Virgin Asphalt Binder Research Articles

Microscopic R-curve simulation study of asphalt material fracture

Cracks can significantly influence the service life of an asphalt pavement. To study the microcracking behavior of asphalt materials, this paper utilized molecular dynamics simulation methods to simulate the tensile fracture process of asphalt materials at the microscopic level and described the fracture behavior using R-curve. Two experimental factors, temperature and loading rate, were selected to simulate the tensile fracture of virgin asphalt binder, aged asphalt binder, and SBS modified asphalt binder, and Microeconomic R-curve were constructed based on the fracture displacement and cumulative fracture energy of asphalt materials. Meanwhile, fracture energy, cohesive energy, and energy rate were used to evaluate the fracture behavior of asphalt materials. The results indicated that the micro-R curve simulated by molecular dynamics can well describe the tensile fracture behavior of asphalt. Among the fracture indicators, fracture energy and energy rate were significantly affected by the type of asphalt, while cohesive energy was significantly affected by the loading rate.

Case Studies of Practices and Lessons Learned When Using Reclaimed Asphalt Shingles in Asphalt Mixtures

The use of reclaimed asphalt shingles (RAS) in asphalt mixtures dates back to the 1990s. RAS contains four to six times more asphalt binder than reclaimed asphalt pavement (RAP), so it is very attractive from a virgin asphalt binder replacement cost-savings perspective, as well as from a sustainability perspective, since over 50% of the carbon footprint of asphalt mixtures comes from asphalt binder production. Using RAS in asphalt mixtures also prevents it from being landfilled. However, asphalt binder in RAS is significantly stiffer than paving-grade asphalt binder, which can lead to stiff asphalt mixtures with poor cracking resistance. Materials, mixture design, and processing and handling developments have helped improve the success of RAS asphalt mixture use. The performance history of RAS mixtures over the past 20 years has shown that with proper engineering and construction it is comparable to virgin asphalt mixtures. In the current study, observations from field visits to six agencies that regularly use RAS in asphalt mixtures were summarized, identifying positive practices and lessons learned. Different agencies had diverse goals when using RAS; those with rigorous specifications and policies obtained good performance from the mixture, especially when closely monitoring it over time. Field performance reviews of in-service pavements up to 9 years old encompassing RAS or RAS and RAP revealed that with appropriate policy, mixture design, and quality control, good performance was achieved. Limiting RAS dosage, ensuring adequate virgin binder in the mixtures and a sufficiently soft blended binder, along with RAS processing and handling, led to positive performance.

Study on effect of thermal, oxidative and ultraviolet coupled aging on rheological properties of asphalt binder and their contribution rates

ABSTRACT This paper aims to investigate the effect of different environmental conditions on the aging properties of virgin asphalt binder and evaluate the magnitude of aging on asphalt binder under different environmental conditions. The effect of thermal, oxidative and ultraviolet aging on the rutting resistance, fatigue resistance and cracking resistance of virgin asphalt binder was characterised based on rheological parameters. The contribution rate of different environmental factors to the aging of asphalt binder was quantitatively analysed. Results showed that high temperature repaired cracks in the asphalt binder caused by ultraviolet aging. The single aging factor of heat, oxygen and light had little effect on the rheological properties of asphalt binder. High temperature and oxygen would accelerate the aging effect of the asphalt binder aging process. Thermal–oxidative–UV-coupled aging had a more pronounced effect on the aging of asphalt binder than thermal–oxidative aging. The fatigue resistance of asphalt binder is more sensitive to the response of aging. The contribution rates of thermal–UV aging, UV–oxidative aging and thermal–oxidative aging were all greater than the sum of the contribution rates of the two corresponding single factors. The aging of asphalt binder was mainly due to thermal–oxidative aging when the aging temperature exceeded 80°C.

