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The thermal cracking behaviour of asphalt pavement is complex and includes thermal contraction, low-temperature relaxation, and low-temperature damage. However, using relaxation characteristics alone instead of low-temperature properties leads to an incomplete evaluation. In this paper, the relationship between viscoelastic properties and relaxation characteristics was analyzed. Based on the time domain characteristics of relaxation, the relaxation rate and cumulative stress at per unit strain rate (CSSR) were proposed as evaluation indexes corresponding to the long-term/short-term characteristics of the relaxation. By combining the relationship among the low-temperature performance obtained by Thermal Stress Restrained Specimens Test (TSRST) and relaxation characteristics, evaluation indexes for the low-temperature performance of asphalt mixture were preferably selected. The results show that asphalt binders dominate the relaxation characteristics of asphalt mixtures, but do not directly replace the low- temperature performance of asphalt mixtures. The relaxation characteristics expressed by the traditional viscoelastic indexes were insufficient to fully evaluate the low- temperature performance of asphalt mixtures. Furthermore, the results of the relaxation characteristic index for evaluating the low-temperature performance were different under different temperature conditions, indicating that performance at a single temperature cannot replace the low-temperature performance at all temperatures. [ABSTRACT FROM AUTHOR]

This study focused on the application of Rayleigh wave technology on a non-destructive determination of dynamic modulus of asphalt mixtures. A 3-D finite element numerical algorithm was developed to simulate Rayleigh wave propagation in a multi-layer half-space system. Numerical analysis verified the feasibility of Rayleigh wave technology to capture the mechanical property differences in shallow structures within asphalt pavements. Then, five asphalt mixtures were used in the experimental application of Rayleigh wave technology. A multichannel simulation with one receiver (MSOR) was adopted to generate Rayleigh waves in asphalt mixture samples. Changes in phase velocity-frequency energy spectra and wave velocity were used to evaluate effects of ambient air temperature and asphalt mixture type on wave propagation evolution in asphalt mixtures. Rayleigh wave technology was introduced to dynamic modulus analysis using various experimental temperatures and asphalt mixtures. Obtained modulus was compared with that using impact resonance method to evaluate the prediction precision for analysis dynamic modulus of asphalt mixtures. [ABSTRACT FROM AUTHOR]

• The optimum preparation technology of CF-GT conductive asphalt mixture with low resistivity are clarified. • The resistance and stress of the mixture have an excellent linear correlation in NPC stage. • The feasibility of applying graphite tailings to prepare the conductive asphalt mixture is demonstrated. The massive accumulation of graphite tailings (GT) brings huge pressure to environmental engineers. Meanwhile, the conductive asphalt pavement industry is suffering from the high construction cost and the complex acquisition of conductive materials. The application of GT in asphalt mixture as a conductive material may be a win–win solution for the above concerns. This study aims to evaluate the feasibility of preparing carbon fiber graphite tailings (CF-GT) conductive asphalt mixture. The optimum preparation technology and material ratio were explored. The service performance tests of the conductive asphalt mixture were conducted, including conductive characteristics, electrothermal performance and pavement performance. Based on the experimental results, 0.3% (mass fraction) 6 mm-polyacrylonitrile (PAN)-based carbon fiber (CF) and 12% (mass fraction) GT were selected as conductive materials to prepare conductive asphalt mixture with resistivity of 5.75 Ω∙m. The addition of GT reduced the resistance by a maximum of 59.8%. The temperature-sensitive and pressure-sensitive characteristics of the mixture have staged characteristics. Moreover, the resistance and stress of the mixture have an excellent linear correlation in the positive pressure coefficient (PPC) effect stage and negative pressure coefficient (NPC) effect stage respectively, especially NPC. Conductive asphalt mixture has a good heating effect after being powered on. GT combined with CF enhanced the high-&low-temperature performance but deteriorated the moisture damage resistance performance of the asphalt mixture. The feasibility of CF-GT conductive asphalt mixture was demonstrated. [ABSTRACT FROM AUTHOR]

