RAP Materials Research Articles

Evaluation on the diffusion-fusion properties and interfacial mechanical behavior of virgin and aged asphalt

To investigate the regeneration mechanisms of rejuvenated asphalt mixtures, molecular simulation techniques were employed to research virgin and aged asphalt's fusion characteristics and interface mechanical properties. The blended zone was identified based on relative density distribution, and a molecular-scale calculation method for the Degree of binder Blended (DOB) between virgin and aged asphalt was proposed. Finally, the influence of DOB on the mechanical properties of the asphalt-aggregate interface was evaluated through interface pull-out tests. The results revealed that the proposed molecular-scale DOB calculation method effectively assessed the blending effectiveness between virgin and aged asphalt. Higher degrees of asphalt aging made it more challenging for aged asphalt to fuse with virgin asphalt, while elevated temperatures facilitated diffusion fusion between them. Under tensile loading, initial cracks were primarily initiated from the rejuvenated asphalt's blended zone. This region represented the weakest area within the interface system and was prone to fracture under load. The increase in DOB significantly improved the interfacial properties of recycled asphalt, with the increase in DOB the interfacial tensile strength increased by 4%–14% and the fracture energy increased by 10%–19%. However, this enhancement effect diminished with an increased degree of asphalt aging. At the molecular scale, increasing DOB improved the interface strength and deformation resistance of rejuvenated asphalt. The molecular simulation results provide theoretical guidance for evaluating the fusion degree of aged asphalt in RAP materials and determining the utilization efficiency of aged asphalt.

Development of Bioregenerant and Its Potential Application: Investigation for Regeneration of RAP Materials

Development of Bioregenerant and Its Potential Application: Investigation for Regeneration of RAP Materials

Optimizing decarbonation and sustainability of concrete pavement: A case study

This study focuses on the actual project of rural road ‘concrete to asphalt’ pavement renovation, deeply integrating the design concept of full structure regeneration and the innovation of in-situ regeneration technology for old cement pavement. Through the life cycle assessment method, an environmental impact quantification assessment model is used. Based on the analysis of the environmental benefits of traditional pavement renovation technology (using multi-hammer crushed stone and hot mix asphalt production technology), the environmental advantages of the full-structure regeneration technology scheme are outlined, including the recycling of recycled asphalt pavement materials, application of emulsified asphalt plant mixing cold regeneration technology, and implementation of resonance crushed stone on-site regeneration technology. At the same time, sensitivity analysis methods are used to deeply analyze the sensitivity of changes in parameters such as surface and base thickness, transportation distance, and environmental factors to the overall environmental impact. The research results indicate that the optimization plan can achieve a 57.97 % reduction in total energy consumption and a 71.45 % reduction in total carbon emissions. Additionally, the recycling and utilization of RAP materials significantly reduce the demand for new mineral materials and asphalt. For a 1-kilometer road surface, mineral materials save up to 82.39 % and asphalt saves up to 27.11 %. The energy consumption and carbon emissions generated during the raw material production stage in both schemes contribute the most to the environmental impact of road construction. The analysis found that the environmental benefits of the optimization plan mainly come from the recycling of the old cement concrete pavement as the base layer after resonance crushing, as well as the use of emulsified asphalt mixture cold recycling instead of the lower layer of hot mix asphalt concrete, achieving full-scale recycling of the pavement renovation. The relevant findings provide a data foundation or the improvement and upgrading of energy-saving and emission reduction technologies in road surface renovation and offer valuable insights for future research on sustainable road surface renovation strategies.

Study on the Performance of High Content RAP Recycled Mixture

The performance of RAP material directly affects the engineering effect of pavement recycling technology. In this study, the performance of high content RAP recycled mixture was analyzed. Through the extraction and screening of RAP materials, it was found that the viscosity of old asphalt increased significantly, the softening point decreased, and the coarse aggregate was refined seriously. The high, low temperature and water stability of high content plant mixed recycled ATB-25 mixture were studied through laboratory tests with different regenerants. The results showed that, compared with the control group, the dynamic stability, freeze-thaw splitting strength ratio and the maximum flexural tensile strain increase rate were: Type A regenerant: 27.48%, 29.45%, 35.71%; Type B regenerant: 16.76%, 21.28%, 38.96%. Comparing the effects of the two kinds of regenerants, after adding Type A regenerant, the mixture has the best high-temperature and water stability, and Type B regenerant is better than Type A regenerant in improving the low-temperature performance. The high, low temperature and water stability of the mixture after adding the regenerant can meet the specification requirements.

