Cold Recycled Mixtures Research Articles

Mechanical properties and enhancement mechanisms of cold recycled mixture using waterborne epoxy resin/styrene butadiene rubber latex modified emulsified asphalt

• CRM containing only fresh aggregate and WSEA has better mechanical properties; • WER/SBR modifier can provide the strengthening and toughening effects on CRM; • Dissipation energy ratio and relaxation time can better evaluate the CRM toughness; • The added fresh aggregates favor toughness rather than mechanical strength of CRM; • Asphalt syncretization occurs in the outermost three layers at RAP aggregate surface. To better understand the enhancement mechanisms of waterborne epoxy resin/styrene butadiene rubber latex modified emulsified asphalt (WSEA) on the mechanical properties of cold recycled mixture (CRM), four types of CRM specimens were prepared to systematically discuss the mechanical property changes based on nanoindentation tests. Then the syncretization state between aged asphalt and WSEA, as well as the microstructures of asphalt-aggregate interfaces were analyzed by Fourier transform infrared spectroscope and scanning electron microscope tests, revealing the performance enhancement mechanisms. Results indicated that the mechanical properties of CRM prepared by fresh aggregate and WSEA were better. Also, the toughness of CRM could be accurately characterized by the dissipation energy ratio and relaxation time rather than the creep compliance. Additionally, the syncretization occurred in the asphalt samples of the outermost three layers at RAP aggregate surface. The added fresh aggregate was beneficial to forming WSEA-fresh aggregate interface, improving the anti-cracking property and moisture stability. Finally, the result reliability of the nanoindentation test was verified by indirect tension tests and conventional tests of pavement performance.

Void distribution, interfacial adhesion and anti-cracking mechanisms of cold recycled asphalt mixture based on AFM and X-ray CT

To reveal the anti-cracking mechanisms of cold recycled mixture (CRM) prepared by waterborne epoxy resin/styrene butadiene rubber latex (WER/SBR) modified emulsified asphalt (EA), the void distributions in CRM were analyzed by X-ray computed tomography. Then a method for calculating the adhesion work of asphalt-aggregate interface was proposed based on atomic force microscope tests. Finally, the anti-cracking properties were discussed by low-temperature bending and semicircular bending fatigue tests. Results indicated that the surface void contents of CRM specimen were all smaller in the middle and larger at both ends along the height direction. The WER/SBR modifier exerted a significant filling effect on the voids, reducing the void content and size. Moreover, WER/SBR modified EA (WSEA) showed stronger adhesion property and deformation resistance. WSEA-fresh aggregate interface had the largest adhesion work of 267.25 mJ/m2. Further, the interfacial adhesion failure between EA and fresh aggregate, as well as the cohesive failure of the syncretic interface between EA and aged asphalt were the main cracking forms of CRM specimen. A three-dimensional network in the WSEA-aggregate interface was formed by the WER/SBR modifier, improving the interfacial adhesion property. The void distributions and interfacial adhesion property in CRM specimen significantly affected the cracking resistance.

Permanent Deformation Assessment of Cold Recycled Asphalt Mixtures

The objective of this study was to evaluate the behavior in terms of the permanent deformation of four cold recycled asphalt mixtures stabilized with asphalt emulsion and foamed asphalt. The analysis was conducted considering three flow number test procedures adapted for cold recycled mixtures: (i) ABNT NBR 16505 (method A); (ii) adaptation of the FN test for CRAM according to Kim and Lee’s method (method B); (iii) 3D-Move analysis software simulation of pavement structures to address the stress magnitude for the FN test (method C). The influence of the curing process on the performance of the materials was also verified. The study used an extensive database of computed pavement responses from the four different asphalt pavement structures of the experimental section subjected to axial loading of a tandem axle using the 3D-Move pavement response analysis program. The FN results using the 3D-Move data (method C) demonstrated the good mechanical behaviour with respect to permanent deformation of the cold recycled mixtures subject to axial stress and temperature. The method proposed by Kim and Lee (method B) showed little efficacy for the analysis of the CRAMs tested in this work. The ABNT NBR 16505 method (method A), conventionally used for HMA, highlighted the influence of temperature (60°C) on the CRAM mixtures. For all FN test conditions, the curing was a preponderant factor for the performance of cold recycled asphalt mixtures and should be carefully evaluated to simulate the early stage of the mixtures in the field. It is also important to verify the influence of humidity and temperature on the permanent deformation mechanism of cold recycled asphalt mixtures.

