Durability Of Asphalt Pavement Research Articles

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.

Warm-Mix Asphalt Containing Reclaimed Asphalt Pavement: A Case Study in Switzerland

Among the technologies proposed for achieving carbon neutralization in asphalt road pavements, warm-mix asphalt (WMA) has garnered increasing attention in recent years. While WMA holds the potential for various environmental and technical benefits, a comprehensive understanding of its implementation, technology selection, and additives is essential for successful application. This study presents a case where a bio-based chemical additive was employed to produce WMA containing 50% reclaimed asphalt pavement (RAP) for a surface course in Bern, Switzerland. To minimize additional variables during testing and analysis, no other additive or rejuvenator was introduced into the mixtures. The testing plan encompassed laboratory tests on samples collected during material placement and recompacted at varying temperatures in the laboratory, as well as cores extracted from the job site. As anticipated, the presence of the chemical WMA additive did not alter the rheological properties of the reference bitumen. Although in the mixture-scale tests, the WMA mixture exhibited comparable properties to the control hot-mix asphalt (HMA), it is not expected that the small dosage of the chemical additive functions the same grade after reheating and compaction. Nevertheless, the cores extracted from the job site proved the efficiency of the applied WMA technology. In addition, consistent with existing literature, the cracking tolerance (CT) index values of 62 for HMA and 114 and 104.9 for WMA mixtures indicated that the latter is less susceptible to cracking. Consequently, this characteristic could contribute to the enhanced durability of asphalt pavements.

Examining the efficacy of promising antioxidants to mitigate asphalt binder oxidation: insights from a worldwide interlaboratory investigation

ABSTRACT Oxidative aging induces significant stiffening of asphalt binders that leads to a pronounced reduction in the overall durability of asphalt pavements. The strategic implementation of antioxidant additives provides a potential solution to alleviate this issue. This work presents results from the second phase of the global consortium for antioxidants research aimed at investigating the effectiveness of potential antioxidants in increasing the durability of asphalt binders. Sixteen laboratories around the world participated in this effort and a total of 28 binders from diverse geographical regions were tested. Two promising antioxidants, namely zinc diethyldithiocarbamate (ZDC) and kraft lignin were evaluated in this phase and blended with the binders at specific proportions. Subsequently, a comprehensive investigation was conducted to assess rheological characteristics and chemical properties of the various blends, utilising Dynamic Shear Rheometer (DSR) measurements and Fourier Transform Infrared (FTIR) Spectroscopy. The findings indicate that additives such as ZDC hold considerable promise as an effective antioxidant, particularly when considering a wide diversity of binders. In general, its incorporation does not compromise the rutting performance of the binders and significantly improves fatigue performance. Therefore, research efforts should be focused on exploring additional facets to assess its practical applicability in field.

Computational Evaluation of the Fracture Behavior of Porous Asphalt Concrete Exposed to Moisture and Salt Erosion.

Salt erosion has an adverse impact on the durability of asphalt pavements. Porous asphalt concrete is particularly susceptible to the influence of salt. In this study, a finite element model was developed to investigate the fracture behavior of PAC exposed to salt erosion. The 2D heterogeneous structure of PAC was generated with an image-aided approach to computationally study the fracture behavior of PAC. Laboratory SCB tests were conducted to validate the finite element model. The simulation results of the SCB tests indicate that the peak load of the PAC decreased by 21.8% in dry-wet cycles and 26.1% in freeze-thaw cycles compared to the control group. The salt solution accelerated the degradation of the durability of PAC under both dry-wet cycles and freeze-thaw cycle conditions, which is consistent with laboratory tests. After flushing treatment before the drying phase, the peak load of the PAC in salt environments increased by 5.3% compared to that of the samples with no flushing. Salt erosion also results in a higher average value of scalar stiffness degradation (SDEG), and the damaged elements were primarily the cohesive elements in the fracture of the PAC. Additionally, the influence of crucial factors including the void content, adhesion and cohesion, and loading rate on the fracture behavior of the PAC was analyzed. As the void content increases, the average SDEG value of the cohesive elements increases and surpasses the average SDEG value of the adhesive elements at a void content of approximately 9%. The performance of the fine aggregate matrix (FAM) has a much greater impact than the FAM-aggregate interface on the durability of the PAC. And there were more damaged CZM elements with the increase in the loading rate. Salt erosion results in higher SDEG values and a larger number of cohesive damaged elements at each loading rate.

