Reclaimed Asphalt Pavement Materials Research Articles

A statistical Review on the Usage of Reclaimed Asphalt Pavement waste as a recyclable material

Construction is a part of human evolution, in ancient times people used wood and stone as construction materials as they were obtained naturally. As time passed, we learned about new methods and materials of construction. We started using concrete, steel, and asphalt as construction materials but these materials were costly and also had ill effects on the environment. In modern times construction techniques should be eco-friendly and economical as well. So, recycling construction and demolition waste is an option to deal with these problems. Reclaimed asphalt pavement (RAP) is a type of construction and demolition waste, which can be recycled after proper treatment. Reclaimed asphalt pavement materials are obtained from the milling of road pavement during reconstruction or maintenance work. These materials are mainly coarse aggregates and asphalt binders. The use of Reclaimed asphalt pavement with virgin crushed aggregates is widely accepted practice in several construction applications as it reduces the cost of construction, transportation, and handling. Properties of reclaimed asphalt pavement wastes are expected to be in an acceptable range with the conventional material but can be used as a partial or whole replacement for conventional materials. Reclaimed asphalt pavement also reduces the consumption or violation of natural resources. One of the primary advantages of using RAP is cost savings. Incorporating RAP into asphalt mixtures can significantly reduce material and disposal costs since it eliminates the need to extract and transport new aggregates. Additionally, RAP can reduce the demand for virgin asphalt binder In this review, a study was done on the usage of Reclaimed Asphalt Pavement as a recyclable construction material, and its physical and chemical characteristics are compared to conclude and provide its statistical review so that it can be used for sustainable construction works.

Effect of RAP fractionation and dosage on design and mechanical behaviour of cold asphalt mixes

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.

Mass-composite activation energies for recycled binder blends

Using reclaimed asphalt pavement (RAP) has become an appealing development for economic and environmental benefits. One of the key issues when incorporating RAP materials is to ensure the performance of recycled binder blends. Despite extensive researches dealing with physical and chemical aspects, concerns about recycled materials combinations remain. This paper focuses on the kinetics of aging, cracking and healing process for blended binders with a novel hypothesis of mass-composite activation energies. Firstly, four blends were prepared with different ratios of virgin bitumen and laboratory-produced RAP binders. Then, Fourier-transform infrared spectroscopy was utilized to track the carbonyl formation in all samples initially and with aging, and aging activation energy (Eacr) was computed in terms of Arrhenius equation. Thirdly, strain-controlled oscillatory measurements were conducted; moreover, representative energy change rates of dissipated pseudo strain energy and recoverable strain energy were obtained to determine the activation energy for cracking (Eac) and healing (EaH), respectively. Finally, hypotheses of mass-composite activation energies were validated with the test results. It shows that Eacr of recycled binder blends are smaller than that of RAP binders, indicating a lower kinetic barrier to oxidation reaction for blended bituminous system. With the increase of RAP binder content, the blends exhibit a decrease in Eac and an increase in EaH, which reveals the adverse effect introduced by oxidation in cracking resistance and healing capability. Excitingly, the measured activation energies of recycled binder blends are consistent with the calculated mass-composite activation energies, which will hopefully provide support for performance estimation.

Uncertainty analysis for the dynamic modulus of recycled asphalt mixtures using unclassified fractionated RAP materials

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.

Effect of asphalt modified with waste engine oil on the durability properties of hot asphalt mixtures with reclaimed asphalt pavement

Abstract The increased demand for asphalt and other materials involved in the construction of pavement led to an increase in the cost of these materials, which calls for searching for alternatives to virgin materials that can be used to produce asphalt mixtures. Reclaimed asphalt pavement (RAP) was employed in this study and regenerated using oxidized asphalt modified with waste engine oil (WEO). This method can achieve economic and environmental benefits. After improving the properties of oxidized asphalt using WEO, it was used with reclaimed asphalt mixtures (RAP). When the RAP was added at ratios of 20, 30, 40, and 50%, an improvement can be noticed in the mechanical performance of the asphalt mixtures renewed with oxidized asphalt and WEO and an increase in its resistance to stripping. When reclaimed asphalt pavement (RAP) is added to hot mix asphalt (HMA) at concentrations of 20, 30, 40, and 50%, respectively, the Marshall stability of HMA is improved by 10, 20, 28, and 9.5%, the flow is declined by 1% for all ratios of RAP except for 50% RAP where the flow decline by 3%, the unit weight is enhanced, the quantity of air voids in the mix is preserved within allowable ranges, and the resistance to stripping is increased by 62, 77, 85, and 76%, respectively. Research also shows that incorporating 40% RAP enhances the resistance to moisture by about 5.9%. The addition of 40% RAP reduced the Cantabro loss values by about 2 and 16% for both aging and non-aging samples, respectively. The rutting resistance increased by 50 and 47% for mixes with 40% RAP at 50 and 60°C, respectively. As a result, it became evident that mixtures containing RAP material could be effectively adapted to satisfy the relevant volumetric and performance requirements.

