Reclaimed Asphalt Pavement Mixes Research Articles

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.

Influence of key parameters on the performance of RAP-inclusive geopolymer concrete pavements: An approach integrating sensitivity analysis

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

Rejuvenating Aged Asphalt Binder from Reclaimed Asphalt Pavement through the Utilization of Waste Cooking Oil

Abstract: This study investigates the use of waste cooking oil to rejuvenate aged asphalt binder from reclaimed asphalt pavement (RAP) in Peshawar, aligning with National Highway Authority (NHA) standards. Aged binder from RAP near Zintara Residence on Peshawar's Ring Road was combined with filtered cooking oil from local restaurants in varying proportions (1% to 5%). The rejuvenated binders underwent extensive physical and rheological tests, showing that certain fractions of cooking oil effectively revitalized the old binder, aligning it with virgin bitumen qualities. Superpave experiments on RAP mixes (30%, 40%, 50%) demonstrated comparable performance to fresh asphalt, particularly at 30% to 40% replacement levels. The results suggest that revitalized RAP holds promise as a sustainable alternative, enhancing asphalt mixes for road construction.

Short-term and long-term aging effect of the rejuvenation on RAP binder and mixes for sustainable pavement construction

• Physical and rheological properties of rejuvenated RAP and virgin binder compared. • Determination of optimum dosage range of the rejuvenator. • Performance evaluation rejuvenated RAP mixes. This investigation analyzes the usefulness of Mahua oil (M-oil) in reclaimed asphalt pavement (RAP) binder which simulates the short-term and long-term aging behavior of asphalt. As the inclusion of a higher amount of the RAP in the bituminous mix is susceptible to fatigue and thermal cracking, the use of a rejuvenator is a suitable option that can reinstitute the properties of the virgin binder. Different percentages of M-oil such as 1%, 2%, 3%, 4%, 5%, and 6% added to the short-term and long-term aged binder. Blended rejuvenated binders were evaluated through various physical properties. It was noticed that the inclusion of a rejuvenator increases the penetration, ductility, and flash point and reduces the softening point, and viscosity. Rheological properties conclude that rejuvenating short-term and long-term aged binder is feasible and can be considered an effective way to recycle the RAP binder. Further, rejuvenated (5% and 6% M-oil by weight of aged binder which is the optimum dosage) mixes were prepared with RAP mixture for short-term and long-term aging conditions to study the mechanical properties, i.e., moisture sensitivity and rutting. Finally, it was concluded that 5% M-oil successfully rejuvenated the RAP mixes in long-term aging conditions.

Evaluation of rutting resistance and moisture susceptibility of high RAP content asphalt mixtures containing bio-based rejuvenators

Hot Mix Asphalt (HMA) incorporating high Reclaimed Asphalt Pavement (RAP) contents can potentially have good rutting resistance due to the higher stiffness of the aged RAP-binder. The use of rejuvenators to enhance the workability and performance of high RAP mixes is becoming a common practice. However, the impact of rejuvenators on the rutting resistance and moisture susceptibility of high RAP mixes has not been studied exhaustively. The Hamburg Wheel-Tracking (HWT) test was used in this study to evaluate the asphalt mixture performance in terms of their resistance to permanent deformation and moisture damage at two conditioning temperatures of 44℃ and 50℃. Highly recycled asphalt mixes containing 50% RAP were prepared with various bio-based rejuvenators and a soft binder to compare with a control mix with 20% RAP content. Different HWT data analysis methods were used to quantify the mix performance. The results indicated that the rejuvenated high RAP mixes showed increased rut depth and higher possibilities of stripping compared to the control mix and the 50% RAP mix without rejuvenators. Regardless of the rejuvenator type and dosage, both the control and the rejuvenated high RAP mixes experienced severe stripping due to the increase in testing temperature. The 50% RAP mix performed best at both test temperatures. Therefore, caution is warranted concerning the adverse effects of rejuvenators or soft binders on the rutting performance and moisture susceptibility of high RAP mixes. Furthermore, traditional HWT parameters could be misleading due to the confounding effects of post-compaction and moisture-induced deformation. Parameters developed by the novel HWT data analysis methods could separately evaluate the rutting resistance and moisture susceptibility.