Effects of Different Antioxidant Intercalated Layered Double Hydroxides on Anti-Aging Properties of Asphalt Binders

This research aims to prepare different antioxidant intercalated layered double hydroxides (LDHs) and compare the thermal oxidation and ultraviolet (UV) aging resistances of different modified asphalts. The ion exchange technique was used to intercalate three different antioxidants: 3-(3,5-di-tert-butyl-4-carboxyphenyl) propionic acid, antioxidant 1222, and sodium dibutyl dithiocarbamate (rubber accelerator TP) into the interlayer of LDHs. The morphology, structures, UV blocking, and free radical scavenging properties of different antioxidant intercalated LDHs were characterized, respectively. The effects of the anti-aging agents on the physical properties (penetration, softening point, ductility, and viscosity); rheological behaviors (complex modulus and phase angle); and functional groups (C=O and S=O) of asphalt both before and after thermal oxidation aging and UV aging were systematically investigated. The results of the crystal structure and functional group analysis show that the three different antioxidants can be successfully inserted into the interlayer of LDHs without destroying their layered structures. Antioxidant intercalated LDHs exhibit a remarkable capacity for absorbing UV rays, coupled with a moderate ability to reflect UV light. Moreover, the inclusion of antioxidants into the interlayers of LDHs confers upon them the ability to scavenge free radicals. After 2 h of reaction, the free radical scavenging rates of LDHs-3, LDHs-1222, and LDHs-TP were 57.7%, 35.6%, and 17.1%, respectively. With an increase in the content of the antioxidant intercalated LDHs, the performance of the modified asphalt varies, and 4% is the optimal content of the anti-aging agents. Asphalts with the three antioxidant intercalated LDHs all had favorable storage stability, and their physical and rheological properties were improved after aging compared to LDHs-modified asphalt. The LDHs-3-modified asphalt showed the best anti-ultraviolet aging effect, while LDHs-1222-modified asphalt showed the best anti-thermal oxidation aging effect. This research lays the foundation for developing aging-resistant asphalt and improving the durability of asphalt pavement.

Thermoreversible aging in asphalt binders

It is an undisputed fact that aging increases the risk of low-temperature cracking in asphalt pavement. Previous studies on aging have focused on oxidative aging, but few studies on thermoreversible aging have been reported. The existing literature has shown that thermoreversible aging has the same effect as oxidative aging on cracking of asphalt pavement in cold region, so it is obvious that the study of thermoreversible aging is of great practical significance to improve cracking of asphalt pavement. This paper introduces the current status of thermoreversible aging research from the concept, mechanisms, characterisation methods and effects, presents the problems of existing research and indicates the direction of further research, which is important for accurately characterising the mechanical properties of asphalt binders, controlling the waste addition ratio and improving the durability of asphalt pavement.

Study on the design and laboratory investigation of permeable semi-rigid base material with large air voids

PurposeTo explore the economical and reasonable semi-rigid permeable base layer ratio, solve the problems caused by rainwater washing over the pavement base layer on the slope, improve its drainage function, improve the water stability and service life of the roadbed pavement and promote the application of semi-rigid permeable base layer materials in the construction of asphalt pavement in cold regions.Design/methodology/approachIn this study, three semi-rigid base course materials were designed, the mechanical strength and drainage properties were tested and the effect and correlation of air voids on their performance indexes were analyzed.FindingsIt was found that increasing the cement content increased the strength but reduced the air voids and water permeability coefficient. The permeability performance of the sandless material was superior to the dense; the performance of the two sandless materials was basically the same when the cement content was 7%. Overall, the skeleton void (sand-containing) type gradation between the sandless and dense types is more suitable as permeable semi-rigid base material; its gradation is relatively continuous, with cement content? 4.5%, strength? 1.5 MPa, water permeability coefficient? 0.8 cm/s and voids of 18–20%.Originality/valueThe study of permeable semi-rigid base material with large air voids could help to solve the problems of water damage and freeze-thaw damage of the base layer of asphalt pavements in cold regions and ensure the comfort and durability of asphalt pavements while having good economic and social benefits.

Study on synergistic effect of multiple physical fields on hot mix asphalt during compaction process.