Influence of epoxy resin polymer on recycled asphalt binder properties

Utilization of high-performance pavement materials with a high reclaimed asphalt pavement (RAP) content is gradually gaining importance given the impetus of green environmental policies. Epoxy resin polymer (EP) can greatly enhance the reuse of RAP materials in asphalt mixture. The influence of EP on the properties of aged asphalt binder was investigated wherein mechanical and chemical properties, and the micro-morphology of binders composed of aged asphalt binder and EP were also evaluated. EP significantly improved tensile, high-temperature, low-temperature, and fatigue properties of aged asphalt binder, and simultaneously reduced concentration of sulfoxide and carbonyl of aged asphalt binder. Increasing EP content reduced the impact of asphalt ageing degree on mechanical properties, micro-morphology, and chemical composition. Furthermore, the construction allowance time of the binder was increased with increasing EP content. At 40% EP content, an effective network structure was formed in the aged asphalt binder, leading to higher tensile elongation, high-temperature rheological properties, and fatigue life as compared to virgin asphalt binder. Meanwhile, low-temperature modulus and sulfoxide and carbonyl concentrations were lower than those of virgin asphalt binder. For application, a recommended EP content of 40% is suggested.

Study on effect of various rejuvenators on virgin asphalt binders suffering various aging conditions and the unified evaluation index

Adding rejuvenator is a feasible method to restore the properties of aged asphalt. Due to the complex rejuvenation mechanism between different rejuvenators and aged asphalt, there is no unified standard to evaluate the rejuvenation effect of rejuvenator. Most of the current research on rejuvenator focus on the characterization of macro mechanical properties of rejuvenated asphalt binder. In order to explore the changes of chemical composition and micromechanical properties of asphalt during aging and rejuvenation, fifteen kinds of virgin asphalt samples at different aging and rejuvenation stages were prepared. A commercial rejuvenator, aromatic oil and warm mix agent were selected as rejuvenators. The fifteen asphalt samples involved various aging methods, including water-ultraviolet aging, water free ultraviolet aging, RTFOT and PAV. Through gel permeation chromatography (GPC), Fourier transform infrared spectrometer (FTIR) and atomic force microscope (AFM) test, the reversibility evaluation index Rw, RC=O, RS=O and RDMT were proposed. These indexes could be used to quantitatively evaluate the rejuvenation effects of rejuvenator on the specific properties of aged asphalt. Based on the linear fitting results among various indexes, micro reversibility index of virgin asphalt (IRIV) was proposed. The results showed that the commercial rejuvenator and warm mix agent had a limited effect on the recovery of chemical composition and molecular weight of aged asphalt. The commercial rejuvenator over restored the micro mechanical properties of aged asphalt. The effect of aromatic oil on micro mechanical properties of aged asphalt was between commercial rejuvenator and warm mix agent. This study provides a way to quantitatively evaluate the rejuvenation effect of rejuvenator on virgin asphalt binder. It is helpful to better understand the aging-rejuvenation process of virgin asphalt binder more comprehensively from chemical and micromechanical properties.

Biomass valorization toward sustainable asphalt pavements: Progress and prospects

To cope with the global climate crisis and assist in achieving the carbon neutrality, the use of biomass materials to fully or partially replace petroleum-based products and unrenewable resources is expected to become a widespread solution. Based on the analysis of the existing literature, this paper firstly classified biomass materials with potential application prospects in pavement engineering according to their application and summarized their respective preparation methods and characteristics. The pavement performance of asphalt mixtures with biomass materials was analyzed and summarized, and the economic and environmental benefits of bio-asphalt binder were evaluated. The analysis shows that pavement biomass materials with potential for practical application can be divided into three categories: bio-oil, bio-fiber, and bio-filler. Adding bio-oil to modify or extend the virgin asphalt binder can mostly improve the low temperature performance of asphalt binder. Adding styrene-butadienestyrene (SBS) or other preferable bio-components for composite modification will have a further improved effect. Most of the asphalt mixtures prepared by using bio-oil modified asphalt binders have improved the low temperature crack resistance and fatigue resistance of asphalt mixtures, but the high temperature stability and moisture resistance may decrease. As a rejuvenator, most bio-oils can restore the high and low temperature performance of aged asphalt and recycled asphalt mixture, and improve fatigue resistance. Adding bio-fiber could significantly improve the high temperature stability, low temperature crack resistance and moisture resistance of asphalt mixtures. Biochar as a bio-filler can slow down the asphalt aging process and some other bio-fillers can improve the high temperature stability and fatigue resistance of asphalt binders. Through calculation, it is found that the cost performance of bio-asphalt has the ability to surpass conventional asphalt and has economic benefits. The use of biomass materials for pavements not only reduces pollutants, but also reduces the dependence on petroleum-based products. It has significant environmental benefits and development potential.

