Strength Of Asphalt Mixture Research Articles

Finite element modelling and indirect tensile strength of SBS and CR modified asphalt mixtures

Different modifications in asphalt mixtures can be employed to improve the performance of asphalt pavements in terms of rutting and fatigue damage resistance enhancement. Performance of asphalt mixtures can be further enhanced with the use of different proportions of modifiers added to bitumen, however the optimum proportion of the modifiers added require further experimentation in terms of indirect tensile strength of asphalt mixtures. This research consists of selection of different proportions of Polymer (SBS—Styrene Butadiene Styrene) and CR (Crumb Rubber) modifiers, that have been used in various amounts at 7% CR, 15% CR, 20% CR, 4% SBS, 7% SBS to base bitumen and the performance has been compared with base asphalt mixture. Indirect tensile strength for each mixtures type has been evaluated in the lab with varying rise time. Furthermore, stiffness moduli of each mixture have been evaluated at four different frequency values of 1.2 Hz, 1.9 Hz, 3.5 Hz and 5 Hz at 20 °C.Moreover, tensile strength for each mixture type and its progression with varying loading rates from 10 MPa/s to 70 MPa/s has been evaluated. A 2D finite element software, ABAQUS has been used to perform microstrain analysis for each mixture type. Fatigue and rutting damage models have been used to evaluate performance of each mixture type. Results show superior performance of SBS-7 and CR-20 mixtures in terms of rutting and fatigue damage resistance when compared to base asphalt. SBS-7 and CR-20 show 28% better performance in terms of fatigue damage resistance when compared to base asphalt. SBS-7 outperforms CR-20 in terms of rutting resistance by 22%.

Modification Mechanism and Performance of High-Content Polyurethane-Modified Asphalt

To explore the influence of the polyurethane blending ratio on the micro-characteristics of polyurethane-modified asphalt, three samples of the modified asphalt with different blending ratios (40%, 50%, and 60%) were prepared. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were employed to elucidate the modification mechanism of polyurethane-modified asphalt. To investigate how the preparation method affects the performance of polyurethane-modified asphalt mixtures, two different preparation methods, namely internal blending and external blending, were adopted. The road performance of the polyurethane-modified asphalt mixtures was evaluated through the utilization of rutting tests, low-temperature trabecular bending tests, and freeze–thaw splitting tests. The FTIR test results indicate that during the modification of polyurethane, there is a change in both the intensity and position of the absorption peak, which affects the local arrangement of the molecular structure. Upon reaching a polyurethane blending ratio of 50%, a cross-linked network structure that is similar to polyurethane is formed. The results of the AFM test demonstrate that an increase in polyurethane content results in a corresponding increase in surface roughness. At a polyurethane content of 50%, the curing reaction is most effective, which is beneficial for enhancing the bonding performance between the asphalt and the aggregate, thereby enhancing the overall water stability of the mixture. The results of the scanning electron microscopy (SEM) tests indicate that the microstructure is more stable when the polyurethane content is 50%. The results of the performance test of the polyurethane-modified asphalt mixture indicate that the dynamic stability of the polyurethane-modified asphalt mixture is approximately four times that of the SBS-modified asphalt mixture. The flexural tensile strength and maximum flexural strain of the polyurethane-modified asphalt mixture are, respectively, 1.5 and 3.2 times those of the SBS-modified asphalt mixture, indicating that its anti-deformation ability is stronger in a low-temperature environment, and it is found that the low-temperature performance of the mixture prepared with the internal blending method is better than that with the external blending method. The splitting strength of the polyurethane asphalt mixture before and after freezing and thawing is greater than that of an SBS asphalt mixture: before freezing and thawing, by about 3.8 times; after freezing and thawing, by about 3 times. Although the freezing and thawing of the polyurethane mixture has damage, it still meets the requirements of the use of pavement materials. It can be observed that the incorporation of polyurethane alters the internal structure of the asphalt, which markedly enhances the properties of the asphalt mixture and offers a novel perspective on the development of modified asphalt materials.