Effect of using recycled aggregates as road subbase materials: A case study from Kuwait City

In the State of Kuwait, the rise of the construction industry increases the construction and demolition activities and generates large amounts of aggregates. This study focuses on the use of recycled aggregates as road sub-base materials. Two different types of recycled aggregates have been used; namely, recycled concrete aggregates (RCA) and reclaimed asphalt pavement (RAP). Three mixtures are formed: control mix, RCA mix, and RAP mix. California Bearing Ratio (CBR) value was used as an acceptance criterion to evaluate the performance of the mixes. Results of CBR test were compared with the minimum limit of CBR value of road sub-base set by the Ministry of Public Work (MPW) specifications (MPW, 2012; section 3), (minimum 30%). The soaked CBR values of the control mix and RCA mix were equal to 73% and 80%, respectively, and they satisfy MPW specification (2012). While the soaked CBR value of RAP mix was equal to 29%, and it did not conform with MPW CBR limit for road sub-base (minimum 30%). The performance of RAP mix was enhanced by following two different scenarios. In the first scenario, the amount of RAP aggregates was decreased by mixing RAP with fresh aggregates. In the second scenario, cement was added to the RAP mix with two dosages, 2% and 4%. Both scenarios gave CBR values that meets the MPW requirement. It was concluded that RCA can be used as sub-base material, while RAP aggregates can be used as sub-base material when mixed with fresh aggregates or by adding cement as a modifier.

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.

Performance assessment of full depth asphalt pavements manufactured with high recycled asphalt pavement content

Reclaimed asphalt pavement (RAP) is generated during road rehabilitation and resurfacing projects. This highly valuable recycled material should be used for manufacturing fresh hot mix asphalt (HMA) for new asphalt pavement layers to ensure the highest added value and minimise environmental impact. The use of RAP is already common practice worldwide; however, incorporating RAP into the manufacturing of HMA is still very minimal in Hungary. As part of a research work HMA containing 20-50% RAP was designed, manufactured and tested. This paper discusses the performance tests carried out on laboratory and plant mixed asphalt mixes; using this data the overall full depth asphalt (FDA) pavement performance was predicted through general mechanistic pavement design. The outcomes of this paper showed that high RAP content asphalt mixes can have superior performance; this disproves the common perception that high RAP mixes are substandard road construction materials. The analysis performed in this paper found that asphalt mixes with high RAP content present low risk for in-situ performance. However, in order to achieve this outcome, the application of correct mix design methodology, appropriate RAP management and suitable asphalt plant capability for mass production are paramount.

Future recyclability of hot mix asphalt containing recycled plastics

The recyclability of reclaimed asphalt pavement (RAP) from conventional asphalt concrete has been well reported in the literature. However, the future recyclability of plastic-modified asphalt at the end of its service life (P-RAP) is still questionable. The lack of studies on the recyclability of P-RAP is mainly due to the current unavailability of the aged material from the field, reflecting that the application of recycled plastics in asphalt is still mainly in the research phase but not widely applied in practice. There is a concern about the ability to recycle P-RAP in the future, as if the material is not recyclable or the addition of P-RAP would significantly reduce the new mix quality compared to conventional RAP. Thus, it is crucial to evaluate the future recyclability of P-RAP prior to the application of plastic in asphalt mixes. This study was carried out to assess the ability to recycle P-RAP produced by three different mixing methods: dry, wet, and mixed methods. First, loose plastic-modified asphalt mixes were produced and aged under certain laboratory conditions before going through a crushing process that ultimately produced P-RAP. Then, P-RAP was incorporated into a new hot mix at a percentage of 30%. A comprehensive mechanical testing scheme was performed to assess the compactability, moisture resistance, cracking tolerance, fatigue resistance, and rutting performance. The study found that recycled plastic-modified asphalt mixes are totally recyclable and provide similar performance to standard RAP mixes. This finding provides confidence for practitioners that recycled plastic-modified asphalt mixes can be reused as conventional RAP after their service life rather than being landfilled or treated as waste.

