Viscosity Of Asphalt Research Articles

Nanomaterials for Modified Asphalt and Their Effects on Viscosity Characteristics: A Comprehensive Review.

The application of nanomaterials as modifiers in the field of asphalt is increasingly widespread, and this paper aims to systematically review research on the impact of nanomaterials on asphalt viscosity. The results find that nanomaterials tend to increase asphalt's viscosity, enhancing its resistance to high-temperature rutting and low-temperature cracking. Zero-dimension nanomaterials firmly adhere to the asphalt surface, augmenting non-bonding interactions through van der Waals forces and engaging in chemical reactions to form a spatial network structure. One-dimensional nanomaterials interact with non-polar asphalt molecules, forming bonds between tube walls, thereby enhancing adhesion, stability, and resistance to cyclic loading. Meanwhile, these bundled materials act as reinforcement to transmit stress, preventing or delaying crack propagation. Two-dimensional nanomaterials, such as graphene and graphene oxide, participate in chemical interactions, forming hydrogen bonds and aromatic deposits with asphalt molecules, affecting asphalt's surface roughness and aggregate movement, which exhibit strong adsorption capacity and increase the viscosity of asphalt. Polymers reduce thermal movement and compact asphalt structures, absorbing light components and promoting the formation of a cross-linked network, thus enhancing high-temperature deformation resistance. However, challenges such as poor compatibility and dispersion, high production costs, and environmental and health concerns currently hinder the widespread application of nanomaterial-modified asphalt. Consequently, addressing these issues through comprehensive economic and ecological evaluations is crucial before large-scale practical implementation.

Viscosity of Asphalt Binder through Equilibrium and Non-Equilibrium Molecular Dynamics Simulations

Viscosity is a curial indicator for evaluating asphalt performance, representing its ability to resist deformation under external forces. The Green–Kubo integral in equilibrium molecular dynamics simulations and the Muller-Plathe algorithm in reverse non-equilibrium molecular dynamics simulations were used to calculate the asphalt viscosity. Meanwhile, the key parameters of both methods were rationalized. The results show that in equilibrium calculations, using a 1/t weighting for the viscosity integral curve results in a well-fitted curve that closely matches the original data. The isotropy of the asphalt model improves for atomic counts exceeding 260,000, rendering viscosity calculations more reasonable. When the viscosity did not converge, it increased linearly with the number of atoms. In non-equilibrium calculations, the number of region divisions had almost no effect on the viscosity value. A momentum exchange period of 20 timesteps exhibits a favorable linear trend in velocity gradients, and an ideal momentum exchange period was found to be between 10 and 20 timesteps. As the model size increased, the linear relationship with the shear rate became more pronounced, and the isotropy of the asphalt system improved. Using an orthogonal simulation box with a side length of 75 Å effectively meets the computational requirements.

Utilization of molybdenum tailings as an alternative mineral filler in asphalt mastic: Rheological performance and environmental aspects

The generation and accumulation of molybdenum tailings (MT) have led to various environmental problems. This paper explores the feasibility of MT as a filler instead of limestone filler (LF) from the perspective of asphalt mastic. The physical and chemical properties of LF and MT are analyzed using Laser particle size, X-ray diffraction, X-ray fluorescence, and scanning electron microscopy tests. Four filler/asphalt weight (F/A) ratios (0.3, 0.6, 0.9, 1.2) are selected to prepare asphalt mastic. The rotational viscosity test, dynamic shear rheometer test as well as bending beam rheometer test, were conducted to study the rheological properties of mastics. Results show that physical interactions dominate the interaction between MT and asphalt. MT particles have large particle size, rough surface and tight internal structure. MT is conducive to bonding with asphalt. MT increased the viscosity, complex modulus, rutting factor and creep stiffness of asphalt. MT reduced the viscosity temperature sensitivity index, phase angle and creep rate. From the perspective of rheological properties, MT has great potential as filler to replace LF in asphalt mixture and reduce environmental pollution.