• Perform fractal and multifractal analysis on the asphalt mixture's aggregate skeleton and void structure. • The influence of design and construction indicators on the microstructural features of pavement materials. • The fractal/multifractal parameters' physical sense and role in characterizing the 3D microstructure are clear. The aggregate skeleton and void structure in the asphalt mixture are critical and highly correlated to the mechanical performance of the pavement. However, the extreme heterogeneity and complexity bring devastating difficulties to characterizing and analyzing the mixtures' mesostructure. Therefore, this study aimed to propose a novel depicting scheme accounting for the size distribution and spatial arrangement of the mixtures' components utilizing the fractal and multifractal analysis. Two compaction methods (Marshell and Superpave) and three design indexes (gradation, NMAS, and compaction work) were adjusted to prepare the samples, which were then scanned and digitally reconstructed. The fractal dimension (D) and related multifractal indicators (i.e., Δ α and Δ f (α)) were determined and applied to quantitative assess the structural changes. Finally, the relationships of design indexes to fractal and multifractal behaviors were comprehensively discussed. Results indicate that fractal and multifractal theories are feasible in describing the heterogeneous particle skeleton and void structure in the asphalt mixture. Firstly, the multifractal approach was proven to allow a more informative characterization of 3D systems than simple fractal theory. Moreover, the excellent correlation between the design/construction and fractal/multifractal indicators has been confirmed for asphalt pavement. Overall, the fractal and multifractal indicators enriched the options for microstructural evaluation, which will be conducive to revealing the relationship between the microstructural characteristics and mechanical performance of the asphalt mixture. [ABSTRACT FROM AUTHOR]

The objective of this study is to expose the effect of a variety of variables including three reclaimed asphalt pavement (RAP) contents, two warm mix asphalt (WMA) additives and a rejuvenating agent (or lack of) on the performance of WMA containing (WMA–RAP) materials. A laboratory study was conducted to evaluate the performance of WMA–RAP mixtures through rutting, bending and freeze-thaw splitting tests. Analysis of variance (ANOVA) was performed to analyse the significant effect of the variables on the performance. The tests results showed that the increased RAP content led to an increased rutting resistance and the decreased resistance to low-temperature cracking and moisture damage. The addition of the rejuvenating agent into the WMA–RAP mixtures can significantly improve the low-temperature cracking and moisture resistance. The ANOVA results showed that the RAP content had a significant effect on the rutting and low-temperature cracking resistance, and moreover, the rejuvenating agent (or lack of) had a large effect on the low-temperature cracking and moisture resistance. [ABSTRACT FROM PUBLISHER]

• Emphasize the impact of meso-structural variability and uncertainty of HMA. • Provide a system for evaluating and analyzing the meso-structural skeleton. • Clarify the relationship between the IC particles and the DASR-based skeleton. The variability and uncertainty bring great trouble to the application and in-depth research of asphalt mixture. This study aimed to detect the microstructural differences between the asphalt specimens after fixing the experimental and environmental inputs. To this end, the digital image correlation (DIC) method was utilized to propose reliable skeletal and disruptive meso-parameters. Besides, the close packing theory and digital sieving technique were combined to classify the internal particles of the mixture structure. Afterward, the stochastic behaviors of the particle systems containing the dominant aggregate size range (DASR) and interstitial component (IC) aggregates were thoroughly discussed. Finally, the disruption effect of IC on the skeletal structure was also investigated. The analysis results show that the microstructure of the asphalt mixture was a typical random system with a great deal of contingency. The aggregate contact index (ACI) was the most variable among the overall skeletal parameters, with a variation coefficient (COV) of 13.24 %. Besides, almost all the microstructural indexes indicated that about 4% of the specimens in parallel tests showed significant variability behavior, e.g., N a ,13.2 > N a ,16.0. Besides, the microstructural uncertainty of the minority class, e.g., the 16-mm aggregates with a 4% ∼7% COV higher than the other classes, was particularly significant. Finally, the interference effect was proven to focus on the contact behavior of DASR particles, thus damaging the DASR-based system. This study not only emphasizes the impact of variability but provides implications for controlling the performance of asphalt pavement. [ABSTRACT FROM AUTHOR]