Performance evaluation of welded galvanized steel wire mesh reinforced asphalt pavements

Welded galvanized steel wire mesh is fabricated from longitudinal and transverse steel wires welded at specific intervals, followed by hot-dip galvanizing. To address the issue of asphalt pavement cracking, this study incorporates the welded galvanized wire mesh between the base and surface layers, thereby reducing the stress-strain levels of the pavement structure and mitigating the stress concentration at cracks. This results in a novel reinforced asphalt pavement structure. To validate the road performance of asphalt mixtures reinforced with welded galvanized steel wire mesh, this paper presents an indoor experimental study comparing various reinforcing materials: unreinforced, glass fiber geogrid, a polyester fiberglass geotextile, and 1.0 mm welded galvanized steel wire mesh. The results demonstrate that welded galvanized steel wire mesh significantly constrains asphalt mixture deformation under wheel loads, enhancing shear strength by 58.9 % compared to unreinforced asphalt mixtures, and exhibiting robust high-temperature deformation resistance. Moreover, the flexural tensile strength of asphalt mixtures reinforced with welded galvanized steel wire mesh increased by 36.3 %, and the maximum bending and tensile strains rose by 79.9 %, showcasing exceptional low-temperature crack resistance and crack propagation properties. Additionally, the fatigue life of the asphalt mixtures was markedly improved. Comprehensive analysis indicates that welded galvanized steel wire mesh is cost-effective, enhances the integrity and continuity of asphalt pavements, and extends their service life. Over the pavement's life-cycle, this method reduces overall investment, providing a robust basis for extensive application of welded galvanized steel wire mesh in asphalt highways.

The Use of Waste Fillers in Asphalt Mixtures: A Comprehensive Review

The asphalt industry has long been challenged with finding sustainable solutions to enhance the performance of asphalt mixtures while mitigating their environmental impact. One promising avenue is the incorporation of waste filler materials into asphalt mixtures. This review explores the feasibility and effectiveness of utilizing waste filler in asphalt mixtures, focusing on its effects on the mechanical characteristics, durability, and sustainability of asphalt pavements. Various waste filler materials, such as rice husk ash, fly ash, and construction and demolition wastes, have been examined in terms of their potential as substitutes for traditional filler materials such as limestone and mineral powders. This review synthesizes literature to assess the impact of waste fillers on the performance of asphalt mixtures, including rutting resistance, fatigue behavior, moisture susceptibility, and aging characteristics. This work begins by examining the interaction of the asphalt fillers to provide clarification. The usage of various waste fillers is then examined. With fewer harmful environmental consequences than traditional cement manufacturing has, waste filler materials improve the strength and durability of asphalt mixtures. This research underscores the promising future of waste filler materials as environmentally friendly and innovative materials. To fully capitalize on their benefits, further research, standardization, and widespread use of waste filler-based products are necessary.

Design of Volume Parameters of Large-Particle-Size Asphalt Mixture Based on the Vertical Vibration Compaction Method

Volume parameters such as the volume of voids (VV), voids filled with asphalt (VFA), and voids in mineral aggregates (VMA) all have significant impact on asphalt mixtures. In this study, the vertical vibration compaction method (VVCM) was employed to produce a large-particle-size asphalt mixture (LSAM-50). The correlations between the mechanical strengths of VVCM specimens, static compression test (PCT) specimens, and in situ core samples were verified. Additionally, the influence of volumetric parameters on the mechanical properties of VVCM specimens was assessed. Based on the principle of optimal mechanical properties, volume parameter design standards for the LSAM-50 asphalt mixture were proposed. Results indicated that the mechanical properties correlation between VVCM specimens and in situ core samples was substantial, reaching over 90%. With increasing VV and VFA, the compressive strength, splitting strength, and dynamic stability of the LSAM-50 asphalt mixture initially increased and then decreased. The design standards for VV were proposed to be between 3.5% and 4.8%, and for VFA between 49.7% and 52.9%. There was no clear correlation between VMA and the mechanical properties of the mixture; hence, based on the standards, the minimum design value for VMA was set at 7.5%.

