distribution) analysis. Results show that the beneficial effects from RAs degrade over time with increase of aging/rejuvenating cycles. Two oils with their molecules that are mainly distributed in the medium molecular size (MMS) range, which compensate the loss of the MMS molecules of the base binder due to aging, show the good effectiveness in restoring not only the complex modulus but also the phase angle of the aged asphalt. And the good correlations between phase angle and MMS as well as LMS proportion indicate the fundamental relationship between binder's molecular distribution and its rheological properties. • Beneficial effects from RAs degrade with increase of aging and rejuvenation cycles. • All study RAs are more effective in softening the modulus than restoring phase angle of aged asphalt. • A good correlation between phase angle and MMS during MARC is revealed. • A preliminary method for effective RA selection is proposed. [ABSTRACT FROM AUTHOR]

Recycling of UV-aged asphalt has been a hot research issue. In this paper, waste cooking oil, plasticizer, toughener, and petroleum resin were used as raw materials for asphalt rejuvenator. This paper explores the effect of regeneration conditions on the regeneration effect of UV-aged asphalt binders through high-temperature rheology and chemical compositions. The paper also attempts to reveal the regeneration mechanism of asphalt binder regeneration using waste cooking oil. Dynamic shear rheology (DSR) and fourier transform infrared (FTIR) spectroscopy assess high-temperature rheological properties and chemical compositions. The Pearson correlation coefficient relates the rheological parameters to the chemical microstructure. And the functional relationship between carbonyl-corrected peak area and aging factor Ai of recycled asphalt and high temperature rheological parameters were established. Molecular simulation investigates WCO-recycled asphalt binder micro-morphology and adsorption mechanisms. The results showed that significant changes in the carbonyl and sulfoxide peak areas affected the high-temperature rheological properties. Regeneration conditions significantly affect asphalt regeneration effectiveness. WCO reduces C O and S O groups, crucial in asphalt viscoelastic behavior. Molecular interaction analysis reveals WCO's regenerative mechanism. This work emphasizes integrating molecular structure, chemical composition, and macroscopic properties in asphalt binder research, providing insights for sustainable pavement practices. • The content of C=O and S=O are the main factors determining the recycling effect of WCO recycled asphalt. • WCO rejuvenator changes the molecular structure of aged asphalt. • The -OH group of WCO increases the interaction between WCO molecules and aged asphalt molecules. [ABSTRACT FROM AUTHOR]

With the application of recycled asphalt pavements, many recycled roads will face secondary regeneration in the near future. The variation in properties of asphalt pavement after primary regeneration will directly affect the quality of secondary recycled asphalt pavement. To investigate the mechanisms and performance of secondary asphalt regeneration, this study conducted laboratory simulations to prepare primary aged asphalt and regenerated asphalt. Building upon the foundation of primary regenerated asphalt, secondary aged asphalt and regenerated asphalt were produced and subjected to testing. Subsequently, changes in the chemical composition, functional group contents, and rheological properties of asphalt, before and after two rounds of regeneration, were analyzed through Thin-Layer Chromatography with Flame Ionization Detection (TLC-FID), Fourier Transform Infrared (FTIR) spectroscopy, and Dynamic Shear Rheometer (DSR) testing. The results indicate that generic fractions can largely be restored to primary regeneration levels during secondary asphalt regeneration by incorporating regenerant and new asphalt. However, the carbonyl and sulfoxide indices are not effectively recovered in the secondary regeneration process, resulting in viscoelastic properties that do not match those of primary asphalt regeneration. • The mechanisms of secondary regeneration of asphalt was revealed. • The microstructure changes of asphalt before and after two times of regenerations were studied. • The performance evaluation of secondary asphalt regeneration was evaluated. [ABSTRACT FROM AUTHOR]

Embracing the principles of circular economy and zero-waste, this study aligns with the United Nations' twelfth sustainable development goal by investigating warm mix recycled asphalt technology as a sustainable solution for utilizing aged asphalt materials. This approach not only enhances pavement quality but also minimizes resource consumption and environmental impact. We critically examine the limitations of conventional warm mix technologies in improving the high and low-temperature performance of aged asphalt and propose innovative solutions. Our research focuses on the rheological characteristics of warm mix reclaimed asphalt, emphasizing the roles of Sasobit, Evotherm M-1, and YDWB-1 warm-mix additive in rejuvenating aged asphalt. We reveal that Sasobit and Evotherm M-1 enhance the asphalt's elasticity, thus improving its resistance to permanent deformation, while YDWB-1 displays unique properties that can influence the asphalt's mechanical behavior in different ways. Our findings suggest optimal mixing ratios for these agents and demonstrate their varied impacts on rutting properties at high temperatures and other mechanical characteristics. The study concludes with insights into the optimal combinations of these warm-mix additives to enhance the high and low-temperature qualities of aged asphalt, marking a step forward in sustainable road construction and material science. • Investigated high and low temperature properties of aged asphalt with Sasobit, Evotherm M-1, YDWB-1. • Conducted comparative analysis of asphalt rheological properties in composite and single warm mixes. • Proposed optimal dosages for various warm mix agents and their combinations. • Demonstrated improved rutting resistance at high temperatures with selected warm mixes. • Revealed significant enhancement in both high and low temperature asphalt performance. [ABSTRACT FROM AUTHOR]

