Void Characteristics Research Articles

Research on void characteristics during compaction of asphalt mixtures

Void is an important manifestation of the strength of asphalt mixture, but few studies have focused on the change of voids during the compaction of asphalt mixtures. The voids of SMA-13 and OGFC-13 were selected as the research objects, and the compaction process of the asphalt mixture was analyzed based on different compaction degree specimens in lab through gyratory compactor. Firstly, CT scanning was used to extract the void structure of the asphalt mixture at different degrees. Secondly, based on the 26-connectivity algorithm, the connected voids and closed voids of asphalt mixture were extracted, and the volume and particle size distribution were analyzed. Thirdly, the gradation of voids was analyzed by the two-parameter Weibull function, and the morphological characteristics of voids were analyzed by roundness, sphericity, and abundance. The results showed that the distribution of cross-section voids ratio and the number of voids of the SMA-13 was more uniform than that of OGFC-13. The characteristic parameters of two-parameter Weibull function showed that with the increase of specimen density, the three-dimensional void size became smaller and smaller, and the void size distribution became more and more uniform. The sphericity and roundness of the voids of SMA-13 and OGFC-13 were less affected by the compaction degree, and the void abundance of the OGFC-13 gradation asphalt mixture was greatly affected. For the connectivity of voids, the closed void volume of OGFC-13 increased with the increase of compaction degree, but the maximum proportion of closed voids in the total void volume does not exceed 10% during the compaction process. For the gradation SMA-13, the compaction degree of 90%∼93% was the boundary interval of connected voids from existence to nonexistence, which may be a critical interval for forming skeleton strength during the compaction process.

Study on Voids and Seepage Characteristics within Rock Fracture after Shear Dislocation Viewing from CT Test and Numerical Modeling

In rock mass engineering, stress balance changes often cause the relative slip of fractures along a wall surface, impacting the seepage behavior of fluid in the fractures. Using computer tomography (CT) scanning, spatial models of fractures with dislocations ranging from 0 to 10 mm were created to explore the relationship between changes in fracture dislocation and changes in fluid flow behavior, respectively. The spatial fractal dimension of cavity distribution within the fractures was calculated using a thin-plate filling approach to characterize the complexity of the fracture cavity distribution. The fluid flow within the dislocation fractures was then simulated using COMSOL, and the effect of cavity alterations in the form of dislocation on the fluid seepage behavior was analyzed using the spatial fractal. The results show that the values of mechanical aperture after dislocation of the fracture obtained by a CT test are normally distributed, the distribution range of mechanical aperture gradually widens with an increase in the dislocation distance, and the average mechanical aperture increases on a logarithmic curve. The relative spatial fractal dimension decreases gradually with an increase in dislocation distance, and the interconnected pathways within the fracture decrease; in addition, it is observed that the change in the relative spatial fractal dimension is closely correlated with the change in the mean mechanical aperture. Numerical simulations of dislocation fracture seepage found that the permeability increases nonlinearly with increasing dislocation distance. When the dislocation distance reaches 5 mm, nonlinear behaviors such as eddy currents occur, and the influence range of eddy currents gradually expands with the increase in dislocation distance under the influence of the boundary. Moreover, the inertia coefficient B in the Forchheimer equation and the critical hydraulic gradient Jc, which can describe the nonlinear seepage characteristics, show a power function decreasing trend with increasing dislocation distance, and the fluid in the fracture is more likely to produce nonlinear flow.

Evolution Characteristics of Void in the Caving Zone Using Fiber Optic Sensing.

Addressing the issue of low filling efficiency in gangue slurry backfilling due to unclear evolution characteristics of voids in the overlying collapsed rock mass during mining, this study utilizes fiber optic sensing technology to monitor real-time strain changes within the rock mass. It proposes a void zoning method based on fiber optic sensing for mining the overlying rock and, in combination with physical model experiments, systematically investigates the dimensions, distribution, and deformation characteristics of rock mass voids. By analyzing fiber optic sensing data, the correlation between the rate of void expansion and the stress state of the rock mass is revealed. The research results demonstrate that as mining progresses, the internal voids of the rock mass gradually expand, exhibiting complex spatial distribution patterns. During the mining process, the expansion of voids within the overlying collapsed rock mass is closely related to the stress state of the rock mass. The rate of void expansion is influenced by changes in stress, making stress regulation a key factor in preventing void expansion and rock mass instability. The application of fiber optic sensing technology allows for more accurate monitoring of changes in rock mass voids, enabling precise zoning of voids in the overlying collapsed rock mass during mining. This zoning method has been validated against traditional theoretical calculations and experimental results. This research expands our understanding of the evolution characteristics of voids in overlying collapsed rock mass and provides valuable reference for backfilling engineering practices and backfilling parameter optimization.