Effect of RAP's preheating temperature on the secondary aging and performance of recycled asphalt mixtures containing high RAP content

Plant-mixed hot recycling technology is widely used. Due to concerns about the road performance of recycled asphalt mixtures with high RAP content, the content of RAP is strictly limited, which has negative impact on ecological and economic benefits. Low preheating temperature of RAP material is an important reason for reduced performance of recycled asphalt mixtures containing high RAP content. At the same time, excessive preheating temperature of RAP materials can cause secondary aging of asphalt in RAP. This study regarded the preheating temperature as a variable. Rheological and spectroscopic tests such as DSR and BBR, and FTIR tests were conducted to investigate the effect of RAP preheating temperature on the secondary aging of RAP. Afterwards, the influence of raising preheating temperature of RAP on the performance of recycled asphalt mixtures was explored synthetically. When the preheating temperature is below 160 ºC, there is no significant secondary aging of aged asphalt in RAP. However, when the preheating temperature increases to 180 ºC, the rheological properties of aged asphalt undergo certain changes. Increasing the preheating temperature of RAP can significantly improve the low-temperature crack resistance and fatigue performance of recycled asphalt mixtures by reason of maximally activating the aged asphalt. Increasing the preheating temperature of RAP does not weaken the high-temperature anti-rutting performance of recycled asphalt mixture. It is recommended to control the preheating temperature of RAP at 160 ºC in the design and production process of hot recycled asphalt mixtures.

Performance Evaluation and Self-Healing Properties of Asphalt Mixtures Containing RAP Materials and Rice Bran Oil Capsules

Performance Evaluation and Self-Healing Properties of Asphalt Mixtures Containing RAP Materials and Rice Bran Oil Capsules

Evaluation of Millability and Recyclability of Asphalt with Paving Interlayers

Abstract Reclaimed asphalt pavement (RAP) has been widely incorporated into roadway base and surface courses, as they provide economic and environmental benefits that lead to sustainable construction practices. However, because of the increasing use of paving interlayers (e.g., geotextiles, geogrids, and geocomposites) during roadway rehabilitation, the likelihood of milling projects involving asphalt layers with paving interlayers (referred to as GRAP) has significantly increased. Consequently, the assessment of potential GRAP reuse in geotechnical and pavement applications becomes essential. This research study aims at evaluating the millability and recyclability of asphalt layers with paving interlayers. Specifically, sections with and without paving interlayers were first milled to evaluate the millability of asphalt layers with paving interlayers. Subsequently, the recyclability of GRAP for the base and surface course of pavements was assessed by quantifying the geotechnical characteristics of millings collected from asphalt layers with paving interlayers, referred herein as geosynthetic RAP or GRAP, and those without paving interlayers (RAP). The evaluation of RAP and GRAP materials for road base suitability included blending them with virgin aggregates and investigating these blends via determination of particle size distribution, binder content, compaction characteristics, abrasion resistance, hydraulic conductivity, and resilient modulus. The evaluation of RAP and GRAP materials for surface course suitability involved preparing asphalt mixtures that incorporated RAP and GRAP and quantifying their particle size distribution, indirect tensile strength, and moisture susceptibility. Comparison of the results obtained from five different base course blends and five different asphalt mixtures demonstrated that the base course blends and asphalt mixtures with GRAP exhibited properties similar to those with RAP. Also, the results of this investigation indicate that asphalt mixtures (surface course) and granular base courses can incorporate up to 30 % and 50 % GRAP, respectively, thus leading to sustainable roadway construction practices.

Study the Effect of using RAP in Warm Mix Asphalt Pavement.