This study aims to supplement the degraded SBS components and improve the road-related properties of Hot in-place recycling (HIR) asphalt mixtures. Under the direct-to-plant process, a composite rejuvenating agent (SBS-CRA) composed of instant SBS, regenerant, and coupling agent is used to regenerate the HIR asphalt/asphalt mixture. Explore the effects of SBS-CRA on the properties and chemical composition of extracted asphalt using rheological and Fourier transform infrared spectroscopy tests. Evaluate the road-related properties and microstructure of SBS-CRA modified HIR asphalt mixtures under the direct-to-plant process through high and low temperature, water stability, fatigue, and scanning electron microscopy tests. And conduct performance verification by paving the test road. The research results indicate that the SBS-CRA can promote extracted asphalt's low-temperature behavior and viscosity while maintaining excellent high-temperature behavior. Under the direct-to-plant process, the SBS-CRA modified HIR asphalt mixture's high and low-temperature behavior and water stability comply with the specified requirements. After SBS-CRA regeneration, the asphalt on the surface of RAP material is smooth. Considering the road-related properties of SBS-CRA modified HIR asphalt mixture, the optimal recommended dosage of SBS-CRA is 5%, and the optimal mixing time of SBS-CRA and RAP material is recommended to be 120 s. At a 5% SBS-CRA content, the fatigue life of the HIR asphalt mixture is 407.9 times higher than that of the neat asphalt mixture. The on-site test results show that the freeze-thaw splitting strength ratio of the HIR asphalt mixture is 88.76%, which meets the specification requirements. The laboratory and on-site test results have proven that applying SBS-CRA in HIR technology is feasible. • Revealed the behavior and mechanism of SBS-CRA recycled asphalt. • Explored the effects of SBS-CRA dosage and mixing time on HIR asphalt mixture under a direct-to-plant process. • Evaluate road performance through laboratory and on-site testing. [ABSTRACT FROM AUTHOR]

Warm mix asphalt (WMA) technology facilitates asphalt mixture production and compaction at relatively lower temperatures. The inclusion of reclaimed asphalt pavement (RAP) material into the WMA mixes will save the natural resources (requirement of virgin aggregate and binder) and enhance the performance of WMA mixtures. This article provides a comprehensive review of available literature on different WMA additives, mix design concepts, challenges of using higher RAP contents, mechanical properties, and performance characteristics of WMA mixes with and without RAP, healing properties of the WMA mixes, life cycle analysis of WMA mixes which augments application of WMA technology more effectively. • Design of WMA and determination of mixing and compaction temperatures using various techniques. • Mechanical properties and performance characteristics of WMA mixes with and without RAP are summarized. • Literature available about healing potential of WMA mixes with and without RAP is summarized. [ABSTRACT FROM AUTHOR]

Recovering aged bitumen from reclaimed asphalt pavement (RAP) is crucial for the evolution of pavement recycling. This study delves deeply into the effects of rejuvenator components on the rheological properties of rejuvenated bitumen across a wide temperature range. The investigation utilized the rolling thin film oven test (RTFOT) and the pressure aging vessel (PAV) test to simulate the short-term and long-term aging of the bitumen binder, respectively. Four distinct rejuvenators were then applied to recover the bitumen at varied aging levels. Detailed chemical analyses, encompassing the four-fraction (SARA) method and Fourier transform infrared spectroscopy (FTIR), were employed to identify the chemical compositions and key functional groups of both the rejuvenators and the rejuvenated bitumen. The rheological behavior of rejuvenated bitumen was assessed through a comprehensive series of tests, including conventional, temperature sweep, frequency sweep, multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests. A Pearson correlation analysis highlighted a significant positive association between specific rejuvenator components, notably asphaltene (As), saturate (S), and aromatic (Ar), and the high-temperature performance of the rejuvenated bitumen. The findings of this research offer insights into the formulation of rejuvenators, potentially enhancing the performance of rejuvenated asphalt pavements and facilitating sustainable infrastructure advancements. • A significant correlation between high-temperature property and component was found. • The deterioration no only relied on the chemical components at low temperature. • MSCR, G-R parameter, and m-valve are more representative to evaluate properties. • The findings of this research offer insights into the formulation of rejuvenators. [ABSTRACT FROM AUTHOR]

