Reclaimed Asphalt Pavement Binder Research Articles

Effect of Bio-Oils and Wastewater Sludge on the Performance of Binders and Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content.

Waste Cooking Oil (WCO), Soy Oil (SO), and Wastewater Sludge (WWS) have great potential to increase reclaimed asphalt pavement (RAP) content for economic and environmental benefits. This study explored the effects of SO and WCO on rutting, fatigue cracking, and low-temperature cracking performance of binders and Hot Mix Asphalt (HMA) with high RAP content. The potential effect of WWS on the performance and compaction efforts of high RAP content mixes at a 10 °C (50 °F) lower compaction temperature than the control compaction temperature was also investigated. The results indicated that 85% of the RAP binders can be incorporated while maintaining similar performance compared to the control by using 15% SO or 12.5% WCO as a rejuvenator with 2.5% virgin binder. Adding 1% WWS by weight of the total binder improved the binder's rheological properties, the mix's cracking performance, and the mix's density at lower compaction temperatures.

Assessment of aging behaviour of reclaimed asphalt binders: multi-scale mechanical and microstructural characterisation

This study provides a comprehensive multi-scale characterization of the aging resistance of reclaimed asphalt pavement (RAP) binder blends. The analysed samples included different dosages of a RAP binder and a recycling agent (REC). At low strain levels (2.5% and 5%), the use of up to 40% RAP did not adversely affect the Nf value; however, the effect of RAP was clear at 10% strain in the macro scale. At the microscopic scale, the AFM analysis showed that among all samples, the 100% RAP binder was affected the least by laboratory aging. However, the aging susceptibility increased as the RAP content increased from 0 to 40%. A plausible explanation is that the effects of laboratory aging (temperature and/or pressure) became more concentrated on the base binder when its quantity decreased in the blends. The use of REC reduced the stiffness of the unaged blends, but its effect diminished upon further aging of the blends.

Prediction and modelling marshall stability of modified reclaimed asphalt pavement with rejuvenators using latest machine learning techniques

The primary problem with the experimental evaluation of Marshall stability (MS) of reclaimed asphalt pavement (RAP) is the inherent complexity and variability involved in the process. Traditional experimental methods for predicting MS can be time-consuming, labor-intensive, and costly. In the present research, an effort has been made to assess the most appropriate machine learning model for the prediction of MS of RAP. The study addresses the problem of accurately predicting MS by using a variety of input parameters derived from experimental work. The data for models was split in 7:3 for training and testing of models. Bitumen content (BC %), virgin binder percentage (VB %), virgin binder performance grade (VB-PG), RAP percentage (RAP %), RAP binder percentage (RAPB %), RAP binder PG (RAPB-PG), rejuvenator type (Rej type) and rejuvenator percentage (Rej %) were applied as input parameters for MS prediction. Several machine learning models including random tree (RT), M5P, Gaussian process (GP), support vector machine (SVM), and random forest (RF) were utilized for determining the most appropriate prediction model. Seven metrics were used for assessing the performance of these models, such as CC, MAE, RMSE, RA, RRSE, WI, and NSE. Based upon these metrics, the RF model is found to outperform the other applied models with the values of CC = 0.9959 and 0.9763, MAE = 0.3129 and 0.7847, RMSE = 0.3976 and 1.0492, RAE = 9.0062 and 21.8247, RRSE = 9.3624 and 23.6832, WI = 0.998 and 0.984 and NSE = 0.991 and 0.944 for training and testing stages, respectively. Also, box plots and sensitivity analysis confirm the superiority of the RF model over other models. Finally, the sensitivity analysis suggests the importance of bitumen content in the prediction of MS of reclaimed asphalt pavement modified with rejuvenators.