Mix design, development, production and policies of recycled hot mix asphalt: A review

Worldwide, flexible pavements are the paramount type of pavements. These national assets can be recycled to serve the next design life without the need to dispose of them in landfill. The old/distressed, flexible pavement material is called, reclaimed asphalt pavement (RAP) material. In view of the sustainable development practice, 100% RAP should be recycled. However, the practical range of RAP incorporation in a drum mix plant ranges from 10% to 50% whereas in a batch mix plant, it is 10%–35%. In a batch mix plant, incorporation of the hot dried RAP (instead of cold RAP feeding) can increase the RAP incorporation level by 20%. Studies recommended that the rejuvenator should be added over the RAP material instead adding with the base binder. The addition of rejuvenator on the RAP conveyor belt (to the pug mill), provided sufficient time for rejuvenating the aged binder coating over RAP aggregates. Further, a thorough knowledge of the mix design process of recycled hot mix asphalt (RAP-HMA) is essential to produce a durable mix. For high RAP content (>20%), the RAP binder properties are important for the mix design process. However, very limited studies discussed (in detail) the recovery process of the RAP binder. The review article through light on the binder recovery process, method of RAP gradation, specific gravity determination for RAP material, minimum desirable properties of the RAP material etc. This review paper also provides a narrative review of the historical development of RAP-HMA technology, technical aspects related to the procurement of RAP material, mix design and production of the recycled mix. Moreover, the international & national policies/laws for construction and demolition waste are discussed. • Parallel heating of RAP in a pug mill increases the mixing ratio. • Performance grade, PG mixing rule was found most reliable. • The mix design process must consider the type of mix plant and RAP feeding method. • Conveyer belt found to be the most promising location for Rejuvenator addition. • The mixing temperature has an equivalent effect as that of a rejuvenator in the recycled mixture. • Stiffness modulus found a promising test to compare the performance of recycled mixtures.

Performance of waste polyethylene modified bituminous paving mixes containing reclaimed asphalt pavement and recycled concrete aggregate

• Waste materials such as RAP, RCA and waste polyethylene can be utilized in place of conventional bituminous paving mixes with improved or similar performance. • Combinations of RAP, RCA and waste polyethylene have profound effect on the rutting, fatigue and moisture damage performance of mix. • Low viscous bitumen can enhance the performance of bituminous mix prepared with a unique combinations of waste and recycled materials (RAP, RCA and waste polyethylene). The present study is an attempt to develop sustainable bituminous paving mixes comprising bulk utilization of waste materials such as reclaimed asphalt pavement ( RAP) and recycled concrete aggregate (RCA), modified by waste polyethylene. Low viscosity grade (VG) bitumens were used as rejuvenators in the modified RAP mixes in this study. For comparison study, a control mix containing conventional stone aggregates (CSA) and VG 40 bitumen was considered. The modified RAP mixes developed were evaluated in terms of performance characteristics and compared with the traditional control mix. Using Marshall tests, the optimum waste polyethylene contents were found to be 6–7% by weight of optimum bitumen content in the respective mix. The modified RAP mixes were found to exhibit higher stability and rutting resistance than the control mix to a significant level. The inclusion of waste polyethylene in modified RAP mixes prepared with RCA or CSA was found to be less susceptible to moisture-induced damage. Significant improvements in the performance of RAP mixes containing CSA or RCA in combination with waste polyethylene were observed. ANOVA analysis indicates that coarse aggregate types have a significant influence on the performance of RAP mixes, especially with the addition of waste polyethylene. It is concluded that the RAP mixes prepared with different combinations of CSA or RCA with waste polyethylene can be considered as a suitable option for CSA-VG40 control mix and thus, can enhance the high and intermediate temperature performances of the RAP mix to a significant level.