The multiple physical fields of hot mix asphalt (HMA) during the compaction process have a significant impact on the durability of asphalt pavement, and this research aimed to evaluate the synergistic effect of the HMA field compaction of multi-physical field evolution during the compaction process. First, the temperature field, structural layer thickness variation, and structural layer density variation were monitored during field compaction. Second, the evolution properties of compaction thickness were obtained under the synergistic influence of multi-physical fields by temperature field and compaction thickness. Finally, the evolution properties of compaction density were obtained under the synergistic influence of multi-physical fields based on the temperature field and structural layer density. The results showed that the field compaction process could be characterized by three stages under the synergistic impact of multi-physical fields. The cooling of the temperature field presents two-stage characteristics. There were cubic polynomial evolution properties for the temperature field versus time and the density versus temperature field. There was an exponential relationship between the thickness of the compacted layer and the number of mills. The aggregate particles showed different motion characteristics in the horizontal and vertical directions and vertical directions. The vertical displacement was larger than the horizontal displacement under the synergistic influence of multi-physical fields during the three stages of compaction. The migration and reorganization of aggregate particles affected the evolution of the multi-physics fields of the compaction process under the action of different compaction modes.

Revealing time-dependent behavior of asphalt binder at low-temperature by crystallization kinetics

To gain deeper insights into the influence of thermal history on wax crystallization and thermoreversible aging for enhanced asphalt pavement durability, this study employed the extended bending beam rheometer (ExBBR) test and modulated differential scanning calorimetry (MDSC) analysis. These techniques were utilized to analyze the crystallization kinetics of diverse asphalt binders under both isothermal and non-isothermal conditions. The ExBBR test results demonstrated that the cold-temperature performance of asphalt binders experiences continuous degradation with an increasing grade loss during conditioning. The Avrami isothermal crystallization kinetic theory proved to be an accurate descriptor of the thermoreversible aging tendency in asphalt binders. MDSC test findings revealed that distinct cooling rates exert an influence solely on specific asphalt varieties, with discrepancies in thermal signals arising from diverse oil sources. The Ozawa exponent, determined through the endothermic background area selected from the baseline, serves as a reliable guide for assessing the degree of thermoreversible aging in different asphalt binders. Crucially, the appearance of crystallizable fractions in asphalt binders with varying thermal histories can be effectively modeled using both isothermal Avrami and non-isothermal Ozawa theoretical frameworks. To conclude, the study undertook the separation of four components of asphalt, analyzing the microstructural evolution of these components under identical test conditions. The contribution of each component to the asphalt crystallization process is comprehensively expounded through considerations of glass transition temperatures, as well as endothermic and exothermic peaks associated with distinct components.

Mechanical, thermodynamical, and microstructural characterization of adhesion evolution in asphalt binder-aggregate interface subjected to calcium chloride deicer

Frigid weather and freezing road conditions in cold regions result in reduced pavement surface friction, compromised vehicle maneuverability, leading to deteriorated transportation safety. Given their effectiveness and low cost, using chloride-based deicing agents such as CaCl2 has become a standard winter maintenance strategy for many highway agencies. However, coupled with freeze–thaw (F-T) cycles, CaCl2 can adversely affect the durability of asphalt pavements and cause complex distresses such as moisture-induced damage, among others. Despite this fact, the mechanisms and the extent of the damage made to the asphalt binder-aggregate interface due to use of chloride salts are not well-understood. This study was undertaken to characterize the mechanisms by which different eutectic concentrations of aqueous CaCl2 solutions and F-T cycles affect the adhesion between asphalt binder and different aggregates through a multi-scale characterization and testing program. Given the rise in use of polymer-modified asphalt binder a PG 64–34 asphalt binder and aggregates of granite, quartzite, and limestone mineralogies were evaluated. More specifically, pull-off strength of the aggregate-binder systems subjected to different aqueous concentrations of CaCl2 and F-T cycles were determined. In addition, surface free energy method as a thermodynamic-based approach was employed to determine the effect of salt concentration on the adhesion and debonding energies, and the moisture-induced damage potential of the binder-aggregate interfaces. Furthermore, atomic force microscopy was employed to evaluate the effect of salt concentration and F-T cycles on surface morphology, nanostructure, and adhesion of the asphalt binder. The applied multi-scale characterization provided invaluable information about the physio-chemical phenomena responsible for the accelerated damage in asphalt binder-aggregate interface when subjected to different aqueous concentrations of CaCl2. Gaining an accurate understanding of the damage mechanism is necessary for developing new materials and methods for combatting salt-accelerated moisture-induced damage in cold regions as a result of winter maintenance operations.