Recycling of arsenic residue to basalt fiber via vitrification

The management of arsenic residue (AR) poses a significant environmental challenge globally. Conventional methods such as landfill, adsorption, and purification often fail to prevent arsenic migration, leading to uncertainties about the final disposition of AR and risks of secondary pollution. Vitrification offers a more stable approach for solidifying AR. This study explores the vitrification mechanism of AR using basalt and evaluates the performance of the resulting fibers. Our findings indicate that increasing the arsenic concentration decreases the high-temperature viscosity of basalt, making fiber drawing more energy-efficient. Incorporating a small amount of arsenic (approximately 0.4 mol%) significantly enhances the tensile strength of basalt fibers (BFs) by 10 %, attributed to reduced viscosity and improved fiber formation with fewer internal defects. Additionally, the flexural strength and stiffness modulus of asphalt mixtures are notably improved with the addition of AR-BF composites. We also examined the solidification and leaching mechanisms of arsenic in the basalt glass system. BFs containing up to 0.4 mol% As2O3 exhibited arsenic leaching levels below the standard threshold (<67.7 μg/dm2) under strong acid/alkali immersion conditions. These results highlight the potential for in-situ curing and recycling of hazardous AR, particularly in the development of mechanically reinforced materials.

Analysis of strength size effect and failure mechanism of asphalt mixtures based on discrete element method

The purpose of this study is to further investigate the strength size effect and failure mechanism of asphalt mixtures and clarify the strength parameter conversion relationship between standard and non-standard size samples. The article established an improved microscopic model for uniaxial compression and indirect tensile testing of asphalt mixtures based on laboratory and discrete element simulation tests. The effects of thickness and gradation on the uniaxial compressive strength (UCS) and indirect tensile strength (ITS) of asphalt mixtures were studied. The loading rates of the UCS and ITS tests were set at 2 mm/min and 50 mm/min, respectively. Additionally, the tensile-compressive stress distribution, crack propagation, and strength contribution rates of different contact types within the sample were investigated during the virtual model loading process. The reliability of the model was validated through laboratory test results. Finally, the strength parameter conversion relationship between standard and non-standard size samples was investigated. The study found that the UCS of asphalt mixtures decreases with increasing thickness, while the ITS increases with increasing thickness, with average reduction and increase rates of 70.69 % and 24.18 %, respectively. The contact fracture ratio and the strength contribution rate of the aggregate-asphalt mortar contacts both exceed 50 %, indicating that the fracture of these contacts is the primary cause of asphalt mixture failure. The use of small-sized samples instead of standard samples in practical applications is promising. These research work outcomes can serve as a theoretical basis for designing asphalt pavement materials and acquiring existing asphalt pavement material parameters.

Evaluation of Compressive Strength of Asphalt Mixture from Marshall Stability and Indirect Tensile Strength

Evaluation of Compressive Strength of Asphalt Mixture from Marshall Stability and Indirect Tensile Strength

Development and evaluation of fiber-enhanced RAP interlayer for HMA overlay treatment

To scientifically and efficiently utilize reclaimed asphalt pavement (RAP) generated during asphalt pavement maintenance, and to promote resource recycling and sustainable development, this paper developed and evaluated the Fiber-enhanced RAP interlayer for HMA overlay and preservation treatments. In this paper, RAP interlayer was designed based on the Response Surface Methodology (RSM) and the pull-out strength and the shear strength of were tested. Through double-objective optimization and analysis, the recommended proportions were determined as 2.22 kg/m2 of rubber asphalt, 10.57 kg/m2 of aggregate, and 30% RAP content. Subsequently, the effects of different basalt fiber contents on the pull-out strength, shear strength, flexural strength, fatigue life, and permeability coefficient of asphalt mixture with interlayer containing RAP were investigated. The results indicated a significant improvement in these properties with an 80 g/m2 basalt fiber content. The performance of asphalt mixture with Fiber-enhanced RAP interlayer was obviously superior to the asphalt mixture with interlayer without fiber and RAP. According to the test results of Digital Image Correlation (DIC), it was found that basalt fibers effectively reduce stress concentration, delaying the initiation and propagation of cracks.