Mechanical properties evaluation of asphalt mixtures with variable contents of reclaimed asphalt pavement (RAP)

This research paper aims to evaluate the performance of hot asphalt mixes containing reclaimed asphalt pavement (RAP) at different percentages. The usage of RAP as a recycled construction material has become a common practice in many countries nowadays. To achieve this objective, experimental tests were conducted on a total of 15 asphalt mixtures prepared with five different contents of asphalt cement, including 3.5, 4, 4.5, 5, and 5.5%. Three Marshall mixes were made for each asphalt content. Following the ASTM standards, Marshall stability and flow tests were performed to determine the optimum asphalt content of each mix tested (i.e., control, 25% RAP, 50% RAP, and 75% RAP mixes, respectively). The results showed an improvement in the stability and flow values with the increase in RAP content. Maximum stability of 15.11 kN was obtained with a 75% RAP mix at 4% asphalt cement content. Notably, as the asphalt content increases, lower air voids values and vice versa, higher voids filled with asphalt were observed for the four tested mixes.

Development of a Model to Estimate Percentage of Reclaimed Asphalt Pavement (RAP) Binder Contribution Based on Design and Performance of Super High RAP Mixes

Reclaimed asphalt pavement (RAP) is one of the most recycled materials. The allowed RAP percentage in asphalt mixes is typically limited because of concerns over variability, binder stiffness, cracking performance, and generally the unknown associated with RAP. With abundant RAP stockpiles, the use of higher percentage RAP in asphalt mix may be warranted if performance can meet or exceed low RAP (LR) mixes (20% RAP or lower). In this study, high RAP (HR) mixes (40% RAP) and super high RAP (SHR) mixes (greater than 40% RAP) were designed, and their performance was compared with LR mixes. Mixes that cover two climates, Eastern and Western Washington, were included in this study. A lower performance grade (PG) virgin binder and a bio-based rejuvenator were used in HR and SHR mixes to allow the blended binder to meet the target PG required by the Washington Department of Transportation (WSDOT). Mix volumetrics and binder PGs of these mixes were designed close to each other, indicating the feasibility to produce RAP mixes up to 100% RAP. Overall, the addition of RAP improves the rutting performance but reduces the cracking performance of SHR mixes. Two measures were evaluated to mitigate SHR mixes’ cracking potential, including adding extra 0.5% virgin binder or 50% rejuvenator above the original dose, which improved the cracking performance of SHR mixes but reduced the rutting resistance. Based on these results, a recycled binder contribution model was developed to estimate the percentage of RAP binder contribution based on rutting and cracking performance testing.

Laboratory based performance evaluation of high content reclaimed asphalt pavement in hot mix

During maintenance, rehabilitation, or reconstruction operations removing existing asphalt pavement materials are common. This practice produces a large amount of reclaimed asphalt pavement (RAP), which contains valuable asphalt binder and aggregate. The road construction and maintenance works depend on the utilization of natural and industrial materials which is limited and scarce. As existing pavement diminishes, obtaining quarry sites is difficult.The objective of this study is to conduct laboratory based- research that investigates and evaluates the performance of hot mix asphalt mixtures containing different amounts of RAP for binder course construction.Quality test for all materials used in the mix was done separately. Marshall Parameter was done for control mix and mix containing RAP to evaluate the mechanical properties of the asphalt binder mixture containing RAP and control mix. To predict the field condition performance test such as moisture susceptibility, indirect tensile strength, and Humberg wheel tracking test was conducted.The obtained result for all mixes is in terms of Marshall Parameter criteria and the performance test proves that the asphalt binder course mix can be successfully produced using RAP material within the specification limit. The study concluded that, using RAP in HMA up to 40% is possible to design a mix that satisfied the required specification for Marshall Property and performance test with low cost than the control mix.

Evaluation of Reclaimed Asphalt Mixtures Modified by Nanoclay Powder on Moisture Damage

Recycling asphalt is a significant stage in pavement industry, yet it can be unfavorable to the durability of the recycled mix due to the loss of binder charachteristics, thus the mixture will be weaker to the external factors like moisture. This study aims to evaluate the influence of nanoclay montmorillonite k10 powder (MMT) on Marshall’s characteristics and moisture resistance in Reclaimed Asphalt Pavement (RAP) mixtures. Three percentages of rejuvenated RAP were used, 30%, 40%, and 50% of the total mixture, these percentages were modified with 0%, 1%, 3%, and 5% nanoclay (MMT) of the neat binder’s weight. Asphalt Cement AC(85-100) was used to rejuvenate the RAP. The Marshall test was conducted on modified RAP to detect the effect on the Marshall stability and flow and air void, indirect tensile strength tests (ITS) were also conducted before and after nanoclay powder addition to compare and assess the resistance of moisture to rejuvenated RAP mixtures. The results of the laboratory tests have shown that the use of 5% nanoclay in the regenerated RAP mixes offers superior performance than without it, where it enhanced stability by 15%, reduced flow by 14.3%, and increased moisture damage resistance by 3.66% all for 50% RAP mixtures.

