In this modern age, manufacturers and investors are always looking for a better and proper solution to improve their investment. So, is bio oil rejuvenate asphalt a proper solution? One of the vegetable-based oils with the greatest potential for use in the revitalization of deteriorated asphalt binders is bio-oil made from soybeans. Soybean oil was used in this laboratory study to characterize and measure the diffusion and rheological characteristics of the bio-oil-rejuvenated aged asphalt binder (BRAA). In the study, an element analyzer (EA), gel permeation chromatography (GPC), and a Fourier infrared (FTIR) spectrometer were each used to compare the chemical structure of the soybean oil. For the purpose of computing the diffusion parameters using molecular dynamic simulations, BRAA molecular models were constructed based on the chemical composition of the bio-oil. The rheological characteristics of the aged asphalt binder rejuvenated with 0%, 1%, 2%, 3%, 4%, and 5% soybean oil, respectively, were measured and quantified using a dynamic shear rheometer (DSR) test device. The results of the laboratory tests show that bio-oil may be able to enhance the phase angle and diffusion coefficients of the aged asphalt binder. Similarly, the BRAA's low-temperature characteristics are improved by the corresponding decrease in the complex shear modulus. 
The diffusion coefficients of the BRAA components are 1.52 108, 1.33 108, 3.47 108, 4.82 108, and 3.92 108 for a bio-oil dosage of 4.0%. Similar to this, the corresponding improvement in BRAA's low-temperature characteristics is suggested by a decrease in the complex shear modulus from 1.27 107 Pa to 4.0 105 Pa. Overall, the study adds to the body of knowledge regarding the potential application of bio-oil derived from soybeans to the rejuvenation of aging asphalt binders. The A-70# petroleum asphalt binder was subjected to short-term aging using the rolling film oven test in accordance with the specifications of AASHTO T 240 13-5. A glass bottle with a diameter of 64 mm and a height of 140 mm was filled with a 350 g sample of the asphalt binder. The glass bottle was then placed inside a rotary oven set to 163 °C and rotated for 85 minutes at a speed of 15 rpm. 4000 mL/min of hot air was continuously administered. In order to simulate long-term aging, the pressure-aging vessel (PAV) was used in accordance with the ASTM D454 13-6, ASTM D6521 13-7, and ASTM D572 13-8 standard test methods. The sample plates containing 50 0.5 g of the asphalt binder from the rolling thin film oven test (RTFOT) were put in the vessel to age for 20 hours at a specified pressure of 2070 kPa and temperature of 100 °C. Around the world, asphalt pavements make up more than 80% of all highways. 
Good skidding and wearing resistance, driving comfortability, low noise, ease of maintenance, and the subgrade's adaptability to deformation are some of the distinctive qualities and benefits that contribute to the widespread use of asphalt pavements. However, due to exposure to shifting traffic loads and changing environmental conditions while in use, the asphalt binder in asphalt pavements ages over time, which is an undesirable phenomenon. The physical and rheological properties of aged asphalt binders have been extensively studied. Although it is thought that various asphalt binders have different anti-aging qualities, the aging process is essentially the same. For instance, the penetration, penetration index, softening point, ductility, and other properties of the asphalt binder change as its aging time increases. Similar to viscosity, complex shear modulus (G*), creep stiffness (S), phase angle () and unrecoverable creep compliance (Jnr) properties of the asphalt binder will typically increase as a function of aging time. The end result of this is that it is demonstrated how aging causes an unfavorable rise in the stiffness and embrittlement of the asphalt binder, which inevitably worsens the performance of the asphalt pavement and manifests as distresses like cracking, moisture damage, aggregate raveling, etc. Therefore, to maintain their properties and performance characteristics over the course of their service lives, asphalt pavements would typically need resurfacing, overlaying, maintenance, and/or rehabilitation. Rejuvenators are frequently used for rejuvenating, restoring, and recycling the aged asphalt binder, including reclaimed asphalt pavement (RAP) and sealing materials, in the case of aged asphalt binders and as part of the pavement maintenance/rehabilitation scheme. 
