Percentages Of Reclaimed Asphalt Pavement Research Articles

A comprehensive evaluation of damping, vibration, and dynamic modulus in reclaimed asphalt pavement: The role of rejuvenators, polymer, temperature, and aging

Reclaimed asphalt pavement (RAP) is increasingly essential in pavement engineering to enhance environmental sustainability. The use of rejuvenators and polymers has solved concerns about the dynamic performance of RAP; however, its damping and vibration properties still need to be investigated. Pavement vibrations pose a threat to public health, impeding sustainability. This research investigates RAP's damping performance, resonant frequency, and dynamic modulus using a non-destructive impact resonance (IR) test. Three RAP percentages (0 %, 50 %, and 100 %), three waste oil rejuvenators (paraffin oil, fatty acid, and base bitumen), and recycled high-density polyethylene (r-HDPE) were employed. Rejuvenators and r-HDPE were used separately and simultaneously at varying percentages. Evaluations were conducted under two conditions (long-term aged (LTA) and unaged) and two temperatures (25 °C and −12 °C). Findings reveal a performance hierarchy: under unaged conditions, rejuvenators exhibit superior efficacy, while simultaneous application of rejuvenator and recycled polymer optimally performs in prolonged aging scenarios. Statistical analyses underscore the pivotal role of rejuvenator quantity, irrespective of recycled polymer presence, aging, and temperature, as determinants in sculpting RAP's damping performance, resonant frequency, and dynamic modulus.

The Effect of Refined Separation on the Properties of Reclaimed Asphalt Pavement Materials

Refined separation not only controls the variability of reclaimed asphalt pavement (RAP), but also improves the mixing ratio of RAP and the quality of recycled asphalt mixtures. This study examines RAP treated with various refined separation frequency parameters, analyzes the variation rules and the variability of RAP aggregate gradation, asphalt content, asphalt properties, and aggregate properties, and calculates the maximum mixing percentage of coarse RAP material by using the gradation variability control method and the asphalt content variability control method. The results show that the variability of gradation and asphalt content of coarsely separated RAP is considerable, and a refined separation process significantly reduces the variability of gradation and asphalt content of RAP; the agglomeration of RAP decreases with an increase in the refined separation frequency; and the RAP agglomeration of three kinds of RAPs (E1, E2, and E3) under a refined separation frequency of 55 Hz reduces by 6.40%, 4.30%, and 4.30%, respectively, as compared with that of coarsely separated RAPs. The asphalt content of the refined separation RAP gradually decreases with an increase in frequency, and the asphalt content of E1 and E2 (55 Hz) was only 0.95% and 1.10%, respectively. The maximum percentage of RAP in recycled asphalt mixtures was calculated using the gradation variability control method and the asphalt content variability control method, respectively. The maximum proportions of RAP were 45% and 33% for A1 (0 Hz), respectively, and the maximum proportions of RAP for E1 (55 Hz) were all 100%. The results of the two methods show that the process of refined separation can increase the maximum proportion of blended RAP materials. They also demonstrate that the refined separation process can increase the maximum blending ratio of coarse RAP materials, thereby improving the quality of the RAP, increasing the proportion of RAP blending, and ensuring the quality of the recycled asphalt mixture. In conclusion, the refined separation process holds promise for maximizing the potential value of RAP and optimizing its recycling, environmental, and economic benefits.

Availability adjusted mix design method as a tool to mitigate the adverse effects of RAP on the performance of asphalt mixtures