Rheological Characterization of Reclaimed Asphalt Binder Blended with The Neat And Sbs-pma Binders

Reusing reclaimed asphalt pavement material guarantees a substantial optimization of non-renewable material resources, emissions reduction, and decreasing landfill space, along with the economic benefits associated with saving the costs of purchasing and transporting new aggregate and asphalt binder for asphalt concrete mixture production. This study aims to investigate the influence of aged asphalt binder from reclaimed asphalt pavement on the virgin asphalt binder’s rheological properties. Therefore, different dosages of RAP binder (20%, 30%, and 40% by weight of the total mix) were blended with neat asphalt binder (40-50), penetration grade (P40), and SBS polymer asphalt (SBS-PMA) binder. Using both traditional and Superpave performance testing methods, the effects of RAP on the blend's consistency, viscosity, softening, elastic recovery, rutting (permanent deformation), fatigue cracking, and low temperature cracking were evaluated. The results revealed that the RAP binder decreased the penetration value of both neat and SBS-PMA binders. The neat asphalt binder’s viscosity and softening point increased with the increase in RAP content, whereas they decreased for SBS-PMA. The RAP binder decreases the SBS-PMA elastic recovery. where the neat asphalt experienced a little improvement in elastic recovery when blended with the RAP binder. The Superpave test results revealed that the RAP binder deteriorates the performance of the SBS-PMA binder at high, intermediate, and low testing temperatures. With the addition of 20%, 30%, and 40% RAP, the high-temperature PG grade of SBS-PMA blends decreased by 0.64%, 0.95%, and 1.10%, respectively, while the low-temperature PG grade increased by 23%, 31%, and 32%, respectively. In contrast, the RAP improves the neat asphalt blend's high-temperature performance grade and deteriorates intermediate and low-temperature performance grades. The addition of 20%, 30%, and 40% RAP increased the neat asphalt blends' high-temperature properties by 1.5%, 3.3%, and 4.5%, respectively. whereas the neat asphalt low-temperature PG grade increased by 5%, 11%, and 15% with the addition of 20%, 30%, and 40% RAP, respectively. In summary, the performance of virgin and RAP binder blends depends on the individual characteristics of the blended asphalt binders

Oxidative aging mechanism of asphalt binder using experiment-derived average molecular model and ReaxFF molecular dynamics simulation

Oxidative aging in asphalt binders has significant negative impacts on asphalt pavement performance. This study investigated oxidative aging of virgin asphalt binder based on average molecular model through Reactive Force Field (ReaxFF) molecular dynamics simulation, which allows for continuous bond breakage and formation. First, experimental characterizations were used to identify the average molecular model of virgin asphalt. Subsequently, using this model, individual and bulk asphalt molecules were subjected to oxidative aging simulations through ReaxFF molecular dynamics. Moreover, the simulated results were validated by structural parameters and physical properties, including carbonyl index, sulfoxide index, density, glass transition temperature and shear viscosity. Results showed that the proposed average molecular model could characterize the structural changes and physical properties of asphalt binders well. The number and specific locations of sulfoxide groups and ketone groups in each SARA fraction were identified. Sulfoxide groups formed earlier than ketone groups. Oxidative aging reaction can be accelerated by increasing the temperature. Temperature had greater influence on the generation of ketone groups than sulfoxide groups. Initial hydroxyl groups on aromatic rings would be oxidized to ketone groups first, followed by hydroxyl groups on benzyl carbons. Not all benzyl carbons were susceptible to oxidation, and some may not be oxidized to ketone groups. Hydroxyl group was found to be the intermediate oxidation product before the formation of ketone group, and it can be used to establish the short-term aged asphalt model.