The current study investigates the integration of Reclaimed Asphalt pavement (RAP) aggregates into geopolymer concrete, thereby providing a promising avenue for reinforcing sustainability in rigid pavement systems. Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) based geopolymer mixes were designed to accentuate the performance with regards to varying molarity of NaOH (10 M-16 M), aggregate replacement levels (0%−100%) and curing periods. The experimental findings revealed a significant decrease in 28 days of compressive and flexural strength within 14 M-100% RAP mixes (57.6% and 39.7%, respectively). Nevertheless, GPC mixes incorporating 50% coarse RAP successfully met the prescribed strength criteria, making them suitable for Pavement Quality Concrete (PQC) applications. Additionally, the assessment of porosity and Water Absorption (WA) revealed a noticeable decrease with an increase in molarity as well as RAP fractions in the mix. Long-term performance was further assessed through resistance to surface abrasion, showing a maximum abrasive depth of 0.302 mm for 10 M-100%RAP mixes, thus affirming the durability of the RAP-GPC system. Rapid Chloride Penetration Test (RCPT) additionally demonstrated that the presence of adhered asphalt in RAP aggregates reduces porosity and enhances resistance to chloride ingress. Subsequently, the microstructural analysis and the study of solid-state NMR aided in comprehending the matrix behaviour, potentially linked to the performance of the mixes. The experimentally obtained compressive strength results were further statistically analysed through the Sensitivity Analysis (SA) approach, thereby providing a comprehensive understanding of the interplay between various strength-affecting parameters. [Display omitted] • RAP in geopolymer offers viability for designing sustainable rigid pavements. • Porosity and water absorption revealed dependence on molarity and RAP%. • Durability assessed through RCPT and abrasion resistance for RAP-GPC mixes. • SEM and MAS NMR aided in comprehending the matrix behaviour. • Sensitivity Analysis explored impact of key parameters on strength development. [ABSTRACT FROM AUTHOR]

The escalating costs of aggregates and stringent sustainable development policies have emphasized the significance of effective high-content recycled asphalt pavement (RAP) regeneration technology. This study aims to present a novel laboratory separation and treatment approach for RAP materials, ensuring optimal performance of high-content RAP recycled asphalt mixtures. The proposed method is compared against factory-separated RAP materials in terms of agglomeration evaluation and mixture performance comparison. High- and low-temperature performance of the recycled asphalt mixture were evaluated through wheel tracking and trabecular bending tests. Furthermore, the moisture sensitivity of the recycled mixture was studied through immersion Marshall and freeze-thaw splitting tests. The uniformity and fusion between aggregates and asphalt in the recycled asphalt mixtures were meticulously analyzed using advanced techniques such as Scanning Electron Microscope and industrial Computed Tomography scans. The laboratory separation method encompasses flexible separation for 5–10 mm RAP materials and rigid separation for 10–20 mm RAP materials. Notably, the laboratory separation methods proved more effective in removing aged asphalt from the surface of 10–20 mm RAP materials compared to factory separation, thereby enhancing the adhesion between aggregates and asphalt and ensuring a more uniform recycled mixture. Although the dynamic stability of recycled asphalt mixture was reduced using laboratory separation, it still meets the requirements of relevant specifications. Moreover, the low-temperature maximum flexural tensile strain of the recycled asphalt mixture increased by 16%, with the residual stability and tensile strength ratio rising by 1.33% and 2.69%, respectively. Compared with the factory separation method, the laboratory separation method reduces the porosity percentage of the recycled asphalt mixture cross-section by 3.47%. Overall, the laboratory separation method for RAP materials provides valuable insights for enhancing the factory processing of RAP materials, contributing to the successful application of high RAP content regeneration technology in the pursuit of sustainable and cost-effective road construction practices. • Proposed a laboratory method and identified suitable parameters for RAP material separation. • Compared the efficacy of the laboratory separation method with the factory separation method. • Established that the recycled asphalt mixture exhibits superior road performance and stability. [ABSTRACT FROM AUTHOR]

In order to improve the utilization of reclaimed asphalt pavement (RAP) in recycled asphalt mixtures (RAMs), RAP was firstly separated into recycled mortar and coarse refined separation recycled aggregates (CRSRAs) with different particle sizes based on a laboratory refined separation method. Meanwhile, the process parameters for RAP separation were optimized by using the orthogonal test method. The related properties of the aggregates before and after refined separation, including residual bitumen binder content, particle agglomeration, angularity, and sphericity, were characterized. The cumulative distribution of sphericity of CRSRAs was fitted with the Weibull function. Asphalt mixtures with 0, 30%, and 50% RAP content were prepared by the Marshall design method. Moreover, the indirect tensile dynamic modulus and fatigue life of these asphalt mixtures after different water immersion periods were evaluated. The results showed that the CRSRAs had a residual binder content less than 1.0% and fewer pseudo particles after refined separation. Furthermore, a bitumen-rich mortar with a particle size less than 2.36 mm and a bitumen content of 10–14% was obtained. Angularity and Weibull fitting results verified that refined separation could homogenize RAP and obtain CRSRAs with a low variability, which helps to prepare better RAMs with high RAP content. RAMs prepared with CRSRAs exhibit superior fatigue performance compared to the traditional RAMs. Their fatigue life was less sensitive to stress changes and fluctuated little with the increasing water immersion time. • A refined separation method was developed in laboratory. • RAP was separated into recycled mortar and coarse refined separation recycled aggregates with different particle sizes. • The process parameters for RAP separation were optimized by using orthogonal test method. • The fatigue performance of recycled asphalt mixtures after different water immersion periods were evaluated. [ABSTRACT FROM AUTHOR]