The use of high percentages of reclaimed asphalt pavement (RAP) in asphalt mixtures offers economic and environmental advantages. However, state agencies place limits on RAP usage to avoid its indiscriminate use without a full understanding of its long-term performance implications. To achieve a more informed and rational use of higher RAP contents, it is essential to quantify recycled binder availability (RBA) and incorporate it into asphalt mixture design. The current design methods often assume complete RBA, leading to less durable mixtures. Standardized mixture design methods fail to rigorously account for the effects of RBA on the volumetric composition of asphalt mixture. Recently, the availability adjusted mixture design (AAMD) method was developed to address these issues by explicitly considering partial RBA in the interpretation of mixture volumetric properties and accounting for the role of RAP agglomerations on aggregate structure. This study tests the hypothesis that the AAMD method can mitigate the adverse performance consequences of RAP through the control of ‘available’ volumetric and effective binder properties. This was achieved by comparing virgin and RAP mixtures designed with similar ‘available’ volumetric properties according to the AAMD method. Additionally, control mixtures with RAP contents ranging from 20 to 35 percent were compared to AAMD mixtures with similar ‘available’ volumetric properties designed with the same RAP content and with 50 percent RAP. The collective results demonstrate that the AAMD method effectively mitigates negative performance consequences of RAP by controlling the ‘available’ volumetric and effective binder properties.

Effect of Polymer-Modified Bitumen and Reclaimed Asphalt Pavement on The Physical Properties of Bitumen

The high cost of road construction due to the energy required for new material production and the environmental impact necessitates the use of reclaimed asphalt pavement (RAP) and other waste materials. This paper examined the effect of using RAP with a PET additive as a rejuvenator. PET additive (2%) was added to the virgin binder (VB) of 60/70 penetration grade to form a Polymer modified bitumen (PMB). RAP percentages used were 30, 40, and 50%, respectively. The physical properties were examined using the penetration, softening point, and ductility. The results show that the physical properties of RAP were improved by utilizing Rap binder (RB) and PMB mix ratio. The penetration and ductility values increased by 46.4% and 66.7%, respectively, with the PMB (30): RB (70) ratio blend, compared to RB: VB blend. This suggests a reduction in brittle behavior and less stiffness with the addition of PMB in the blend, enhancing the flexibility of the RAP. Although both mixtures blended with RB exhibited softening points within the acceptable range, improved performance was observed with RB/PMB mix blend over RB/VB blend when used in hot asphalt mixture.

Understanding the State Agency Policies toward RAP Usage in the United States: State of Practice

The usage of Reclaimed Asphalt Pavement (RAP) material is a highly resource-conservative, economical, and sustainable practice in flexible pavement construction. However, its usage in hot mix asphalt (HMA) is capped at 25% by the majority of state transportation agencies due to its aging levels, stiffness characteristics, and handling capabilities, which may result in early-age pavement distress. Though researchers suggest methodologies to increase RAP usage, higher RAP percentages in asphalt pavements require the support of state authorities. The main objective of this paper is to provide information on how different states design their mixtures with high RAP percentages. This study reviewed the current state of practice of fifty (50) state DOTs in the United States (US) with respect to RAP usage and the factors governing its regulations. It was observed that the limit of RAP content is mainly governed by traffic levels, gradation, binder content, and stiffness contributed by RAP and layer position in a pavement structure. The specifications also suggest that apart from volumetric and performance justification, blending charts, fractionation, and virgin binder grade selection would facilitate the use of higher RAP content in HMA. Controlled mixture design abiding by state specifications can increase the allowable RAP to 40–100%.

Influence of reclaimed asphalt pavement (RAP) and recycled asphalt shingle (RAS) binder availability on the composition of asphalt mixtures