Visco-plastic deformation characteristics of accelerated-aging asphalt mixture containing reclaimed asphalt pavement regenerated with crumb rubber based on Hamburg Wheel-Track test

The regeneration of the reclaimed asphalt pavement (RAP) with incorporation of crumb rubber was a cleaner alternative for reducing the fossil and ore resources consumption. For the desert area like Egypt, the rut of reclaimed pavement was principal contradiction during a long service. This work mainly characterized the visco-plastic deformation of accelerated-aging rubberized reclaimed asphalt mixture based on Hamburg Wheel-Track test. Four mixtures were designed by two contents of RAP (15% and 30%), two contents of crumb rubber (5% and 15%), and two asphalts (pen-#70 and pen-#90). Specifically, this work focused on the determination of accelerated aging effect, and analysis of rutting deformation fitting including overall deformation and visco-plastic deformation. Then, effect of accelerated aging time and material compositions on visco-plastic deformation was analyzed. In addition, the correlation analysis among indicators evaluating rutting deformation of mixture was conducted, and the correlation analysis between rutting deformation of mixture and average recovery rate at 3.2 kPa of extracted bitumen was completed. The results demonstrated that the accelerated aging equivalent factor of sunlight was approximately 6, meaning that one day of accelerated aging was equivalent to six days of natural aging in Cairo. With the accelerated aging time increased, resistance to rutting deformation of rubberized reclaimed asphalt mixture was promoted with the incorporation of RAP, crumb rubber and soft matrix binder. Meanwhile, dynamic stability, derived from fitting curve of visco-plastic deformation, was positively correlated with accelerated aging time, and it could accurately evaluate visco-plastic deformation characteristics of reclaimed mixture. Finally, visco-plastic deformation characteristics of reclaimed mixture was closely related to the permanent deformation resistance of binder at high temperature.

Evaluation of degree of blending and interaction between aged and virgin asphalt binders using rheological and fracture measurements

Evaluating the blending and interaction processes between aged and virgin asphalt binders is significant for enhancing the performance and longevity of asphalt pavements, particularly when using Reclaimed Asphalt Pavement (RAP). The primary aim of this research is to investigate the optimal conditioning time for diffusion process between virgin and aged binders. To simulate age-hardened RAP binder, asphalt binders were artificially aged in a forced draft oven at 163 °C for five hours, followed by additional aging at 85 °C and 110 °C over periods of 5, 7, and 10 days. The research assessed the degree of blending and interaction between aged and virgin binders in two phases using rheological and fracture measurements. In the first phase, the study explored the effects of various conditioning temperatures and durations (135 °C and 165 °C for 15, 30, and 60 minutes) on the diffusion and blending of the asphalt binders. Results indicated that the interaction between aged and virgin binders depends on the temperature and duration of conditioning; notably, complete blending was achieved at 165 °C after 60 minutes. The second phase investigated the impact of aged binder content on the rheological and fracture characteristics of the blended binders. Findings showed that fracture energy and peak load decrease with an increase in aged binder content. Specifically, increasing the aged binder content from 10 % to 30 % resulted in an approximate 23 % reduction in fracture-related parameters, while increasing the aged binder content from 50 % to 70 % led to an approximate 51 % reduction. Additionally, analysis of the complex shear modulus across different blends revealed an increase in modulus and high-temperature performance proportional to the percentage of aged binder, suggesting a hardening effect in the blended binder. Overall, this study underscores the significance of understanding the interactions between aged and virgin binders to optimize the diffusion and blending processes, ultimately enhancing the performance of asphalt pavements containing recycled materials.

Optimising waste cooking oil as rejuvenator for recycled mixtures: a laboratory-based approach

Global waste accumulation necessitates sustainable pavement solutions. This study focuses on sustainable pavements by adopting the waste-to-wealth approach using waste cooking oil (WCO) as rejuvenator to incorporate higher reclaimed asphalt pavement (RAP). A novel approach optimises WCO for recycled mixtures with different field RAP contents. The optimum WCO was assessed for mixtures with laboratory-aged RAP, considering binder performance, properties of laboratory-aged RAP binder, and moisture susceptibility. Optimum dosages were then determined for the mixtures with field RAP without compromising moisture susceptibility. These dosages depend on the percentage and viscosity of the extracted binder of field RAP. Results indicated that the recycled mixture with field RAP and corresponding optimum WCO assessed from the proposed method exhibited satisfactory moisture susceptibility unlike the recycled mixtures without WCO. Also, the method suggested a way to estimate the total optimum binder content, if higher RAP is being used considering the inactive binder of RAP.

