Typical Asphalt Research Articles

Rheological Properties and Modification Mechanism of Emulsified Asphalt Modified with Waterborne Epoxy/Polyurethan Composite.

In research aimed at improving the brittleness of WER (waterborne epoxy)-modified emulsified asphalt, commonly encountered issues are that the low-temperature performance of this type of asphalt becomes insufficient and the long curing time leads to low early strength. Matrix-emulsified asphalt was modified with WPU (waterborne polyurethane), WER, and DMP-30 (accelerator). Firstly, the performance changes of modified emulsified asphalt at different single-factor dosages were explored through conventional performance tests and assessments of its adhesion, tensile properties, and curing time. Secondly, based on a response surface methodology test design, the material composition of the composite-modified emulsified asphalt was optimized, and its rheological properties were analyzed by a DSR test and a force-ductility test. Finally, the modification mechanism was explored by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that WER can improve the adhesion strength of modified emulsified asphalt and greatly reduce elongation at break. WPU can effectively improve the elongation at break of composite-modified emulsified asphalt, but it has a negative impact on adhesion strength. DMP-30 mainly affects the curing time of modified emulsified asphalt; EPD (composite modification) can effectively improve the high-temperature rutting resistance of matrix-emulsified asphalt, and its low-temperature performance is significantly improved compared with WER-modified emulsified asphalt. The EPD modification process mainly consists of physical blending. In the case of increasing the curing rate, it is recommended that the contents of WER and WPU be lower than 10% and 6%, respectively, to achieve excellent comprehensive performance of the composite modification.

Evaluation for coarse aggregate distribution of asphalt mixtures based on the two-dimensional digital image analysis

Meso-structure is one of the major sources of macro-performance in asphalt mixtures. The research on aggregate distribution state is of great significance for the further improvement of asphalt mixture macro-performance. However, the variations of research methods among prior works hamper the deduction of the holistic potential and promising directions of coarse aggregate distribution analysis from current research findings. This work comprehensively verified the quantifying ability of aggregate distribution state indices and their correlation with rutting performance under an advanced digital image processing technique and a wide range of asphalt mixture types, and aims to provide a reference of the holistic potential and promising directions of coarse aggregate distribution analysis for subsequent research. To this end, eleven typical asphalt mixtures’ aggregate distribution state and rutting performance were measured, quantified, and correlated. The results show that Kpe nears or more than 0.56 can be the sign of coarse aggregates effectively interlocked while it nears or less than 0.26 is the opposite; Uarea nears or less than 2 % can be the sign of reaching a coarse aggregate distribution equilibrium; Δorien approaches 6.21 can be the sign of reaching a coarse aggregate orientation equilibrium; mixtures with a nominal maximum aggregate size of 10 mm are disabled in gathering contact chains. Moreover, these coarse aggregate distribution state quantifying indices proposed in existing research can indeed describe the meso-structural features of asphalt mixtures to a certain extent. However, these indices fail to capture the underlying meso-structural features relating to rutting performance and lead to limited applicability. Furthermore, the poor performance of these coarse aggregate distribution state quantifying indices in the global fitting mainly comes from their incompatibility with changes in nominal maximum aggregate size.

Research on the micro-mechanism and factors of hot recycled asphalt binder cracking

The poor low-temperature performance of recycled asphalt is the primary cause of the recycled asphalt disease. However, further strengthening is required to analyze the molecular-level cracking of recycled asphalt. This article presented a comprehensive investigation of the cracking phenomenon of recycled asphalt at both the macro and micro levels. This was achieved through the utilization of experimental tests and molecular dynamics simulations. In this study, pressure-aged asphalt was subjected to 40 h of aging. The aged asphalt was divided into three groups: 30% RAP (reclaimed asphalt pavement) recycled asphalt, 50% RAP recycled asphalt, and 70% RAP recycled asphalt. The three groups were then analyzed in terms of three major indexes. Linear amplitude scanning (linear amplitude sweep, LAS) was conducted on the three groups. The mechanical response law of asphalt was obtained, and it was found that the coefficient of strength of recycled asphalt increased with the increase of RAP dosage. At the same time, the fracture energy density decreased subsequently. Furthermore, the fracture energy density of aged asphalt was 7% lower than base asphalt's. Subsequently, this study examined the four fractions and C=O and S=O functional groups of five types of asphalt and constructed the molecular structures and models of stable base asphalt and aged asphalt. Subsequently, this article constructed a fusion model of new and old asphalt, analyzed the fusion process of new and old asphalt, and studied the factors affecting the blending degree of new and old asphalt. Finally, the factors affecting the cracking performance of rejuvenated asphalt, including the blending degree, the content of the four fractions, and the addition of the rejuvenator, were investigated. The impact of each influencing factor on the cracking performance of recycled asphalt was analyzed from multiple perspectives. In conclusion, the findings of this study provide a valuable guide for interpreting the tensile properties of reclaimed asphalt and the influence of rejuvenators.