Sustainability is providing the needs without compromising the ability of the strategical forming to meet their requirements. The production of warm asphalt mixtures using recycled pavements produces economic and environmentally friendly mixtures, which is the most important advantage of this work. This research aims to determine the effect of recycled asphalt concrete (RAP) on the indirect tensile strength of warm asphalt mixtures and Marshall Properties. Models of warm asphalt mixtures using Aggregate from the Al-Nibaay quarry, Asphalt with a degree of penetration (40-50) from the refinery of the cycle, and obtained Recycled asphalt concrete from Salah Al-Din Road, Al-Ameriya area in Baghdad are prepared. Use five ratios of (0, 10, 20, 30, and 40%) of recycled asphalt concrete. Marshall Design method is adopted to estimate the perfect existence of the asphalt cement for sample preparation. The mixtures properties, volumetric properties, and indirect tensile strength test are evaluated to assess bonding strength. Results show that the increase in the replacement percentage of RAP causes an increase in flow and air void and decreases the bulk density, voids in mineral aggregate (VMA), and voids filled with Asphalt (VFA). Stability increases with increased RAP content until it reaches its peak and falls. The highest stability value is at 30% RAP by 58%, about the indirect tensile strength test. The increase in the RAP ratio increases the tensile strength and the bonding between the components. So including RAP material in warm asphalt mixtures improves properties and meets performance requirements.

The Effect of Incorporating 100% of Undiluted and Diluted Reclaimed Epoxy Asphalt Materials into Pervious Cement Mixes

In order to improve the sustainability of road pavements, transportation agencies should consider designing pavements with recycled materials such as reclaimed epoxy asphalt pavement. Epoxy asphalt has recently attracted significant attention from the pavement community as a superior-performing binder that can help achieve long-lasting pavements. The recyclability of a proven long-life pavement material, such as epoxy asphalt, has now become one concern in promoting the use of epoxy asphalt binder in road pavements. Due to its thermosetting nature, the usual process of reclaiming asphalt pavement cannot be performed on epoxy asphalt pavement. Recent studies have investigated utilizing reclaimed epoxy asphalt materials in asphalt mixtures as black rock. In light of this, examining the use of reclaimed epoxy materials in cement-concrete mixes is important. The use of reclaimed epoxy asphalt materials in pavement construction is expected to gain more popularity and become a new sustainable construction option in various sustainable pavement applications in the near future. The main objective of this study is to investigate the effects of incorporating 100% reclaimed epoxy asphalt (hereinafter referred to as “epoxy RAP”) and reclaimed diluted epoxy asphalt materials (hereinafter referred to as “diluted epoxy RAP”) into cement-concrete mixes on the performance of the mixtures. The study also examined the effects of replacing cement with 5% silica fume on the performance of reclaimed mixtures. Five different mixtures were fabricated and tested in terms of density, void content, permeability, and compressive strength. Results of the density test revealed that replacing 100% natural aggregates with epoxy RAP and diluted epoxy RAP materials reduced density by an average of 10%. However, void content was found to increase with the incorporation of epoxy RAP, even when replacing Portland cement with silica fume. Regarding permeability, mixtures containing 100% epoxy RAP and diluted epoxy RAP materials have significantly higher permeability values compared with the natural mix value. However, adding 5% silica fume significantly reduced the permeability. Compressive test results indicated that substituting 100% of aggregates with epoxy RAP or diluted epoxy RAP materials would reduce compressive strength by 55% on average. Furthermore, adding silica fume to reclaimed mixes was found to have no apparent effect on compressive strength.

Perspectives on the utilization of reclaimed asphalt pavement in concrete pavement construction: A critical review

Since the last decennium, there is an expanding interest to assess the possibility of recycling materials from the construction sector. The increasing interest to recycle materials is due to the environmental advantages such as conserving existing pristine natural resources and minimizing the overall quantity of materials destined to end up in landfills. One such material which has recently gained importance is the Reclaimed Asphalt Pavement from the demolished flexible pavement, referred to as RAP. The RAP material has been widely experimented with as a potential replacement for pristine aggregates (both Coarse and fine aggregate) in the construction of concrete pavements. Its strength and durability parameters are assessed in comparison to conventional concrete. However, is RAP a promising alternate material for pristine aggregates as it seems to be? With this question, this review paper aims to understand the feasibility and constraints of RAP usage in concrete pavements. The review attempted to refer all possible research materials available online and offline. Conference materials, technical reports, IRC code books, books and book chapters, etc were studied to understand the RAP concrete for future research. The literature reviews are based on the growth phases that the RAP material has taken in the construction industry. Furthermore, it was observed that very few efforts were taken by the researchers to improve the strength of RAP-concrete and there is a need for more attempts to enhance and enrich the potential usage of RAP in concrete pavements. This review is expected to expose the new dimensions required by academicians and researchers to effectively utilize RAP for sustainable concrete pavements in India.