Establishing Strategies to Improve Cracking Resistance of High Recycled Binder Ratio Asphalt Mixtures

This study aims to investigate promising mitigation strategies for improving the cracking performance of high recycled binder ratio (RBR) asphalt mixtures. Moisture-resistant aggregates that do not require anti-stripping agents, reclaimed asphalt pavement (RAP), and recycled asphalt shingles (RAS) were sampled for this study from sources in two climatic zones, south and north. The south-moisture-resistant (SR) mixtures were designed with 0.16 and 0.29 RBRs with RAP, while the north-moisture-resistant (NR) mixtures included 0.21 and 0.37 RBRs with RAP and 0.44 RBR with RAP/RAS. The mitigation strategies evaluated included a softer binder, a different binder source with higher ΔTc, a recycling agent (RA), reduced recycled binder availability (RBA), polymer-modified asphalt (PMA), and hybrid approaches including softer binder + RBA and PMA+RBA. The Indirect Tensile Asphalt Cracking Test (IDEAL-CT) and Disc-Shaped Compact Tension (DCT) test were conducted to capture intermediate-temperature and low-temperature cracking performance, respectively. In addition to the cracking tolerance index (CTindex), an IDEAL-CT interaction diagram analysis was added to further understanding the effect of mixture variables on cracking performance. The findings suggest that while no single strategy works for all RBR mixtures tested, RA, RBA, softer binder, or their combinations yield adequate cracking performance depending on factors including RAP binder stiffness and quantity, RA dose, climatic zone, and RBA.

Laboratory and Field Performance Evaluation of Cracking of Airfield Warm Mix Asphalt with Reclaimed Asphalt Pavement at the National Airport Pavement and Materials Research Center

The U.S. Federal Aviation Administration is exploring initiatives to decrease transportation greenhouse gas emissions by developing carbon reduction strategies, including using low-embodied carbon materials, such as reclaimed asphalt pavement (RAP), in airport pavement construction. However, verifying RAP’s viability for airfield pavements with laboratory and field performance measures is essential. This study compared the cracking susceptibility of a P-401 hot mix asphalt and warm mix asphalt (WMA)+RAP airfield mixes using laboratory performance tests and conducted a preliminary evaluation of pavement responses from accelerated pavement testing (APT) fatigue tests. The observations and outcomes presented in this paper found that adding 20% of recycled materials with WMA additives had a decreasing impact in mix performance but did not overly affect the asphalt mix properties, as cracking properties from the different test procedures were found with comparable outcomes. Additional observations from strain gauges and temperature probes in the National Airport Pavement and Materials Research Center test cycle 2 APT fatigue test sections showed that the maximum tensile strains in the WMA surface lane 5 south section were consistently higher than those in the WMA+RAP lane 6 south section, which may be because of the higher load level that it was exposed. Additionally, the hardened or aged RAP binder in the entire lane 6 south section may have increased its stiffness, resulting in lower strain levels than in the lane 5 south section. Notably, both sections showed an increase in tensile strains with an increase in asphalt concrete temperature, which confirmed the temperature dependency behavior of asphalt concrete.