Performance of rubber modified asphalt mixture with tire-derived aggregate subgrade

The objective of this research is to investigate the long-term performance of rubber-modified asphalt mixture (RMA) on Tire-Derived Aggregate (TDA)-replaced saturated subgrade as a drainage material. In lab testing setup, the mixtures were subjected to a 5-day conditioning at 85°C to ensure complete long-term aging. A series of laboratory and field tests were conducted. The study found that the surface course rubber mix had the best-cracking resistance than the leveling course control mix and surface layer control mix. Additionally, the fracture energy of the surface layer rubber mix was 17.4–21.9 % higher than that of the surface layer control mix. After the long-term aging condition, all three types of hot mix asphalt (HMA) exhibited exceptional resistance to deformation. Rubber-modified asphalt improved fatigue properties and crack performance. In summary, implementing RMA in pavement construction improved the pavement's thermal cracking and fatigue properties and significantly reduced pavement noise. TDA has potential as a fill material in subgrade applications, and rubber-modified asphalt shows promising performance for asphalt pavement.

Fracture characteristics of SMA mixtures with hydrated lime through the semi-circular bending approach

Stone Mastic Asphalt (SMA) is a composite mixture made up of high-quality crushed stone, fine aggregates, an asphalt binder, and a significant percentage of mineral filler in contrast to conventional mixtures. Renowned for its durability and rolling resistance, it is predominantly employed as a surface “wearing” course on main roads subjected to heavy traffic, but it can also be used as a binder course under specific project requirements. In this study, we investigated the effect of hydrated lime as a partial replacement of limestone filler at various concentrations on the mechanical and cracking resistance characteristics of 10-mm SMA mixtures. The semi-circular bending (SCB) test, which is pivotal for understanding the cracking mechanism was used to assess the mixtures performance-related response to this distress type. The mixture cores were produced with granite aggregates, limestone filler as natural filler, hydrated lime as natural filler replacement, and a 30/45 penetration asphalt type. Mixtures containing 1.1 %, 2.2 %, and 3.4 % of hydrated lime by weight of aggregates were evaluated, in addition to a control mixture without hydrated lime. The factors considered for comparing the mixtures included: load and deformation curves, stiffness, fracture toughness, fracture energy, and flexibility index of the mixtures. The experimental program also comprised a set of various test temperatures (0°C, 10°C, and 20°C) to better understand the cracking mechanism. Experimental results indicated a significant performance-dependency on the HL concentration and the test temperature. Precisely, it was found that the mixture with the highest hydrated lime content (3.4 %) exhibited the best cracking performance at 0°C and 20°C, making it a suitable filler replacement concentration. However, at 10°C, the mixture containing 2.2 % hydrated lime showed the most consistent performance overall, suggesting and important improvement in asphalt mixtures’ cracking resistance. Overall, these findings obtained from the SCB test approach substantiate the potential benefit of hydrated lime filler replacement in optimizing the cracking performance and durability of SMA mixtures under varying temperature conditions and loading regimes.