To improve the availability of reclaimed asphalt pavement (RAP) in recycled hot mix asphalt (HMA), this study is focused on the mechanical performance of recycled HMA, which is beneficial for environmental conservation and consistent with the concept of sustainability. To alleviate the heterogeneity of the material composition of recycled HMA and enhance the usability and applicability of research means, micromechanical modeling is used to examine the modulus of recycled HMA, which is a critical parameter for asphalt pavement analysis. In this investigation, a four-layer built-in micromechanical model was constructed and derived to characterize recycled HMA. The micromechanical model indicated that the modulus of recycled asphalt was the main factor influencing the modulus of recycled HMA. Thus, the following study took the modulus of recycled asphalt as the main study subject. The frequency sweep test and three-point flexure beam test for recycled asphalt were designed and conducted to clarify the change trend of influence factors and further verify the reasonability and feasibility of the micromechanical model. Considering the diffusion behavior of the rejuvenator, the change trends of the factors are explored. The curing time apparently influences the modulus of recycled asphalt, followed by the curing temperature and the rejuvenator proportion. Finally, analytical results from micromechanical model matched well with the experimental results. The results of this study may be valuable for predicting the dynamic moduli of recycled HMA. • A four-layer built-in micromechanical model for recycled HMA is derived and validated. • The modulus of recycled asphalt prominently affects the modulus of recycled HMA. • The diffusion behavior of rejuvenators is considered in modulus research. [ABSTRACT FROM AUTHOR]

Emulsified asphalt cold recycled technology has received great attention for its low carbon and environmental protection. There have been many researches on the performance improvement of emulsified asphalt cold recycling mixture (CRME) and its achievements, but there lacks systematic sorting. Based on this, this study summarizes the related research from the performance formation mechanism and influencing factors. Firstly, the demulsification mechanism of emulsified asphalt and the performance formation mechanism of CRME are summarized. Secondly, the influence of asphalt material (type and content), aggregate type (new aggregate, RAP), gradation, additives (regenerant, cement, fiber, etc.), water consumption and fabrication methods on CRME performance is analyzed. Finally, the future development of CRME is prospected. In the future, the fusion characteristics of old and new asphalt on RAP surface can be studied from multi-scale perspective. Besides, we can combine genome to construct CRME material library and improve the preparation technology standard of CRME pavement. • The development status of emulsified asphalt cold recycling technology was reviewed. • The influence of different factors on the strength of recycled mixture was analyzed. • The optimal dosage range of different influencing factors was summarized. • The development of emulsified asphalt cold recycling technology was prospected. [ABSTRACT FROM AUTHOR]

The asphalt mixtures containing reclaimed asphalt pavement (RAP) are gradually used in pavement. When the RAP content exceeds 25%, the influence of RAP properties on the performance of the asphalt mixture becomes more pronounced. To address this barrier, the incorporation of regenerating agents is adopted to soften RAP asphalt and ensure the performance of the asphalt mixture. Currently, research on the effect of regenerating agents is rapidly advancing, but there remains limited exploration of their inherent characteristics. This study employs advanced tools such as molecular dynamics (MD) simulations and density functional theory (DFT) to investigate the chemical properties and material attributes of regenerating agents. Fourteen common regenerating agents are selected, which can be classified into eight categories (A∼H) based on their structural features. The results reveal that linear alkanes and cycloalkanes are nonpolar surfaces due to their inherent structural characteristics, resulting in larger fraction free volume (FFV) values within the molecular structure. Considering the molecular weight and intermolecular interactions, these components exhibit a higher diffusion coefficient (D) value. In contrast, aromatics with benzene rings experience enhanced polarity and intermolecular interaction due to conjugated electron pairs forming π-π interactions, leading to reduced FFV values and D values. Moreover, the increase in molecular weight of aromatics significantly reduces both intermolecular interactions and D values. The carboxyl group in fatty acids leads to higher polarity, resulting in stronger intermolecular interactions and lower FFV values and D values. However, after esterification, the properties of fatty acid esters show improvement. Glycerol, with its hydroxyl group having the strongest polarity, exhibits a dense arrangement with the highest density and solubility parameters, which may exceed that of asphalt and may not be suitable as a rejuvenator. The investigation reveals that the polarity of regenerating agents is positively correlated with density, cohesive energy density, and solubility parameters. • The inherent characteristics of fourteen regenerating agents are investigated within the realms of quantum chemistry and molecular dynamics. • Linear alkanes all belong to nonpolar surfaces and have better diffusion coefficients. • The polarity of regenerating agents is significantly correlated with the density and cohesive energy density, as well as solubility parameters. [ABSTRACT FROM AUTHOR]