Mixed Heat Transfer in a Double Barrel with Differential Velocity based on CFD-DEM and Experiment

Abstract A double barrel with differential velocity (DBDV) was proposed to improve the mixture quality. Temperature is one of the indexes to evaluate the mixture quality. At present, there are few studies on the heat transfer of DBDV. The heat transfer of particles in DBDV was studied by CFD-DEM to deeply understand the proposed DBDV. The heat transfer process in DBDV was analyzed. The distribution law of temperature field under the coupling effect of particles and fluid was obtained. The influence of fluid speed on particle temperature and the regeneration proportion in DBDV were analyzed and compared with the existing double barrel. And the main heat transfer mode of particles in DBDV was to be obtained. The results show that the mixture temperature in the proposed DBDV is generally higher than that in the existing DB. And the mixture produced by DBDV is not only friendly to the environment, but also the mixture temperature can meet the construction requirements even if more than half of the RAP materials are added to the mixture. Compared with DB, the addition proportion of DBDV is increased by 9.38% - 20.70%. And the reliability of the simulation work was verified by the indoor experiment platform, which lays a foundation for the application of DBDV.

Regeneration mechanisms of aged SBS modified asphalt from RAP materials: Molecule structure, morphology, phase transition, and interface adhesion characteristics

In this study, the environmentally friendly rejuvenators with waste thermal conductive oil, polymer, and the interfacial reinforcing agent were prepared. And the influence of the different rejuvenators on the rejuvenation mechanisms of aged SBS modified asphalt was characterized by different scales including the molecule structure, morphology, phase transition and interface adhesion characteristic, and macro performance. The results show that the thermal-oxidative aging process increases the molecular weight of asphalt, promotes the SBS phase to agglomerate, and decreases the high and low temperature performance, thermal stability, and adhesion. When the rejuvenator was added, the molecular weight distribution of asphalt binders can be improved, while adding the regenerant-II can supplement the SBS modifier and reform the cross-linking structure. Furthermore, the regenerant-II has a better recovery effect on the morphology structure and resumes the thermal behavior. And then softening point and ductility can be recovered by 89.7% and 94.8% of the original SBS modified asphalt. Under the action of the interfacial reinforcing agent, the regenerant-III could increase the adhesion work to 95.49% of the original SBS modified asphalt.

Fracture studies on basalt fiber reinforced asphalt mixtures with reclaimed asphalt pavement derived aggregates and warm mix additives

The Indian Ministry of Road Transport and Highways’ (MoRT&H) recommended grade II Bituminous Concrete mixture, hitherto referred to as Asphalt Concrete (AC) was investigated during this present research study. Different AC mixtures, with 2 % to 4 % of Sasobit warm mix additive by weight of the asphalt binder, 20 % to 40 % of RAP derived aggregates as replacement to the virgin aggregates and 4 % to 8 % of basalt fibres by weight of the binder as the additive, were investigated during this research study.In addition to the fundamental binder tests, micro structural investigations namely X-Ray Diffraction (XRD) and Fourier-Transform Infrared spectroscopy (FT-IR) were also carried out to understand the crystallographic structure and the functional groups present in the binder, respectively. The efficacy of the WMA and basalt fibre addition in the AC mixtures with RAP derived aggregates was verified through the standard Immersion Type-Hamburg Wheel Track Test (IHWTT) for assessing the rut resistance; through the standard Semi-Circular Bending (SCB) tests for assessing fracture behaviour, and through indirect tensile fatigue test to assess fatigue resistance. It was observed that the AC mixture, with 30 % RAP materials by weight percentage of total aggregates, 6 % chopped basalt fibres by weight percentage of binder and 4 % Sasobit warm mix additive dosage by weight percentage of binder, was found meeting the target AC mixture performance standards.