Grey correlation analysis of asphalt-aggregate adhesion with high and low-temperature performance of asphalt mixtures

The adhesion work and force of the five types of asphalt to andesite were measured using surface energy and pull-out tests, respectively. Various tests were operated to estimate the high and low-temperature characteristics of the five types of asphalt mixtures: high-temperature rutting, low-temperature bending, indirect tensile creep, and thermal stress restrained specimen tests. Furthermore, the high and low-temperature evaluation index, adhesion work, and adhesion force of these asphalt mixtures were analyzed using grey correlation analysis. The results show that compared with the adhesion work, the actual contact between mineral aggregate and asphalt in the pull-out test leads to the difference in adhesion force and work measured by SBS-modified, SBR-modified, and extreme cold asphalt. The correlation degree of adhesion work and force to the evaluation indexes of high and low-temperature properties in asphalt mixture is roughly the same, and the adhesion work has a more momentous impact on the high and low-temperature properties in asphalt mixtures. The adhesion work and force correlate best with low-temperature bending test parameters and thermal stress restrained specimen test (TSRST) parameters related to fracture failure of asphalt mixture, followed by the indirect tensile creep test parameters. It shows that the adhesion work and force significantly impact the low-temperature characteristics of asphalt mixture more than their high-temperature stability.

A study on the mechanisms and influencing factors of interfacial physicochemical interactions between asphalt and mineral aggregates based on multiscale evaluation methods

The elucidation of interfacial physicochemical mechanisms between asphalt and mineral aggregates is vital for comprehending the interface formation in asphalt mixtures and enhancing their performance. To this end, multiscale evaluation methods were used to investigate the mechanisms and influencing factors of interfacial physicochemical interactions between asphalt and mineral aggregates (IPIAMA). Initially, the dynamic shear rheometer (DSR) was used to measure the complex shear modulus (G*) of various asphalt mastics. Subsequently, the interface film thickness was calculated using G* in conjunction with the Hashin and Mori-Tanaka (MT) micromechanical models. This indicator facilitated quantitative assessments and the analysis of influencing factors. The results indicated that the MT model underestimated the interface film thickness by approximately 0.08–0.29 % compared to the Hashin model, a discrepancy attributable to assumptions regarding aggregate particle interlocking. Moreover, the interface film thickness systematically varied with factors such as aggregate content, type of aggregate, and type of asphalt, ranging from 0.24 to 0.53 μm. To further elucidate the IPIAMA mechanisms behind these variations, the fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and the ultraviolet test (UV) testing were conducted. FTIR tests demonstrated that the primary components of mineral aggregates—dolomite, calcite, and quartz—contributed to the physical adsorption increments on asphalt functional groups by 0.0185, 0.0509, and 0.004, respectively. SEM images revealed that dolomite and calcite possessed more surface fissures and pores than quartz. XPS tests showed that calcium carbonate and magnesium carbonate chemically reacted with asphalt, resulting in electron shifts of 0.9 eV and 1.1 eV, respectively, while silicon oxide only exhibited electron shifts when combined with a silane coupling agent-modified asphalt. UV tests demonstrated that lighter asphalt fractions were preferentially absorbed into the pores and micro-cracks of mineral aggregates. Consequently, the complex IPIAMA involved physical adsorption, chemical reactions, and selective absorption, strongly correlating with factors such as mineral composition, surface morphology, and asphalt type.

Study on the Factors Affecting the Self-Healing Performance of Graphene-Modified Asphalt Based on Molecular Dynamics Simulation.

To comprehensively understand the impact of various environmental factors on the self-healing process of graphene-modified asphalt, this study employs molecular dynamics simulation methods to investigate the effects of aging degree (unaged, short-term aged, long-term aged), asphalt type (base asphalt, graphene-modified asphalt), healing temperature (20 °C, 25 °C, 30 °C), and damage degree (5 Å, 10 Å, 15 Å) on the self-healing performance of asphalt. The validity of the established asphalt molecular models was verified based on four physical quantities: density, radial distribution function analysis, glass transition temperature, and cohesive energy density. The simulated healing time for the asphalt crack model was set to 200 ps. The following conclusions were drawn based on the changes in density, mean square displacement, and diffusion coefficient during the simulated healing process under different influencing factors: Dehydrogenation and oxidation of asphalt molecules during the aging process hinder molecular migration within the asphalt crack model, resulting in poorer self-healing performance. As the service life increases, the decline in the healing performance of graphene-modified asphalt is slower than that of base asphalt, indicating that graphene-modified asphalt has stronger anti-aging properties. When the vacuum layer in the asphalt crack model is small, the changes in the diffusion coefficient are less pronounced. As the crack width increases, the influence of various factors on the diffusion coefficient of the asphalt crack model becomes more significant. When the crack width is large, the self-healing effect of asphalt is more dependent on these influencing factors. Damage degree and oxidative aging have a more significant impact on the healing ability of graphene-modified asphalt than healing temperature.