Reclaimed asphalt pavements (RAP) and recycled asphalt shingles (RAS) are incorporated in the production of new asphalt mixtures to reduce cost, waste, and the consumption of virgin materials. The use of recycled asphalt materials (RAM) is limited by controlling agencies due to the uncertainties regarding their impacts on the volumetric composition and long-term performance of the asphalt mixtures. Recycled binder availability (RBA), which reflects the proportion of the recycled binder that is available to blend with virgin asphalt in an asphalt mixture, is currently neglected by the majority of mix design methods adopted by highway agencies, despite complete RBA being considered an unrealistic scenario. An incorrect assumption of the RBA in mixture design has important consequences on the inferred asphalt mixture volumetric properties, and consequently on the performance. A recently created method, so-called Availability Adjusted Mix Design (AAMD), proposes a revised interpretation of the volumetric properties of asphalt mixtures and design of the aggregate structure on the basis of partial RBA caused by agglomerations of RAM particles. The AAMD method is used in this study to evaluate the impacts of RBA on the volumetric properties of a diverse set of surface asphalt mixtures. The impacts of the RBA on the inferences of asphalt mixture composition are assessed for each mixture and the viability of using fixed RBA values for RAP and RAS sources in the state of North Carolina is assessed by comparing the inferred asphalt mixture composition yielded from the source-specific RBA versus the average RBA of the pool of recycled materials studied. The results show that the volumetric properties change considerably as a function of the assumed RBA, and the use of the AAMD becomes crucial for mixtures containing as little as 15 percent RAP and/or 4 percent or RAS. The use of a fixed RAS RBA value, calibrated as the average of a representative set of RAS stockpiles, versus the source-specific values has negligible impacts on the inferred volumetric properties of mixtures containing permissible RAS contents in North Carolina. Conversely, the use of source-specific RAP RBA values is recommended, which can be quantified through comparative sieve analysis of RAP and recovered RAP aggregate.

Evaluation of thermal cracking probability for asphalt concretes with high percentage of RAP

The paper presents determination of the probability of thermal cracking of asphalt mixtures with different reclaimed asphalt pavement (RAP) content on the basis of laboratory tests and analytical evaluation using thermal stress development method. Probability was evaluated taking into consideration: the type and gradation of the mixture and the quality and content of RAP. Thermal stresses were determined using two models: elastic and viscoelastic. Addition of RAP decreases the low-temperature properties of all the tested asphalt mixtures. In the case of wearing and binder courses, addition of 20% of RAP increases the cracking temperature by around 5–6 °C.

Investigating the cracking performance of asphalt mixture containing RAP using different cracking indices

Due to environmental benefits and economic issues, the use of reclaimed asphalt pavement (RAP) in asphalt mixtures has become a necessity. However, mixtures containing RAP have poor performance against cracking at different temperatures due to excessive stiffness and aged binder. Therefore, evaluating the cracking performance of RAP is of great importance. In this research, the semicircular bending (SCB) test was used to evaluate fracture characteristics. For this purpose, the indicators of peak load (Pmax), fracture energy until failure (FEUF), fracture energy after failure (FEAF), fracture strain tolerance (FST), and power (P) are used. The SCB test was performed at 25 °C and − 12 °C, and all indicators were calculated at intermediate and low temperatures. Three different percentages of RAP (0%, 50%, and 100%) were used. Also, three different rejuvenators, Waste Engine Oil (WEO), Oleic Acid (OA), and Vacuum Bottom (VB), were used with four different doses. Then recycled high-density polyethylene (r-HDPE) in four different amounts (0%, 3%, 5%, and 7%) was used separately and in combination with rejuvenators to prepare the samples. Also, to expand the application of SCB tests worldwide, and due to the availability and simplicity of the Marshall device, non-standard samples with a diameter of 100 mm made by this device were used. Experimental results showed that the use of a rejuvenator alone, as well as in combination with the recycled polymer, could improve the cracking resistance of asphalt mixtures at medium and low temperatures. Results showed that VB performed best at 25 °C and OA at − 12 °C. An increase of 53% was seen in the FST index for the VB rejuvenator and 62% in the OA rejuvenator. Also, VB (at 25 °C) and OA (at −12 °C) improved crack propagation resistance by 62% and 94%, respectively. To evaluate the results, statistical analyzes were used. The statistical results showed that using the Marshall compaction device to make the samples has a suitable accuracy. In addition, the statistical results showed that the fracture behavior of mixtures containing RAP at a temperature of 25 °C differs from a temperature of − 12 °C.