Modern Oil Rejuvenate
A rejuvenated asphalt binder made from leftover soybean oil may be superior to conventional mineral oil rejuvenators in quality and this rejuvenate is wanted in the modern age. According to information from reputable research organizations, 6030.8 million tons of soybeans were produced worldwide in 2020. The growth statistics show that there are many sources of soybean oil. As a result, if soybean oil waste can be encouraged for use in recycling applications, it can serve as a viable substitute and be used to significantly lower the cost of technologies for regenerating asphalt pavement. Rejuvenators, which are added to oxidized asphalt binders, are made from aromatic hydrocarbon oils, primarily from petroleum. However, this kind of oil easily volatilizes during the mixing and construction processes because it has a high concentration of cancer-causing polycyclic aromatic hydrocarbons (PAHs). It's possible that base oils will no longer be used as a rejuvenator of conventional PAHs as a result of growing environmental and public health concerns. Renewable resources that are good for the environment could eventually replace conventional petrochemical products. Low volatility and low toxicity are advantages of using bio-oil as a bio-binder, and it has the potential to be developed into rejuvenators for aging asphalt binders. A review of biochar-based catalysts for chemical synthesis, the production of biofuels, and pollution control was developed by Xiong et al. 
The chemical makeup of bio-oil produced by a quick pyrolysis, cooling, and condensation process is similar to that of petroleum asphalt binders and contains more maltene. In order to demonstrate that bio-oil can successfully soften old asphalt, Chen et al. selected three samples of vegetable oil that shared the same physical characteristics as their virgin binders. Based on a lab simulation, the amount of asphaltenes in aged asphalt was reduced after adding bio-oil. Since bio-oil softens aging asphalt binder, it satisfies the fundamental criteria for an asphalt binder rejuvenator. Raouf investigated the physical and chemical characteristics of three various bio-oils used as binders for bio-asphalt, namely oak, switchgrass, and corn straw. It was discovered that the viscosity, temperature, and shear rate logarithmic linear relationships of the oak-based bio asphalt binder were comparable to those of the petroleum asphalt binder. The bio-binder, however, was discovered to be more temperature-sensitive than the conventional petroleum asphalt binder. The characteristics of a bio-binder produced from swine manure were researched by Fini et al. The findings indicate that while adding a bio-binder to an asphalt binder may enhance its low-temperature properties and workability, it has the opposite effect on its high-temperature properties. With the addition of 10% bio-binder, Yut et al. discovered that a bio-binder made of swine manure may be used as an asphalt binder modifier to lower the cracking temperature of PG 64-22 asphalt binders by approximately 4.2–4.6 °C (by weight of the asphalt binder). In their study, Zofka and Yut extracted bio-oils from used coffee grounds and found that neither the bio-oils nor the base asphalt binder's antioxidant properties changed how sensitive it was to temperature. However, Jalkh et al. 
found that mixing the extracted bio-oil with an asphalt binder restores the asphalt binder's linear behavior, accelerates the blend matrix's softening process, and reduces the blend matrix's susceptibility to long-term damage under low stress levels. Wen et al. on the other hand found that the addition of used cooking oil reduces resistance to rutting and fatigue. Using a dynamic shear rheometer (DSR) test apparatus, Chen examined the effects of used cooking oil and cotton seed oil on the high-temperature performance of revitalized asphalt binders. Similar to this, Tang compared the oxidative stability of three bio-oils made from corn stover, oak wood, and switch grass, as well as their capacity to restore deteriorated asphalt binders. According to the study's findings, bio-oils may be able to reduce oxidative aging and revitalize deteriorated asphalt binder. The use of rejuvenators or modifiers made from soybean oil, referred to herein as SBO, has also been investigated in some studies, as reported in the literature. When soy fatty acids (SFAs) were added in small proportions to asphalt binders during high-temperature rheological tests, Seidel discovered that the asphalt binders became less rigid and easier to work with. Elkashef et al. used the DSR, BBR, FTIR, and GC-MS tests to investigate the physical and chemical characteristics of an old asphalt binder that had been revitalized with SBO. According to the test results, an asphalt binder's low-temperature and fatigue performance can be significantly enhanced by the SBO rejuvenator, including a decreased sensitivity to temperature. 