Evaluation of Bonding Adhesion Strength and Failure Modes of Different Types of Cutback Asphalts

Evaluation of Bonding Adhesion Strength and Failure Modes of Different Types of Cutback Asphalts

Effects of different penetration‐grade asphalt binders on the microstructure, mechanical, and aging properties of cold‐mixed epoxy asphalt binder

AbstractThe aim of this research was to investigate asphalt effects on the storage stability, mechanical properties and micro‐properties of cold‐mixed epoxy asphalt binder (CEAB). Firstly, four CEAB were prepared with four base asphalt types and storage stability, miscibility analyses were performed by fluorescence microscopy (FM). Then, cured CEAB and epoxy resin (ER) were treated by ultraviolet aging. Tensile test, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy were applied to clarify the mechanical properties and micro‐properties of aged and unaged CEAB. Also, bending beam rheometer (BBR) tests were conducted to study low‐temperature performance of CEAB. The results revealed that the CEAB prepared with asphalt with penetration grade 60 ~ 80 presented superior storage stability, miscibility, mechanical properties and that prepared with penetration graded 80 ~ 100 showed slightly better low‐temperature performance. Moreover, asphalt properties were found to have little impacts while epoxy resin played a key role in the mechanical properties of CEAB. Glass transition temperature () of the CEAB containing penetration‐graded asphalt 80 ~ 100 decreased more significantly than that with penetration‐graded asphalt 60 ~ 80, and it was also found that the CEAB prepared with base asphalt with higher molecular weight polydispersity index had better ductility performance.

Characterization of light components in rubber-oil mixtures reclaimed asphalt and their effect on the self-healing performance of asphalt

The aging process of asphalt pavement results in the loss of light components (saturates and aromatics) in asphalt, necessitating the use of regenerators for restoration. The study examined the variation pattern of light components in reclaimed asphalt and their effect on the self-healing performance of asphalt after regeneration. Two types of aged asphalt were analyzed using low-temperature co-pyrolysis products of waste tire crumb rubber (WTCR) and waste cooking oil (WCO). The reclaimed asphalt was fractionated into light components using the SARA (saturates, aromatics, resins, and asphaltenes) method. The regenerator containing the highest concentration of light components was identified through the Soxhlet extraction test. The compound compositions and functional groups of the light components in reclaimed asphalt were characterized using gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). Moreover, the self-healing performance of the reclaimed asphalt was evaluated using a dynamic shear rheometer (DSR). The results indicate that the 260-1-WROM regenerator produced an optimal content of light components under pyrolysis conditions at 260 °C for 1 h. Incorporating the 260-1-WROM regenerator in RTFO resulted in an increase in hopanoids, oxygenates, heterocyclics, and aromas. Similarly, the PAV regeneration process exhibited elevated levels of paraffins, hopanoids, oxygenates, alkanes, heterocyclics, and aromatic compounds. However, the presence of 260-1-WROM failed to increase the contents of steroids. Both types of reclaimed asphalts exhibited superior self-healing capabilities compared to 70#A, RTFO, and PAV. This suggests that 260-1-WROM effectively restored the light components in the aged asphalt, thereby optimizing the flowability of the reclaimed asphalt and enhancing its self-healing properties. Given the above findings, the recommended dosage for 260-1-WROM is 8 % for RTFO and 10 % for PAV.