Significant Effect of Vacuum Bagging Processing on Inter-Laminar Shear Strength and Voids of Composite in Oven Cure

Autoclave had been constrained to longer time consumption, higher production costs and excessive residual stress. The challenges regarding with out-of-autoclave (OOA) cure involved the need to devise the techniques in preserving high quality of composite product during service life. The current work was proposed to quantify the impact and influence of pre-forming parameter variations in vacuum-bagging-only with oven curing (VBO-oven cure) of OOA manufacturing composite processing on the inter-laminar shear strength (ILSS) of low-cost conventional composite laminates. The relationship of ILSS and void quality characteristics was also investigated. Series of conventional lower-cost glass/epoxy aerospace-grade material was fabricated using 16 different processing routes in conventional oven. Burn-off and ILSS test was conducted based on ASTM standard to compute the ILSS and void content of cured laminates. Scanning electron microscopy (SEM) analysis was performed on the post-test ILSS coupons to evaluate the relationship between void characteristics and ILSS. Results indicated that mould release type and intensifier contributed highest effects towards ILSS of approximately 31.3% and 27.6%, respectively. The assessment of ILSS-void relationship was further carried out and it was found that void geometry has a greater influence towards ILSS than the void content of composite laminate. The combination of these factors in processing routes yielded the lowest ILSS and void content at 24.85 MPa and 5.74%, respectively. These concluded that an optimized manufacturing technique could be expanded from the optimum settings of these processing parameters.

Three-Dimensional Analysis of Porosity in As-Manufactured Glass Fiber/Vinyl Ester Filament Winded Composites Using X-Ray Micro-Computed Tomography

AbstractFilament winding is a technique to manufacture tubular composite structures and, therefore, is among the most appealing techniques for fabricating critical structures such as hollow tubes. Despite the recent advances, these structures are prone to a varying degree of porosity that may affect their mechanical performance. Therefore, the accurate detection and quantification of the manufacturing porosity is crucial. Micro-CT is most suitable for performing this activity at various scales. This work employs micro-CT for studying porosity inside an as-manufactured filament-winded composite structure. Void characteristics like volume, orientation, size, and relative volume fraction inside the hoop and helical layers are quantified inside a representative curved panel extracted from a glass fiber-vinyl ester tubular composite structure, which has not been studied in detail previously. It was observed that most voids are present in the matrix region. The voids are elliptical rod-like and spherical, with the latter present in the helical layers, which also host the majority of voids and the highest void volume fractions. The voids are highly aligned along the fiber orientation direction with higher misorientations for helical layers than the hoop layer. Large voids in base layers were created due to gaps formed during the winding process. Hence, the main goal of this study is to measure the voids' characteristics and the volumetric fraction during the stacking of filament wound hoop and helical layers during a generic filament winding pattern. The data can be further exploited as input for modeling filament winded composites in the presence of voids by researchers.

Microscopic void characteristics of OGFC in Sponge City and its effect on noise reduction performance using X-ray CT

This study aims to evaluate how material composition and microscopic void characteristics affect the noise reduction performance of open-graded friction courses (OGFC). X-ray computed tomography (CT) and image processing were employed to analyze the microscopic void characteristics of different OGFC mixtures. Sound absorption tests were conducted, revealing a direct link between OGFC's noise reduction performance and its microscopic void features, particularly connected air voids and void area. This relationship is linear, with every 1 % increase in air voids resulting in a 4.93 % average sound absorption coefficient increase. When air voids are similar, coarser gradations and larger nominal maximum aggregate sizes (NMAS) correspond to higher noise reduction levels, particularly for high-frequency noise. The most significant impact on microscopic void properties comes from the 9.5 mm and 4.75 mm mesh sizes, followed by 1.18 mm, while the 2.36 mm sieve exhibits a weaker correlation. These findings are crucial for enhancing OGFC pavement's noise-reduction capabilities, especially in Sponge Cities, and extending the acoustic lifespan of pavement.