Field Performance Evaluation of Base Course Constructed with Reclaimed Asphalt Pavement and Virgin Aggregate Blends

Abstract This study presents the results of four years of data collection from a test site that is constructed as part of an actual roadway. The focus of the study was to evaluate the possibility of achieving similar or better performance characteristics from base course sections constructed with reclaimed asphalt pavement (RAP) blends compared to sections with 100 % virgin aggregate (VA). Two base course sections were constructed by blending VA with 20 % RAP and two with 30 % RAP (four RAP-VA sections). Blends were achieved using fine processed RAP with two different average binder contents (4.9 and 5.6 %). Additionally, two sections were constructed with 100 % VA for comparison. During construction, strain gauges were embedded into the asphalt and base course layers. Long-term performance evaluations were monitored based on data from the strain gauges and in situ testing. Falling weight deflectometer and light weight deflectometer tests were used to evaluate modulus values, and the results showed that all sections constructed with RAP-VA blends had equal or greater modulus values than the 100 % VA sections. International roughness index tests coupled with data from strain gauges were used to evaluate deformations. The results showed that three of the four RAP sections had deformations close to or less than 100 % VA sections (desired outcome). The only exception was in the section constructed with 30 % RAP with lower binder content (4.9 %). Findings from this study showed that field evaluations require multiple methods of testing, and modulus-based measurements alone should not be relied on for performance evaluations. This study demonstrated that it is possible to design base course sections with RAP that perform similar to or better than 100 % VA. A proper blend requires the gradation and binder content of RAP to be characterized and the percentage of RAP blended with VA to be determined based on these properties.

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.

Fatigue and stiffness characteristics of asphalt mixtures made of recycled aggregates

This research studies the stiffness characteristics and fatigue life of several asphalt mixtures made of recycled glass, reclaimed asphalt pavement (RAP), and recycled concrete aggregate (RCA). Experiments were carried out at 5–35 °C, loading frequencies of 0.1–20 Hz, and at two microstrain levels of 200 and 400 µm/m. To date, the effect of extensive parametric combinations of loadings, microstrain levels, and temperatures on asphalt mixtures made entirely of recycled materials (RM) has not been undertaken. The findings exhibited superior stiffness characteristics and improved fatigue life of some RM mixtures compared to control mixtures. The next step of this study included the optimization of three existing fatigue life prediction models. In addition, a prediction model was developed based on nominal maximum aggregate size (NMAS), percentage of RCA, and percentage of RAP in the asphalt mixture. The optimized models resulted in a much higher coefficient of determination (R2) and P-value (likelihood) in the statistical T-test compared to the existing prediction models utilized in this study. The developed model yielded R2 values close to 0.99 between measured and predicted fatigue life, indicating an enhanced accuracy in the prediction. Comparison of the estimated dissipation energy of mixtures supported and validated the fatigue testing outcomes.

Performance Evaluation of Extracted Asphalt Binders from Field Cores Containing Recycled Components: Load- and Non-Load-Associated Cracking Resistance

Modifying asphalt mixtures with recycled components is common practice due to their environmental and economic merits. However, due to the oxidized air-blown asphalt binders in recycled asphalt shingles (RAS) and aged binders in reclaimed asphalt pavement (RAP), adopting RAP and/or RAS as recycled components in asphalt mixtures influences the performance of the overall asphalt binder in these mixtures. The percentages of recycled components and performance grade (PG) of virgin asphalt binders (VABs) in the asphalt mixtures govern the performance of the overall asphalt binder. Therefore, the main idea of this study was to investigate the effect of the percentages of RAP/RAS and PGs of the VABs on the load- and non-load-associated cracking resistance of the extracted asphalt binders (EABs) from field cores. Rheological tests were performed on the EABs to assess the load-associated cracking (fatigue cracking) and non-load-associated cracking (low-temperature and block cracking) resistance. The VAB's PGs, mixtures' ages, and the percentages of RAP/RAS affected the EABs' cracking resistance. When compared to EABs from mixtures with lower amounts of RAP, employing RAS in the asphaltic mixtures improved EABs' resistance to fatigue and block cracking. However, using RAS deteriorated EABs' resistance to low-temperature cracking. Increasing the RAP's percentage in the asphaltic mixtures decreased the cracking resistance of the EABs. Strong relationships were established between EABs' load- and non-load-associated cracking resistance.