The Performance of Modified Asphalt Mixtures with Different Lengths of Glass Fiber

AbstractOne practical option for modifying an asphalt mixture’s performance is to use additives. This will help the mixture perform better against the damaging effects of traffic, loads, and climatic variations. In this regard, glass fiber (GF) has drawn much interest because of its positive effect. Therefore, this paper attempts to study the effect of glass fiber length and content on the performance and strength of asphalt mixtures. It also aims to determine the optimum glass fiber content and the best glass fiber length of modified asphalt mixtures. An experimental program is carried out, which includes the Marshall test, volumetric properties, freeze-thaw splitting test, immersion Marshall test, and wheel tracking test to characterize related properties of glass fiber incorporated in asphalt mixtures. Seven different percentages (0, 0.25, 0.5, 0.75, 1, 1.25, and 1.5) of glass fiber by total weight of aggregates in three various lengths are used to design 19 asphalt mixtures. Based on the results obtained, the performance of the asphalt mixture was enhanced remarkably after adding glass fiber. The use of various lengths of glass fiber led to a better-quality asphalt mixture in terms of volumetric properties, moisture damage resistance, and permanent deformation resistance. Specifically, asphalt mixtures made with (0.5%) glass fiber illustrated the highest quality, and adding (20 mm) length of glass fiber was better than (10 mm and 30 mm) glass fiber lengths. The results also show that adding (10 mm and 30 mm) lengths of glass fiber can improve the resistance of asphalt mixtures to water damage and permanent deformation compared with the control mixture (M0). The findings indicate the applicability of 20 mm glass fiber length in asphalt mixtures to achieve better resistance against moisture and reduce the chance of irreparable permanent deformation under growing traffic loads and hot climate changes. Although the inclusion of glass fiber in asphalt mixtures led to a modest increase (6%) in overall cost, the effective improvement in performance and extension of the service life of the asphalt pavement constitute a convincing argument for this approach, making it an attractive option. Finally, it was concluded that a higher amount of glass fiber (i.e., &gt; 0.5%) and a length greater than (20 mm) could diminish the positive effect of glass fiber to improve the properties of glass fiber asphalt mixtures.

Aging Resistance Evaluation of an Asphalt Mixture Modified with Zinc Oxide

The phenomenon of the oxidation and aging of asphalt binders affects the strength and durability of asphalt mixtures in pavements. Several studies are trying to improve the resistance to this phenomenon by modifying the properties of the binders with nano-particles. One material that shows promise in this field is zinc oxide (ZnO), especially in improving ultraviolet (UV) aging resistance. Few studies have evaluated the effect of these nano-particles on the thermo-oxidative resistance of asphalt binders, and, on hot-mix asphalt (HMA), studies are even more scarce and limited. Therefore, in the present study, the resistance to thermo-oxidative aging of an HMA manufactured with an asphalt binder modified with ZnO was evaluated. An asphalt cement (AC 60–70) was initially modified with 0, 1, 3, 5, 7.5, and 10% ZnO (percentage by weight of asphalt binder; ZnO/AC in wt%), and then exposed to aging in Rolling Thin-Film Oven tests (RTFOT) and a Pressure Aging Vessel (PAV). Penetration, viscosity, and softening point tests were performed on these binders, and aging indices were calculated and evaluated. Samples of HMAs were then manufactured using these binders and designed by the Marshall method, determining the optimum asphalt binder content (OAC) and the optimum ZnO/AC ratio. Control (unmodified) and modified HMA were subjected to short-term oven aging (STOA) and long-term oven aging (LTOA) procedures. Marshall, Indirect Tensile Strength (ITS), and resilient modulus (RM) tests were performed on these mixtures. LTOA/STOA results of the parameters measured in these tests were used as aging indices. In this study, ZnO was shown to increase the thermo-oxidative aging resistance of the asphalt binder and HMA. It also contributed to an increase in the resistance under monotonic loading in the Marshall and ITS tests, and under repeated loading in RM test. Likewise, it contributed to a slightly increasing resistance to moisture damage. The best performance is achieved using ZnO/AC = 5 wt%.