Plastic Waste Sheets Effects on Reclaimed Asphalt Pavement Performances

Abstract This paper aims to examine physical and mechanical performances of a Reclaimed asphalt pavement (RAP) material reinforced with 5 to 15 mm size sheets of plastic waste. The three types of plastic used in the study are: low density polyethylene (LDPE), high density polyethylene (HDPE) and polyethylene terephthalate (PET) with 1%, 1.5%, and 2% dosage by weight of aggregates. Obtained Duriez test results testify to a 9% to 30% improvement in moisture resistance for all types of plastic compared to virgin mixture while for LDPE waste plastic type workability test attests an acceptable compaction condition for RAP material with less than 1.5% of waste plastic. Nevertheless, it has been noticed an increase in void index and compaction difficulties starting from 1.5% dosage, resistance to rutting has also improved with the addition of waste plastic, an improvement in fatigue strength was also observed particularly at 2% dosage.

A novel method for enhancing coating performance of emulsified asphalt mortar to RAP in cold recycled mixture

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.

Effect of Fractionation Process and Addition of Composite Crumb Rubber-Modified Asphalt on Road Performance Variability of Recycled Asphalt Mixtures with High Reclaimed Asphalt Pavement (RAP) Content

The application of reclaimed asphalt pavement (RAP) can help reduce resource waste and environmental pollution in road construction. However, so far, only a small percentage of RAP materials can be used in road construction. The key obstacles to the application of a recycled asphalt mixture (RAM) with high RAP content are the variability of RAP materials and the difficulty of fully rejuvenating aged asphalt. However, there is still a lack of research on the effect of the variability of RAP materials and recycled asphalt on the quality control of a RAM. Therefore, this study investigates the effects of sieve pretreatment of RAP material using 4.75 mm sieve mesh and the use of composite crumb rubber-modified asphalt (CCRMA) to reclaim aged asphalt on the road performance and frame variability of reclaimed asphalt mixtures. Therefore, this study investigates the effects of the fractionation process of RAP material using 4.75 mm sieve mesh and the use of CCRMA to reclaim aged asphalt on the road performance of a RAM. The results show that the fractionation process can effectively reduce the mitigation of RAP agglomeration and reduce the variability of gradation, which in turn reduces the variability of road performance. The incorporation of CCRMA can effectively improve the high-temperature stability performance and low-temperature cracking resistance. The dynamic stability and the fracture energy of the CRAM (RAM prepared using CCRMA) were four and one and a half times as large as that of the NAM (RAM prepared using base asphalt), respectively. The fractionation process of RAP material and the utilization of CCRMA could help reduce the variability of the RAM while improving the road performance of the RAM.

Tailored enhancement of reclaimed asphalt pavement with waste engine oil/vacuum residue blend as rejuvenating agent

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.

Material and mix design aspects of hot recycled asphalt mixes: A review.

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

Study on the Adhesion Characteristics of Asphalt-Aggregate Interface in Cold Recycled Asphalt Mixtures

The reclaimed asphalt pavement materials have been used for sustainable cold-recycling, significantly benefiting air quality and resource conservation, while its microscale interface properties greatly affected road performance during the cold-recycling processes. In this investigation, the cold recycled asphalt mixtures were prepared with different mixing proportions, considering the effects of cement content and mixing water amount. The adhesion characteristics of the asphalt-aggregate interface in different cold recycled asphalt mixtures have been comprehensively investigated based on the atomic force microscopic (AFM). The microscale morphology and the adhesion properties, including roughness, inclination angle, adhesion force, Derjaguin–Muller–Toporov (DMT) modulus, and dissipated energy were evaluated at the interface and noninterface regions. The micromorphology results showed that the addition of cement could enhance the roughness and inclination in interface regions. In addition, the content of mixed water showed the most significant effect when the water amount was 80%. The results showed that the adhesion force, DMT modulus, and dissipated energy increased with the addition of cement, indicating that the cement could improve the microscale mechanical properties of cold recycled asphalt mixtures. With the increase of mixing water content, the adhesion characteristics showed varied results, and the optimum water content of 80% contributed to the adhesive properties. In addition, the adhesion force, DMT modulus, and dissipated energy were all higher in the interface region by comparing with the noninterface region. The correlations between the macroscale splitting tensile strength and microscale adhesion characteristics of cold recycled asphalt mixtures were established.