Emulsified asphalt mortar (EAM) is prone to agglomeration and has poor adhesion to reclaimed asphalt pavement material (RAP) with residual-aged asphalt, which can deteriorate the durability of emulsified asphalt cold recycled mixture (EA-CRM). In this work, silane coupling agent (SCA, 3.75 wt% and 6.25 wt% by weight of emulsified asphalt) and polycarboxylate superplasticizer (PCS, 3.75 wt%, 7.5 wt%, and 11.25 wt%) were used to modify the EAM in order to improve the coating performance of EAM on RAP. Seven kinds of samples with different modifier dosages were prepared. Modification mechanism, micro-morphological changes, workability, rheological property, and coating degree of EAM on RAP were investigated. Furthermore, action mechanism of the SCA/PCS composite modifier (SPCM) in EAM/RAP and the cost-benefit were analyzed. Results show that EAM is physically modified by SPCM. Carboxylic group and polyethylene glycol side chain in PCS possess excellent improvement on the workability of EAM, while silanol group generated by hydrolysis of SCA plays a major role in improving coating performance. An appropriate dosage of SPCM can improve the workability of EAM, and enhance its shear deformation resistance and elastic properties. Meanwhile, SPCM can improve the coating degree of EAM on RAP, but SPCM with a PCS dosage exceeding 7.50 wt% can cause EAM to slightly detach from RAP surface. Therefore, 6.25 wt% of SCA and 7.50 wt% of PCS were proposed to modify EAM to obtain the best overall performance. The application of SPCM had a good cost performance and additional environmental benefits based on the optimal dosage. This work provides a novel method to enhance the coating performance of EA-CRM while facilitating the expansion of RAP applications. [Display omitted] • SPCM was prepared to enhance the coating performance of EAM and RAP. • The optimum dosage of SCA and PCS in SPCM was obtained. • PCS had good improvement on the workability of EAM. • SCA made the connection between EAM and RAP more tightly. • Action process of SPCM on EAM/RAP and its cost-benefit were analyzed. [ABSTRACT FROM AUTHOR]

In view of the cold winter in northern China and the large temperature difference between day and night, the asphalt pavement has been in low temperature service for a long time, in addition to experiencing the aging effect of water and salt erosion, jointly leading to a particularly serious pavement cracking phenomenon. Therefore, a quantity of Reclaimed Asphalt Pavement (RAP) is produced for the repair and renovation of old roads. Faced with the problems of inadequate reuse rate of RAP and high energy consumption of thermal regeneration, it is of great practical significance to explore the technology of warm mix regeneration. In order to study the adaptability of recycled SBS modified asphalt mixtures to low temperature after complex environmental erosion (long-term aging, water freeze-thaw cycle, and salt freeze-thaw cycle), two mixing methods, including hot mixing and warm mixing, were selected, and a Semi-Circular Bending Test was performed. SCB and Digital Image Correlation (DIC) techniques were used to evaluate the low temperature properties of recycled asphalt mixtures by fracture toughness, fracture energy and horizontal strain density damage. Combined with an Atomic Force Microscope (AFM) test, the microscopic analysis of recycled asphalt was carried out to verify the mechanism of low temperature cracking. The results showed that the low temperature cracking resistance of the reclaimed asphalt mixtures with warm mix was slightly worse than that with hot mix. The overall low temperature cracking resistance of the reclaimed SBS modified asphalt mixtures decreased with the increase in RAP content. The low temperature performance of the warm-mixed reclaimed asphalt mixtures deteriorated greatly when the RAP content was 80 %. The influencing factors of environmental conditions on the low temperature cracking resistance of the warm-mixed recycled SBS modified asphalt mixtures were listed as below: long-term aging > salt freeze-thaw cycle > water freeze-thaw cycle. The influence of salt on the stress field of crack tip and the microstructure of recycled asphalt after freeze-thaw was greater than that of water erosion. The changes of the microscopic adhesion were in good agreement with the macroscopic test results, which could be employed as the index evaluating the low temperature crack resistance of the warm-mixed SBS modified asphalt mixtures. The addition of warm mixing agent would play a positive role in the low temperature crack resistance of recycled asphalt mixtures with a RAP content of less than 60 % to a certain extent, so warm-mixed recycled asphalt mixtures were more suitable for the application in northern areas. • Explored the low-temperature cracking behavior and cracking mechanism of warm mix asphalt mixture. • Adverse effect of RAP content on low-temperature crack resistance of warm-mix asphalt mixture. • The micro index Fa can predict low-temperature cracking of recycled mixtures. [ABSTRACT FROM AUTHOR]