Field performance of bitumen emulsion Cold Central Plant Recycling (CCPR) mixture with same day and delayed overlay compared with traditional rehabilitation procedures

Cold Recycled Mixtures (CRM) offer many benefits, including cost-effectiveness and sustainability. Large existing Reclaimed Asphalt Pavement (RAP) stockpiles that represent an environmental and storage challenge can be used for bitumen emulsion Cold Central Plant Recycling (CCPR). A pavement rehabilitation demonstration project using Cold Recycled Mixture with Bitumen Emulsion (CRM-E) as binder course with 100% RAP was carried out on August 25, 2020. The project was divided into three sections to evaluate the mill and pave strategy using CRM-E as an alternative to traditional Hot Mixture Asphalt (HMA). The wearing course was the same asphalt concrete for the three sections. The difference between Section 1 and 2 that used CRM-E was to either pave the asphalt concrete overlay on the same day or to delay its application for 3 days to give additional time for the CRM-E to cure. Section 3 had no CCPR and consisted of two HMA layers. The field performance of the rehabilitated sections was monitored in 4 phases after 14 days, 3 months, 6 months and 12 months. The performance of the sections was assessed based on Falling Weight Deflectometer (FWD), field rutting measurements and cracking distress surveys. Cores were also taken over time to compare the CRM-E and HMA binder course properties in terms of resilient modulus, dynamic creep, indirect tensile strength and tensile strength ratio. The research showed that CRM-E and HMA performance was similar in terms of FWD deflections, field rutting, in situ cracking, and moisture resistance of the field cores. CRM-E showed superior performance in terms of resilient modulus and dynamic creep compared with asphalt concrete binder course based on testing of field cores taken after 6 and 12 months. The research showed that same day CRM-E HMA overlay is a viable construction option.

Study on Cold Recycled Asphalt Mixtures with Emulsified/Foamed Asphalt in the Laboratory and On-Site

Millions of tons of reclaimed asphalt pavement (RAP) and reclaimed aggregate or reclaimed inorganic binder stabilized aggregate (RAI) is produced every year in China. The cold recycled mixture (CRM) technology reduces fuel consumption, emissions, and cost and utilizes the high content of RAP. In this paper, six types of CRM with varying RAP/RAI composition and asphalt binders were investigated. The laboratory tests included strength indicators, high temperature stability, low temperature crack resistance, water stability, and dynamic modulus. A full-scale trial section was constructed after the laboratory tests. Except for low temperature failure strain without secondary compaction in the mixture design, test results illustrated that the performances of different CRMs met the specifications. The cement addition limited the thermo-viscoelastic behavior of the CRM. The RAI contents had reduced the water sensitivity of CRM, and the emulsified asphalt CRM had better performance than the foamed asphalt CRM. The performances of samples cored from the test section in the field met the specifications and were lower than that in the laboratory. The curing conditions in the field were not as effective as in the laboratory. The curing conditions and compaction method should simulate the conditions in the field to guide the CRM selection and mixture design.

Multi-scale finite element simulation of asphalt mixture anti-cracking performance

This study investigates the anti-cracking performance and cracking mechanisms of asphalt mixtures. The results of experimental tests were compared with simulated tests of asphalt mixtures based on the multi-scale finite element method (FEM). The FEM considered the mesostructure of the asphalt mixtures, the internal viscoelasticity of asphalt mortar, and the asphalt mastic-aggregate interface. Coarse aggregates were generated based on the polygonal random aggregate generation and placement method. Numerical cracking models of the asphalt mixtures were established by the multi-scale FEM and fracture tests were simulated according to the experimental test conditions. The reliability of the simulations was verified by comparison with the experimental test results. The influences on cracking behavior were investigated, with an energy-saving and economical alternative mixture—cold recycled mixture (CRM)—used for comparison. The simulations were highly accurate and could effectively simulate the asphalt mixtures’ cracking processes and mechanisms. The cracking behavior was directly related to notch length, test temperature, void content, and mixture type. A significant difference in the macroscopic anti-cracking performance of hot mixture asphalt and CRM was found. According to the simulations of crack development, there is a 'critical point' of crack propagation from the interface to the interior of the mortar. The mesoscale influences on the cracking behavior of asphalt mixtures are discussed and ranked in terms of importance.