Analysis of the self-healing mechanism of TB compound-modified asphalt based on molecular dynamics

To investigate the intrinsic self-healing behavior of terminal blend (TB)-modified asphalt (TBMA), this study establishes four models of matrix asphalt, TBMA, TBMA containing styrene-butadiene-styrene (TB_SBS), and TBMA containing ethylene vinyl acetate (TB_EVA) based on molecular dynamics, and the self-healing ability of the four types of asphalt was evaluated by means of the diffusion coefficient, diffusion activation energy, and pre-exponential factor. Finally, the study analyzes and validates the self-healing performance of the asphalt through fatigue shear-healing tests. The results showed that the self-healing potentials of the four types of asphalt, as determined by the diffusion coefficient, diffusion activation energy, and pre-exponential factor, were (in descending order) TB_SBS, TBMA, TB_EVA, and matrix asphalt. In addition, the diffusion coefficient of the TBMA was increased relative to the matrix asphalt, SBS polymer further increased the diffusion coefficient, and EVA modifier had an inhibitory effect, which was related to the viscoelasticity and mechanical performance of the material. Besides, the diffusion coefficient enhancement effect of the SBS modifier on the TBMA was greater than the inhibition effect, which mainly derived from the enhancement of the diffusion coefficient of lightweight components in significantly enhancing the self-healing ability the TBMA. From microscopic and macroscopic scales, the shear-fatigue healing tests showed excellent correlation with the simulation results, demonstrating that molecular dynamics can be used to model the self-healing process of asphalt.

Synergistic enhancement of rheological and anti-aging properties of asphalt modified with bio-oil and layered silicate

Applying bio-oil to asphalt pavement effectively reduces the dependence on traditional petroleum asphalt in pavement industry. However, the utilization of bio-oil can encounter rutting and aging issue of modified asphalt. To solve the aforementioned issue, two kinds of organic layered silicates with typical structures were adopted to enhance the high-temperature and anti-aging performance of the bio-modified asphalt. The modification mechanism and the synergistic effect of bio-oil and organic layered silicate on asphalt were explored through rheological characterization, infrared spectroscopy tests, gel chromatography tests, etc. Results showed that the incorporation of layered silicate in bio-modified asphalt can improve asphalt-filler interaction and hence the high-temperature and fatigue performance of asphalt. When the content of layered silicate is 5 %, the negative effect of Castor oil on the high-temperature performance of asphalt can be eliminated. Still, for Turpentine wood oil and Straw oil, the content of layered silicate is 7 %, which shows the same effect. The waste bio-oils can balance the low-temperature performance of asphalt modified with layered silicates. Furthermore, the addition of layered silicates was effective to reduce oxidation reaction and improve the anti-aging performance of bio-oil modified asphalt. When the ratio of layered silicate to bio-oil is 1 1, the composite-modified asphalt maintains the best anti-aging performance. Specifically, Castor oil, Straw oil, and OMMT are more suitable, and Turpentine wood oil and OREC are more appropriate. According to the quantification of the functional group aging index, the SI and CI of the optimal ratio of different types of bio-oil asphalt are Castor oil: 61.64 % and 59.41 %, Turpentine wood oil: 50.02 % and 53.57 %, Straw oil: 50.01 % and 55.05 %. Composite modified asphalt can be applied to complex service conditions.

Microanalysis of behavior characteristics for asphalt binders on different mineral surfaces based on MD and SEM

To investigate the influence of different minerals on the behavior characteristics of asphalt binders at micro scale, molecular dynamics (MD) and scanning electron microscopy (SEM) were combined to study the interaction of asphalt binders and different mineral surfaces. Firstly, commonly used aggregates were analyzed by X-ray diffraction (XRD), and the main mineral categories were obtained, including quartz, albite, biotite and calcite. Secondly, the asphalt-mineral micro models were established by combining the reasonable asphalt micro model and mineral micro model, and the interface behavior characteristics were analyzed by MD simulation. Finally, the interface structure of asphalt and minerals was observed through SEM testing, which intuitively revealed the behavior characteristics of asphalt on different mineral surfaces. The results show that the relative concentration distribution of asphalt binders at the asphalt-mineral interface is relatively high, and it can be affected by mineral category, surface structure state and asphalt type. The transition zone of biotite, albite and asphalt interface is relatively wide, which means that the influence of biotite, albite and asphalt diffusion characteristics is relatively obvious, and the interface interaction ability is relatively strong. The study reveals the behavior characteristics of asphalt binders on different mineral surfaces, and provides a research basis for exploring the structural stability of asphalt-aggregate interface.