Improvement of pavement engineering properties with calcium carbide residue (CCR) as filler in Stone Mastic Asphalt

Characteristics of pavement material are crucial factors in improving the stability and durability of asphalt pavement due to the poor performance of traditional asphalts. Reusing industrial waste in asphalt concrete production can address these concerns, reduce environmental problems and preserve resources. There have been few studies on the effects of using industrial waste materials on Stone Mastic Asphalt (SMA) properties. This paper examines the impact of Calcium Carbide Residue (CCR) as a filler in SMA. The study evaluates control samples, those with Rock Powder (RP) and Ordinary Portland Cement (OPC) filler, and those with CCR using Marshall stability (MS) and Indirect Tensile Strength (ITSdry and ITSsat) tests. Results show positive effects of CCR and RP on asphalt sample strength. The highest MS, MQ, and TSR values were observed in samples containing CCR80 %+RP20 %. These indices increased 45 %, 35 %, and 51 %, respectively, compared to control samples. The alkaline CCR material forms strong bonds with acidic bitumen, producing asphalt more resistant by 97 % compared to control samples. SMA modified with CCR + RP was also found to be less sensitive to water damage than traditional SMA with RP or OPC filler. The rough texture of CCR may positively affect the strength and durability of asphalt mixtures against moisture damage. Using CCR as a filler in SMA can enhance pavement engineering properties, reduce production costs and environmental problems, and develop sustainable asphalt mixtures for practical application. The main novelty of this research is the use of CCR and RP combination in SMA mixtures.

Freeze-Thaw Damage Mechanism Analysis of SBS Asphalt Mixture Containing Basalt Fiber and Lignocellulosic Fiber Based on Microscopic Void Characteristics.

Freeze-thaw effects pose the significant challenge to asphalt pavement durability, leading to various types of distress and deterioration. This study investigates the freeze-thaw damage mechanism of Styrene-Butadiene-Styrene (SBS) asphalt mixtures containing reinforcement fibers, specifically basalt fiber as well as lignocellulosic fiber, through a microscopic void characteristics analysis. This investigation aims to understand how the presence of basalt fiber as well as lignocellulosic fiber influences void characteristics for SBS asphalt mixtures during freeze-thaw cycles. A comprehensive experimental program was conducted for the void and mechanical characteristics, which involved the preparation of SBS asphalt mixtures containing basalt fiber as well as lignocellulosic fiber. The mechanical performances of the two types of asphalt mixtures decrease with more freeze-thaw cycles. The decline is faster initially and gradually slows down. Basalt-fiber-modified SMA-13 has higher air void content and mechanical properties compared to lignocellulosic-fiber-modified SMA-13, indicating that adding basalt fibers improves the mechanical performances of SMA-13 asphalt mixture. Both types of asphalt mixtures experience increasing damage with more freeze-thaw cycles, indicating irreversible damage. The stability damage levels are similar, but basalt-fiber-modified SMA-13 has lower splitting strength damage and stiffness modulus damage compared to lignocellulosic-fiber-modified SMA-13. This suggests that adding basalt fibers enhances the resistance to freeze-thaw damage. Surface wear of asphalt mixtures under repeated freeze-thaw cycles is a complex and dynamic process. Fractal theory can uncover the mechanism of surface wear, while describing surface wear behavior and void deformation characteristics using fractal dimension, angularity, roundness, and aspect ratio is a logical and effective approach. The findings provide insights into freeze-thaw damage mechanisms at the microscopic level, highlighting the effects of reinforcement fibers. They provide valuable insights that can be used to optimize the design and maintenance of asphalt pavements.