Fiber-Emulsified Asphalt Cold-Recycled Mixture Produced Using Vertical Vibration Compaction: Performance Study

Fiber-Emulsified Asphalt Cold-Recycled Mixture Produced Using Vertical Vibration Compaction: Performance Study

Effects of Freeze–Thaw Cycles on Performance and Microstructure of Cold Recycled Mixtures with Asphalt Emulsion

Although it is widely recognized that freeze–thaw cycles have a great influence on the properties of asphalt pavement, a quantitative understanding of how freeze–thaw cycles affect cold recycled mixtures with asphalt emulsion (CRME) is so far still lacking. The main objective of the paper was to investigate the performance and microstructure of CRME under freeze–thaw cycles with different water saturation conditions. For this, air voids, high-temperature stability, low-temperature cracking resistance, and moisture susceptibility of CRME were analyzed based on laboratory tests. The micro-morphology and chemical composition of cement asphalt emulsified compound mortar were observed by scanning electron microscopy (SEM). Results showed air voids of CRME increase as freeze–thaw cycles increase; the high-temperature stability, low-temperature cracking resistance, and moisture susceptibility of CRME decrease as freeze–thaw cycles increase; the asphalt strips from the surface of hydration products, and the composite structure mainly consists of hydration products as freeze–thaw cycles increase; the microstructure of CRME is destroyed. The freeze–thaw cycles have a negative effect on the CRME performance and microstructure.

A Sustainable Cold-Recycled Solution for the Surface Finishing of Unpaved Rural Roads.

This paper presents the results of an experimental investigation which was carried out with the purpose of assessing the performance-related properties of an emulsion-based cold-recycled mixture to be employed as a sustainable solution for the surface finishing of unpaved rural roads. This mixture contained significant quantities of recycled components (reclaimed asphalt and mineral sludge), and its composition was fine-tuned by following an innovative mix design procedure. Properties of these mixtures were studied by means of laboratory tests which considered key parameters, such as flowability, indirect tensile stiffness modulus, indirect tensile strength, moisture susceptibility and resistance to permanent deformation. It was found that, by means of the proposed mix design procedure, optimal dosages of the recycled components can be identified, thereby ensuring the achievement of the desired properties in terms of high workability and adequate stiffness and strength.

Aggregate packing characterisation of cold recycled mixtures

ABSTRACT Despite its significant role in cold recycling mix design and construction process, the effect of reclaimed asphalt pavement aggregates’ gradation and physical properties are relatively less understood. The ambiguities associated with the gradation effect led to challenges in determining the best practices in gradation control and stockpile management and blending in both cold-in-place and central plant recycling operations. Therefore, the main goal of this paper is to quantify the impact of gradation changes and proportioning of reclaimed asphalt pavement aggregates on the packing characteristics and performance of cold recycled mixtures. Binary blends consisting of fine and coarse reclaimed asphalt pavement stockpiles were combined to obtain fourteen gradations using a volumetric aggregate proportioning technique. The compatibility of five of the most prominent binary aggregate packing models was evaluated in cold recycling application. The modified Toufar model was able to accurately predict the blend of fine and coarse aggregates that offers the optimum packing prediction. Complex modulus tests showed linear viscoelastic characteristics of the cold recycled mixtures as well as the sensitivity to the packing states. In essence, this research shows the effectiveness of applying volumetric packing principles and aggregate proportioning techniques to achieve improvements in cold recycled mixtures’ volumetric and mechanical performance.

Effect of Fine Aggregate Gradation on Macro and Micro Properties of Cold Recycling Mixture Using Emulsified Asphalt

In order to explore the influence of fine aggregate on the macro and micro properties of cold recycling mixture using emulsified asphalt (CRME), mechanical and microscopic property tests were carried out. The indirect tensile strength (ITS), unconfined compressive strength (UCS) and triaxial shear strength of different fine aggregate gradation was measured for analyzing the effects of fine aggregate on the mechanical strength, triaxial shear resistance and fracture energy of CRME. Meanwhile, the surface morphologies and air voids distribution of different CRME were observed by scanning electron microscopy (SEM) and X-ray computed tomography (X-ray CT). The results show that fine aggregate has a significant effect on the mechanical strength and shear resistance of CRME. With the same water and asphalt content, the fracture energy and failure strain of the mixture with less fine aggregate (G3-2) decreased by 16.2% and 18.2%, respectively. The less content of powder there was, the fewer cement hydration products there were due to some cement being coated by emulsified asphalt and the “cement hydration products fiber” length being shorter. Approximately 70% of the AFt hydration products in the G3-2 mixture were in the range of 1–4 μm, while those in the G1 mixture were in the range of 4–8 μm. With the increase in filler content, the number of air voids in the volume range of 0.5 mm3 ≤ V < 5 mm3 in CRME decreased, and the number of air voids in the volume range of V < 0.5 mm3 significantly increased, while the equivalent radius of air voids decreased slightly with the increase in filler content.