Mass-composite activation energies for recycled binder blends

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

Incorporating Environmental Impact Analysis into Louisiana’s Balanced Asphalt Mixture Design

To meet the asphalt pavement industry’s net zero carbon emission goals, increasing reclaimed asphalt pavement (RAP) levels to greater than 25% is considered a critical tactic. However, many state departments of transportation are cautious in adopting high RAP content into their designs because of durability issues resulting from aged RAP binders. This paper assesses the effectiveness of using the Lewis acid catalyst, FeCl3, in improving the cracking resistance of high-RAP asphalt mixtures to meet Louisiana’s balanced mixture design (BMD) criteria, and lower embodied carbon of asphalt mixtures. Four asphalt mixtures were designed and tested against permanent deformation, intermediate- and low-temperature cracking, and durability. Mixture 1 is conventional, which contains performance grade (PG) 76-22 polymer-modified asphalt binder with no RAP. Mixture 2 is unmodified PG 67-22 and 30% RAP without catalyst. Mixtures 3 and 4 incorporated an unmodified asphalt binder PG 67-22, a catalyst, and 30% and 50% RAP, respectively. A life cycle assessment (LCA) analysis was conducted on asphalt mixtures that complied with Louisiana’s BMD specifications to quantify global warming potential improvements. Because the performance of both mixtures is expected to be similar, the scope of the LCA analysis was limited to only those life cycle stages that are expected to be different, modules A1–A3 (i.e., cradle-to-gate stages). Results showed that the use of FeCl3 can improve asphalt mixtures’ cracking resistance containing high RAP contents, whilst it did not have a negative impact on permanent deformation resistance. Further, the addition of FeCl3 to asphalt mixtures with 30% and 50% RAP levels showed a reduction in greenhouse gas emissions by 28% and 43.4%, respectively.

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.

Effect of design parameters on degree of blending and performance of recycled hot-mix asphalt incorporating fine reclaimed asphalt pavement particles

Due to the rich binder content and high economic benefits of fine reclaimed asphalt pavement (RAP) particle, more and more attention has been paid to the effective design of recycled hot-mix asphalt (HMA) incorporating this material. This research explored the effect of design parameters on degree of blending (DoB) and performance of recycled HMAs incorporating fine RAP particles. Six groups of mixes were designed, including one no blending group, four experimental groups, and one full blending group. The different parameters of preheating temperature, compaction effort, asphalt content (AC), and blending duration, were involved in this research. It can be found that the recycled HMAs incorporating fine RAP particles under the traditional design proved to the risks in water stability and low-temperature performance. By rising the preheating temperature, decreasing compaction effort and increasing AC, or extending the blending duration, more RAP binder would be activated and blended with the virgin binder, and the poor rheological performance of recycled HMAs can be restored. The different design parameters have different effects on the performance. Besides, the actual contribution of DoB to performance was quantified. With an increase in DoB by 10%, the tensile strength ratio, shear strength, fracture energy, fracture strength, and abrasion loss percentage of recycled mixes can improve by around 15%∼28%, 0.15–0.34 MPa, 180–1969 J·m2, 0.25–0.34 MPa, and 7–18%, respectively. In addition, design incorporating fine RAP particles generally can bring significant advantages in energy consumption and CO2 emission.

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

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

Effects of multiple recycling on the performance characteristics of asphalt binder using different recycling agents

The process of reclaimed asphalt pavement (RAP) recycling may occur multiple times during the life of the pavement. This study investigates the effect of multiple recycling on binder properties by employing a virgin 3045 PEN grade binder that was aged in the laboratory intended to simulate aging of binders in RAP. The aged binder was rejuvenated using two bio-oils and one softer binder. The doses of the bio-oils and softer binder were determined by matching the continuous high-temperature performance grade (PGH) of the rejuvenated RAP binder to that of the virgin binder. This aging and rejuvenation cycle was repeated three times. Finally, fatigue and rutting performance of the binder was evaluated for the three reuse levels. Results indicate that the material can be reused up to three cycles keeping good performance on fatigue or rutting. However, care should be taken regarding the cumulative effect of bio-oils causing an over-softening effect on the of the RAP.

Development of a novel infrared methodology to assess the degree of blending in cold and warm recycled asphalt mixtures incorporating a bituminous or bio-based virgin binder

2/3 of the reclaimed asphalt pavement (RAP) amount is used for recycling of European asphalt mixtures. An issue that remains unresolved is the blending between the RAP binder and the new binder. Using infrared microscopy, the binder blending is assessed in low-energy mixtures using a bituminous or bio-based binder. Infrared data were acquired and quantified using average and standard deviation indicators; their evolution is monitored over 3 months. A relationship between the average and the binder concentration is highlighted. Binders homogeneity depends on the RAP content and virgin binder. On cold mixes, infrared data evolve over time, highlighting emulsion curing.