Roles of waste carbon fibers on the efficiency of multiple induction heating healing behavior in asphalt mixture for sustainable infrastructure

This study systematically investigated the potential of waste carbon fibers (WCFs) as a sustainable solution in enhancing the multiple induction heating healing of asphalt mixture, thereby tackling two major concerns: the environmental impact of WCFs and the durability of asphalt pavement. Firstly, four groups of asphalt binder samples with different WCFs contents were prepared. The viscosity and workability of WCFs modified asphalt binder were analyzed. Next, asphalt mixture containing 2% steel fibers was prepared at the optimal WCFs content, while control groups without WCFs were prepared with 2% and 4% steel fibers content. A comprehensive study was conducted on the induction heating rate, effective heating depth and surface temperature cooling rules of the asphalt mixture. Finally, by conducting multiple "fracture-healing" tests, the influence of WCFs on the healing efficiency of asphalt mixture was analyzed. The results revealed that WCFs increased the viscosity of the virgin asphalt, but excessive WCFs content hindered the workability. The optimal WCFs content was determined to be 1% (by weight of asphalt binder). WCFs enhanced the thermal conductivity of the asphalt mixture, accelerating heating and improving vertical heat transfer while reducing surface temperature decline. During multiple "fracture -healing" processes, the inclusion of WCFs enhanced the mechanical strength of the asphalt mixture, improved its healing efficiency, and increased the number of healings. Even after five cycles, the specimen with the most damage still showed a fracture energy recovery rate (FERR) of over 30%. In conclusion, WCFs significantly enhanced the multiple induction heating healing efficiency of the asphalt mixture.

The Properties of Modified Bagasse Fiber/Nano-TiO2 Composite Asphalt in a High-Temperature and High-Humidity Salt Environment.

The southern tropical coastal areas of China are high-temperature and high-humidity salt environments, which hinder the durability and service life of ordinary asphalt pavement. To enhance the durability of asphalt pavement in these areas, modified bagasse fiber combined with nano-TiO2 was used to improve the corrosion resistance of asphalt pavement in high-temperature and high-humidity salt environments. The micro-morphology, high-temperature oil absorption, high-temperature heat resistance, and hygroscopicity of bagasse fiber modified using three silane coupling agents combined with NaOH were compared, and the best silane coupling agent/NaOH modification scheme for bagasse fiber was found. Based on conventional physical tests (penetration, softening point, ductility), rheological property tests (rotational viscosity, dynamic shear rheological test, multi-stress creep recovery test, linear amplitude scanning test), and a four-point bending fatigue test of the asphalt mixture, the properties of modified bagasse fiber asphalt binder and mixture after cyclic dry-wet erosion under pure water and salt solution (NaCl, Na2SO4) were determined, and the effects of the erosion environment and fiber ratio on the basic physical and rheological properties of the asphalt were clarified. Compared with the silane coupling agents KH550 and KH590, the bagasse fiber modified with KH570/NaOH had a better high-temperature oil absorption capacity, heat stability capacity, and matrix asphalt compatibility. The worst erosion environment was Na2SO4, but the increase in test temperature and fiber content weakened the sensitivity of the asphalt binder performance in different erosion environments. The erosion capacity order was as follows: Na2SO4 > NaCl > pure water. In the worst erosion environment, 0.5% modified bagasse fiber/Nano-TiO2 asphalt binder (Bn-570-0.5) had the best corrosion resistance in a high-temperature and high-humidity salt environment. The penetration, softening point, creep recovery rate R3.2, non-recoverable creep compliance Jnr3.2, and fatigue life after long-term aging (with 5% strain) of Bn-570-0.5 were, respectively, increased by -16.9%, 37.5%, 37.95%, -27.86%, and 38.30% compared with unblended base asphalt binder (B). In addition, the four-point flexural fatigue life of Bn-570-0.5 was 169.2% higher than that of the unblended base mixture.

Skid-resistance durability and wear/polish-resistance behaviors of ultra-thin friction course designed based on the differential polishing of aggregates

To improve the skid-resistance durability of asphalt pavements in a cost-effective manner, this study introduced a differential-polishing principle based on blending various aggregates. SMA-5 ultra-thin friction courses (UTFC) were prepared using mineral aggregates consisting of 88# calcined bauxite and limestone blended in six proportions. Long-term simulated traffic polishing tests were performed on six types of UTFC surfaces in the laboratory. Direct skid-resistance indexes, BPN20 and μ80, were used to evaluate skid resistance at low and high velocities after different polishing cycles, respectively. Surface texture evolution during long-term polishing was analyzed using bearing area ratio, mean profile depth, and fractal dimension D. Additionally, an attenuation prediction model for skid resistance was developed. Aggregate mechanical properties affecting skid-resistance durability of UTFC were investigated through grey correlation analysis. The results show that a significant differential-polishing effect was generated during long-term polishing due to large differences in the two aggregates’ wear/polish resistance, which can effectively reduce the attenuation rate of skid resistance of UTFC and improve skid-resistance durability by decreasing wear loss of UTFC surface aggregate and forming texture structure difference between aggregates to maintain rough surface texture. The reasonable blending proportion of 88# calcined bauxite was determined to be 40%–60% of the mineral aggregate mass. It was also found that the developed predictive model can reflect the attenuation law of skid resistance, and PSV and LAA loss of aggregates are well correlated with the skid-resistance durability of UTFC.