Laboratory aging method for simulating the extracted aged asphalt from reclaimed asphalt pavement

This study compared the performance of extracted asphalt and laboratory aged asphalt. The five-year service asphalt mixtures were used for extraction in this study. The laboratory aged asphalt experienced the Rolling thin film oven (RTFO) aging the Pressure aging vessel (PAV) aging with variable duration (5, 10, 15, 20, and 25 hours). By comparing the softening point, viscosity, and rheological properties of both, an aging simulation protocol was established. For laboratory aged asphalt binder, the softening point increases by 3.56 %, 5.68 %, 7.43 %, 8.16 %, and 8.74 % at PAV aging times of 5 h, 10 h, 15 h, 20 h, and 25 h, respectively. The rutting index and viscosity of the aged asphalt gradually increases with the PAV duration. There is a substantial increase in creep recovery rate and a significant decrease in non-recoverable creep compliance for aged asphalt. The rheological aging index demonstrates a linear increasing trend. The sulfoxide (SO) and aromatic (CO) aging indexes of the laboratory-simulated aged asphalt progressively rise with prolonged PAV aging time. The SO and CO aging indexes of the extracted asphalt consistent with RTFO aged asphalt experienced PAV aging 20 and 25 hours. The extracted asphalt can be simulated in the laboratory under standard RTFO conditions and a 22.26 hours PAV duration at a pressure of 2.1 MPa ± 0.1 MPa. This study introduces a methodology for simulating asphalt aging in an authentic service environment by adjusting the laboratory aging test conditions.

Investigation on rheological properties and aging mechanism of asphalt under multiple environmental conditions

Under climatic conditions such as high temperature plus ultraviolet radiation and water, the mechanical properties of asphalt pavement will be significantly attenuated. Present research mainly focused on thermal oxidation and ultraviolet radiation aging, and there were many controversies about the effect of water on the aging performance of asphalt. In addition, the relationship between the aging behavior of asphalt under complex environments and the standard PAV test needs to be further clarified. This research comprehensively evaluated the rheological properties, microscopy, and functional group of matrix asphalt, SBS, and high viscosity modified asphalt under different climatic conditions. Compared with thermal oxidation aging, daily exposure to UV radiation can increase the aging degree of matrix and modified asphalt by about 5 % and 1.5 %, respectively. Compared with thermal oxidation aging, the presence of water and the coupling effect of UV and water can reduce the aging degree of asphalt by 3.5 % and 2.6 %, respectively. After 5 days of thermal oxidation and UV coupling, the aging degree was close to or even greater than that of the PAV experiment. Asphalt aging caused an upward shift in the complex modulus master curve, and a downward shift in the phase angle master curve of matrix asphalt and high viscosity modified asphalt. Due to the synergistic effects of hardening and polymer degradation, the phase angle master curve of SBS modified asphalt showed an upward trend in the low frequency range. Under the influence of climatic conditions, the polymer of asphalt would degrade, the particle size of the polymer phase decreased, and the brightness of fluorescent image became darker. The rich polymer phase structure of high viscosity modified asphalt enabled it to maintain excellent mechanical properties even after long-term aging.

Influence of graphene on the composite modified asphalt based on viscoelastic and elastic properties

In order to explore high-viscosity, high-elasticity composite modified asphalt materials suitable for drainage pavements, different dosages of graphene-modified asphalt and graphene composite-modified asphalt were prepared. Elastic recovery efficiency and rotational viscosity as the main experimental indicators for modified asphalt are employed to determine the optimal dosage of graphene and help conduct a study on the viscoelastic properties, analyzing the fatigue performance of the modified asphalt through linear amplitude sweep (LAS). Based on molecular dynamics simulation (MD) to build an asphalt model, the study on viscoelastic properties uses calculated viscosity and the asphalt glass transition temperature range (Tg) obtained from simulation results as indicators to verify the optimal dosage of graphene. Scanning Electron Microscopy (SEM) is utilized to reveal the effects of different dosages of graphene modification. The research results indicate that the optimal dosages of graphene in graphene-modified asphalt and graphene composite-modified asphalt are 0.1 % and 0.2 %, respectively. At these concentrations, graphene significantly enhanced the elastic recovery properties of the matrix asphalt (113 % increase) and the composite-modified asphalt (28 % increase). In terms of rotational viscosity, the matrix asphalt saw a 54 % rise with the addition of graphene, while the composite-modified asphalt experienced a substantial 151 % increase. Notably, the incorporation of graphene also resulted in a rise in the glass transition temperature and a reduction in the length of the graphene-modified asphalt, signifying an improvement in its elastic properties. Furthermore, the calculated viscosity of the graphene-modified asphalt and composite-modified asphalt surged by 47.49 % and 64.01 %, respectively. Additionally, SEM results indicate that differences in the effects of graphene modification are primarily due to the dispersion and coating extent of graphene.