Effect of aging and blending duration on the degree of blending and performance of recycled hot-mix asphalt (HMA)

ABSTRACT This research explored the effect of aging and blending duration on the degree of blending (DoB) and performance of recycled HMAs, as well as the actual contribution of DoBs to the performance of recycled HMA. Nine groups were designed, including one group designed as “full blending group”; one group designed as “no blending group”; and seven experimental groups designed as “partial blending groups” under the different combinations of RAP materials and blending durations. The volumetric indicators, DoB, moisture susceptibility, high- and low-temperature performance of each group were assessed. It was found that prolonging the blending duration can effectively restore the performance of recycled HMAs containing RAP with serious aging. With the extension of blending duration by 180s, more RAP binder was activated, and the DoB of blended mixes enhanced by around 5%~30%, resulting in about 2%~16%, 8%~21%, and 7%~15% improved in the tensile strength ratio, shear strength, and fracture energy of recycled HMAs. In addition, the result also showed that about 10% increase in DoBs, corresponding to RAP binder activated by about 0.15% in this research, can contribute to around 1%~25%, 5%~16%, and 3%~24% improve in the water stability, high- and low-temperature performance of recycled HMAs, respectively.

Determination of Marshall parameters of bituminous mix by using non-destructive testing method

Non-destructive test (NDT) is a fast, easy, cost-effective in-situ method of inspecting, testing, evaluating the different materials, component assemblies, etc. Ultrasonic Pulse Velocity (UPV) test is one of the best NDT methods frequently used for cement concrete for evaluating various parameters e.g., strength, life, crack depth, corrosion, etc. Conventional destructive test (e.g., Marshall Test) is performed to determine the optimum bitumen content (OBC) and various Marshall parameters of bituminous concrete. Destructive tests are laborious, time-consuming, costly, moreover; it is impossible to find the in-situ characteristics of pavement by destructive test. In recent times, the UPV test has been emerging for bituminous concrete work. However, much reliability of non-destructive test on bituminous mix has not been developed. In this study, the Proceq UPV apparatus has been used to determine the dynamic modulus by a non-destructive test. To implement such study different proportions of virgin aggregate and of RAP material such as 0:100, 10:90, 20:80, 30:70, 40:60 and 50:50 % was utilized to fabricate the bituminous concrete (BC). Correlations between dynamic modulus and stability, flow value, density, OBC (Optimum bitumen content) have been developed. These correlations can predict Marshall strength and parameters of conventional and non-conventional bituminous mix using the UPV apparatus. The results suggested that the 40:60% RAP-modified BC mix has executed superior results than the other mixes.

%100 Geri Dönüştürülmüş Asfalt Kaplamanın Türkiye'de Soğuk Karışım Bakım Malzemesi Olarak Kullanılabilirliğinin Deneysel Olarak İncelenmesi

In this study, the usability of 100% RAP as a cold patching material (CPM) was experimentally investigated. As part of this study, first, the RAP material has been characterized to determine its binder content and particle size distribution of the extracted aggregate. Then, three sets of RAP specimens (each set has three specimens) were prepared. These specimens were conditioned at 22°C, 40°C and 45°C for three hours. Then, the specimens were compacted with 75 Marshall hammer blows. The compacted specimens were then tested for their Marshall stability, and flow at 22°C. Air contents of the test specimens were also determined . It was observed that as conditioning temperatures of the compacted test specimens increased, their Marshall stability test results increased but their flow and air content test results mostly decreased. Marshall stability test results of all three sets of specimens were well above the specification limits. Moreover, all test specimens except for only one specimen conditioned at 22°C met the flow and air content criteria. It could be concluded that 100% RAP could be used as a CPM especially above 22°C. If it is needed to be used at around 22°C, it must be ensured that it is well compacted so that its air content is below 8% for a durable and comparably long-lasting cold patching application.