Investigation of nanoscale interfacial bonding properties in foamed asphalt cold recycled mixtures under chloride salt erosion

Salt-induced erosion from de-icing salts in Northern China and sea salt in Eastern coastal areas significantly compromises asphalt pavement integrity. A selection was made of four different types of foamed asphalt with different levels of water content, two types of aged asphalt, and three typical minerals (α-quartz, calcite, and bauxite), in addition to three chloride salt solutions (NaCl, CaCl2, MgCl2). It was found that (1) in dry conditions, the moisture level of foamed asphalt noticeably influences the adhesive performance at the juncture between asphalt and aggregates. Unlike acidic minerals, the bond strength between alkaline and neutral minerals and foamed asphalt increases as the water content of the foamed asphalt rises; (2) chloride salt solutions presence and increased levels significantly reduced the bond strength between asphalt and aggregates, particularly impacting neutral and alkaline minerals (in the presence of 10 % NaCl solution, the work of adhesion was reduced by 83.82 % and 87.48 %, respectively); (3) the influence of diverse chloride salts on the interfacial adhesive performance of asphalt mixtures varied, with the three chloride salts reducing the asphalt-aggregate interfacial adhesion work by 44.52 %, 21.90 %, and 34.94 %, respectively. (4) the investigation determined that the mineral composition considerably influences the hygroscopic sensitivity of asphalt mixtures. Minerals of an acidic nature exhibit superior moisture resistance when juxtaposed with alkaline counterparts, recommending the adoption of acidic aggregates in scenarios demanding elevated mixture stability.

Quantitative characterization of fusion state of virgin and aged asphalt using nano-ferrous ferric oxide tracer

The exact evaluation of the fusion rate of virgin and aged asphalt is essential to optimize the performance of the recycled asphalt mixture. The fusion rate index was developed by tracing the distribution of tracer asphalt, which contains nano-ferrous ferric oxide (nano-Fe3O4) tracer. Laboratory fusion simulation tests were performed on three types of asphalt to obtain different fusion states, and fatigue tests were performed to evaluate the influence of the fusion rate on the fatigue life of the recycled asphalt. It was found that the tracer asphalt containing 4% nano-Fe3O4 shows the optimal trace effect, and the developed fusion rate index can quantitatively characterize the influence of different factors on the fusion state of the recycled asphalt. The fusion state is closely related to the fatigue performance of recycled asphalt, and the fusion rate index can fairly evaluate its fatigue performance. The relationship between the fusion rate and the fatigue life of recycled asphalt depends on the factors that cause the fusion rate variation. Under the influence of the amount of rejuvenator, the fatigue life of recycled asphalt grows exponentially with increasing fusion rate due to enhancement of molecular motion as well as a supplement of lightweight components. Under the influence of heat preservation treatment, fatigue life increases linearly with increasing fusion rate. The proposed fusion rate index can be utilized to quantitatively characterize the fusion state of virgin and aged asphalt, thus providing a simple way to guide the practical application of recycled asphalt.

Characteristics and analysis of static strain response on typical asphalt pavement using fiber Bragg grating sensing technology

To study the real internal strain response of asphalt pavement and provide crucial data for optimizing pavement design. By burying the fiber grating sensors on site, the strain tests of four asphalt pavement structures under different working conditions were carried out, and the results showed that the static strain time curve is viscoelastic and conforms well to the Bugers model, and the fitting coefficient of determination is 0.98. The strain response of the asphalt surface courses of the four pavement structures under static load shows a double hump variation with the transverse position, with peaks occurring directly beneath the wheel load center. The transverse strain fluctuated between tension and compression, mirroring changes in the lateral position. While longitudinal strains, always tensile, were symmetrically aligned with the centerline of the longitudinal sensors, this pattern differed notably from that of the transverse sensors. In the base layers, the strain profile typically presented a single peak, located at the wheel gap, underscoring a critical area of stress concentration. Numerically, the peak strain of asphalt surface course is larger than that of base course. The most unfavorable loading position of the base course occurs at the wheel gap of the lower base course. The most adverse loading position of the surface course appears at the wheel load at the bottom of the upper or middle course. The research results can provide data support for improving the design method of asphalt pavement.

Effects of a Complex Environment on Fatigue and Self-Healing Characterization of Asphalt Composites Containing Rock Asphalt.

