Reclaimed Asphalt Pavement Content Research Articles

Aging sensitivity of recycled binder blends based on assessment of rheological, chemical, and nano-mechanical properties

ABSTRACT Economic and sustainability factors drive the increased use of reclaimed asphalt pavement (RAP) in road construction. Recycling agents, or rejuvenators, enhance the rheological properties of aged RAP binders, thereby improving asphalt pavement performance. However, a comprehensive understanding of the impact of recycling agents on binder properties and aging characteristics remains critical. This study investigates these effects through an extensive characterisation of RAP binder blends, focusing on rheological, chemical, and nano-mechanical properties. Key findings reveal that higher RAP content correlates with elevated levels of carbonyl (C=O) and sulfoxide (S=O) bonds, indicating increased oxidative aging. The absorbance aging index (AAI), derived from the SAR-AD (Saturates, Aromatics, Resins, Asphaltene Determinator) test, effectively detected variations in chemical fractions due to laboratory aging and RAP content. Atomic Force Microscopy (AFM) further quantified changes in the DMT (Derjaguin, Muller, Toropov) modulus with increasing RAP proportions. The Aging Rate (AR) parameter was also used to evaluate the impact of RAP and recycling agents on aging. Recycling agents improved rheological properties and reduced polar associations within RAP binder blends but also heightened aging susceptibility. This research provides critical insights into the interplay between RAP, recycling agents, and aging, offering a foundation for optimising sustainable pavement solutions.

Roller Compacted Concrete for Road Base Layer with RAP and Steel Fibers: Viscous Properties and Description of Experimental Sites

A high-performance composite material consisting of reinforced compacted cement concrete including Reclaimed Asphalt Pavement (RAP) has been investigated. This composite material is used as a base layer in combination with an asphalt overlay for heavy traffic roads. Steel fibers are used to minimize crack opening. RAP is added to preserve raw material and to comply with sustainable development, especially in the case of in-situ treatments. Composites with different RAP and fiber content and cement content were studied both in laboratory and on site. The laboratory study is divided into two parts. First, classical standard tests for road concrete were carried out: compressive strength, compressive modulus and tensile splitting strength, with a view to the design of pavement structures to be used on site. Secondly, more comprehensive rheological tests, such as complex modulus and fatigue tests, were performed to obtain a better knowledge of material behavior. Then, on-site behavior was studied from two experimental sites. The presence of bitumen in cement-treated composites induces an increase of viscous properties, observed mainly on the phase angle. These composites respect the time-temperature superposition principle and can be fitted by a visco-elastic rheological model.

Reclaimed Asphalt Pavement in Concrete Pavements: Properties, Microstructure, and Design

Reclaimed asphalt pavement (RAP), when used as aggregate in concrete, is known to reduce the bulk concrete strength and modulus but not dramatically impact shrinkage, durability, or fracture properties, especially at lower replacement levels. This article presents an overview of RAP aggregates in concrete as it pertains to its effect on properties, microstructure, and pavement design. The mechanisms resulting in decreased strength and modulus for concrete containing RAP have been linked to: (1) the larger, more porous interfacial transition zone (ITZ) and (2) the dominance of an asphalt cohesion failure instead of an asphalt-cement adhesion failure. Despite these reductions in mechanical properties, multiple field studies have indicated that concrete with RAP can perform comparably to conventional concrete pavements, particularly when 10-15% RAP is used. The flexural capacity of concrete slabs with 22% RAP has shown similar behavior to virgin aggregate concrete given the similarities in fracture properties. Fatigue and accelerated pavement testing of rollercompacted concrete with high RAP contents (50-100%) have indicated a reduced fatigue life relative to plain concrete, requiring a slightly thicker design. Based on the literature, RAP aggregate replacement levels less than 25% can be used in concrete pavements without a significant change to the structural design.

Recycled used cooking oil (UCO) as a rejuvenator in high content reclaimed asphalt pavement (RAP) mixes: A life cycle assessment (LCA).