Study on compaction characteristics and mechanical performance deterioration of large stone porous asphalt mixes

Large stone porous asphalt mixes (LSPM) have advantages in promoting pavement performance, including cracking resistance, rutting resistance, and moisture susceptibility. Engineering practice demonstrates that performance degradation is crucial and has an impact on the durability and service life of asphalt pavement. Therefore, this paper aims at investigating the damage characteristics of LSPM as well as proposing the corresponding control methods. Firstly, a simulation device is designed to carry out the temperature cooling testing of LSPM in the laboratory. Then, the variation of air void contents in LSPM was analyzed with different testing temperatures, loading times, and freeze–thaw cycles. LSPM macro-mechanical strengths and cracking resistance were measured during freeze–thaw cycles. The outcome demonstrates that different sections cool at various rates and for varying lengths of time. The effective compaction time and compactness are directly related to the ambient temperature. Paving at medium and high temperatures is an efficient way to increase the compactness of LSPM. The testing temperature, loading time, and freeze–thaw cycles have significant influences on the change of air void contents, while the influence of load strength is low. The penetration shear strength decreases as the number of freeze–thaw cycles increases, and the change trend gradually decreases. Freeze-thaw cycles will lessen the anti-cracking performance of LSPM. Strictly regulating construction parameters, air void content, and drainage conditions could increase the LSPM asphalt pavement's durability and service life. The change in pore structure composition is the primary factor influencing the damage performance of LSPM.

Microstructural characteristics evolution of asphalt mastics under cyclic environmental temperature variations

Environmental temperature-effect is the primary factor responsible for asphalt pavement failure. Asphalt pavement exposed to the atmosphere is constantly subjected to the thermal cycles induced by environmental temperature fluctuations, and the resulting thermal cracks significantly reduce the durability of asphalt pavement. Nevertheless, the influence of cyclic temperature variations on the performance degradation of asphalt binder materials is often overlooked. To address this, accelerated thermal cycling test was conducted on two asphalt mastics to simulate repeated environmental temperature variations. Dynamic shear rheological test (DSR) and atomic force microscopy test (AFM) were performed to characterize the evolution of the macroscopic rheological properties and microstructural characteristics under five cyclic temperature ranges. Pearson correlation analysis was utilized to explore the correlation between macro and micro properties. Following thermal cycling, it was observed that the two asphalt mastics experienced a decline in their viscous properties and became more elastic, resulting in a decrease in their stress relaxation capacity and asphalt-aggregate interaction on a macroscopic level. The microstructure transitioned from a multiphase to a homogeneous structure, while the expansion of the valley structure indicated the accumulation of microscopic defects. The larger the temperature variations and the higher the cyclic temperatures are, the more severe the deterioration in the viscoelasticity and microstructures of asphalt mastics is; the degradation of the micromechanical characteristics directly affects the macroscopic rheological properties. The bee structure ratio, the adhesion, and relaxation properties are sensitive to cyclic temperature variations and recommended to characterize the thermal cycling resistance. In comparison to 90# asphalt mastic, the SBS modified asphalt mastic exhibits great resistance to thermal deterioration. This study deepens the understanding of the causes of asphalt pavement performance deterioration in regions with frequent environmental temperature fluctuations.

Anti-skid durability of porous drainage asphalt mixture based on discrete element

In order to improve safety indicators such as the skid resistance and durability of road, the discrete-element method is used to study the proportion of the asphalt mixture, and the spatial structure of the coarse aggregates and asphalt mortar are compared and analysed. Relevant models are established to compare their pendulum values and structural depth attenuation. When the fine aggregate is limestone and the surface polishing times do not exceed 3500 times, the 7/3S1 asphalt mixture has the best pendulum value. However, as the polishing times continue to increase, the mixture ratio also changes. Compared with the 7/3S1 asphalt mixture, the 8/2S1 asphalt mixture has better effect. When the fine aggregate is replaced by limestone, no matter what form the coarse aggregate is, the pendulum value has been improved to a certain extent comparing with the previous mixture. A2S2, 5/5S2, 7/3S2 and 8/2S2 blends, compared with A2A2, 5/5A2, 7/3A2 and 8/2A2 blends, the pendulum value was increased by 1.7, 0.5, 2.3 and 2.1%, respectively. The study shows that in different proportions of coarse aggregates, as the surface texture richness of the blended aggregate increases, the differences between the aggregates also increases, and skid resistance and durability are also enhanced. The research results provide a blending method to increase the skid resistance and durability of asphalt pavement.