Interface Interaction of Waste Rubber–Asphalt System

Asphalt pavement construction is a large-volume project, with the ability to recycle the industrial waste and reduce carbon emissions. Rubber-modified asphalt is a carbon-neutralized asphalt-based material, facilitating the recycling of waste rubber materials and improving the road performance of the asphalt mixture. To evaluate the interface interaction of the rubber–asphalt system and its effect on the viscosity characteristics of rubber-modified asphalt, the contact properties of rubber particles in asphalt were analyzed on a microscopic level. Rubber swelling tests and solvent elution tests were conducted on the rubber–asphalt system under different preparation conditions. The swelling ratio, degradation ratio, and swelling–degradation ratio were proposed to evaluate the interface interaction. The results show that the interface interaction of the rubber–asphalt system can be divided into the following three stages: swelling, effective degradation, and over-degradation. The degree of swelling is mainly affected by the content and size of the rubber particles and it is physically condensed, while the degradation is mainly affected by the preparation temperature and preparation time. The effective interface interaction greatly affects the viscosity with the building of the stable three-dimensional network structure. The stronger the interface interaction, the greater the viscosity of the rubber-modified asphalt, except for the 25% content of rubber particles. The gel film will be generated on the surface of the rubber particles throughout the swelling and effective degradation, increasing the viscosity of the rubber-modified asphalt.

Effect of surfactant modified phosphogypsum whisker on service performance of asphalt based on multi-scale experiments

The development of modern chemical technology had inevitably produced massive phosphogypsum (PSP), the accumulation and storage of PSP had caused serious economic losses and environmental pollution. As the secondary refining product of PSP, the application of phosphogypsum whisker (PSW) to asphalt pavement not only effectively mitigated the adverse impact of PSP on the economy and environment, but also promoted the resourceful utilization of solid waste. However, since PSW was an inorganic material, it was difficult to fuse well with asphalt. Therefore, to enhance the compatibility of PSW with asphalt, this study investigated the modification process of PSW by using four surfactants to modify PSW with organic coating. The effect of surfactants on the surface activity of PSW was evaluated by relevant tests, and the surface enhancement modification mechanism and microstructure of surfactants on PSW were investigated, and then the effect of surfactant-modified PSW (MPSW) on the service performance of asphalt was evaluated. The results showed that the surfactant covered the surface of PSW by intermolecular forces and chemical bonding, which enhanced the surface activity of PSW. The compatibility of PSW with asphalt was enhanced by surfactant, and the MPSW 10599was just physically blended with virgin asphalt. Although the brittleness of virgin asphalt was enhanced to a certain degree by MPSW, the thermophysical properties of virgin asphalt at low temperature was significantly improved, and the incorporation of MPSW enhanced the thermal stability and flame retardancy of virgin asphalt. The incorporation of MPSW would slightly increase the viscosity of virgin asphalt, but the viscous activation energy was reduced and the temperature sensitivity was improved. Furthermore, the low temperature performance of virgin asphalt was improved to a certain degree with the incorporation of MPSW, while the improvement effect was not significant once the temperature was close to the glass transition temperature. Finally, combined with the relevant test results, the recommended dosage of MPSW in asphalt was 10% in this study, and the surface modification of PSW by surfactant was a multifunctional method of powder modification.

Research on Low-Cost High-Viscosity Asphalt and Its Performance for Porous Asphalt Pavement.