Effect of MIST Conditioning on Moisture-Induced Damage of RAP Mixes Using Elastic Moduli and Stress–Strain Behavior

Moisture-induced damage of asphalt pavements constitutes a primary distress. To quantify the extent of moisture-induced damage efficiently, a moisture-induced stress tester (MIST) was developed. This study adopts varying stress cycles of MIST to condition the asphalt mixes without and with reclaimed asphalt pavement (RAP) to ascertain their moisture-induced damage resistivity. Hence, the control mix (0% RAP) and mixes containing 10%, 20%, 30%, and 40% RAP by weight were prepared and conditioned using 0, 1,000, 2,000, 3,500, 5,000, and 10,000 stress cycles of MIST. Thereafter, an indirect tensile (IDT) strength test was conducted on the prepared mixes. Using analytical approaches, the biaxial state of stress was defined to compute the static (ES,H) and average modulus (ES,A). Increasing stress cycles of MIST decreased the stiffness of control and RAP mixes. The compressive stress–strain curve (SSC) was plotted and utilized to compute the linearity and toughness index (TI) of control and RAP mixes. Increasing stress cycles of MIST were observed to increase the ductility of control and RAP mixes, whereas prepeak linearity was observed to reduce it. The TI increased with the increase in stress cycles of MIST. New moisture damage ratios (MDRs) were computed by utilizing ES,H and ES,A and compared with the commonly adopted tensile strength ratio (TSR). Based on such MDRs, it was concluded that RAP improves the moisture-induced damage resistivity of asphalt mixes. Statistical analysis indicated that both ES,H and ES,A have the potential to be good indicators of moisture-induced damage of control and RAP mixes.

Utilization of Reclaimed Asphalt Pavement Material in Wet Mix Macadam (W.M.M)

Reclaimed asphalt pavement (RAP) is one of the innovative and effective technologies in many places in the world. The utilization of RAP is rapidly increasing popularity and becoming an emerging technique in India. As per IRC-120:2015, removing or reprocessing pavement materials containing aggregates that are bitumen coated is termed as RAP. These materials are gained through a process in which the existing surface pavement is reclaimed and reused after processing for reconstruction, resurfacing, or repaving. Well graded and high-quality aggregate are achieved from this process. Proper utilization of RAP with specified properties and specified percentages, not only serve as an alternative useful pavement material but also helps in reducing the usage of natural construction material, that will directly reduce the overall cost of projects. By conducting tests as per MoRTH specifications (5th Revision), the various characteristics of RAP material and fresh aggregates are observed. The main objective of the study is to carry out the performance tests: Modified Proctor test on fresh material as well as on material mixed with reclaimed asphalt pavement i.e. 10%, 20%, and 30% of total mix and to achieve optimum moisture content and maximum dry density by using Modified Proctor Test. Attempts are carried out to design a new pavement using Indian Road Congress (I.R.C-37:2018) guidelines and utilization of RAP material. Economic benefits are calculated in terms of fresh and RAP (10%, 20%, and 30%) mix material pavement.