Application of bio-resin in road materials: Rheological and chemical properties of asphalt binder modified by lignin-phenolic resin

The development of new sustainable green road materials with bio-resin is a hot topic in pavement engineering. To improve the efficiency of lignin as a sustainable pavement material, an asphalt binder modified by lignin-based resin was prepared, and its properties were evaluated. Firstly, lignin was extracted from biomass (corn straw) by thermochemical method to prepare lignin-based phenol formaldehyde (LPF) resin. After that, LPF resin-modified asphalt and phenol formaldehyde (PF) resin-modified asphalt were prepared. Then the effects of LPF resin and PF resin on asphalt properties were evaluated by chemical analysis and rheological performance tests. The results showed that lignin was involved in resin synthesis, LPF resin with PF resin had similar thermogravimetric curves, and the thermal stability of LPF resin was slightly lower than PF resin. Both LPF resin and PF resin can increase the proportion of large-size molecules and elastic components of asphalt binder and enhance its high-temperature deformation recovery ability. Moreover, the fatigue performance and aging resistance of the binder were also enhanced by the addition of LPF resin and PF resin. Although the addition of LPF resin and PF resin will increase the G-R parameters of virgin asphalt binder, it can reduce the effect of aging on the G-R parameters of asphalt binder. It seems that LPF resin and PF resin can improve the cracking resistance of asphalt binders.

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.

Effects of recycling agents and methods on the fracture and moisture resistance of asphalt mixtures with high RAP contents

The design guidelines for recycled asphalt mixtures recommend rejuvenating the oxidized binder by adding recycling agents, which are viscosity and, consequently, temperature-reducing additives. As it is a component of recent use in pavement and its variety, there has yet to be a consensus on the determination of the recycling agent content or the ideal moment of its addition in the recycled asphalt mixture production process. This study aimed to analyze the fracture and moisture performance of asphalt mixtures with the addition of high contents of RAP (25%, 50%, 75%, and 100%) and two recycling agents (ADCAP WM and residual engine oil) in stages distinct from the production of recycled asphalt mixture (directly to the RAP and directly to the virgin asphalt binder). The recycling agents were added at 12%, 15%, and 18% residual engine oil by mass of RAP and 2%, 2.5%, and 3% of ADCAP WM by the total mass of asphalt binder. The asphalt mixtures were submitted to mechanical tests of tensile strength, resilient modulus, ice and thaw cycles, bending fracture, and fatigue life. The results showed that adding residual engine oil in the asphalt binder enables using up to 75% of RAP. In the case of ADCAP WM additions, identical additions of RAP can be performed. Mixtures with ADCAP WM showed higher consumption of fracture energy, while blends with residual engine oil showed a lower slope of the post-peak curve. Conditioning by the freeze–thaw (F-T) cycle method increased the susceptibility of mixtures to the deleterious effect of water. Statistical analyzes showed that the parameters RAP content, recycling agent, and time of addition of the recycling agent presented adequate significance for the analyzed tests. The maximum RAP content to be applied should be 75%, and adding ADCAP WM directly to the binder showed slightly better results than the other combination.

Sustainable recycling of polyethylene waste through utilization in asphalt paving applications

One the enormous amount of waste polyethylene (PE) materials amassing in Iraq is posing an expensive landfill and disposal issue. The current study examines the potential for employing PE as a partial replacement for environmentally friendly pavement construction. Different amounts of PE were used to partially replace asphalt cement (3 %, 6 %, 9 %, and 12 % by weight). The PE-substituted asphalt (PESA) binders were subjected to the rheological and compatibility properties. Additionally, two asphalt concrete (AC) mixtures-one control and one PEAC-were created for the mechanical and durability experiments. Among the parameters assessed during the tests are the following: adhesion to a variety of substrates and substrate surfaces; elongation at room temperature (aging index); flexibility at elevated temperatures (cracking index); temperature susceptibility; compatibility; and the extensional viscosity of the PESA binder as well as the extensional viscosity of the PESA-mixture (PESAM). Furthermore, the mechanical and durability properties of AC and PEAC mixes were examined using the Marshall stability, Marshall quotient, static indirect tensile strength at 25 and 60°C, tensile strength ratio, and resilient modulus 25°C tests. Results show that PESA binder outperforms virgin asphalt binder in terms of cracking and temperature resistance. PEAC mixture exhibits higher stability, indirect tensile strength, moisture resistance and resilient modulus than AC mixture. According to standard and durability testing, replacing virgin binder with six percent PE can be recyclable and suitable for use as sustainable material for paving applications.