A mechanistic-empirical approach to estimate the degree of Reclaimed Asphalt Pavement (RAP) bitumen activity

Coating studies and other mechanical methods to estimate DoA necessitate sophisticated equipment, skilled workforce, and huge amount of RAP material for testing. Hence, the present study proposes a simple mechanistic-empirical approach to estimate DoA with reasonable accuracy without requiring experiments on RAP material. Coating studies were carried out on several experimental combinations with varying mixing parameters and RAP characteristics. It was found that the liquid bridge theory along with a shift factor function can successfully be used to estimate DoA. A regression model with an adjusted coefficient of determination (R2-adj) of 0.70 was developed to establish the shift factor function.

Influence of epoxy resin polymer on recycled asphalt binder properties

Utilization of high-performance pavement materials with a high reclaimed asphalt pavement (RAP) content is gradually gaining importance given the impetus of green environmental policies. Epoxy resin polymer (EP) can greatly enhance the reuse of RAP materials in asphalt mixture. The influence of EP on the properties of aged asphalt binder was investigated wherein mechanical and chemical properties, and the micro-morphology of binders composed of aged asphalt binder and EP were also evaluated. EP significantly improved tensile, high-temperature, low-temperature, and fatigue properties of aged asphalt binder, and simultaneously reduced concentration of sulfoxide and carbonyl of aged asphalt binder. Increasing EP content reduced the impact of asphalt ageing degree on mechanical properties, micro-morphology, and chemical composition. Furthermore, the construction allowance time of the binder was increased with increasing EP content. At 40% EP content, an effective network structure was formed in the aged asphalt binder, leading to higher tensile elongation, high-temperature rheological properties, and fatigue life as compared to virgin asphalt binder. Meanwhile, low-temperature modulus and sulfoxide and carbonyl concentrations were lower than those of virgin asphalt binder. For application, a recommended EP content of 40% is suggested.

Laboratory Evaluation of Emulsion-Treated Base Layer Mixes Incorporating Reclaimed Asphalt Pavement Materials

Emulsion-Treated Base (ETB) is one of the most preferred base layer stabilization methods in which dense graded aggregates are treated with a slow setting bituminous emulsion. To reduce the cost of ETB and minimize the need for virgin aggregates, it is essential to evaluate the possibility of incorporating higher dosages of Reclaimed Asphalt Pavement material (RAP) in ETB. The present study evaluates the effect of RAP incorporation in ETB at dosages of 0%, 25%, 50%, 75%, and 100%. The effects of RAP incorporation were studied in terms of RAP mixing and RAP blending methods. RAP mixing is a process in which a definite proportion of RAP is added to virgin aggregates of a given gradation without a target gradation, while in RAP blending, virgin aggregates of required aggregate sizes are blended to RAP with the objective of achieving a targetted dense aggregate gradation. In this study, RAP was characterized using cohesion tests, fragmentation tests, and other physical properties recommended by the International Union of Laboratories and Experts in Construction Materials, Systems, and Structures (RILEM) Technical Committee. When 50% RAP was added to ETB using the RAP mixing method, the Maximum Dry Density (MDD) of the mix decreased by 4.4%, but in using RAP blending, the reduction in MDD was only 1.3%. ETB prepared with up to 75% RAP, 3% emulsion, and 1% cement, using the RAP blending method, was found to satisfy the minimum indirect tensile strength requirement of 225 kPa (specified by TG 2 2009 and IRC 37 2012), and exhibited appreciable rutting resistance and a tensile strength ratio of more than 0.7. This study identified that 50% RAP incorporation in ETB using blending gives the best performance in terms of cohesive and adhesive strength, moisture resistance, and resistance to permanent deformation.