Cracking Performance Evaluation of RAP Mixes

Cracking is one of the most common pavement distresses that affect the design life and durability of hot-mix asphalt pavements. The evaluation of cracking resistance is essential in pavement design. Several laboratory tests and performance indicators are used to evaluate cracking resistance. This study examines the sensitivity of various cracking tests and performance indicators to the change in mix composition and evaluates the variability and correlation between various cracking performance indicators. The cracking performance indicators used in this study are IDEAL-CTIndex, cracking resistance index (CRI), Nflex, WeibullCRI, fracture energy (Gf), IDTStrength, IDTModulus, and flexibility index (FI). The results showed that IDTModulus and IDTStrength captured the change in binder content, binder grade, and RAP content. Other indices, including IDEAL-CTIndex, WeibullCRI, CRI, and Nflex, were sensitive to binder content and to only one RAP source. RAP source was found to have a significant effect on cracking performance in this study. The results also showed that high RAP content (up to 50%) provided performance comparable to that of the control mix depending on the RAP source. In addition, cracking performance could be improved by increasing the binder content in mixes with stiffer RAP materials. This indicates the importance of balanced mix design when incorporating RAP materials in asphalt mixes.

Effects of Physical Hardening on Low-Temperature Properties of Asphalt Binders Containing Reclaimed Asphalt Pavement

Abstract Reclaimed asphalt pavement (RAP) materials are widely used in sustainable construction of the asphalt pavement, which has evident advantages in solving the problem of material costs and waste disposals. However, there are few studies on the influence of RAP materials on the physical hardening of asphalt binders. In this paper, the physical hardening rate from the dynamic mechanical analysis test and grade loss deduced by the extended bending beam rheometer experiment were used to characterize the physical hardening of the RAP-modified asphalt binder at low temperatures. The results show that the loading time–conditioning time superposition principle is suitable to determine the physical hardening rate of RAP-modified asphalt binder through a smooth master curve and verification of the typical 2S2P1D rheological model, and grade loss can be predicted by the physical hardening rate using their good correlation. The RAP binders can accelerate the degree of physical hardening and increase the thermal stresses of the asphalt binder, and these effects are more evident for the RAP binder with longer aging time and higher content. The base asphalt with less wax content will act as a regenerant, which can accommodate more content of the RAP materials to produce a new usable asphalt binder.

Study on performance deterioration regularity of hot regenerated asphalt mixture under multiple aging factors

Several elements, including ultraviolet light, humidity, temperature, vehicle load, etc., have an impact on the asphalt pavement concurrently during the road service process, gradually diminishing the road’s service level. The self-created Life Cycle Analysis System (LCAS) was employed to simulate the cumulative effects of multiple aging components during the service process. The freeze–thaw splitting test, dynamic creep test, and notched semi-circular bending test were conducted after the hot recycled and the fresh asphalt mixtures were subjected to varying durations of simulated aging. The results indicate that initially, the road performance of the hot recycled asphalt mixture is comparable to the fresh asphalt mixture. However, the fresh asphalt mixture outperforms the hot recycled mixture in all but water stability over time. The attenuation degree of the flow number (FN) differs by 22.5% between the two kinds of mixtures, while the fracture energy differs by 53.3%. The performance of the hot recycled asphalt mixture degrades much more rapidly than that of the fresh asphalt mixture. The LCAS method can well simulate the actual service environment of asphalt pavement constructed with RAP materials and provide help for the performance evaluation of RAP pavement in road engineering and subsequent related research.

Development of mechanical properties predictive model of extracted asphalt binder based on long-term field asphalt pavements

This paper was to develop a prediction framework for obtaining the rheological properties of extracted and recovered asphalt binders utilizing mixture performance and other factors such as in-place air voids, pavement structure, traffic level, and aging duration. A total of 21 field projects consisting of 66 pavement sections were included in the analysis, which were located in different climatic zones with various RAP contents, traffic levels, pavement structures, pavement age, and material properties. Results indicate that the neural network can be successfully adopted to predict cracking-related binder properties consisting of effective asphalt binder, G*sin(δ) and binder fracture energy, and rutting-related binder properties including high temperature performance grade (PG), MSCR Jnr3.2, and R3.2. Both prediction and validation models worked well for pavement sections with varied contents of RAP when new data was introduced.