Study on the mixing process improvement for hot recycled asphalt mixture

Existing studies have shown that the mixing process of hot recycled asphalt mixture has a considerable effect on its performance. The conventional mixing process applied widely in pavement industry, mixed the RAP and virgin aggregate first. Then asphalt binder was added for the second mixing. This conventional mixing process, however, ignored the asphalt-adsorbing capacity of different aggregates, may resulting in the heterogeneity of recycled asphalt mixture after mixing. Adjusting the mixing sequence of RAP, virgin asphalt binders and aggregate is confirmed as an effective way to solve the above-mentioned issue. However, the change in the demand for virgin asphalt binders for each mixing step, which is raised from aggregate gradation and different RAP content, is not taken into consideration in this improved method. In view of this weakness, this study proposed an improved mixing technique for hot recycled asphalt mixture, which comprehensively considered the mixing sequence of materials and determined the amount of asphalt binders added for different RAP content based on the specific surface area of aggregates. And the prediction formula for the amount of virgin asphalt added each step is further proposed from the perspective of aggregate specific surface area. Several laboratory experiments were conducted to verify the feasibility of this improved technique. The results indicated that, the improved mixing technique could contribute to enhancing the water stability, low temperature cracking resistance and fatigue performance of hot recycled asphalt mixtures. And the higher the content of the RAP used in recycled mixture, the stronger the improvement of the improved mixing process.

Experimental investigation on the performance of the asphalt mixture with ceramic fiber

Ceramic fiber (CF) as a kind of industrial waste is widely used for the sake of waste utilization and environmental protection. In this study, three kinds of industrial waste ceramic fibers, CF-A (NC1260 spinning CF), CF-B (NC1260 blowing CF), and CF-C (NC1430 spinning CF), were used to develop a ceramic fiber modified asphalt mixture (CFMAM) to meet the increasing demand for asphalt pavement construction. Firstly, the optimum asphalt content of the CFMAM was determined by the mix design with the 0.3%wt fiber content. Secondly, the high-temperature stability and low-temperature cracking resistance of CFMAM were evaluated by rutting test, beam bending test and splitting test, respectively. The results showed that the CF-A and CF-C had the same positive influences on the mechanical properties and pavement performance of asphalt mixture, while the CF-B exhibited fewer positive influences. Then, the moisture susceptibility performance was tested by immersed Marshall test and freeze-thaw splitting test. The CFMAM with CF-A showed better properties than that of CF-B, CF-C, and virgin asphalt binder. Finally, the scanning electron microscopy (SEM) experiment was conducted to analyze the adsorption effect of fiber on asphalt mortar and the reinforcement effect on the mixture. It was observed that the fiber and asphalt had good wettability and dispersibility in the mixture.

Effect of aging, testing temperature and relative humidity on adhesion between asphalt binder and mineral aggregate

The adhesion between asphalt binder and mineral aggregate directly determines the performance of asphalt pavement, which could be effected significantly affected by light, oxygen, water and other natural conditions. In order to investigate the effect of different environmental conditions on the adhesion between asphalt binder and mineral aggregate, virgin asphalt binder with 70 (0.1 mm) penetration and SBS modified asphalt before and after aging were used as test samples in this study. The effect of aging, testing temperature and relative humidity on adhesion between asphalt binder and mineral aggregate was quantitatively analyzed by using the surface energy theory. The results show that aging reduced the content of resin, increase the content of asphaltene, which resulted in the deterioration of adhesion performance of asphalt binder. The anti-aging performance of SBS modified asphalt was better than virgin asphalt binder in terms of adhesion. The work of adhesion between asphalt binder and mineral aggregate increased when the testing temperature of asphalt binder increased from 0 °C to 80 °C. The work of adhesion between virgin asphalt binder and material aggregate increased much higher than SBS modified asphalt. Asphalt binder was not sensitive to the change of relative humidity, but the total amount of surface energy parameters of the mineral aggregate decreases linearly with the relative humidity increasing. The work of adhesion between asphalt binder and granite aggregate was more likely to be affected by external gaseous water molecules. In order to simulate the real hydrodynamic pressure, the pull-off test was improved by adding ultrasonic wave. The ultrasonic tests' results show that the water invaded the interface between asphalt binder and material aggregate, accelerated the adhesion failure. A strong linear correlation exists between the work of adhesion and the ultrasonic pull-off strength.