Recyclability of reclaimed asphalt rubber pavement

Rubberized asphalt technology has been developed and applied in the production of hot-mix asphalt (HMA) for several years, as it represents a profitable solution to dispose of the waste rubber from end-of-life tires and to improve bitumen rheological and mechanical behaviour. However, the question about the recyclability of reclaimed asphalt rubber pavement (RARP) into new HMA has not been still solved. To this aim, the present study dealt with characterization of HMA including 30% RARP, in comparison with reference mixtures with 30% of ordinary reclaimed asphalt pavement (RAP) and with only virgin materials. The experimental programme included the preliminary analysis of RARP and RAP binders, then the HMA design and testing in terms of strength, stiffness, linear viscoelastic properties and fatigue resistance. The results demonstrated that RARP can be recycled into new mixtures without negatively influencing the overall HMA performance. In particular, the RARP entailed an increase of mix stiffness and brittleness, but with a lower severity with respect to RAP. The use of a rejuvenating agent allowed achieving a mechanical behaviour similar to that of the reference mix with only virgin components.

Multiscale Characterization of Rejuvenated RAP Binders

Abstract Reclaimed asphalt pavement (RAP) is increasingly being utilized in asphalt pavements because of the high cost and scarcity of virgin asphalt materials. However, because RAP is a stiff material, it requires careful engineering to prevent cracking. Recycling agents have shown the ability to partially restore the properties of RAP binders if applied in a proper type and dose. Many studies investigated the impact of recycling agents when added to blends of virgin and RAP binders, but only a few investigated their effectiveness when applied to only RAP binders. The aim of this paper is to investigate the effect of various types and doses of recycling agents on the properties of RAP binders. Rheological properties were measured using a dynamic shear rheometer (DSR). Fourier-transform infrared spectroscopy was utilized to measure the degree of oxidation of the rejuvenated RAP binders. Furthermore, atomic force microscopy (AFM) tests were conducted to measure the morphology and modulus of rejuvenated RAP binders at the nanoscale. Finally, AFM measurements were used to calculate a rejuvenation index (RI), which was developed in an earlier study by the authors to assess the effectiveness of recycling agents in resisting the adverse effects of aging. DSR results demonstrated that the inclusion of recycling agents lowered the stiffness of the RAP binders. AFM morphology images revealed the presence of a large number and varying sizes of phase associations in the RAP binders. These phase associations became more pronounced with aging. Some recycling agents partially reversed the aging effect by reducing the area occupied by these associations. Nonetheless, after long-term aging, the effect of recycling agents diminished. The results of this study revealed that characterizing rejuvenated RAP binders at both the microscale and macroscale levels can indicate the effectiveness of recycling agents and aid in the selection of type or dose of recycling agent.

Laboratory evaluation on the aging susceptibility of reclaimed asphalt bitumen containing low-viscosity binder and cooking oil waste

This study investigates the use of cooking oil waste (COW) and low-viscosity binder (LVB) to improve the performance of reclaimed asphalt pavement (RAP) binders and promote the consumption of by-product materials. The aging resistance capacity of experimentally aged asphalt binders with COW as rejuvenators and recently synthesized high-penetration asphalt binders was evaluated using the Rolling Thin Film Oven Test (RTFOT) and the Pressure Aging Vessel (PAV) tests. The Dynamic Shear Rheometer (DSR) Test, Hamburg Wheel Tracking, and Overlay Tester (OT) were used to evaluate the dynamic shear characteristics and performance of the modified RAP mixture. The test results show that using low-viscosity binder (LVB) positively affected the quality of reclaimed asphalt binder after prolonged aging periods. Additionally, the dynamic shear modulus of the AP1 mixture was 5% less than the reference mixture after the PAV condition, indicating a reduced stiffness effect. Considering the performance of reinforced RAP mixture, all RAP mixtures withstood a load of 20,000 cycles settling under 20 mm after 10,000 cycles. In mix COW1, COW5, and LVB, the final settlement was 3.75 mm, 3 mm, and 2.66 mm. Meanwhile, the load reductions of the above mixes were 73.3%, 74.2%, and 76.4% after 1000 OT cycles. In conclusion, utilizing LVB in RAP binder can produce equivalent benefits as applying a rejuvenator additive, even at a high asphalt content (40%) threshold. This research can offer insights into improving the performance of RAP binders in service and promoting the development of green construction.