To develop a cost-effective, high-viscosity asphalt for porous asphalt pavement, we utilized SBS, tackifier, and solubilizer as the main raw materials, identified the optimal composition through an orthogonal experiment of three factors and three levels, and prepared a low-cost high-viscosity asphalt. We compared its conventional and rheological properties against those of rubber asphalt, SBS modified asphalt, and matrix asphalt, employing fluorescence microscopy and Fourier transform infrared spectroscopy for microstructural analysis. The results indicate that the optimal formula composition for high-viscosity asphalt was 4-5% styrene-butadiene-styrene (SBS) + 1-2% tackifier +0-3% solubilizer +0.15% stabilizer. The components evenly dispersed and the performances were enhanced with chemical and physical modification. Compared with SBS modified asphalt, rubber asphalt, and matrix asphalt, the softening point, 5 °C ductility, and 60 °C dynamic viscosity of high-viscosity asphalt were significantly improved, while the 175 °C Brookfield viscosity was equivalent to SBS modified asphalt. In particular, the 60 °C dynamic viscosity reaches 383,180 Pa·s. Rheological tests indicate that the high- and low-temperature grade of high-viscosity asphalt reaches 88-18 °C, and that high-viscosity asphalt has the best high-temperature resistance to permanent deformation and low-temperature resistance to cracking. It can save about 30% cost compared to commercially available high-viscosity asphalt, which is conducive to the promotion and application of porous asphalt pavement.

Effects and molecular mechanisms of jet ablation and fuel corrosion on separation failure of the asphalt-aggregate interface in airport asphalt pavements

To guide the improvement of asphalt pavement durability in airports, the effects and molecular mechanisms of jet ablation and fuel corrosion on separation failure of the asphalt-aggregate interface were investigated in this study using molecular dynamics simulations and density functional theory method. Firstly, tensile separation behaviors of the virgin, aged, and fuel-corroded asphalt-aggregate interfaces were simulated under different loading rates to evaluate their tensile strength and fatigue cracking resistance, and the experimental data were also used to verify the reliability of the simulation results. Subsequently, the molecular mechanisms of jet ablation and fuel corrosion on the separation failure of the asphalt-aggregate interface were analyzed by calculating the work of adhesion, work of cohesion, flowability parameters, and intermolecular binding energy. The results show that the aged specimen has higher ultimate tensile strength and fracture energy, but its flexibility and fatigue cracking resistance are significantly reduced. This is because the polar oxygen-containing groups generated during high-temperature aging enhance the intermolecular binding energy of the asphalt, but this also restricts the diffusion of asphalt molecules, resulting in greater frictional resistance and viscosity of asphalt during shear deformation, and thus loss of mobility and self-healing properties. On the contrary, since the light and medium oils soften and dilute the asphalt, and also weaken the intermolecular binding energy of asphalt, the fuel corrosion reduces the ultimate tensile strength and fracture energy of the asphalt-aggregate interface system, resulting in insufficient overall strength and load-bearing capacity.

Microscopic mechanism and effect analysis of polymer modifiers on embrittlement and viscosity behaviour of asphalt

To support the research and development of asphalt binder with low embrittlement point in cold areas, the microscopic mechanism and effect of polymer modifier on embrittlement and viscosity of asphalt were analysed by molecular dynamics method. The mixed molecular models of three polymer modified asphalt commonly used in cold areas and the interactive molecular models of each component of asphalt and modifier were established. The micromechanical properties of high-content polymer modified asphalt were studied by three important indices, namely brittleness point, shear viscosity and elastic modulus, and the interaction behaviour of each component of asphalt and modifier molecules was analysed by the layer model. The following conclusions were obtained: The brittleness point of modified asphalt can be decreased by increasing the polymer modifier content, with a notable reduction of 25.54 % observed when the content reaches 7.5 %. However, this is accompanied by a subsequent increase in shear viscosity at mixing temperatures, with the highest increase reaching 16.9 %. At low temperature environment, the diffusion rate of the modifier is closely related to its own type, temperature and the type of asphalt components, and in different modified asphalt, the law of the diffusion rate of each asphalt component is not completely consistent, so it is necessary to fully consider the influence of the proportion of asphalt components, and choose the modifier sensitive to the corresponding components. The above research results have an important guiding role in the scientific formulation of the design and test scheme of low-brittleness-point asphalt binder and the completion of the research and development of low-brittleness-point asphalt binder for cold areas.