Study of the inter-diffusion characteristics and cracking resistance of virgin-aged asphalt binders using molecular dynamics simulation

• Inter-diffusion behavior between virgin and aged asphalt binders were investigated. • The degree of blending between virgin and aged asphalt binders were determined at the molecular level. • The cracking patterns of partial blending and total blending were distinguished. • The relationship between degree of blending and cracking resistance of blended asphalt were explored. To investigate the inter-diffusion characteristics and cracking resistance of blended asphalt binders, the virgin-aged asphalt models were developed through the molecular dynamics (MD) simulation. Based on the mass density profiles of virgin and aged asphalt binders, the effect of temperature on the inter-diffusion coefficients was analyzed. According to the spatial distribution of atoms, different blending states including partial blending and total blending were distinguished. The cracking resistance of blended asphalt binders was characterized by the fracture energy obtained from the stress-displacement responses. Relationship between degree of blending and cracking resistance was explored. Results show that high temperatures can increase the inter-diffusion coefficients of virgin and aged asphalt binders by enhancing the intramolecular potential energy and Van der Waals (VdW) interaction energy. Compared to aged asphalt binder, the virgin asphalt binder may be more susceptible to temperature. Under tensile loading, the crack always initiates in the blending zone of partially blended asphalt binders. However, for the totally blended asphalt binder, the crack is more likely to occur at localized defect locations which is randomly distributed. The ability of blended asphalt binder to withstand deformations becomes better, but the maximum tensile strength decreases a lot as the temperature increases. There is a positive correlation between the degree of blending and fracture energy of blended asphalt binders, indicating that the asphalt binder with a higher degree of blending has better cracking resistance. The results of MD simulations can help determine how much aged binder can be mobilized to blend with virgin binder and help select appropriate virgin binders or other additives that can improve the blending between virgin and aged asphalt.

Study on the blending behavior of asphalt binder in mixing process of hot recycling

The blending behavior of aged and virgin asphalt binder is one of the most critical problems in the mixing process of hot recycling. To accurately measure the participation degree of aged asphalt and optimize the mixing process of hot recycling, a series of laboratory tests were designed by using magnetite aggregate and thin-layer chromatography with flame ionization detection (TLC-FID) for the first time. In this study, 24 different lab-mixing conditions were deliberately adopted to investigate the impact on the DoB of aged and virgin asphalt binders, including mixing amount of RAP, mixing amount of rejuvenating agent, mixing time, mixing temperature, mixing orders and the thickness of asphalt film. The results indicated that the aged and virgin asphalt cannot be completely blended in the mixing process and DoB is only about 40–60 % in general. The DoB decreases with the increase of asphalt film thickness and it decreases by 30 % when asphalt film thickness is 9 µm. DOB increased with the content of RAP and rejuvenating agent up to 70 % which same as mixing sequence. Although the mixing time and temperature can promote DOB, the mixing time and temperature should be controlled within 240 s and 170 °C, otherwise the accuracy of DOB will be affected.

Chemical and thermodynamic properties of palm oil-based materials and their impact on recycled binder blends

• We characterised chemical and thermodynamic properties of palm oil-based materials. • We assessed the impact of adding these agents to binder blends of an HMA with high RAP. • Surface free energy was used to assess the adhesion quality and durability of the bonds between aggregates and recycled binder blends with these agents. • Key chemical compounds present in the palm oil materials contributed to the rejuvenation effectiveness. • Palm oil-based materials are promising candidates to be used as rejuvenators in HMA with high RAP. Rejuvenators are agents added during the production of hot mix asphalts with high contents of reclaimed asphalt pavement (RAP) to restore some properties of the aged RAP binder. These materials can be obtained from numerous sources; hence, their chemical composition and physical properties vary greatly, which can have an impact on the final mixtures’ properties. This work assesses key chemical properties of crude palm oil and two of its solid by-products to understand their rejuvenation effect on a blend of a virgin and an aged RAP asphalt binder. The evaluation included thermogravimetry analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and chromatography analysis. Besides, surface free energy measurements (SFE) on the recycled binder blends (i.e., virgin asphalt binder, RAP asphalt binder and rejuvenator) and of two aggregate sources were used to evaluate the impact of the palm oils in the adhesive bonds’ quality and moisture sensitivity of the recycled binder blends-aggregates systems. Results indicate that the palm oil materials have good thermal stability and contain several large molecular size (LMS) compounds that contribute to the rejuvenation effect. Besides, recycled binder blends produced with the palm oil materials developed strong adhesive bonds in dry and wet conditions. Overall, results highlight the potential of palm oil and its solid by-products as rejuvenators for high RAP content asphalt mixtures.