Impact of Engine Oil as a Rejuvenator on the Properties of RAP Containing Asphalt Mixtures

In order to build roads in more sustainable and environmentally friendly ways, reclaimed asphalt pavement (RAP) must be used in large quantities. Using RAP, new asphalt can be produced with a small amount of raw materials, thus reducing the energy required to extract and refine new materials and the waste generated from demolishing old asphalt pavements. The high stiffness of RAP mixtures can make it difficult to use RAP in amounts greater than 30%. Several methods can be used to overcome this difficulty, one of which is the addition of rejuvenating agents. Therefore, this study investigated the possibility of using pure engine oil (PEO), studied its effect as a regenerating agent for RAP, and determined the optimal percentage of PEO. Three percentages of RAP were used to demonstrate the viability of using high percentages of RAP in the asphalt mixture: 25%, 50%, and 75%. In addition, four PEO percentages were tested, namely 2, 4, 6, and 8%, to determine the ideal amount that helps the RAP regain its properties. The research revealed that RAP is appropriate for hot asphalt mixtures, producing results that outperformed the virgin mixture. Furthermore, the optimal PEO percentage ranged between 4% and 6%. This study concluded that employing RAP in significant quantities in addition to PEO while sustainably building roads is feasible.

Dilauryl thiodipropionate as a regeneration agent for reclaimed asphalts

Constructing asphalt pavements using reclaimed asphalt pavement (RAP) instead of exclusively virgin materials can significantly reduce environmental impacts and costs. However, the adverse effect of the aged RAP binder on asphalt mixtures’ workability and pavements’ performance restricts the percentage of RAP added to asphalt mixtures. As a solution, regeneration agents can be used to restore (even if partially) the physical, rheological, and chemical properties lost during the aging of the pavement in the field. Therefore, this paper evaluates the feasibility of using Dilauryl thiodipropionate (DLTDP) as a regeneration agent for RAP binders. This study considered two RAP binders (artificial and field). The impact of the DLTDP on the continuous performance grade of each RAP binder was investigated using the Dynamic Shear Rheometer (DSR). The antioxidant and regenerative effects of DLTDP on RAP binders were assessed by Fourier Transform Infrared spectroscopy (FTIR) and SARA fractionation. The adhesion between each RAP binder and granite aggregate (at dry and wet conditions) was evaluated using the bitumen bond strength (BBS) test. The rheological results indicated the softening effect of DLTDP on RAP binders. This softening effect may be explained by the increase of the maltene fractions (resins) and the reduction of the asphaltene fraction. Additionally, regenerated binders showed better oxidative aging and moisture susceptibility resistance than non-regenerated binders. Overall, the results indicated that adding DLTDP to RAP binders partially restored RAP binders' rheological and chemical composition to the target neat asphalt binder without significantly compromising the adhesion properties and rutting resistance. Moreover, the mentioned results verified the great potential of using DLTDP as a regeneration agent for RAP binders, making it possible to produce good-performing asphalt mixtures with a high RAP percentage.

Evaluating Rutting Resistance of Rejuvenated Recycled Hot-Mix Asphalt Mixtures Using Different Types of Recycling Agents.