In recent years, asphalt pavement has been subjected to varied environmental conditions during its service life, conditions that predispose it to deformation and cracking. To enhance the performance of asphalt pavement, rock asphalt has been selected as a modifier due to its good compatibility with virgin asphalt binder and its ability to improve the fatigue cracking resistance of asphalt mixtures. Although scholars have conducted some studies on rock asphalt mixtures, research on the fatigue and self-healing performance of these mixtures under conditions such as ultraviolet (UV) aging and freeze-thaw remains limited. This paper presents findings from a study that employs a combined fatigue-healing test to assess the impact of such complex environmental factors on the fatigue and self-healing properties of fine aggregate matrix (FAM) mixtures containing three types of rock asphalts, i.e., Buton, Qingchuan (QC), and Uintaite Modifier (UM). The analysis of fatigue-healing test results, grounded in viscoelastic continuum damage (VECD) theory, indicates that rock asphalt can extend the fatigue life of FAM mixtures, albeit with a concomitant decrease in their self-healing capabilities. The study further reveals that UV aging, freeze-thaw, and UV aging-freeze-thaw conditions all led to a diminution in the fatigue and self-healing properties of FAM mixtures. However, FAM mixtures containing rock asphalt demonstrated greater resilience against these reductions. Atomic force microscope (AFM) results indicate that UV aging reduced the number of bee-structures and enlarged their area, whereas the incorporation of rock asphalt enhanced the uniformity of these structures' distribution, thereby improving the fatigue cracking resistance of FAM mixtures. Fourier transform infrared spectroscopy (FTIR) analysis reveals that while UV aging increased the carbonyl and sulfoxide indices within the asphalt binder, rock asphalt is effective in mitigating this effect to a certain degree, thereby enhancing the aging resistance of FAM mixtures.

Study on the Long-Term Salt Release Characteristics of Self-Melting Ice Asphalt Mixtures and Their Impact on Pavement Performance.

Self-melting ice asphalt pavement materials inhibit pavement freezing and improve driving safety. This paper aims to study the long-term salt release characteristics of self-melting ice asphalt mixtures and the impact on pavement after complete salt release. Firstly, a method to accelerate the rapid release of salt based on the Los Angeles abrasion tester. Then, long-term salt release patterns were elucidated under the influence of deicing agent dosage, type of asphalt, and type of gradation. Finally, a quantitative analysis of the pavement performance after complete salt release is conducted. The results indicate that the release efficiency of the Los Angeles abrasion tester method has increased by 91 times compared to the magnetic stirrer immersion flushing method and by 114 times compared to the natural soaking method. The SBS-modified self-melting ice asphalt mixture possesses a longer duration of salt release, but the uniformity of salt release is inferior. Salt release duration is directly proportional to the dosage of deicing agents. SMA-13 self-melting ice asphalt mixture exhibits poorer uniformity in salt release. After complete salt release, high-temperature stability of self-melting ice asphalt mixtures decreased by 31.6%, low-temperature performance decreased by 15.4%, water stability decreased by 26.7%, and fatigue life decreased by 35.9%.

Multi-scale analysis of virgin/aged/recycled asphalt self-healing performance based on molecular simulation and micro-macro tests

Conventional macro-micro experiments have not fully elucidated the thermal self-healing mechanism of virgin, aged, and recycled asphalt at the molecular level at different temperatures. Molecular dynamics and macro-micro experiments were used to investigate the multi-scale mechanism of thermal self-healing of nano-cracks in three asphalt types. The molecular characteristics (concentration, energy changes, and molecular diffusion properties) of the three asphalt types were simulated during self-healing using molecular dynamics simulations Macro-micro experimental tests were conducted to validate the simulation results. The self-healing process was analyzed at multiple scales, and correlation analysis between the self-healing parameters and the macroscopic healing characteristics was performed at nano- and microscopic scales. The results showed that the relative concentration increased significantly from 0 mol/L to 0.6 mol/L in the 60–80 Å range during the long-distance self-healing phase (0–40 ps), promoting the rapid reorganization of molecules around cracks and the formation of self-healing networks. The van der Waals forces were the dominant forces affecting self-healing, and the transition from repulsive to attractive forces promoted the self-healing of cracks. This study clarifies the thermal self-healing mechanism of asphalt cracks at multiple scales, ensuring the sustainable use of asphalt materials.