Kajian Nilai Keawetan Reclaimed Asphalt Pavement Dengan Pemanfaatan Buton Granular Asphalt Pada Lapis Perkerasan Ac-Wc

Reclaimed Asphalt Pavement (RAP) is the residual waste generated from the dredging of damaged road pavements. Usually this RAP material is thrown away so it is rarely reused. In fact, RAP material that has become waste and is no longer used can be used as an added ingredient in the manufacture of new asphalt concrete with rejuvenator. This study aims to determine the durability value of reclaimed asphalt pavement with the use of buton granular asphalt (BGA) as a rejuvenating agent in the gradation of the Laston mixture (AC-WC) against the IRS value. The first testing stage is to test the characteristics of the reclaimed asphalt pavement material and then continue with the marshall test. The optimum asphalt content value obtained after testing is at 5,28% of the total aggregate. The reference used in testing the characteristics of Marshall and IRS is the specification of Bina Marga in 2018 revision 2. The results of the IRS test using the optimum asphalt content of 5,28% with the addition of BGA show that along with the increase in the level of BGA in the AC-WC mixture by using RAP, the ability of the mixture to withstand the load increases and the flexibility of the mixture decreases, so that the asphalt's durability increases, represented by the IRS test of 30 minutes and 24 hours which shows the durability value with 0% BGA content, the value is 112,70%, with the addition of BGA 1% obtained a value of 118,87%, BGA 2% 121,50% and with the addition of 3% BGA content which was 125,11% in the Laston mixture (AC-WC). So from the test results, the IRS value meets the requirements of the 2018 Highways Specification of 90%, so it is concluded that the results of the tests carried out meet the durability requirements and can be applied in the field.

Research on pavement performance of recycled asphalt mixture based on separation technology of asphalt and aggregate in RAP

Asphalt-aggregates separation of reclaimed asphalt pavement (RAP) with bio-oil as solvent is an economical, simple, and efficient method to recycle RAP materials. The byproducts of asphalt-aggregates separation of RAP are recycled aggregates and blends of bio-oil and old asphalt (BBOA). In this paper, to improve the recycling rate of BBOA and recycled aggregate after asphalt aggregate separation, Buton Rock Asphalt (BRA) is used as a high-temperature property modifier to compensate for the aging resistance and high-temperature of BBOA. The physical properties of rock asphalt modified bio-oil asphalt (RMBA) with different amounts of BBOA were studied by viscosity, frequency scanning, multiple stress creep, bending beam rheology, and aging tests. At the same time, recycled aggregates of different particle sizes and RMBA were used to prepare asphalt mixture with diverse mix design methods. The pavement properties of the recycled asphalt mixture were evaluated by rutting resistance, low-temperature bending beam, freeze–thaw splitting, and fatigue tests. The results show that RMBA realizes the complementary advantages of BRA as a high-temperature modifier and BBOA as a low-temperature performance modifier. The recommended dosage of RMBA is 20 %rock asphalt and 7 %BBOA. Under different preparation methods, the pavement performance of rock asphalt modified bio-oil asphalt mixture, asphalt mixture containing coarse recycled aggregate, and asphalt mixture containing oil sand meet the requirements of asphalt pavement design specifications, the preliminary realization of 100% recycling of RAP.

Evaluation of the structural performance of the geocell-stabilized flexible pavement

Geocell can provide sustainable solutions for the pavement infrastructure as it allows the utilization of reclaimed and inferior quality base aggregate materials as infill materials. The benefits of using geocell have been well established in the literature; however, lack of knowledge regarding the field performance hinders transportation agencies from designing flexible pavement with such products. This study aims to determine the contribution of geocell towards pavement system performance based on non-destructive field testing. The existing road section of a Farm to Market Road was replaced with different thicknesses of geocell-reinforced base layer filled with reclaimed asphalt pavement (RAP) material. The performance of the reinforced sections was verified with the profiler test and rutting measurements. Falling weight deflectometer (FWD) tests were conducted on different test sections to capture the pavement responses. Field data showed that geocell allowed the maximum usage of RAP material and enhanced its performance. The back-calculated in-situ modulus showed that the additional confinement provided by the geocell ranged between 8 and 20 psi. The increase in confinement indicated an increase in resilient modulus, which was further calculated for each geocell-reinforced section. Geocell also helped to restrict the differential movement of the subgrade by providing uniform support, which resulted in a smoother road structure with less rutting and longitudinal cracking.

Utilization of reclaimed asphalt pavement (RAP) materials in HMA mixtures for flexible pavement construction

Production of more RAP material waste arises the problem of deposition. To overcome this problem, RAP materials are recycled and re-used in different layers of pavement which will reduce the cost of pavement construction, reduce the environmental pollution. So, partial replacement with natural aggregate (NA) is an alternative for conservation of natural resources. RAP materials contain bitumen on their surface which will reduce the amount of natural bitumen. Replacement of RAP materials with natural aggregate needs suitable blending proportion. This paper represents laboratory evaluation of replacement of Reclaimed Asphalt Pavement (RAP) materials, a varying percentage of 0 to 30% blended with natural aggregate in terms of Marshall Stability, Indirect Tensile strength and Tensile Strength Ratio to be used in hot mix asphalt (HMA) mixtures for construction of surface course of flexible pavement. Marshall Stability, Indirect Tensile strength and tensile strength ratio (wet and dry condition) of natural aggregate blended with RAP 0%, 10%, 20% and 30% were tested and found 20% RAP mix is suitable for the bituminous road construction.