Effects of utilization of rejuvenator in asphalt mixtures containing recycled asphalt pavement at high ratios

This study investigated the properties of asphalt mixtures, including recycled asphalt pavement, at high ratios. In addition, to improve the properties of asphalt mixtures containing recycled asphalt pavement, bitumen was modified with a rejuvenator at proportions of 2, 4, and 6% and used together with 35, 40, and 45% recycled asphalt pavement. Based on test results, the strength of asphalt mixtures increased as the ratio of recycled asphalt pavement added to asphalt mixtures increased. In addition, all combinations of recycled asphalt pavement and rejuvenator agent had higher indirect tensile strength values according to the reference mixture. The rutting resistance of asphalt mixtures increased as the ratio of recycled asphalt pavement added to the asphalt mixtures increased. Asphalt mixtures containing 45% recycled asphalt pavement and 2% rejuvenator-modified bitumen showed the best rutting resistance. The significance of the obtained results was determined with appropriate statistical analysis. So, it has been determined that the rejuvenator used in this study can effectively improve the properties of asphalt mixtures containing recycled asphalt pavement. Finally, the rejuvenator agent used in this study allowed the utilization of recycled asphalt at a higher ratio than the amount specified in the Highway Technical Specification.

Characterization of viscoelastic behavior of basalt fiber asphalt mixtures based on discrete and continuous spectrum models.

In order to analyze the differences between the master curves of relaxation modulus E(t) and creep compliance J(t) obtained from discrete and continuous spectrum models, and to comprehensively evaluate the effect of basalt fiber content on the viscoelastic behavior of asphalt mixtures, complex modulus tests were conducted for asphalt mixtures with fiber content of 0%, 0.1%, 0.2% and 0.3%, respectively. Consequently, the master curves of Viscoelastic Parameters of asphalt mixtures were constructed according to the generalized Sigmoidal model(GSM) and the approximate Kramers-Kronig (K-K) relationship. Then, transformation of master curves using discrete and continuous spectrum models to obtain the models of E(t) and J(t) containing all viscoelastic information. Also, the accuracy of the models of E(t) and J(t) was evaluated. The results show that the addition of basalt fibers improves the strength, stress relaxation and deformation resistance of asphalt mixtures. It is worth noting that basalt fibers achieve the improvement of asphalt mixtures by changing their internal structure. Considering the different viscoelastic master curves at four dosages, the optimum fiber dosage was 0.2%. In addition, both discrete and continuous model conversion methods can obtain high accuracy conversion results.

Shear strength parameters for porous asphalt mixtures: From macro to meso

The shear strength of asphalt mixtures significantly influences the rut resistance of flexible pavements. Existing methods predominantly address macroscopic aspects, failing to unveil the underlying mechanisms. Moreover, experimental determination of shear strength parameters is time-consuming, but there is a lack of simple prediction methods. This study explores correlations between macroscopic parameters (friction angle and cohesion) and key mesoscopic shear-related factors in Porous Asphalt Mixtures (PAMs) using multiscale triaxial compressive tests, dynamic shear rheometer tests, and sessile drop tests. The research reveals that PAM is influenced not only by aggregate interlock but also by stiff mastic, resulting in a reduced friction angle at a lower temperature. Regression analyses establish a prediction formula for PAMs, incorporating the friction angle of the aggregate skeleton and the complex modulus of the mastic. A correlation function, inspired by Griffith's fracture theory, was also proposed to link PAM's cohesion with the complex modulus and the work of cohesion of mastic, and the friction angle of PAMs. Predictions for PAM's friction angle and cohesion align well with macro-level experimental results, with all the coefficients of determination of over 0.94. These findings enhance the understanding of asphalt mixture shear strength formation and enable shear-resistance optimisation from meso-level.