This study investigates the primary data collected at a used cooking oil (UCO) recycling facility to quantify its environmental impact when used as a rejuvenator in high content reclaimed asphalt pavement (RAP) mixes. Annual energy consumption data sets on transportation, storage, filtration, machinery, and purification are assessed using the life cycle assessment (LCA) methodology with the LCA software Simapro 9.4 to evaluate the influential parameters and processes in reducing emissions. Pearson correlations of the production process show a higher association of carbon footprint with two dominant recycling factors: (1) electricity consumption (r=0.89) and (2) fuel consumption for transportation (r=0.37). A comprehensive LCA conducted on asphalt pavements with various RAP contents shows that a 28.81% reduction of carbon emissions can be achieved during the construction phase by adding 60% rejuvenated RAP. However, the relative uncertainty around RAP moisture content at the time of usage and faster pavement deterioration over the service life when high RAP content is incorporated into asphalt mixes might hinder the environmental advantage of adding RAP during the maintenance phase. Non-properly treated, blended, and rejuvenated RAP can be susceptible to early cracking, thus resulting in increased periodic maintenance. Moreover, the break-even point of economic appraisal suggest over 50% RAP content is beneficiary even at the higher discount rates (12%). Conducted LCA and sensitivity analyses emphasise the importance of collecting primary data from recycling facilities and considering both the construction and maintenance phases for implementing effective sustainable strategies.

Towards a durable and sustainable warm mix asphalt: techno-economic and environmental evaluation considering balanced mix design approach

Towards a durable and sustainable warm mix asphalt: techno-economic and environmental evaluation considering balanced mix design approach

Laboratory investigation on the properties of asphalt concrete containing reclaimed asphalt pavement (RAP) and waste polyethylene terephthalate (PET)

ABSTRACT In this research, PET particles at levels of 0%, 3%, 6%, and 9% (by the weight of asphalt binder) were added to asphaltic mixtures containing 0%, 10%, 20%, and 30% of RAP, and then their effects on volumetric and Marshall properties, Indirect Tensile Strength (ITS), creep, and fatigue behaviour were explored. Results demonstrate that Marshall stability increases with RAP addition, but decreases with the introduction of PET particles. While the ITS improves with added RAP, the highest ITS value resulting from PET addition is observed at a 3% PET content. Mixtures containing 20% RAP and 3% PET exhibit the highest resistance against moisture-induced damage. Based on dynamic creep test results, resistance to rutting decreases as PET content increases, whereas it improves with added RAP. Stress-controlled fatigue tests revealed that RAP incorporation enhances the fatigue resistance of mixtures, with this improvement growing alongside higher RAP content. However, PET particles reduce this property. Ultimately, the study's results suggest that RAP materials can offset the negative effects of PET, and with regulated quantities of both PET and RAP materials, asphalt mixtures containing these waste materials can perform comparably to conventional mixtures.

Predicting and optimizing the mechanical properties of rejuvenated asphalt mix with RAP content

Predicting and optimizing the mechanical properties of rejuvenated asphalt mix with RAP content

Impact of adding warm asphalt mix additives on recycling milled coatings: performance evaluation.

The use of warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) technologies presents challenges in optimizing binder activation and mechanical performance in asphalt mixtures. This study aimed to evaluate the effects of three WMA additives (sunflower oil, WarmGrip®, and natural zeolite) and different RAP contents (30% and 70%) on the rheological and mechanical properties of recycled asphalt mixtures. The research focused on assessing the degree of RAP binder activation, determining the extent of partial activation, and analyzing the impact on tensile strength, moisture resistance, modulus, fatigue life, and deformation resistance. The methodology included chemical and rheological analysis of RAP and modified binders, as well as mechanical testing of recycled mixtures. Results indicated partial RAP binder activation, with 96.16% activation in mixtures containing 30% RAP and 80.77% in those with 70% RAP. Sunflower oil acted as a rejuvenator, reducing binder stiffness and decreasing the maximum PG temperature by 6 °C. The use of natural zeolite improved moisture resistance, resulting in TSR values 20% higher than those of conventional hot mixtures with the same RAP content (70%). Warm recycled mixtures demonstrated enhanced fatigue life and moisture resistance, particularly with WarmGrip®. Overall, the incorporation of WMA additives allowed for enhanced fatigue life and deformation resistance in recycled mixtures, enabling the use of up to 70% RAP without compromising mechanical performance. The findings support the potential of WMA and RAP additives to improve sustainability, cost-effectiveness, and durability in asphalt pavement construction.