• The voxel-based morphological process optimized the automatic extraction procedure of digital aggregates. • A robustness and accuracy analysis map was designed based on the virtual gradation of asphalt mixture. • The three-dimensional reconstruction algorithm can be evaluated quantitatively and then optimized purposefully. • Four types of internal defects generated by the traditional pixel-based method were detected. Three-dimensional image reconstruction plays a pivotal role in microstructure information extraction and virtual mechanical experiments of asphalt mixture. However, the traditional pixel-based reconstruction algorithm tends to be powerless in processing three-dimensional (3-D) mesostructure. Therefore, this paper aims to develop a robust and accurate algorithm for high-quality aggregate particle extraction. To this end, the global thresholding and three-dimensional mathematical morphological methods were conducted directly based on voxel operation. Then the calculated weight-based gradation was utilized to develop the robustness and accuracy analysis map (RAAM), which assesses and compares the traditional and novel reconstruction algorithms. As a sequence, the voxel-based method had higher accuracy and lower perturbation sensitivity than the existing procedures. Additionally, the computed efficiency was improved dramatically by breaking tight bounds and conservatism. Finally, the inevitable algorithm defects caused by multiple morphological treatments in the traditional method have disappeared in the novel one. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sessile drop method can characterize surface free energy of viscoelastic materials. [•] Column wicking technique can characterize surface free energy of solid powders. [•] Specific surface area effects interaction between asphalt and fillers remarkably. [•] The adhesion work can response the moisture sensitivity of asphalt mixtures. [•] A good correlation exists between complex modulus G ∗ and work of adhesion. [Copyright &y& Elsevier]

Abstract: Low temperature cracking is the major damage in asphalt pavement, and many test methods have been used to evaluate the anti-cracking property of asphalt mixture. This paper evaluates the low temperature performance of asphalt mixture using four tests namely: beam bending test, indirect tensile test, contraction coefficient test and thermal stress restrained specimen test. Five types of asphalt mixtures namely: A, B, C, D and E were evaluated. Results show that compared with the thermal stress restrained specimen test, beam bending test, indirect tensile test and contraction coefficient test are not appropriate for the evaluation of asphalt mixtures low temperature performance. Moreover, results of gray relational analysis demonstrate that the bending strain energy density is significantly correlated to fracture temperature. It is reasonable to adopt the critical values of bending strain energy density to evaluate the low temperature performance of asphalt mixture in the absence of fracture temperature. [Copyright &y& Elsevier]

Volumetric properties are essential for a better understanding of how to design the mixtures. Due to the irregularity of aggregate shape, these properties vary randomly with the same gradation. In this paper, the volumetric properties [bulk specific gravity (γf), air voids (VV), voids in mineral aggregate (VMA), and voids filled with asphalt (VFA)] were determined on two mixtures types, namely, A and B. These mixtures were statistically analyzed using different distribution methods. Seventy-two samples of Mixture A and 52 of Mixture B were fabricated using the Marshall design method. Results of the study showed that the Weibull distribution could reflect the probability distribution law of the volumetric properties of the mixtures. The two-parameter Weibull distribution function appears to be more appropriate or use with γf and VFA, whereas the three-parameter Weibull distribution function was most appropriate for VV and VMA. The analysis of test results also revealed that there are significant differences in the volumetric properties of the two mixtures tested at the same confidence level. The confidence interval decreases with a decrease in reliability. [ABSTRACT FROM AUTHOR]

• The equivalence of strain method and strain rate method was assessed. • A novel method termed local fitting method based on strain rate was developed. • A comparison of difference models based on strain method and strain rate methods was performed. To accurately determine the flow point of asphalt mixture, the flow number test was performed, and an analysis was conducted on the methods of calculating flow point. Three defects of the existing methods were highlighted, and a novel method termed local fitting method was proposed. The flow number and flow rate were both considered in this research. Strain method and strain rate method were proved to be not equivalent and the extensively employed strain method might present a misleading flow point. In addition, the four-step algorithm of the local fitting method based on strain rate was developed, and the optimal range coefficient K of the present study was calculated as 1.5 based on the alteration trend of flow point. A comparison of the local fitting method and the global fitting method was performed, and significant differences were identified in the fitting curves and calculated results. Moreover, equivalence of Francken and Hoerl strain rate models from the two methods was also assessed, and it was found that significant differences might exist between the two models when using global fitting method, whereas no significant difference was identified based on local fitting method. The novel local fitting method was considered a better analytical procedure to determine the flow point of asphalt mixtures. [ABSTRACT FROM AUTHOR]