Performance characterization and microscopic properties of asphalt modified with rapeseed heavy oil-activated waste rubber powder

To improve the waste rubber powder modified asphalt viscosity is high, poor storage stability, and other shortcomings, 40 mesh, 60 mesh, and 80 mesh are three kinds of mesh rubber powder using rapeseed heavy oil pre-swelling activation way to prepare modified asphalt, improve the waste rubber powder modified asphalt storage stability and reduce the viscosity. The optimum blending amount of rapeseed heavy oil-activated waste rubber powder was determined by setting three oil-rubber ratios, and the unactivated waste gum powder modified asphalt was set as a control group, and the physical, rheological, and microscopic properties of the asphalt were evaluated accordingly. The optimum preparation parameters under the premise of setting the total dosage of modifier as 20% were: the mass ratio of rubber powder to rapeseed oil was 2:1, and the mesh size of rubber powder was 80 mesh. Rapeseed heavy oil-activated waste rubber powder modified asphalt storage stability and low-temperature performance improved, viscosity decreased, but high-temperature performance decreased at the same time. Compared with the unactivated waste rubber powder modified asphalt, the softening point decreased by an average of 16%, the needle penetration increased by an average of 19%, the ductility increased by an average of 44%, the viscosity decreased by an average of 22%, and the softening point difference decreased by an average of 44%. In the high-temperature rheological performance test set temperature interval, the rutting coefficient G*/sinδ decline, creep stiffness Ѕ, and creep rate m have increased. Therefore, rapeseed heavy oil activation can effectively improve the overall stability of waste rubber powder-modified asphalt and can reduce the overall viscosity, which is conducive to the uniform dispersion of rubber powder in asphalt.

Investigated on hot mix epoxy resin used in steel bridge deck pavement affected by collaborative toughen

The hot-mix epoxy resin commonly used in the market has insufficient toughness, resulting in cracking of steel bridge deck pavement. To obtain the excellent toughness of hot mix epoxy resin, the collaborative toughen is put forward to overcome the shortcoming. In order to character epoxy resins and epoxy asphalts affected by toughening agent, standard test method of tensile properties for plastics is used. The synergistic toughening mechanism and lyotropy of 1# rubber additive and 2# rubber additive are approved by analyzing scanning electron microscope. Synchronous thermal analyzer is applied to study reactivity of epoxy resin. The viscosity, reactivity and rheological performance of epoxy asphalt, which affected by toughen agent, are investigated by Brinell rotary viscometer and Dynamic shear rheometer respectively. According to the results, the excellent epoxy resin is obtained, when the dosage of toughen agent is 15 %. The activation energy of epoxy resin before and after toughen are 48.6 KJ/mol and 42.4 KJ/mol, respectively. Besides the toughen agent can reduce the viscosity of epoxy asphalt. Finally, R1 and R2 can enhance the elastic of epoxy asphalt and reduce the glass transition temperature of epoxy asphalt. In summary, with R1 and R2 added, the toughen of epoxy resin improved obviously. The application of toughened epoxy resin to the pavement of orthotropic steel bridge deck will has a very broad prospect.

Microcosmic mechanism of asphalt-aggregate interface adhesion failure under freeze-thaw cycles based on molecular dynamics

ABSTRACT In order to investigate the micro-mechanisms of adhesive failure at the asphalt-aggregate interface under freeze-thaw cycling, this study presents a novel model for freeze-thaw cycling of asphalt mixtures constructed using molecular dynamics. The model is employed to explore the micro-mechanisms of adhesive failure between asphalt and aggregate surfaces under freeze-thaw cycling conditions. Utilising the four-component model of asphalt, asphalt molecules were constructed, with silicon dioxide and calcium carbonate chosen to represent acidic and alkaline aggregates, respectively. Subsequently, an asphalt-aggregate-water freeze-thaw cycling model was developed. Building upon this foundation, the variations in interface interactions between asphalt and the two types of minerals were analysed under the same freeze-thaw cycling conditions but differing freeze-thaw cycle counts. This analysis was conducted through the examination of Radial Distribution Function (RDF), water molecule coordination numbers, and hydrogen bond quantities at the interfaces between asphalt and the two mineral types. The research findings indicate that acidic aggregates exhibit a greater affinity for water molecules compared to alkaline aggregates. Hydrogen bond interactions exist between aggregates and water molecules, with the hydrogen bond energy being greater than the interactions between asphalt molecules and aggregate surfaces. The cohesive energy decreases with an increasing number of freeze-thaw cycles, leading to a gradual reduction in asphalt viscosity and facilitating the detachment of asphalt from the aggregate surface. Consequently, acidic aggregates tend to absorb water molecules more readily, and water can lower the viscosity of asphalt molecules, ultimately resulting in the macroscopic delamination of asphalt from the aggregate surface. These research outcomes provide valuable theoretical guidance for a deeper exploration of the adhesive failure mechanisms in asphalt-aggregate interactions.