Hot asphalt recycling in cold climate: performance-based mixture design and a test section in the Swiss Alps

The use of high reclaimed asphalt pavement (RAP) content in the production of hot asphalt mixtures increases the risk of pavement cracking, especially in locations with cold climate and high temperature fluctuations. Here we used a performance-based mixture design approach to prepare three plant-produced hot asphalt mixtures for base, binder and foundation courses containing between 60% and 85% RAP and paved them at 1900 m altitude in the Swiss Alps. The mixture performance-based test and road core test results demonstrated that it is possible to ensure the required mixture performance even when using high RAP content so long as the homogeneity of RAP is ensured. The conventional mixture quality control requirements were fulfilled as well. As a result of the research, recommendations for designing mixtures containing high RAP content for high altitude roads are proposed.

Utilizing waste engine oil and Sasobit to improve the rheological and physiochemical properties of RAP

This study objective to assess the effects of Waste Engine Oil (WEO) and Sasobit on improving the rheological and physicochemical properties of Reclaimed Asphalt Pavement (RAP), both of which are considered waste materials. Seven asphalt mixes were prepared with varying percentages of these materials. The study included rheological testing, Fourier Transform Infrared Spectroscopy (FTIR) analysis, cost–benefit analysis, and final stage to select blend selection. Highway agencies typically limit RAP usage to 20% due to concerns such as fatigue and low-temperature cracking. To address these issues and increase the RAP content, rejuvenators are often required to soften the aged binder. This study investigated the use of WEO and Sasobit as rejuvenators, with WEO added at dosages of 4% and 8%, and Sasobit at 1%, 2%, and 3%. The penetration and viscosity methods were employed to determine the optimal amounts of WEO and Sasobit. The selected mixtures were tested for rutting resistance, fatigue performance, and low-temperature cracking susceptibility. FTIR was used to further analyze the blends, along with a cost analysis. The results indicated that 4% WEO was effective in rejuvenating 25% of the reclaimed binder, offering a cost-effective solution. While Sasobit did not function as a rejuvenator, it proved beneficial as a viscosity reducer.

Cement-grouted bituminous mixtures containing reclaimed asphalt pavement material: design and mechanical properties

The design and mechanical properties of cement-grouted bituminous mixes (CGBM) containing reclaimed asphalt pavement material (RAP) will differ from that of virgin CGBM due to the presence of RAP material. Research studies have solely reported the micromechanical behaviour of CGBM-RAP mixes. The current study aims to design and evaluate the mechanical properties of CGBM-containing RAP material (0, 20, 35, and 50%) and compare it with the properties of a bituminous concrete (BC) mix. It was observed that the permeability of the porous asphalt mixture decreased with an increase in RAP content, which hindered the full-depth grout penetration. Grout penetration studies were conducted to identify suitable cement grout. CGBM-RAP mixes had better mechanical properties and lower temperature susceptibility when compared to CGBM without RAP and bituminous mixture due to the higher stiffness imparted by the blended binder and cement grout. The physical properties of blended binders correlated well with the mechanical properties of CGBM.

Engineering Properties of Road Paving Mixtures with High Content of Reclaimed Asphalt and Recycled Waste Plastics.