Performance of High Content Reclaimed Asphalt Pavement (RAP) in Asphaltic Mix with Crumb Rubber Modifier and Waste Engine Oil as Rejuvenator

The utilisation of reclaimed asphalt pavement (RAP) as a suitable substitute for natural aggregate and binder offers an energy-saving and cost-effective approach to enhance the performance of asphalt mix. Realising the potential use of RAP as a promising recycling technique, many countries are seeking to recycle RAP as part of the global effort to address the rising challenge of climate change and contribute to a sustainable environment. This study aimed to develop an integrated approach to determine the amount of RAP to be used in an asphaltic concrete wearing course with 14 mm nominal maximum aggregate size (ACW14). The RAP was incorporated with two waste materials comprising waste engine oil (WEO) as a rejuvenator and Crumb Rubber (CRM) as a binder modifier. A total of five different mixes, which include R0 (control mix), R30, R50, R70, and R100 (replacement of 30%, 50%, 70%, and 100% of RAP aggregates in the mix, respectively) were evaluated. The Marshall parameters, resilient modulus (MR), indirect tensile fatigue, moisture susceptibility, and mass loss (ML) tests were conducted to investigate the performance of each mix. Finally, an arbitrary scale was developed to optimise the RAP content. The results showed that the Marshall parameters, moisture susceptibility, and ML values of the RAP mixes met the criteria outlined in the standard. According to the MR performance, the R50, R70, and R100 mixes were more resilient than the R0. In terms of fatigue resistance, the R30, R50, and R70 mixes showed better performance than the R0. Overall, the collective performance of all RAP mixes was above the R0 and it increased with the increment of RAP content. Therefore, it was possible to design ACW14 mixes with up to 100% RAP in combination with WEO and CRM.

Rejuvenator effectiveness in reducing moisture and freeze/thaw damage on long-term performance of 20 % RAP asphalt mixes: An Australian case study

Due to hoisted ecological and economic awareness, the use of Reclaimed Asphalt Pavement (RAP) in road pavements is universally recognized as a practical choice to limit the use of raw material, such as aggregates and bitumen, and reduce construction costs. Despite the environmental and economic benefits, in any given year of their service life pavements undergo a range of conditions that may affect their long-term performance. These may include moisture damage and freezing and thawing, for instance. This study presents a laboratory investigation that has been conducted on asphalt mixes containing 20 % RAP material, commonly used by the Australian road industry, to analyse the effect of moisture and freeze/thaw cycles on asphalt long-term performance. The use of a rejuvenator was tested to evaluate any potential increase in durability due to the improved degree of blending and activation of the RAP binder in the asphalt mix. In addition to the standard tensile strength ratio (TSR), asphalt samples were tested - before/after moisture and freeze/thaw damage - under cyclic loading for the assessment of the residual stiffness value, moisture-affected residual fatigue life and rutting. Results highlighted how the use of the rejuvenator can contribute to slow down the deterioration of RAP mixes and reduce moisture and freeze/thaw damage effects on pavement durability.

Fatigue and Healing Characteristics of RAP Mixtures

The healing properties of bituminous mixes prepared using reclaimed asphalt pavement (RAP) material are different from those of virgin mixes because the chemical characteristics of RAP binder blends are different (depending on the extent of aging) compared to virgin binders. Very limited research work has been reported in the literature on the healing potential of RAP mixtures. The current study aims to examine the fatigue and healing characteristics of RAP mixtures with varying rest periods between loads. To this end, different blends of RAP and virgin binders (VG30) were prepared at varying proportions (0%, 15%, 25%, 35%, and 45%) of RAP material in mix. The fatigue lives of different RAP mixes were evaluated by varying the rest period (400, 650, 900, and 1,400 ms) between load pulses. The healing potential of the mixes was evaluated in terms of the slopes of the lines drawn between fatigue life and rest period. The fatigue life of a mix increased with increases in the proportion of RAP in the mix. The degree of healing indicated by the slope of log (fatigue life) versus log (rest period) line was found to depend on RAP content and rest period. Mix time lag (between the peaks of stress and strain), a viscoelastic property of the mixes, was determined from the stiffness modulus test. Different rheological and chemical characteristics of the binder blends and the time lag values of the mixes were correlated with the fatigue lives and healing indexes of the mixes. The Superpave binder fatigue parameter (G*sinδ) and the mix time lag were observed to have good correlation with the fatigue life of RAP mixes. Surface free energy and different aging indexes of the binders (ICO and ICH) showed good correlation with the healing index of the mixes. Flow (consistency) parameters, such as softening point and viscosity at 60°C, correlated well with the healing index. These correlations are expected to improve understanding of the fatigue and healing behavior of RAP mixes.