Performance evaluation of asphalt binders incorporating surface-modified diatomite and bio-oil: A value-added utilization of natural resource

To study the effect of surface-modified diatomite (SMD) on bio-asphalt performance, the asphalt binders incorporating SMD and bio-oil (SMDB) was prepared with different dosages. The high-temperature characteristics of SMDB were assessed by consistency test, viscosity test, and dynamic shear rheometer (DSR). Meanwhile, the low-temperature characteristics of SMDB were evaluated by bending beam rheometer (BBR) and ductility test. The compatibility of SMDB was assessed by a storage stability test and a Fluorescence microscope (FM). The adhesion and chemical composition of SMDB were analyzed using the sessile drop method and Fourier transform infrared (FTIR) spectroscopy, respectively. Finally, the moisture stability and high-temperature properties of the SMDB mixture were studied using the tensile strength ratio (TSR) test and wheel track test, respectively. The preliminary results of this work show that the addition of SMD increases the viscosity, softening point, fatigue index, and rutting factor of asphalt and reduces the penetration. It is found that SMD improves the anti-aging performance, adhesion performance, and high-temperature stability of SMDB. Although SMD has a negative effect on the low-temperature properties and fatigue resistance of asphalt, the characteristics of SMDB at low temperatures are still superior to those of virgin asphalt. SMD at low content had little effect on the fatigue resistance of the bio-asphalt. Moreover, it is found that SMD is better than the original diatomite in enhancing bio-asphalt properties more significantly. In addition, the blending among SMD, asphalt matrix, and bio-oil is the physical modification, and the mixture has excellent storage stability. Finally, the mixture property testing results indicate that SMD improves the rutting and moisture resistance of the SMDB mixture.

Study on the Performance of High Content RAP Recycled Mixture

The performance of RAP material directly affects the engineering effect of pavement recycling technology. In this study, the performance of high content RAP recycled mixture was analyzed. Through the extraction and screening of RAP materials, it was found that the viscosity of old asphalt increased significantly, the softening point decreased, and the coarse aggregate was refined seriously. The high, low temperature and water stability of high content plant mixed recycled ATB-25 mixture were studied through laboratory tests with different regenerants. The results showed that, compared with the control group, the dynamic stability, freeze-thaw splitting strength ratio and the maximum flexural tensile strain increase rate were: Type A regenerant: 27.48%, 29.45%, 35.71%; Type B regenerant: 16.76%, 21.28%, 38.96%. Comparing the effects of the two kinds of regenerants, after adding Type A regenerant, the mixture has the best high-temperature and water stability, and Type B regenerant is better than Type A regenerant in improving the low-temperature performance. The high, low temperature and water stability of the mixture after adding the regenerant can meet the specification requirements.

Numerical simulation on the processing of crumb rubber modified asphalt by ultrasound and mechanical stirring

Based on the existing modified asphalt production equipment, the power ultrasonic is integrated into the existing stirring dispersion technology, and the FLUENT fluid simulation is used to combine ultrasonic and stirring. Stirring and ultrasonic two motion forms were realized step by step, and the movement states of crumb rubber modified asphalt were simulated under the interaction of ultrasonic and stirring, which provide a new method for the research of crumb rubber modified asphalt production equipment. The results show that under the action of ultrasound, only positive pressure exists in the modified asphalt flow field after adding the cavitation model, and the maximum absolute pressure can reach about 1200kPa. With the increase of ultrasonic time, the air content rate under the tool head is periodic and regular changed and will gradually increase, the number of cavitation bubbles will continue to increase, and the cavitation intensity will increase. The influence of asphalt viscosity on the volume fraction of cavitation bubbles was studied, when the viscosity of the system is 0.8 Pa?s, it is more conducive to the occurrence of cavitation, The process of ultrasonic synergistic stirring is conducive to inhibiting the segregation phenomenon of crumb rubber modified asphalt.