Rheological Characterization of Reclaimed Asphalt Binder Blended with The Neat And Sbs-pma Binders

Reusing reclaimed asphalt pavement material guarantees a substantial optimization of non-renewable material resources, emissions reduction, and decreasing landfill space, along with the economic benefits associated with saving the costs of purchasing and transporting new aggregate and asphalt binder for asphalt concrete mixture production. This study aims to investigate the influence of aged asphalt binder from reclaimed asphalt pavement on the virgin asphalt binder’s rheological properties. Therefore, different dosages of RAP binder (20%, 30%, and 40% by weight of the total mix) were blended with neat asphalt binder (40-50), penetration grade (P40), and SBS polymer asphalt (SBS-PMA) binder. Using both traditional and Superpave performance testing methods, the effects of RAP on the blend's consistency, viscosity, softening, elastic recovery, rutting (permanent deformation), fatigue cracking, and low temperature cracking were evaluated. The results revealed that the RAP binder decreased the penetration value of both neat and SBS-PMA binders. The neat asphalt binder’s viscosity and softening point increased with the increase in RAP content, whereas they decreased for SBS-PMA. The RAP binder decreases the SBS-PMA elastic recovery. where the neat asphalt experienced a little improvement in elastic recovery when blended with the RAP binder. The Superpave test results revealed that the RAP binder deteriorates the performance of the SBS-PMA binder at high, intermediate, and low testing temperatures. With the addition of 20%, 30%, and 40% RAP, the high-temperature PG grade of SBS-PMA blends decreased by 0.64%, 0.95%, and 1.10%, respectively, while the low-temperature PG grade increased by 23%, 31%, and 32%, respectively. In contrast, the RAP improves the neat asphalt blend's high-temperature performance grade and deteriorates intermediate and low-temperature performance grades. The addition of 20%, 30%, and 40% RAP increased the neat asphalt blends' high-temperature properties by 1.5%, 3.3%, and 4.5%, respectively. whereas the neat asphalt low-temperature PG grade increased by 5%, 11%, and 15% with the addition of 20%, 30%, and 40% RAP, respectively. In summary, the performance of virgin and RAP binder blends depends on the individual characteristics of the blended asphalt binders

Laboratory and numerical investigation on the behavior of reclaimed asphalt pavement (RAP) as railway track subballast layer

The use of asphalt mixtures in different places of the structure of railway tracks has been increased, given their acceptable performance and properties. Using bituminous materials in subballast layers is of great importance due to the structurally, vibrationally, and geometrically improving properties of these infrastructures. In order to enhance the mechanical behavior of railway tracks under heavy loads and high-speed trains, the tendency to use sustainable development approaches such as reuse of discarded and recycled materials has increased. The asphalt is recycled in the maintenance activities of road pavements and, in some cases, reused in the road construction and pavement industry, raising the question of whether reclaimed asphalt pavement (RAP) mixtures can be utilized in railway tracks? Has not been so extensively studied on RAP materials to be used as an interlayer in the structure of railway tracks. Accordingly, the present study seeks to investigate the behavior of these materials as the railway tracks subballast by experimental and numerical through structural approach. Given the complex behavior of these materials due to their bitumen aging, researchers are concerned about the quantity of them that can be reused. In this study, subballast layers containing RAP with percentages varying from 25 % to 100 % without any additive material and thicknesses from 5 cm to 20 cm were numerically modeled. At first, the behavioral models of the RAP materials without any additive material in a laboratory were determined for the model inputs. Using the dynamic modulus and relaxation behavior remarkably helped to identify the behavior of these materials. Numerical models were developed for RAP materials by assuming the linear elastic (LE) behavior for granular materials and linear viscoelastic (LVE) behavior for RAP materials. A conventional ballast track model with granular subballast was also simulated for validation and comparison. Eventually, by evaluating the effect of using RAP on the track settlement, the tensile strain of the bottom of the subballast layer, and compressive stress imposed on the subgrade, the subballast layer with 100 % RAP and a thickness of 20 cm was found to have the best performance, reducing the mentioned Strain and Stress parameters by 40 %. Accordingly, such a layer can be utilized as a simple permanent solution to improve the stiffness and performance of tracks.