Life cycle assessment of eco-friendly asphalt pavement involving multi-recycled materials: A comparative study

In this research, a comparative Life Cycle Assessment (LCA) is conducted to evaluate the environmental potential of utilizing multi recycled materials in asphalt pavement construction. These Materials are Reclaimed Asphalt Pavement (RAP), Off-spec Fly Ash (OFA), and a Food Waste Bio-oil (FWBO). A comparative analysis is performed on producing one ton of asphalt mixture considering multiple scenarios, which stem from virgin materials extraction, recycled materials production, transportation, and asphalt mix production. The study analyzed six percentages of RAP replacement to aggregate and asphalt binder , 0%, 15%, 30%, 50%, 80%, and 100% RAP. Moreover, two proposed products substituted 11% virgin asphalt binder by weight in the different mixtures. The first product is the FWBO, which is utilized alone as an asphalt binder rejuvenator with the highest two RAP rate scenarios: 80 and 100%. The second product is a blend of the OFA with the FWBO with a 2:1 ratio, which is evaluated with all the investigated scenarios. After assessing the baseline scenario, two alternative scenarios are investigated. The first alternative is utilizing natural gas to replace the commonly used Heavy Fuel Oil (HFO) in the asphalt mix production process. The second alternative scenario is changing the FWBO extraction technique from Soxhlet to Ultrasonic Assisted-oil Extraction (UAE). Open-LCA software is used for modeling all the investigated scenarios in the light of TRACI v.2.1 impact assessment methodology in this case study. The results show a reduction in environmental impacts with RAP utilization and the new eco-friendly products. Shifting asphalt mix plant fuel to natural gas instead of HFO offers considerable potential environmental benefits. Adopting the UAE as FWBO rejuvenator extraction method showed less energy and solvent consumption than the Soxhlet extraction, resulting in less environmental impacts.

Research on the Ability of Bio-rejuvenators to Disaggregate Oxidized Asphaltene Nanoclusters in Aged Asphalt.

A real rejuvenator must have the ability to disaggregate oxidized asphaltene nanoclusters. However, few studies pay attention to the topic, and there is a lack of comparison of the disaggregation ability of different rejuvenators. Thus, the disaggregation ability and regeneration mechanism of three bio-rejuvenators (waste cooking oil (WCO), waste wood oil (WWO), and straw liquefied residue oil (SLRO)) on oxidized asphaltene nanoclusters were studied in this paper. Laboratory tests and molecular dynamics (MD) simulation were used to compare the effectiveness of the three bio-rejuvenators and reveal its corresponding mechanism. It is found that these bio-rejuvenators have a softening effect on aged asphalt binder, but not all of them can disaggregate oxidized asphaltene nanoclusters. The introduction of WWO and WCO can effectively disturb the nanoclusters caused by the increase of polar functional groups during the oxidation process. The effect of WWO is more significant, but neither of them can restore the asphaltene dispersion to the virgin asphalt binder. SLRO has an adverse effect on the disaggregation of oxidized asphaltene nanoclusters. WCO, WWO, and SLRO showed different disaggregation mechanisms, including ″pull-out, intercalation, and compression″, respectively. WCO and WWO can increase the activation energy reduced by aging in a short aging time, and SLRO makes the activation energy lower. Such findings can help enterprises screen more reasonable rejuvenators to facilitate the recycling of reclaimed asphalt pavement (RAP) materials and promote the sustainable development of the construction industry.