Use of the Iron Chloride Type of Lewis Acid Catalyst in High Reclaimed Asphalt Pavement Content Asphalt Mixtures

The use of reclaimed asphalt pavement (RAP) as a partial replacement for virgin aggregates and asphalt binders has received considerable attention recently. This approach is one of many promising methods for improving sustainability. However, many state Departments of Transportation are cautious in adopting high RAP content into their designs because of cracking and durability issues resulting from the aged RAP binder. A Lewis acid catalyst has been used to modify the asphalt binder’s chemical composition and disrupt the associated molecules formed in the aged RAP binder. The objective of this study is to assess the effectiveness of the use of a Lewis acid catalyst in improving the cracking resistance of an asphalt mixture containing high RAP contents. A suite of laboratory mechanical tests was performed, namely, the dynamic modulus test for linear viscoelastic properties; the semi-circular bend, Illinois flexible index, ideal cracking tolerance, and simplified viscoelastic continuum damage tests for fracture and fatigue resistance; the loaded wheel tracking test for rutting resistance and moisture susceptibility; indirect tensile creep compliance and strength tests for low-temperature cracking resistance; and the Cantabro abrasion test for durability. Further, AASHTOWare Pavement ME software was used to predict the long-term performance of asphalt pavements containing mixtures with high RAP contents and a Lewis acid catalyst. Results showed that the use of the Lewis acid catalyst can disrupt associated molecules formed in the aged RAP binder. Thus, asphalt mixtures containing high RAP contents (recycled binder ratio > 0.20) and a Lewis acid catalyst exhibited similar performances to conventional mixtures. Further, Pavement ME predicted fatigue cracking was lower for a structure containing a FeCl3-modified mixture as compared to a similar one with no FeCl3, illustrating the effectiveness of FeCl3.

Optimizing the Effective Use of Reclaimed Asphalt Pavement in Local Roadways

This study involved the construction of eight test sections in the City of Columbus, Ohio, to evaluate the effects of using different reclaimed asphalt pavement (RAP) contents and types of rejuvenator on the performance and properties of asphalt mixes used for local roads. The first section (control section) had a mix with 20% RAP and PG 64-22 binder. While three sections had mixes with 30%, 40%, 50% RAP, PG 64-22 binder, and Sylvaroad rejuvenator (tall oil), three other sections had mixes with the same RAP percentages and binder but used Hydrolene (aromatic extract) as the rejuvenator. Finally, the last test section was constructed using a mix with a 30% RAP and PG 64-28 binder (softer binder). Specimens were compacted in the laboratory from loose mixes that were obtained during the construction of each test section. Laboratory tests were conducted to evaluate the resistance of the prepared samples to moderate-temperature cracking, low-temperature cracking, rutting, and moisture damage. The test results showed that Hydrolene was more effective than Sylvaroad in improving the moderate-temperature cracking resistance of RAP mixes with more than 30% RAP. In addition, the tests results showed that the 30% RAP, 40% RAP, and 50% RAP mixes had similar low-temperature cracking resistance to that of the control. The laboratory test results also showed that mixes with 30% and 40% RAP had acceptable resistance to moisture damage. Furthermore, all mixes had acceptable rutting resistance. Finally, preliminary field evaluation showed that there were no observed distresses in the test sections after 7 months of construction.