• Diffusion and adsorption behavior of emulsified asphalt on aggregate surface. • Comparing the affinity of anionic and cationic emulsified asphalt to aggregates. • Exploring the roles of water, emulsifier, and asphalt in the adsorption process. • Relating diffusion and adsorption characteristics to interface strength in the emulsified cold recycled mixture. The utilization of emulsified asphalt is widespread in the recycling of asphalt pavement due to its eco-friendliness and energy efficiency. While numerous research studies have been conducted on the mixture design and strength assessment of emulsified asphalt, the mechanism by which it diffuses and adheres to the aggregate surface remains inadequately comprehended. This study developed molecular dynamics models to investigate the diffusion behavior of emulsified asphalt on the aggregate surface to clarify the role of emulsifier, water, and asphalt in the adsorption process from a molecular perspective. Interface models are established according to the diffusion state for interfacial adhesion evaluation. The results show that the movement of water molecules is the driving force for the entire emulsified asphalt to adsorb to the aggregate surface, whether the aggregate is silica or reclaimed asphalt pavement (RAP). Compared with anionic surfactant Sodium Dodecylbenzene Sulfonate (SDBS), cationic emulsifier Cetyltrimethylammonium Chloride (CTAC) has a better affinity, stronger adsorption, and higher interfacial adhesion energy with silica. Compared with RAP, emulsified asphalt is more readily adsorbed to the surface of silica. It is concluded that emulsifiers have two distribution conformations during the adsorption process, delamination, and aggregation, with delamination exhibiting stronger interface strength with silica than aggregation. When the emulsified asphalt spreads on the RAP surface, the penetration of water molecules into the aged asphalt layer in the RAP structure reduces the structure's water resistance. These results can provide a molecular perspective for understanding the internal structure of emulsified cold recycle mixture (ECRM) and link the adsorption behavior of emulsified asphalt on aggregate surfaces with the internal interface strength of ECRM. [ABSTRACT FROM AUTHOR]

• Cement-stabilized reclaimed asphalt pavement (RAP) and marginal lateritic soil (MLS) was studied. • Temperature profile of highway pavement structure in tropical climate was presented. • High temperature adversely affected the strength and stiffness of cement-stabilized RAP-MLS blends. • Increases in MLS and cement contents can reduce the viscoelasticity of RAP aggregate. • Relationships between E 50 and ITS versus UCS were given. This article investigated the effects of temperature on the variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement (RAP) and marginal lateritic soil (MLS) as a sustainable bound base course of flexible pavement. A site investigation to assess the temperature profile of highway pavement in the northeast of Thailand was conducted to find the temperature variation of pavement structure in tropical country. Laboratory tests including unconfined compressive strength (UCS), modulus of elasticity (E 50), and indirect tensile strength (ITS) tests were conducted on cement-stabilized RAP and MLS blends at varying mix proportions and temperatures. It is evident that the temperature significantly affects the strength and stiffness of specimens containing RAP due to the presence of bitumen covering the RAP aggregate. The additional MLS and cement can reduce the viscoelasticity of RAP aggregate. The strength reduction due to the temperature is characteristic of the RAP mixtures with MLS and cement. The normalized relationships of UCS and temperature and the empirical correlations between E 50 and ITS versus UCS were presented. This set of relationships is a valuable tool for the mix design of cement-stabilized RAP and MLS blends as a bound base course in tropical countries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Up to 50 % reclaimed asphalt can be used in polymer-modified pavements. • Polymer-modified wearing coarse was constructed with 30 % RAP. • 65% RAP used in unmodified binder course—with good performance. • Recommendations for PmB mixture design with RAP content are provided. While recycling of Reclaimed Asphalt Pavement (RAP) is accelerating, road owners still often restrict the use of RAP in polymer-modified pavement. Here we used a balanced mixture design for preparing polymer-modified asphalt mixtures for wearing and binder courses having 30 % to 60 % RAP content. Findings from the paved test section show that it is possible to design polymer-modified mixtures with 30 % to 50 % RAP that have a good crack propagation resistance, high fatigue resistance, acceptable stiffness, and sufficient rutting resistance. Based on the findings, recommendations for RAP use in polymer-modified layers are provided. [ABSTRACT FROM AUTHOR]

[Display omitted] • 30% RAP utilization: enhancing sustainability in asphalt practices. • Hybridized rejuvenating agent: exploring the synergy of VR and WEO as hybridized rejuvenating agent. • Thorough analysis: comprehensive examination of asphalt , encompassing physical, rheological, and performance attributes. • Enhanced performance for RAP mixtures: encouraging results with VR/WEO blend, signifying improved performance for mixtures. In recent years, there has been a noticeable increase in the production of Reclaimed Asphalt Pavement (RAP) resulting from the maintenance and rehabilitation activities conducted on asphalt pavements. However, the presence of aged binder in RAP gives rise to asphalt mixtures with unfavourable characteristics. To address this concern, the use of rejuvenating agents has been examined as a viable solution to restore the properties of aged asphalt. In this study, an investigation was undertaken to assess the efficacy of incorporating waste engine oil (WEO) and vacuum residue (VR) as hybridized rejuvenating agents for RAP. Various characteristics including penetration, softening point, ductility, viscosity, and stiffness were measured to ascertain the optimal dosage of the hybridized rejuvenating agent. Subsequently, the performance of the rejuvenated asphalt was evaluated through Marshall tests, indirect tensile strength (ITS), moisture damage, and Kim tests, comparing it with different samples. Moreover, the Creep compliance, semi-circular bending (SCB), and Cantabro loss measurements were employed in the evaluation. The findings of the study indicate that a 6.5% hybrid rejuvenator composed of WEO and VR effectively rejuvenates asphalt mixtures containing 30% RAP material by softening the aged binder. Furthermore, the rejuvenated mixture exhibited significant improvements when compared to both the virgin asphalt and RAP mixtures. In conclusion, the incorporation of WEO and VR as a hybridized rejuvenating agent showcases promising results in enhancing the performance of RAP mixtures. This, in turn, contributes to sustainable and efficient pavement practices. [ABSTRACT FROM AUTHOR]