Unified Characterization of Rubber Asphalt Mixture Strength under Different Stress Loading Paths

Unified Characterization of Rubber Asphalt Mixture Strength under Different Stress Loading Paths

Study of Crumb Rubber as Binder Material in Asphalt

Asphalt is a mixture of aggregates, bitumen, quarry dust, and cement. As an addition in hot mix asphalt mixtures, recycled tire rubber known as "crumb rubber" is regarded as an environmentally friendly building practice. The laboratory hot mix asphalt design tests were conducted according to Marshall method procedure. In this study, three different crumb rubber contents (10%, 15%, and 20% by weight of bitumen), and three different bitumen contents (4%, 5%, and 6%) with a penetration grade 60/70 were investigated. The Marshall stability value and durability properties were taken into account in a comparison study between the standard and modified asphalt concrete mixtures. The strength and performance of asphalt mixtures tended to improve with the addition of crumb rubber. As some of the test results were within the acceptable range, the findings indicated that crumb rubber is advised for use as an addition in asphalt mixtures. Besides, the durability of asphalt mixtures also needed to be concerned.

Study on induction healing properties of OGFC asphalt mixture with high elasticity and high viscosity modifier

Induction healing is a promising preventive maintenance method of asphalt pavement, but the healing properties of Open-Graded Friction Course (OGFC) asphalt mixture with high elasticity and high viscosity modifier (HEV) were not clear. OGFC asphalt mixture used for induction heating was prepared by adding steel wool fibers and HEV. The effects of HEV and steel wool on the properties of OGFC mixture were studied. The particle loss resistance, water stability, porosity, induction heating and self-healing properties of OGFC-13 asphalt mixture with different steel wool contents were measured. The results showed that HEV slightly improved the properties of resistance to particle loss, fracture strength and water stability of OGFC-13 asphalt mixture, had little effect on the induction heating rate and porosity, but reduced the healing rate by 10%. The addition of steel wool to OGFC-13 can enhance the particle loss resistance, heating rate and healing effect, and the optimal dosage is 8% of the volume fraction of bituminous binder. The healing rate rose steadily as the heating temperature increased. At the optimal healing temperature of 110 ℃, healing depth ratios of the mixtures without and with HEV were 56.3% and 43%, respectively, and the fracture energy healing rates were 72.4% and 63.1%, both at a high healing level. The incorporation of steel fibers and HEV reduced the porosity and water permeability of OGFC very slightly, and the porosity and water permeability of OGFC did not change significantly after induction heating. It is concluded that induction heating has a potential to heal the cracks within OGFC mixture with HEV to prevent surface raveling which is the primary damage of OGFC.

Performance of Hybrid Asphalt Mixture through the Stability and Tensile Strength

Introduction: The stability and tensile strength of asphalt mixtures play a crucial role in pavement durability, primarily due to the challenges associated with cracking. This study investigates the utilization of a hybrid asphalt mixture comprising hybrid materials: Palm Oil Fuel Ash (POFA), garnet waste and sawdust to enhance the modified asphalt performance. Aims: The objective is to examine the hybrid materials’ influence towards the mechanical properties of the hybrid asphalt mixture, specifically focusing on the Indirect Tensile Strength (ITS) as well as the Marshall stability test. Methods: To achieve this, hybrid materials were finely ground and sieved to 25µm before being incorporated into the mixture. The Marshall mix design procedure was conducted, utilizing hybrid binders at concentrations of 0% (control), 3% 6%, and 9%. The effects of the hybrid asphalt mixture on stability, flow, stiffness, and ITS were assessed at the optimal binder content. Results: The findings indicate that the hybrid asphalt mixture reveals enhanced Marshall stability, stiffness, flow, and ITS values compared to conventional asphalt mixtures. Notably, hybrid asphalt mixtures with 6% binder concentration demonstrate the most significant enhancement in terms of Marshall stability and ITS. Conclusion: This correlation suggests that the incorporation of POFA, garnet waste, and sawdust as hybrid materials in the hybrid asphalt mixture possesses a positive effect on the overall mechanical properties of the pavement. Highlights: • POFA, garnet waste, and sawdust increased the stability of the hybrid asphalt mixture. • POFA, garnet waste, and sawdust increased the tensile strength of the hybrid asphalt mixture. • Hybrid asphalt mixture performs positively towards flow and stiffness.