Growing environmental pollution worldwide is mostly caused by the accumulation of different types of liquid and solid wastes. Therefore, policies in developed countries seek to support the concept of waste recycling due to its significant impact on the environmental footprint. Hot-mix asphalt mixtures (HMA) with reclaimed asphalt pavement (RAP) have shown great performance under rutting. However, incorporating a high percentage of RAP (>25%) is a challenging issue due to the increased stiffness of the resulting mixture. The stiffness problem is resolved by employing different types of commercial and noncommercial rejuvenators. In this study, three types of noncommercial rejuvenators (waste cooking oil (WCO), waste engine oil (WEO), and date seed oil (DSO)) were used, in addition to one type of commercial rejuvenator. Three percentages of RAP (20%, 40%, and 60%) were utilized. Mixing proportions for the noncommercial additives were set as 0-10% for mixtures with 20% RAP, 12.5-17.5% for mixtures with 40% RAP, and 17.5-20% for mixtures with 60% RAP. In addition, mixing proportions for the commercial additive were set as 0.5-1.0% for mixtures with 20% RAP, 1.0-1.5% for mixtures with 40% RAP, and 1.5-2.0% for mixtures with 60% RAP. The rutting performance of the generated mixtures was indicated first by using the rutting index (G*/sin δ) for the combined binders and then evaluated using the Hamburg wheel-track test. The results showed that the rejuvenated mixtures with the commercial additive at 20 and 60% RAP performed well compared to the control mixture, whereas the rejuvenated ones at 40% RAP performed well with noncommercial additives in comparison to the control mixture. Furthermore, the optimum percentages for each type of the used additives were obtained, depending on their respective performance, as 10%, 12.5%, and 17.5% of WCO, 10%, 12.5-17.5%, and 17.5% of WEO, <10%, 12.5%, and 17.5% of DSO, and 0.5-1.0%, 1.0%, and 1.5-2.0% of the commercial rejuvenator, corresponding to the three adopted percentages of RAP.

The Effect of CKD and RAP on the Mechanical Properties of Subgrade Soils

The construction of pavement layers on subgrade soil with good characteristics decreases the thickness of these layers, which in turn lowers the cost of building and maintaining roadways. However, it is impossible to avoid constructing pavements on unsuitable subgrade due to a number of limitations. Using conventional additives like lime and cement to improve subgrade properties results in additional costs. As a result, utilizing by-products (cement kiln dust and reclaimed asphalt pavement) in this field has benefits for the environment, economy, and technology. Large amounts of cement kiln dust (CKD), a by-product material, are produced in Portland cement factories. On the other hand, large amounts of reclaimed asphalt pavement (RAP) are accumulated as a result of the rehabilitation of old roads. This paper discusses using CKD and RAP to improve the characteristics of poor subgrade layers by conducting a series of Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) tests on samples of natural soil and soil stabilized with different percentages of CKD and RAP with different curing times to investigate their impacts on soil properties. The curing was carried out by wrapping the stabilized samples with several layers of nylon and then placing them in plastic bags at room temperature. The compaction results illustrated that the addition of CKD increases OMC and decreases MDD, in contrast to RAP, which decreases OMC and increases MDD. The addition of CKD and RAP led to a significant and unexpected increase in the CBR values. The results show that the soaked and unsoaked CBR values improve from 3.4% and 12.1% for natural soil to 220.1% and 211%, respectively, after adding 20% CKD and curing the samples for 28 days. Also, the addition of 25% RAP to soil-20% CKD blend increased the soaked and unsoaked CBR values to 251% and 215%, respectively. All the additions resulted in a significant reduction in swelling.

Evaluation of pavement materials for Dense Bituminous Macadam layer using Reclaimed Asphalt Pavement (RAP)

As a sustainable and eco-friendly alternative to fresh or new materials for road construction and maintenance, recycled or reclaimed asphalt pavement (RAP) is being used more frequently. There are no specific criteria, norms, or methods for identifying recovered asphalt materials in India or other developing nations. Classifying the RAP materials that are now accessible for use in road construction is therefore urgently necessary. Costs associated with highway projects can be cut by 25–30% by reusing these materials. There have been some reported studies in India where new materials were swapped out for RAP in the binder course, but there are undoubtedly many more that have not yet been documented. The goal of the current experiment is to determine the aggregate mix percentage for DBM layers with various percentages of RAP. The RAP sample was taken from the NH209 Kanakpura Road.