Research on High-Temperature Rheological Properties of Emulsified Asphalt Mastics and Their Influencing Factors

The high-temperature rheological properties of emulsified asphalt mastics have a significant impact on the service performance of cold recycled mixtures with asphalt emulsions. In this paper, a dynamic shear rheological (DSR) test and a multiple stress creep recovery (MSCR) test are carried out to analyze the influence of tunneling coal gangue powder (TCGP), portland cement (PC), limestone powder (LP), and four kinds of filler binder ratio (F/B) on the high-temperature rheological properties of emulsified asphalt mastics before and after rolling thin film oven test (RTFOT) ageing. Based on the principle of time–temperature equivalence and a viscoelasticity material model, the main curve of emulsified asphalt mastics under frequency scanning test is established, and the rheological properties of emulsified asphalt mastics in a wide frequency domain are analyzed. Finally, the grey entropy theory is used to quantitatively analyze the correlation between different high temperature performance evaluation indices of emulsified asphalt mastics. The results show that the RTFOT ageing process can significantly enhance the high temperature deformation resistance of emulsified asphalt residue and its mastics. The rutting factor (G*/sin δ) of emulsified asphalt mastics increases exponentially with the increase of F/B, while the phase angle is less affected. TCGP mastics and PC mastics have better high temperature performances than those of LP mastics. The most suitable range of F/B is 0.9~1.2 when TCGP is used as the filler, and 1.2~1.5 when PC or LP is used as the filler. Grey entropy correlation analysis shows that there is a good correlation between the two evaluation systems of the DSR test and the MSCR test, and both can evaluate the high-temperature performance of emulsified asphalt mastics.

Molecular dynamics simulation on cohesion and adhesion properties of the emulsified cold recycled mixtures

To explore the interface behavior between emulsified asphalt and aggregate/reclaimed asphalt pavement (RAP), molecular dynamic simulation is carried out in this paper. Molecular models of emulsified asphalt and reclaimed asphalt pavement are constructed. Basic properties, such as density, Solubility parameter, etc., are calculated and compared with actual test data for verification. The emulsifier content, moisture, and temperature effect on adhesive condition of the asphalt-aggregate interface in cold-recycled asphalt emulsion mixture at the molecular scale are investigated and compared. Two types of emulsified asphalt are selected in the paper. The simulation results show that cetyltrimethylammonium chloride emulsified asphalt has stronger adhesion to silica at high temperatures, while sodium dodecylbenzene sulfonate emulsified asphalt has better resistance to water damage. Both virgin asphalt and emulsified asphalt have weak adhesion to the RAP, which means it is necessary to use modifiers and additives to enhance interfacial adhesion. Cohesion failure or adhesion failure between emulsified asphalt and silica can happen at different temperatures. This study on the interfacial properties of emulsified asphalt nanocomposites will be helpful to further understanding the strength formation mechanism of the emulsified cold recycled mixtures.

Dynamic Characteristic Master Curve and Parameters of Different Asphalt Mixtures

Using an AMPT tester and based on laboratory tests, this paper performed a comparative study on the dynamic characteristics of different asphalt mixtures, analyzed the influence of different asphalt binders on the characteristic parameters of the dynamic modulus master curve and the phase angle master curve of asphalt mixture, and expounds the evaluation function of the phase angle master curve for mixture relaxation characteristics. The results show that the modulus master curve parameters of the asphalt mixture are closely related to voids in the mineral aggregate, mixture density, and asphalt content of the asphalt mixture. For the same kind of asphalt mixture, because the gradation of mineral aggregate is fixed and the volume parameters are almost the same, the ultimate modulus of the mixture at different temperatures is unique; when the temperature changes or the asphalt changes, the shape parameter β of the modulus master curve changes regularly, which brings different dynamic responses, and the lower β will show the characteristics of a higher modulus. Asphalt is the source of the viscoelasticity of the asphalt mixture. Although the influence of particle gradation of the mixture will bring about the change of modulus, the phase angle of the mixture depends on the viscoelastic properties of asphalt, and the initial phase angle in the main curve is positively correlated with asphalt penetration and negatively correlated with the softening point and viscosity, while the peak phase angle A is negatively correlated with penetration, and the softening point viscosity is positively correlated. The viscoelastic interval, represented by ω, is negatively correlated with penetration but positively correlated with the softening point and viscosity. The peak position, parameter ωc, of the phase angle master curve can evaluate the relaxation characteristics of the mixture, and the crack resistance of different mixtures can be compared without complex model calculation. In the comparison of the relaxation time of asphalt mixture, the relaxation time of foam cold-recycled mixture is the largest, which is significantly higher than that of other forms of cement mixture; the emulsified asphalt cold-recycled mixture is equivalent to AC20 and LSPM30 mixtures; the SBS-modified asphalt mixture has the best relaxation characteristics.