Rutting has always been considered the main disease in asphalt pavement. Dealing with rutting disease would be benefitted by understanding the formation of rutting and testing the rutting performance of mixtures more reasonably. The objective of this paper is to systematically investigate the rutting mechanism by employing a self-designed rutting tester along with the corresponding numerical simulations. The deformation of different positions of the existing tracking tester was found to be inconsistent, and the loading was not in line with reality. Accordingly, a more practical tester was proposed: the reduced scale circular tracking (RSCT) tester integrates the functions of asphalt mixture fabrication and rutting monitoring. The results demonstrated that the loading of the new tester is closer to the actual situation. In addition, determining the stress and displacement characteristics of particles in the asphalt mixture was found to be difficult due to the limitations of the testing methods. Therefore, a two-dimensional virtual rutting test based on the RSCT was built using PFC2D (Particle Flow Code 2 Dimension) to investigate the mechanism of formation in rutting and to obtain the corresponding guidance. The numerical simulation showed that all particles of the specimen tended to move away from the load location. The main cause of rutting formation was the eddy current flow of asphalt mastic driven by coarse aggregates. The aggregates with diameters ranging from 9.5 to 4.75 mm were observed to have the greatest contribution to rutting deformation. Therefore, the aggregate amount of these spans should be focused on in the design of mixture grading. [ABSTRACT FROM AUTHOR]

Warm mix asphalt mixtures have the advantages of energy saving, emission reduction and good road performance. Zeolite asphalt mixtures, as a warm mixing technology, have been applied in the world. To understand the warm mix mechanism of zeolite warm mix asphalt mixture, the mesoscale structure of zeolite asphalt is studied. Micro computed tomography (CT) is utilized to obtain the internal structure image of zeolite-modified asphalt and asphalt mixture. The quantity and volume of voids are used as internal void distribution evaluation indexes. The results indicate that with respect to the void distribution in zeolite-modified asphalt, with the increase of temperature, there is an obvious evolution trend of smaller voids to larger voids. With respect to the voids in the zeolite-modified asphalt mixture, the zeolite asphalt mixture is equivalent to hot mix asphalt mixture when it is above 120 °C, while below 120 °C, the maximum and average void volumes increase significantly, making it difficult for the mixture to achieve ideal compaction effect. [ABSTRACT FROM AUTHOR]

An asphalt mastic imparts most of its characteristics to the asphalt concrete mixture and also dictates several forms of distresses in asphalt mixtures and pavements. Several studies have demonstrated that the interaction between asphalt binder and mineral fillers has a significant impact on the properties and performance of asphalt mastics and mixtures. The objective of this study was to investigate the nature of binder adsorption on mineral filler surface while simultaneously quantifying the influence of such adsorption on the properties of the binder in the immediate vicinity of the interface and bulk. An adsorption test using mineral fillers and binders was conducted to achieve this goal along with measurements of asphaltene content and rheology on the original binder and the residual binder from the adsorption tests. Results show that polar fractions preferentially adhered to the surface of the mineral filler. Such preferential adsorption resulted in a significant increase in the complex modulus of the adsorbed or fixed asphalt with a concomitant decrease in the complex modulus of the free or bulk asphalt binder. These changes in complex modulus varied only slightly as a function of the frequency. The magnitude of adsorption was dictated by the mineral nature of the surface and more importantly by the specific surface area of the particles. The findings from this study are useful to better understand and model the failure mechanisms in the micro structure of asphalt composites. [ABSTRACT FROM AUTHOR]

• The influence of preheating conditions and size effect on the blending phenomena were evaluated through 3D-FIT method. • The difference of asphalt blending between virgin and RAP aggregate were also investigated. • The longer curing time does not mean better blending, which exists a limited value and an optimal storage time. • Smaller sizes of virgin aggregate can mobilize more active reclaimed asphalt from RAP aggregate. The blending phenomena between virgin and reclaimed asphalt is a significant concern in asphalt paving, which play a crucial role in the final performance of the recycled asphalt mixture. Although past studies broadly discussed the asphalt blending by various test methods, the blending process holds 3D features due to the different aging degrees of reclaimed asphalt and different dispersity of virgin asphalt. The three-dimensional observation in the asphalt blending is still limited. Simultaneously, many factors (e.g., preheating temperature and time, transportation temperature, storage time, and aggregate gradation) will affect the blending process. The relationships between those factors and the blending phenomena are still unknown. To overcome this problem, this paper proposed a 3D fluorescence image method by laser scanning confocal microscopy and artificial aggregate. The artificial aggregate in the wooden cube form was used to analyze the blending process of virgin and RAP aggregate in three-dimension, respectively. Meanwhile, preheating conditions and size effect on the blending phenomena were also evaluated. The results indicate that temperature presents a more significant influence on the blending than the curing time. A longer curing time does not mean better blending, which exists a limited value and an optimal storage time. Compared to RAP aggregate, more homogeneous blending occurred on virgin aggregate after 2 h curing time at 180 °C, so the blending process on virgin aggregate should also be considered by researchers. This study may help to explain the production of recycled asphalt mixture and understand the blending phenomena in asphalt paving. [ABSTRACT FROM AUTHOR]