Study on the shear strength of asphalt mixture by discrete element modeling with coarse aggregate morphology

High shear strength is crucial for asphalt pavements to resist permanent deformation at high temperatures, which is largely determined by the skeletal structure of coarse aggregates. In this study, four size ranges of polyhedral coarse aggregate clumps were built to simulate the morphology and dimensional characteristics of coarse aggregate. Subsequently, virtual triaxial shear tests were simulated using discrete element models. Three gradation types were analyzed to study the effects of aggregate structure, granularity composition, and coarse aggregate modulus on the shear strength of asphalt mixtures. The results show that it is feasible to obtain accurate morphological features of coarse aggregates by controlling the minimum diameter of the filled spheres in a polyhedral coarse aggregate box when constructing a discrete element model. The virtual triaxial shear test model developed in this study can be effectively utilized to simulate the shear mechanical properties of asphalt mixtures under various confining pressures. The numerical simulation results indicate that the cohesion of asphalt mixture AC-13 is the best, while the internal friction angle and shear strength of SMA-13 are the highest. The ranking of factors that affect the cohesion and internal friction can be summarized as: aggregate structure ≫ coarse aggregate modulus > granularity composition, while the order of factors that affect the shear strength is: aggregate structure ≫ granularity composition > coarse aggregate modulus. This indicates that the aggregate structure is crucial for the high-temperature performance of asphalt mixtures. This study addressed the issue of high variability in laboratory test results for macroscopic properties of asphalt mixtures and analyzed the skeleton role of coarse aggregate in asphalt mixtures from a mesoscopic perspective. The findings parameters for explaining the strength mechanism. The discrete element models also facilitate the optimization of asphalt mix design with reduced labor and time consumption on laboratory testing.

Evaluation of the interface adhesion mechanism between SBS asphalt and aggregates under UV aging through molecular dynamics

The bonding characteristics between asphalt and aggregates have an important role in influencing the strength of asphalt mixtures. To clarify the bonding mechanism at the interface between SBS asphalt and aggregates under UV aging conditions, this research developed molecular models of the interface between SBS asphalt and representative aggregates including quartz (granite), augite (basalt), and calcite (limestone). Subsequently, dynamic simulations were performed on the interface models to assess the adhesive properties. Adhesion work was employed to assess the interfacial adhesion performance between SBS-modified asphalt and various types of aggregates. The results demonstrated that SBS asphalt exhibited significantly higher adhesive work with alkaline aggregates, following the order of limestone > basalt > granite in terms of adhesive strength. The dominant contributor to adhesive work was van der Waals interactions, with electrostatic interactions playing a crucial role in influencing variations in adhesive work among different aggregates. After the aging-induced fracture of SBS materials, there was a noticeable increase in the gap between them and the aggregates, resulting in a significant reduction in the adhesion effectiveness between SBS and aggregates. Aged asphaltene and colloid exhibited heightened polarity, resulting in enhanced electrostatic interactions between asphalt and aggregates, thus reducing adsorption distances and elevating adhesive work. This research provides comprehensive evaluation of the bonding mechanism between asphalt and aggregate under UV aging conditions at the molecular level, and provides guidance for the design of durable asphalt pavements.