Fatigue crack evolution and characteristic of cold recycled asphalt mixture in different dimensions

This paper aims at investigating the fatigue crack evolution and crack characteristics of cold recycled asphalt mixtures with asphalt emulsion (CRME) in different dimensional. Firstly, the fatigue resistance performance of specimens was studied by means of SCB fatigue test. A CMOS industrial camera was used to record the full process of SCB fatigue test. Then, X-ray CT technology was utilized to analyze the fatigue crack development rule and cracking behavior of CRME. Finally, SEM was used to investigate the microstructure and fatigue mechanism of CRME. The results indicate that the fatigue resistance of CRME is increased with the increase of curing time. The number of loading cycles when initial fatigue cracks appear in the surface of CRME during the fatigue test is recorded. More loading cycles when initial fatigue cracks appear, the longer the final fatigue life of the CRME is. Moreover, the fatigue crack mainly propagates through the internal air void in CRME, the increase of air void content under fatigue loading can reflect the fatigue damage to CRME. In addition, the cement hydration products and asphalt membrane formed by demulsification of emulsified asphalt are gradually combined to form a dense spatial structure to improve the fatigue cracking resistance of CRME during curing process. The research is meaningful to further understand the mechanism of fatigue cracking for cold recycled mixtures, and provide theoretical support for improving the fatigue cracking resistance.

Evaluation of Full-Depth Reclamation and Cold Central-Plant Recycling Mixtures for Laboratory Compaction, Mechanistic Response, and Performance Properties

Cold recycled mixtures (CRM) are gaining wider acceptability in the United States for rehabilitating existing pavement or new construction while reducing construction costs, environmental impacts, and construction time. However, the technology is still in development owing to inconsistency in design and limited research on mechanistic and engineering properties. To this end, this study evaluates full-depth reclamation (FDR) and cold central-plant recycling (CCPR) materials for evaluating (i) laboratory compaction protocols, (ii) mechanistic properties, and (iii) engineering performances. Two compaction methods—the Superpave gyratory compaction and the modified proctor—were developed for designing test specimens with adequate design properties. The mechanistic properties resilient modulus ( MR) and dynamic modulus (| E*|) were evaluated. Laboratory performance testing such as Texas overlay tester, semi-circular bending, and a modified Hamburg wheel tracking (HWT) were performed. This study also proposed a new parameter, loading limit ( Nmax), based on the modified HWT test configuration. The study found that the FDR exhibits less temperature dependency compared with the CCPR while subjecting to loading. Based on damage properties such as critical fracture energy, J-integral, crack propagation index, and Nmax, the CCPR exhibits more flexibility and damage resistance than FDR.

Evaluation on long-term performance of emulsified asphalt cold recycled mixture incorporating fly ash by mechanistic and microscopic characterization

In this paper, the long-term performance of emulsified asphalt cold recycled mixture (CRME) incorporating fly ash was investigated. The dosages of fly ash included 0.75%, 1.5% and 3.0%, and the long-term service conditions of CRME were simulated by curing in an oven at 60 °C for different ages. Mechanical performance of CRME under different curing ages were obtained through indirect tensile strength (ITS), Marshall stability, low-temperature ITS and freeze-thaw ITS tests, and the microstructures were characterized by optical microscope, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM) tests. The results show that, as the curing age increases, the ITS, flow value, and low-temperature indirect tensile strain of CRME with fly ash increase first and then decrease, while the Marshall stability and freeze–thaw ITS ratio (TSR) always show a gradual increase trend. By comparing the CRME with cement, the CRME with fly ash throughout the long-term curing process exhibits the higher ITS and low-temperature anti-cracking performance and the lower high-temperature stability and water stability. Optical microscope, XRD and ESEM analysis indicate that the dissolution of fly ash particles and the demulsification of asphalt emulsion particles occur simultaneously during the curing ages. After a certain curing age, a dense structure composed of asphalt binders, dissolved and undissolved fly ash particles is formed. Also, the fly ash replacing cement in CRME can effectively reduce the energy consumption and carbon emission.