Research has been devoted to understanding the interaction between a rejuvenator and an aged asphalt binder in order to define the interfacial reaction between the two. Regarding rejuvenation mechanisms and the use of bio-oil rejuvenators like SBO, the diffusion mechanism between the rejuvenator and the aged asphalt binder is thought to be one of the most technical concerns. Karlsson used the FTIR-ATR tests to analyze and successfully model the internal diffusion behavior of microencapsulated rejuvenators in old asphalt binders. Molecular dynamic (MD) simulations were used by Ding to investigate the diffusion between fresh and used asphalt binders. Bio-oil with aromatic chemical compounds and compounds containing oxygen was put to the test by Girimath et al., who discovered that it could enhance the properties of asphalt binders. Using gel permeation chromatography (GPC), Yang et al. examined bio-binders and discovered that the elements of bio-oil are comparable to those of asphalt binders. The GPC (gel permeation chromatography) method was used to successfully validate the MD simulation results, and the resulting data shows that the diffusion of large molecules in the asphalt binder is a crucial component of the diffusion of asphalt binders. The diffusion behavior of rejuvenators and asphalt binders was studied using MD simulations and the diffusion coefficient concept by Xiao, Zadshir, and Xu. To validate the MD simulation results, laboratory tests (such as the DSR, FTIR, etc.) were also carried out. 
According to the study's findings, both laboratory testing and MD simulations were effective at simulating and quantifying rejuvenator diffusion behavior as well as its effects on the molecular structure and thermodynamic characteristics of the asphalt binders in RAP materials. In this study, the molecular structure of bio-oil was determined using an element analyzer (EA), gel permeation chromatography (GPC), and Fourier infrared spectrometer (FTIR) in order to increase the utilization ratio of RAP and comprehend the diffusion and rheological properties of bio-oil-rejuvenated aged asphalt (BRAA). Building molecular models of BRAA and using MD simulations to establish the diffusion parameters. A DSR test device was used in the study to measure and quantify the rheological characteristics of BRAA. In this study, molecular dynamic simulations and lab tests were used to examine the diffusion and rheological characteristics of soybean bio-oil, which was used to revive aged asphalt binder (BRAA). The following conclusions and suggestions were reached based on the study's findings: Compared to the base asphalt binder, BRAA showed lower VOC emissions and greater environmental friendliness; The bio-oil, which was derived from soybeans, was found to have a molecular weight of 280–282 g/mol and could be represented by either the chemical formula C18H32O2 or C18H34O2. The bio-oil showed potential to improve diffusion and encourage the regeneration of the worn-out asphalt binder for the materials evaluated; 
The bio-oil that was under consideration, which was made from soybeans, showed signs of solubility in the aged asphalt binder and had the potential to enhance its viscoelastic characteristics, facilitate diffusion, and encourage regeneration. The diffusion coefficients of the BRAA components were 1.52 108, 1.33 108, 3.47 108, 4.82 108, and 3.92 108 for a bio-oil dosage of 4.0%; According to the BRAA regeneration mechanism, the chemical diffusion of the bio-oil improved molecular movement within the old asphalt binder, including supplanting the aromatics and saturates components to form a new stable asphalt binder matrix system. Overall, the research shows that bio-oil made from soybeans is a promising regeneration agent for revitalizing worn-out asphalt binders, with 4.0 weight percent being the possible ideal dosage. While the study's findings are tenable, further investigation into various base asphalt binders, as well as other laboratory tests like cracking and moisture evaluation, as well as field validation, are called for in future studies. Future research should investigate the use of FTIR indices as a quantitative measure of absorption and an indicator of the rejuvenation effects to further support the findings/results reported here. However, the study adds to and enriches the existing/current literature by providing a datum reference for using soybean-derived oil as a potential regenerant agent to renew deteriorated asphalt binders, which advances the state-of-the-art.