Effects of laboratory preheating procedures on recycled binder contribution in asphalt mixtures

Recycled asphalt material (RAM) preheating procedures for fabricating laboratory-mixed asphalt mixture samples vary considerably, which may impact the recycled binder contribution. That is, the percentage of the recycled binder that is mobilized and incorporated into the virgin binder within the asphalt mixture. Three different preheating procedures were used to fabricate samples of four asphalt mixtures from different sources in the laboratory. In one procedure, both the virgin aggregate and RAM were conditioned to slightly above the mixing temperature. In another, the RAM was heated to 110 °C and combined with RAM preheated slightly above the mixing temperature. In the third method, the virgin aggregate was superheated and mixed with recycled material at room temperature. Three of the study mixtures contained reclaimed asphalt pavement (RAP) with contents spanning 21 to 40 percent and the fourth contained 25 percent RAP and 4 percent recycled asphalt shingles (RAS). Recycled binder contribution in the fabricated mixtures was quantified using tracer-based microscopy. Complete recycled binder contribution was not achieved in any of the laboratory-mixed samples. The two preheating methods that did not utilize superheating yielded statistically equivalent recycled binder contribution results for the three RAP mixtures. The superheating procedure yielded significantly higher recycled binder contribution compared to the other methods in some cases. The mixture with RAS demonstrated greater sensitivity in recycled binder contribution to the preheating procedure compared to the RAP only mixtures. The results of this study suggest preheating procedures should be specified to minimize variability in laboratory-fabricated asphalt mixture samples.

Rheological Characterization of Asphalt Binders Containing Rejuvenated Reclaimed Asphalt Pavement

The use of reclaimed asphalt pavement (RAP) in freshly hot mixed asphalt (HMA) can save on material costs, preserve energy, and protect the environment. Employing limited amount of RAP in the production of asphalt mixes can result in similar performance as normal mixtures. However, adding more RAP can reduce the HMA’s mixing efficiency and could make the asphalt mixture more susceptible to fatigue and low-temperature cracking. Vegetable oil can act as a rejuvenator and reduce the HMA deficiencies with a high RAP percentage. This study investigated the potential effect of two vegetable oils; namely soybean oil (SOY) and sunflower oil (SnF), as rejuvenators on the properties of asphalt binders that contain 40% of RAP binder. To determine the optimum dosage of the rejuvenators (SOY and SnF), the properties of the rejuvenated RAP binders were carried out by conducting the penetration, softening point, viscosity, dynamic shear rheometer (DSR), and bending beam rheometer (BBR) tests. The test results indicated that vegetable oils could provide better fatigue and low-temperature cracking resistance with acceptable rutting performance. Furthermore, it is observed that, for the abovementioned properties, the addition of the 6%SOY and 3%SnF were more feasible in restoring the 40RAP binder to its original properties.

Thermal, chemical and rheological properties of asphalt binders extracted from field cores

The intermediate-temperature performance of extracted asphalt binders (EABs) is altered when recycled asphalt shingles (RAS) and/or reclaimed asphalt pavement (RAP) are included in asphalt mixes. This happened as a result of the RAP’s aged asphalt binder and the RAS’s oxidized air-blown asphalt. Thus, the rheological properties of EABs from field cores were examined at intermediate temperatures. The fatigue life and the Superpave fatigue cracking parameter were among the rheological properties. Thermogravimetric analysis and Fourier transform infrared were used to analyze EABs’ thermal and chemical characteristics, respectively. The relationships between EABs’ fatigue cracking resistance, thermal, and chemical characteristics were scrutinized. Ages of mixes, percentages of RAP and/or RAS, and intermediate performance grade (PG) temperatures of virgin asphalt binders (VABs) controlled the resistance of EABs to fatigue cracking. Considering VABs with the same intermediate PG temperatures, EABs from older mixes with higher RAS percentages had higher resistance to fatigue cracking than those from younger mixes with lower RAP percentages. When RAP percentages in asphalt mixes were increased, EABs’ resistance to fatigue cracking deteriorated. Thermal and chemical analyses along with rheological characteristics are suggested as indicators of EABs’ intermediate-temperature performance.