The final composition of asphalt binder in an asphalt mix can vary depending if it is a neat, virgin binder, or a blend of neat binder with reclaimed asphalt pavement (RAP), modifiers, and/or rejuvenators. As recycling of asphalt concrete becomes more commonplace worldwide, so too must be the use of chemical rejuvenators which can restore the original properties of the associated asphalt binder, contributing to the performance and therefore sustainability aspect of this material. In this context, this work aimed to evaluate the influence of rejuvenation in different proportions of aged and unaged binder, as well as the best way to dose rejuvenators, taking into consideration aspects that go beyond the Superpave Performance Grading characterization of binders. In the first phase of this study, when rejuvenator contents based on low PG recovery were proportionally added to different aged/unaged binder blends, it was observed that restoration of ductility and strength of the rejuvenated aged binder was limited. However, when an additional cycle of aging was applied to simulate the new service life of recycled material, the rejuvenated recycled material generally performed better than unrejuvenated recycled material. This long term effect can better differentiate the performance of different rejuvenators. Afterwards, the dosing procedure was investigated using an extensive range of dosages. An optimal dosage determination approach was developed and verified by means of the rejuvenation of aged asphalt mixtures from the rheological, mechanical, and chemical perspectives. Finally, the differences between laboratory-aged binder and laboratory-aged mixtures when rejuvenators are used was investigated, and it was determined that the mechanisms of rejuvenation at the two scales are not completely alike. Key findings also include the importance of re-aging asphalt binder blends before testing when a rejuvenator is used and the dominance of unaged binder within binder blends with limited replacement with recycled asphalt. Overall, this work opens the door to future studies of rejuvenation of asphalt using different approaches than those which have been conventionally used, including consideration of amount of replaced binder, using nonlinear viscoelastic characterization, fundamental chemical studies, and the method of addition based on mixture versus binder scale studies. • Re-aging should be performed when testing rejuvenated binders to choose optimum dose. • Rejuvenation has different mechanisms at the binder and mixture scales. • Multiple indicators should assess optimum rejuvenator dose based on cracking resistance. • Ratio of recycled asphalt should also be considered when using rejuvenators • Amount of unaged binder can control cracking asphalt controls cracking. [ABSTRACT FROM AUTHOR]

• Rejuvenated asphalt binders were subjected to re-aging. • The properties of the rejuvenated asphalt binders change rapidly first and slowly later. • More dosage of rejuvenator exhibited more obvious effects on the aging rheological behavior. • Aged asphalt binder was less affected by re-aging. The use of rejuvenator can potentially restore original properties of reclaimed asphalt pavement (RAP) materials to achieve the purpose of reuse, but less attention has been paid to the aging properties of rejuvenated asphalt binders. In this study, original asphalt binder, aged binder and the rejuvenated binders with 3 %, 6 %, and 9 % of rejuvenator by total weight of binder were prepared first. Then the five rejuvenated binders were subjected to the oven aging. Based on the results from Fourier Transform Infrared Spectroscopy and Dynamic Shear Rheometer, the chemical and rheological properties of the five binders were investigated due to re-aging. It is showed that the of carbonyl index of the rejuvenated binders and original binder increase rapidly during the fast-aging state and then slowly during the constant-aging state, while aged binder increases approximately linearly. The rheological properties indexes such as complex shear modulus, phase angle δ, crossover frequency, crossover modulus, rheological index, G-R parameter and rutting factor of the five binders were determined, and the variation of these indexes are similar or opposite to carbonyl index during aging. Aging performances of the five binders were investigated using the oven aging indexes. It is showed the rejuvenated binders with more dosage of rejuvenator have faster aging rate and more obvious effects on the aging rheological behavior. The rheological properties of the aged binder are less affected by the re-aging. Among the rheological property indexes, the G-R-based oven aging index is most susceptible to the re-aging. There are some certain close relationships between the chemical property change and rheological property evolution during re-aging for the five binders, without considering the aging times and the dosage of rejuvenator. [ABSTRACT FROM AUTHOR]