Interfacial bonding property and microscopic damage mechanism of bitumen-aggregate in salt-freeze-thawing environment

Deicing salt or snow-melting agent has a corrosive effect on the pavement, which reduces the durability of asphalt pavement. The interfacial bonding properties of bitumen-aggregate is one of the main factors affecting the durability of asphalt mixture. To evaluate the interfacial bonding properties of bitumen-aggregate and reveal the damage mechanism under salt-freeze-thaw coupling effect, the bitumen-aggregate samples with the same film thickness were formed by controlling the applied load. The corrosion of deicing salt on bitumen-aggregate and bitumen film samples was simulated by freeze-thaw cycles in 1 %, 3 % and 5 % NaCl solution. The pull-off test of SBS modified bitumen-aggregate after salt-freeze-thaw cycles was conducted. The Fourier transform infrared spectrometer (FTIR) test was carried out to qualitatively and quantitatively analyze the impact of salt-freeze-thaw coupling effect on bitumen functional groups. The surface morphology of bitumen samples treated in salt-freeze-thawing environment was also scanned by atomic force microscopy (AFM) in tapping mode. The results illustrate that the pull-off strength of bitumen-aggregate decreases sharply first and then the decrease rate slows down with the rise of salt-freeze-thaw coupling cycles. The carbonyl index and sulfoxide index of SBS modified bitumen increases, and the butadiene index decreases after freeze-thaw cycles in NaCl solution. The environment of salt erosion and freeze-thaw cycle accelerates the deterioration of SBS modifier and reduces the distinction of various phases in bitumen binder. Then the Ra and Rq of SBS modified bitumen decreases significantly in salt-freeze-thawing environment. The decrease of butadiene index and root mean square roughness leads to the weakening of adsorption between SBS modified bitumen and aggregate, which is the main reason for the damage of interfacial bonding performance of bitumen-aggregate. In summary, the salt-freeze-thawing environment damages the bonding performance of bitumen-aggregate. The damage law and deterioration mechanism of bonding properties of bitumen-aggregate presented in this paper provides some references for the optimal design of asphalt mixture in salt-freeze-thawing environment.

Experimental Investigation of LDPE and EVA on Asphalt Binder

Abstract: This research study aims to investigate the impact of incorporating Ethylene Vinyl Acetate (EVA) and Low-Density Polyethylene (LDPE) on the properties of asphalt binder. The use of polymer-modified asphalt binders has gained significant attention in recent years due to their potential to improve the performance and durability of asphalt pavements. EVA and LDPE are two commonly used polymers that have shown promise in enhancing the rheological and mechanical properties of asphalt binders. The experimental investigation involved the preparation of asphalt binder samples with varying percentages of EVA and LDPE, ranging from 0% to 8% by weight. A series of laboratory tests were conducted to evaluate the effects of polymer modification on the fundamental properties of asphalt binder. These tests included penetration, softening point, ductility, viscosity, and dynamic shear rheometer (DSR) tests.The results of the study indicated that the addition of EVA and LDPE led to notable improvements in the rheological and mechanical properties of asphalt binder. Increased polymer content resulted in reduced penetration values, higher softening points, and improved resistance to rutting and deformation. Additionally, the modified binders exhibited enhanced viscosity and elastic behavior, as indicated by the DSR tests. The study also investigated the compatibility between EVA/LDPE and asphalt binder through microscopy and chemical analysis techniques. The findings of this experimental investigation contribute to the understanding of the effects of EVA and LDPE on asphalt binder performance. The results highlight the potential of these polymers in enhancing the resistance to rutting and deformation of asphalt pavements. This research can serve as a basis for further studies on polymer modification of asphalt binders and aid in the development of improved asphalt pavement materials with enhanced durability and longevity.