• Propose a novel model termed ISO model for density prediction of asphalt mixture. • Clarify the effect of moisture on the dielectric property of asphalt mixture. • Quantitively estimate the moisture content in wet asphalt mixture. The density of asphalt mixture is a key quality property for in-situ pavement. And moisture within asphalt mixture easily results in various premature distresses on pavements. The basic goal of the present research is to investigate the estimation of both the density and moisture content within asphalt mixture using an electromagnetic (EM) technology. For this purpose, a generalized mixing formula was innovatively developed to predict the density of dry asphalt mixture regarding Influence coefficient v and Shape factor u based on EM mixing rules. Three types of asphalt mixture (AC-13, AC-20, and AC-25) specimens were fabricated in the laboratory with the same binder, asphalt content, and aggregate type, varying the density levels. Permittivity test of the specimens were conducted to obtain relative permittivity data. Using a nonlinear fitting method for the relationship between the bulk specific gravity and the relative permittivity of dry specimens, the optimal values of parameters v and u were determined to be 5.1 and −4.5 in the generalized mixing formula, defined as Influence and Shape Optimization (ISO) model. Moreover, considering the effect of water phase, a modified ISO (MISO) model was performed to estimate the moisture content of wet asphalt mixture. The main findings of the laboratory and field studies demonstrated that the ISO model was suitable for the density prediction of AC asphalt mixture within a reasonable error of 2%; and the MISO model predicted the moisture content with high R2 value not less than 0.74. [ABSTRACT FROM AUTHOR]

• Explicit the particle distribution of pavement surface sediment. • Clarify the clogging process of permeable asphalt mixture. • Explore the void variation of permeable asphalt mixture in the clogging process. • Analyze the influence parameters of clogging characteristics of asphalt mixture. Characterizing the clogging process of permeable asphalt mixtures helps clarify the permeability of permeable pavements. This study aimed to determine the clogging characteristics of permeable asphalt mixtures. By analyzing the particle size of pavement surface sediment, the size of clogging particle was determined in the range from 0.15 to 2.36 mm. Five types of permeable asphalt mixtures were synthesized, and the clogging characteristics test was performed with the independently developed multidirectional permeability test instrument. The variation of the permeability in the clogging process was explored. Subsequently, the internal void of permeable asphalt mixtures was characterized by computerized tomography. As suggested from the results, the void evolution at different depths of specimen varied with the rise in the number of clogging particles. It was reported that the clogging process of permeable asphalt mixtures consisted of four stages, i.e., fast clogging, clogging recovery, gradual clogging and clogging acceleration. Under the clogging effect, the permeability of permeable asphalt mixtures could vary from non-Darcy to Darcy permeability, and the variation speed of the transverse permeability was faster than that of the vertical one. Lastly, the effects of water head height, the gradation type of permeable asphalt mixtures and clogging particles on the clogging characteristics were analyzed. [ABSTRACT FROM AUTHOR]

• Developed a multidirectional water-filled void content test apparatus. • Experimental investigated Non-Darcy permeability of permeable asphalt mixture. • Analyzed the effect of structure characteristics of asphalt mixture on flow regime. • Clarified the effect of asphalt mixture permeability on fluid flow. The flow regime of the fluid refers to all kinds of motion forms of fluid, and the fluid flow regime in permeable asphalt mixture impacts the permeability of the structure. Accordingly, as the flow regime of fluid in permeable asphalt mixture is clarified, the permeability can be delved into. This study aimed to explore the flow regime of fluid in permeable asphalt mixture. Five types of permeable asphalt mixtures were synthesized. By developing a multidirectional water-filled void content test apparatus and computed tomography, the differences in void content and void diameter in vertical and horizontal directions of asphalt mixture were analyzed. Subsequently, the permeability test of permeable asphalt mixture was performed using self-developed multidirectional permeability test apparatus. The results suggest that Darcy permeability changes to non-Darcy permeability in the process of fluid flow in the asphalt mixture. On that basis, the transition of flow regime in permeable asphalt mixture was analyzed. The results suggest that the variation of flow regime is consistent with the variation of fluid from Darcy to non-Darcy permeability. The flow regime is affected by the anisotropy, gradation type of asphalt mixture and flow space. The permeability of permeable asphalt mixture is associated with the transition point of fluid flow regime. The higher the permeability, the higher the critical Reynolds number will be. [ABSTRACT FROM AUTHOR]