Effect of warm mix agent on the chemo-mechanical performance of binder with different oil sources

In this study, three typical oil source asphalt binders, Karamay asphalt A, CNOOC 36-1 asphalt B, Qinhuangdao CNPC asphalt C, were selected to prepare asphalt binders together with the warm mix agent Evotherm M1. The effects of warm mix agents on asphalt from different oil sources were experimentally studied via dynamic shear rheological (DSR), thermogravimetric analysis (TG), and Raman spectroscopy tests. The asphalt binders with different oil sources exhibit different properties. The rheological test results indicate that the addition of warm mix agent can slow down the decrease of asphalt viscosity during the aging process and the aging of asphalt. The results of the thermogravimetric test showed that the residual mass of asphalt with the addition of a warm mix agent significantly decreased after aging. Warm mixing agents can slow down the conversion of lightweight components to heavy components during the aging process of asphalt. By calculating the reflectivity of asphalt in Raman spectroscopy, it can be concluded that the reflectivity of asphalt decreases after adding a warm mix agent. The warm mixing agent reduces the degree of thermal evolution of asphalt. Warm mixing agents can make the chemical components in asphalt relatively stable and less prone to further pyrolysis or cracking reactions.

Impact of diamond nanothread on the viscosity of asphalt binder: Insights from atomistic simulations

Viscosity stands as a pivotal property within asphalt binder, exerting influence not only over the pavement quality and construction efficiency but also over energy consumption and harmful gas emissions. Lower viscosity at the mixing temperature can reduce the energy consumption and emissions remarkably. As such, extensive efforts have been devoted to tailor the viscosity of asphalt by adding nanomaterials. Through atomistic simulations, this work provides an in-depth assessment on the viscosity of asphalt binder modified by ultrathin diamond nanothread (DNT). It is observed that the addition of DNT can reduce the viscosity of asphalt, a phenomenon traced back to the sp3-bonded nature of DNT that prevents the formation of π - π bonds with asphaltene molecules. Notably, samples endowed with higher count of stacked asphaltene molecules tend to display higher viscosity. Further investigation reveals that the sample with aggregated DNTs exhibits a lower viscosity, as the aggregated DNTs exert a more subdued influence on asphalt molecule mobility. Specifically, DNTs are found to promote the mobility of all molecules, and a remarkable enhancement on the mobility of saturated molecules is observed. This distinct behavior sets them apart from single-walled carbon nanotubes (SWNTs), where viscosity rises with increasing content due to the SWNT-induced aggregation of asphaltene molecules. Overall, this work unveils the intricate mechanisms influencing the viscosity of asphalt binders through diamond nanostructures. These findings could be beneficial for the design of asphalt binders with tailored rheological properties.

Evaluating the Influence of Waste Cooking Oil Molecular Structure on Aged Asphalt Modification

Recycling aged asphalt pavement has become increasingly important due to its environmental and economic advantages. Asphalt, serving as the binding agent for aggregates, plays a crucial role in pavement integrity. The deterioration of asphalt binder properties upon aging poses a significant challenge to asphalt pavement recycling. Consequently, various rejuvenators have been developed to restore aged asphalt binder properties and facilitate pavement reclamation. Waste cooking oil (WCO) is a widely used rejuvenator that mitigates the high viscosity and brittleness of aged asphalt, preventing cracking. WCO consists of triglycerides (TG) and free fatty acids (FFA), each with distinct molecular structures. In this study, molecular dynamics simulations were employed to investigate the individual effects of 10 wt.% TG and FFA on the viscosity, self-diffusion, and microstructure of aged asphalt at 1 atm and 404 K. The results demonstrate that both TG and FFA can reduce the viscosity of aged asphalt, albeit through different mechanisms. TG and FFA, characterized by high molecular mobility when dispersed in aged asphalt, enhance its mobility and reduce its viscosity. Additionally, TG effectively disrupts preferential interactions among asphaltenes, preventing their self-aggregation. In contrast, FFA has a limited impact on reducing these interactions. Furthermore, the study delves into the entanglement behaviors of FFA and TG with varying chain lengths within aged asphalt. Shorter chain lengths, as opposed to longer ones, exhibit a lower likelihood of entanglement with other asphalt molecules, resulting in increased molecular mobility and reduced asphalt viscosity. The fundamental insights gained from this research serve as a valuable reference for the application of waste cooking oil in the recycling of aged asphalt pavement. By shedding light on underlying molecular dynamics, this study contributes to the development of more effective and sustainable approaches to asphalt recycling.