[Display omitted] • EP improved the low-temperature and fatigue properties of aged asphalt binder. • The fatigue properties of ERA binder steadily improved as the EP content increased. • After a phase transition occurred, the properties of the binder significantly changed. • EP changed the concentration of functional groups in aged asphalt binder. • The property gap between EA and ERA was not significant under the same EP content. The reutilization of reclaimed asphalt pavement (RAP) is gaining importance in meeting the objectives of green and sustainable environmental policies. Meanwhile, epoxy asphalt (EA) is not widely used due to its high price. To facilitate the utilization of EA in RAP recycling, this study adopted an epoxy polymer (EP) to prepare the recycled asphalt binder and investigate the effects of different EP content on the properties of aged asphalt binder. Evaluation encompassed mechanical, microstructural, and chemical characteristics of EP-recycled asphalt (ERA) binders, which were compared against virgin EA binders. The addition of EP can significantly enhance the tensile strength, high-temperature properties, low-temperature properties, and fatigue resistance of the aged asphalt binder. However, the elongation of the aged asphalt binder became worse. As the EP content increased from 30% to 50%, the tensile strength, high-temperature properties, fatigue resistance, and construction allowance time of ERA consistently improved, while the elongation of ERA steadily decreased. A phase transition occurred between asphalt binder and EP phase as EP increased from 40% to 50%, resulting in a rapid increase in tensile strength, high-temperature properties, and fatigue resistance of ERA, as well as a significant reduction in elongation and low-temperature properties of ERA. The concentration of sulfoxide decreased as the EP content increased. The performance gap between EA and ERA was not significant under the same EP content. The EP content had a greater impact than the aging degree of asphalt binder on the properties of the ERA. A recommended EP content of 40% was suggested. [ABSTRACT FROM AUTHOR]

• Limited effect of regeneration on the restoration of micelle structural stability. • Recycled asphalt properties are affected by the stability of the micelle structure. • Stable micelle structure enhances recycled asphalt performance. The research is focused on the asphalt colloid system and provides a detailed analysis of why the effective recovery of low-temperature performance and fatigue performance is challenging during the regeneration of aged asphalt. This study initially examined the alterations in the stability of colloidal structures and micelle structures while rejuvenating aged asphalt. These were performed through four-component analytical tests and asphaltene-resin (A-R) adsorption experiments, respectively. Subsequently, the impact of the regeneration process on the low-temperature performance and fatigue performance of aged asphalt was assessed using bending beam rheometer (BBR) tests and linear amplitude sweep (LAS) tests, respectively. In addition, linear regression analysis was employed to determine the relationship between the stability of colloidal and micelle structures and the performance of recycled asphalt in terms of low-temperature and fatigue resistance. The results show that regeneration of aged asphalt results in 100% recovery of colloidal structural stability, while the maximum recovery of micelle structural stability is only 68.2%. The stability of the micelle structure in recycled asphalt is primarily influenced by the proportion of aged asphalt to virgin asphalt. When the mass ratio of aged asphalt to virgin asphalt is 2:8, the stability of the micelle structure can be restored to 58.1%. However, when the mass ratio is reversed to 8:2, the stability of the micelle structure can only be restored to 21.6%. The impact of the regeneration agent on the recovery of micelle structure stability is minimal. Out of all the samples that underwent regeneration, the highest level of enhancement in the stability of the micelle structure achieved by the rejuvenators was approximately 15%. Linear regression analysis showed that the low-temperature performance of recycled asphalt was significantly affected by the stability of the colloid and micelle structure. The fatigue performance of recycled asphalt was only significantly affected by the stability of the micelle structure. Therefore, enhancing the stability of the micelle structure in recycled asphalt can effectively improve its low-temperature and fatigue performance. This study provides valuable insights into the underlying factors contributing to the subpar low-temperature and fatigue performance of recycled asphalt. Moreover, it contributes to the development of more effective rejuvenators for aged asphalt recycling. [ABSTRACT FROM AUTHOR]

• The degree of blending is assessed in warm and cold recycled mixtures. • The influence of the virgin binder (bitumen, bio-based binder, emulsion) is studied. • A methodology is developed using the infrared microscopy in micro-ATR mode. • Infrared data acquired over time highlight the emulsion curing in cold mixtures. • Infrared microscopy is adapted to analyze mixtures containing a bio-based binder. 2/3 of the reclaimed asphalt pavement (RAP) amount is used for recycling of European asphalt mixtures. An issue that remains unresolved is the blending between the RAP binder and the new binder. Using infrared microscopy, the binder blending is assessed in low-energy mixtures using a bituminous or bio-based binder. Infrared data were acquired and quantified using average and standard deviation indicators; their evolution is monitored over 3 months. A relationship between the average and the binder concentration is highlighted. Binders homogeneity depends on the RAP content and virgin binder. On cold mixes, infrared data evolve over time, highlighting emulsion curing. [ABSTRACT FROM AUTHOR]