• The real shape of particles was considered in the modeling process. • Analyze the effect of particles shape on the overall of the mixture skeleton and the particles themselves. • U 3 D is proposed to evaluate the particles distribution uniformity. Mixture skeleton is the main body bearing the load of asphalt mixture, and particle shape is an important factor affecting the meso -structure of mixture skeleton. Based on the minimum bounding box theory, obtain particles geometry by Digital Image Processing (DIP), and calculate the shape indices: angularity index (A 1) and flat-elongated index (F 1). By using discrete element method (DEM) software PFC3D , five mixture skeletons were built with different integrated angularity (A m) and flat-elongated particles content (F m). And analyzed air void, particles distribution and particle angle of mixture skeletons. The results show that A m has no obvious effect on the air void ratio, but increasing F m can increase the air void ratio. In addition, the index U 3 D was proposed to evaluate particles distribution on 3D scale, and found that small particles are more likely to have better distribution uniformity. And uniformity of particles distribution in mixture skeleton will increase with the increase of A m. For particles, angle will be increase with the increase of F 1. However, if F 1 is too large, particle angle will decrease due to the embedding effect. These studies and results analyzed that how can particles shape affect meso -structure of mixture skeleton. [ABSTRACT FROM AUTHOR]

Moisture vapor diffusion resulting from the difference in relative humidity between air and pavement material contributes to moisture damage. Understanding moisture vapor diffusion in asphalt pavement is the first task in the analysis of moisture damage. Analysis was conducted in an automated environmental chamber with a temperature precision of ± 0.5 °C and relative humidity precision of ± 3%. Moisture uptake profiles for fine aggregate mixtures (FAMs) under various environmental conditions (relative humidity and ambient air temperature) and constituent materials (aggregate and asphalt binder) were measured. Preliminary data analysis showed the existence of Non-Fickian diffusion behavior. Therefore, two non-Fickian and one Fickian models were introduced to fit the measured moisture uptake data and determine FAM diffusion characteristics, such as diffusion coefficient, diffused moisture phase, and time-variable diffusion. Based on the variation in FAM diffusion characteristics under various experimental conditions and constituent material combinations, sensitivity analysis was conducted with one-way ANOVA and the determinants of FAM vapor diffusion characteristics were proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] WMA mixtures containing high percentage of RAP were produced using different WMA additives. [•] WMA additives lowered the mixing and compaction temperatures of mixtures. [•] Performance evaluation on rutting, low temperature cracking, moisture damage, aging, and fatigue of mixtures. [•] Effect of WMA additives and RAP on the performance of mixtures was pronounced. [Copyright &y& Elsevier]

• Perform dynamic tracing of moisture flow with Freeze-Thaw (F-T) cycles by X-ray CT. • Observe anisotropy of wetting front migration in asphalt mixes under F-T cycles. • Analyze impact of F-T cycles in temporal variation of seepage velocity. • Discuss evolution of initial inertia region in asphalt mixes under F-T cycles. • Clarify high sensitivity of F-T cycles in vertical velocity with small pore size. This study aims to understand the evolution of dynamic moisture flow in asphalt mixtures exposed to freeze-thaw cycles. X-ray CT was utilized to capture the moisture dynamics in unsaturated asphalt mixtures during simulated rainfall events. Three main characteristics of the dynamic flow behaviors within asphalt mixtures were measured and monitored, including wetting front position, directional velocity of wetting front, and inertia influence region. It was found that at a specific infiltration rate, freeze-thaw cycles increased the vertical flow penetration and decreased the horizontal flow penetration for both wetting front position and directional velocity, suggesting that seepage anisotropy was exacerbated in asphalt mixtures. The initial inertia of water droplet was mostly converted towards the vertical direction under freeze-thaw effect. As a result, the shape of water transmission was converted from a hemispherical shape to a slender shape under freeze-thaw cycles. Linear regression analysis between direction velocity growth rate in particular samples and freeze-thaw cycles to pore structure was conducted, and it was found that compared with dense-graded mixtures, open-graded mixtures displayed larger slopes for horizontal flow, and smaller slopes for vertical flow, demonstrating the non-negligible effect of pore structure on dynamic flow evolution under freeze-thaw cycles. [ABSTRACT FROM AUTHOR]