Analysis of the Impact of Redispersible Polymer Powder on the Water and Frost Resistance of Cold-Recycled Mixture with Bitumen Emulsion

The subject of the research presented in the article is the assessment of the effect of redispersible polymer powder (RPP) on water and frost resistance of a cold-recycled mixture with bitumen emulsion (BE-CRM). The article presents the results of research on the influence of polymer powder EVA based on polymer (polyethylene-co-vinyl acetate) on the properties of BE-RCM. The impact analysis was determined using the assumptions of the Box-Behnken experiment plan in which three components are controlled. In this case, the variables were the content of: polymer, cement and asphalt emulsion. All ingredients were dosed with a step of 1.5% of the percentage share in the mixture composition. Polymer and Portland cement in an amount of 0.5% to 3.5%. On the other hand, the pure asphalt originating from the asphalt emulsion was 0.0%, 1.5% and 3.0%, respectively. The scope of the tests included the determination of: mixture density, void content (Vm), water absorption (nw), intermediate tensile strength (ITS), to water (TSR) as well as water and frost according to AASHTO T283.

Influence of Confinement Pressure on the Mechanical Response of Emulsified Cold-Recycled Mixtures

Cold recycling of asphalt pavement is an effective rehabilitation technique in terms of saving natural resources and cost of construction. The current study focuses on cold-recycled asphalt mixture designated as emulsified cold-recycled mixture (ECRM) that contains 100% reclaimed asphalt pavement material and slow-setting asphalt emulsion. Here, a repeated haversine compression test is conducted with and without confinement pressure at six temperatures (0°C, 10°C, 20°C, 30°C, 40°C, and 50°C) and 10 frequencies (25, 20, 10, 5, 2, 1, 0.5, 0.2, 0.1, and 0.01 Hz). The stress–strain–time response of ECRM is investigated, and it is observed that the influence of confinement pressure is negligible in the temperature range of 0°C–10°C, whereas it is significant at temperature 30°C and higher, irrespective of the frequency of loading. However, at 20°C, the influence of confinement pressure is negligible at higher frequencies (25–10 Hz), and it is significant at lower frequencies (less than 10 Hz). The viscoelastic response of ECRM is seen at all temperature, frequency, and confinement conditions of loading from the analyzed Lissajous plots. The dynamic modulus and phase angle are computed using the regression and the fast Fourier-transform (FFT) methods. The dynamic modulus and phase angle master curve is then generated using a free-shifting approach and a model-based approach. The model-based approach involves the numerical solution of the exact Kramers–Kronig relations combined with the generalized logistic sigmoidal model. The FFT-based dynamic modulus is used to construct a master curve with the generalized logistic sigmoidal model. Such a model-based master curve resulted in excellent predictive capabilities for dynamic modulus, and hence it is suggested for ECRM.

Long-term effects of RAP on the mechanical properties of cold recycled mixtures

ABSTRACT This paper investigates the long-term influence of aged asphalt in reclaimed asphalt pavement (RAP) on the mechanical properties of the cold recycled mixture (CRM) with emulsified asphalt. Firstly, RAP was simulated by the long-term aging method. On this basis, indirect tensile strength tests were conducted to discern the long-term strength with different aged asphalt dosages (0%, 2%, and 4%) and aging degrees (0, 4, 8, and 15 h) of RAP. After accelerated curing, the indirect tensile strength (ITS) and fracture energy () were measured and the area ratio of uncoated aggregates of the fractured surface (Ra ) was established by image processing to reflect the long-term growth mechanism of strength. Considering the unfavourable states, interfacial drawing and shear tests were executed with different aging degree, load, interfacial contact and thickness of aged asphalt films. Results indicated that the strength increased with aged asphalt dosages of RAP, whereas aging degree had the opposite effect. Moreover, aging degrees, clean surface and external load are all salutary to the long-term adhesion of CRM, obviously. Therefore, it is proved that RAP makes contributions to the long-term growth in mechanical properties of CRM, which is also significant to sustainable asphalt pavement maintenance.