Great efforts have been made in recent years by the scientific community and the asphalt industry in developing sustainable technologies for the production of asphalt mixtures for road paving applications, pursuing the use of ever higher quantities of recycled materials. In this regard, the challenge is to define the optimal formulation of the mixture which allows the various component materials to be synergistically combined without compromising the performance and durability of the asphalt pavement. In such a context, the experimental study described in this paper aimed to provide a contribution to research by investigating sustainable asphalt mixtures containing 50% reclaimed asphalt pavement (RAP) and polymeric compound composed of 100% recycled plastics. A wide set of mixtures was prepared in a laboratory by employing different dosages of polymeric compound added via the hybrid method at various binder contents. For comparison purposes, an additional set of reference asphalt mixtures containing standard polymer-modified binder (PmB) and virgin aggregate without RAP was prepared and tested. The experimentation focused on the main engineering properties of the asphalt mixtures, including their workability, volumetric properties, and mechanical characteristics. The experimental study involved a preliminary trial phase to establish an appropriate laboratory mixing procedure. The results obtained from the experimentation indicated that recycled waste plastics have good potential for use in asphalt mixtures with high contents of RAP, provided that the quantity of added plastics is adequately balanced.

Experimental investigation and statistical analysis of performance of ceramic fiber-reinforced warm asphalt mixtures containing reclaimed asphalt pavement

Experimental investigation and statistical analysis of performance of ceramic fiber-reinforced warm asphalt mixtures containing reclaimed asphalt pavement

FIELD PERFORMANCE OF HOT IN-PLANT PRODUCED ASPHALTIC CONCRETE WEARING COURSE (ACWC) WITH 30% RECLAIMED ASPHALT PAVEMENT (RAP)

Hot in-plant recycling stands as an effective yet underutilized method in Malaysia for reusing pavement milling waste, resulting in insufficient established benchmarks and validated trials. The Utilization of Reclaimed Asphalt Pavement (RAP) can divert a significant amount of waste asphalt millings from landfills, while conserving energy and natural resources. This study focused on the recycled mixture, ACWC-30RAP, which integrated 30% Reclaimed Asphalt Pavement (RAP). In July 2022, a 400 m trial lay was conducted from KM413.90 to KM414.30 Southbound (SB), Section C3, along the PLUS North-South Expressway (NSE). Field tests were systematically conducted on both the ACWC-30RAP and conventional ACWC20 mixtures at different phases including month-6, month-9, and month-12 post-construction. The primary objective was to assess fundamental properties related to the structural stiffness of pavement layers as well as the pavement performance and condition for both trial sections using various field testing including Falling Weight Deflectometer (FWD) and Multi-Laser Profiler (MLP). Following the 12-month trial period, both the ACWC-30RAP and conventional ACWC20 mixtures experienced actual traffic loading and environmental conditions. Remarkably, the ACWC-30RAP demonstrated comparable field performance as the conventional ACWC20. This alignment in performance signified a promising avenue for employing the recycled mixture with high RAP content. Using ACWC-30RAP can also provide economic benefit, reducing the production cost by approximately 25%. In essence, the ACWC-30RAP had achieved an equivalent level of confidence to the conventional ACWC20 mixture, which was exclusively composed of virgin materials. cts.

Performance restoration of aged SBS-modified asphalt in RAP via dry-process SBS modifier diffusion at the interface of aggregate-aged asphalt-virgin asphalt

Performance restoration of aged SBS-modified asphalt in RAP via dry-process SBS modifier diffusion at the interface of aggregate-aged asphalt-virgin asphalt

Towards the high RAP dosage obtained by refined processing influence on comprehensive performance of recycled asphalt mixture

Towards the high RAP dosage obtained by refined processing influence on comprehensive performance of recycled asphalt mixture

The influence of residual asphalt material in the mechanical behaviour of soil-RAP mixtures for use in paving

ABSTRACT The evaluation of Reclaimed Asphalt Pavement (RAP)’s suitability for pavement layers, optimises resource use, reduces environmental impact, and supports cost-effective practices. In this sense this study aimed to characterise soil-RAP mixtures to ensure they meet the quality standards required for pavement applications. The study examined two types of soil mixtures: one soil-RAP aggregates and the other soil-virgin aggregates (VAM) to understand the impact of residual asphalt binder on aggregate particles. Various mass contents (30%, 50%, 70%, and 90%) were tested alongside conventional soil-gravel mixtures with equivalent proportions and gradation of RAP and VAM. Additionally, the study investigated the effect of adding 2% cement on the performance of both recycled soil-RAP mixtures and conventional soil-gravel mixtures. The analysis includes granulometry, Atterberg Limits, MCT (Miniature, Compacted, Tropical) classification, soil chemical characterisation and microscopic images, compaction in Modified Proctor Energy, CBR, Resilient Modulus tests and stress–strain analysis. The results have revealed that the residual asphalt binder, surrounding RAP aggregates, has reduced the soil mixtures’ strength for different RAP contents. However, the study demonstrated that the addition of cement rendered the soil-RAP mixture feasible, enabling the application of the studied mixtures of RAP to constitute subbase and base layers.

Effect of Chemical Composition on Rheological Properties of Asphalt Binders Modified with Rap Binders and Rejuvenator

Conventional rejuvenating agents such as virgin binders, polymers and so on, poses environmental, technical, and economic challenges. The objective of this study is to investigate the interaction between chemical components and rheological behavior of hot mix asphalt modified with RAP binder and diesel engine waste oil (DEWO) as rejuvenator. 7.2% DEWO was added to the RAP binder to achieve the modified binder (MB), and the effects of the rejuvenator through the MB were evaluated at varying percentages (0 to 100% by weight of the virgin binder) using Dynamic Shear Rheometer (DSR) under short and long-term aging at high and intermediate temperatures, as well as low temperatures using Bending Beam Rheometer (BBR). Saturates, aromatics, resins, and asphaltenes (SARA)-separation, Indirect tensile stiffness modulus test (ITSM), and fatigue life test were also employed to investigate the interaction between chemical components and rheological properties of binder. Results indicated that incorporating 50% modified RAP binder significantly enhanced the performance of the asphalt mixtures, it was also discovered that 100% of RAP content meets standard specifications when modified with oil rejuvenators. This research suggests that large quantities of diesel engine waste oil can be diverted from landfills and employed as useful resource in asphalt production.

Sustainability of Asphalt Mixtures Containing 50% RAP and Recycling Agents

The substitution of virgin asphalt binder with reclaimed asphalt pavement (RAP) has environmental and economic merits, however, cracking susceptibility arises due to the aged asphalt binder within RAP. The objectives of this study are to (1) enhance the cracking resistance of asphalt mixtures containing 50% RAP utilizing recycling agents (RAs) derived from six petroleum-based and bio-based materials, (2) conduct an environmental impact assessment (represented by global warming potential “GWP”) for high-RAP mixtures including RAs, and (3) estimate the cost effectiveness of including high-RAP content in asphalt mixtures. Based on the RAP asphalt binder performance grade (PG), base asphalt binder PG, and RAP content, the RA contents were determined to achieve a target asphalt binder of PG 76-22. A control mixture was benchmarked for comparison, specified for high-traffic volume roads, and contained PG 76-22 polymer-modified asphalt binder. The engineering performance of studied asphalt mixtures was evaluated using the Hamburg wheel-tracking (HWT), semi-circular bend, Illinois flexibility index, Ideal cracking tolerance, and thermal stress-restrained specimen tensile strength tests. It was found that petroleum-derived aromatic oil, soy-based oil, and tall oil fatty acid-based RAs demonstrated a successful restoration of aged RAP asphalt binder without compromising the permanent deformation resistance. The 50% RAP mixtures emitted less GWP by 41% and 42.9% using petroleum- and bio-oil RAs, respectively, and achieved a 31% cost reduction compared to the control mixtures.

Influence of field aging on viscoelastoplastic performance of rubberized asphalt mixtures incorporating reclaimed asphalt pavement in arid urban climate

Influence of field aging on viscoelastoplastic performance of rubberized asphalt mixtures incorporating reclaimed asphalt pavement in arid urban climate