Study on sound absorption characteristic of porous asphalt mixture based on macroscale and mesoscale analysis

To explore the sound absorption characteristics of porous asphalt mixture, the effects of macroscopic parameters of asphalt mixture on sound absorption coefficient (SAC) were studied by the sound absorption coefficient test, and the mesoscopic void structure was investigated by industrial computed tomography (CT) and three-dimensional (3D) reconstruction techniques. The results show that the SAC can be increased by increasing the porosity or thickness and reducing the NMAS. The increase of porosity and the decrease of pavement thickness can better absorb high frequency noise (above 1000 Hz). Through the grey correlation analysis, it can be seen that the SAC of porous asphalt mixture is most affected by the porosity. There is a strong linear relationship between the microscopic void characteristic of porous asphalt mixture and the peak and mean value of SAC.

Bamboo fiber‐reinforced epoxy composites fabricated by vacuum‐assisted resin transfer molding (VARTM): Effect of molding sequence and fiber content

AbstractFabricating bamboo fiber‐reinforced epoxy composites (BFREs) using the vacuum‐assisted resin transfer molding (VARTM) process has many advantages, such as low cost, high product quality, controllability, and broad applicability. However, the immature fabrication process seriously affects product performance and hinders the full exploitation of the advantages of the VARTM process. The effects on the physical‐mechanical and thermal properties of BFREs by molding sequence and fiber content were investigated in this study. The molding sequence of fiber compression followed by resin injection was beneficial to ensure hermeticity, thus reducing the voids in the BFREs. The mechanical properties of BFREs gradually increased with increasing fiber content. With 50 wt% fiber content, the bending strength and modulus, shear strength, and impact toughness of BFREs reached 71.27 MPa, 6.78 GPa, 11.68 MPa, and 5.45 kJ/m2, respectively. Although the thermal stability of the BFREs was slightly lower than that of pure epoxy, the bamboo fibers' high rigidity evidentially increased the epoxy's dynamic mechanical properties. The life cycle assessment indicated that the BFREs effectively reduced the environmental impacts and production energy consumption compared to the glass fiber correspondent. The VARTM‐fabricated BFREs have great potential for construction, transportation, household items, packaging, sports equipment, and leisure goods applications.Highlights Fiber compression followed by resin injection could ensure great hermeticity. Micro‐CT accurately measured the void characteristics of the composites. Voids had detrimental effects on the properties of the composites. Dense bamboo fiber preforms enhanced the mechanical properties of epoxy. Bamboo fibers reinforcing epoxy reduced the impact on the environment.

Effects of freeze–thaw cycles on micro and meso-structural characteristics and mechanical properties of porous asphalt mixtures

Abstract Porous asphalt concrete (PAC) have a typical big void-skeleton structure, and porous asphalt mixtures with large voids are more prone to freeze–thaw damage. As a result, research on the influence of freeze–thaw cycles on the micro-structure and mechanical characteristics of porous asphalt mixes offers a theoretical framework for overcoming water stability concerns in porous asphalt mixtures in practice, as well as for further popularization and application. In this study, styrene–butadiene–styrene (SBS)-modified asphalt and high viscosity modified asphalt were constructed on the basis of the original asphalt, and the mix proportions of asphalt mixes PAC-13, AC-13, and SMA-13 were designed. To begin, molecular dynamics simulations were used to look into the effects of freeze–thaw cycles on asphalt–aggregate interface adhesion and mixture micro-mechanical properties. Second, the effects of freeze–thaw cycles on the void characteristics of porous asphalt mixtures were explored utilizing digital image processing technologies. Finally, the freeze–thaw split test was utilized to evaluate the macroscopic mechanical properties of a porous asphalt mixture after freezing and thawing cycles. According to the study findings, high viscosity modified asphalt made with 4% SBS/8% TPS has the greatest performance. The application of SBS/TPS-modified asphalt can considerably improve the damage resistance of porous asphalt mixes. The micro-structure and mechanical qualities of porous asphalt mixtures are damaged by freeze–thaw cycles, and the damage gets worse as the number of cycles rises. The study’s conclusions provide a theoretical justification for the application of porous asphalt pavement.

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.

Self-healing properties of steel slag asphalt mixture based on experimental characterization and 3D reconstruction

Asphalt pavement is susceptible to cracking which affects its service life. And self-healing technology helps to heal micro-cracks in mixture at an early stage, but its mechanism of action at the mesoscale is still unclear. Therefore, the composition of steel slag asphalt mixture (SSAM) was designed, microwave heating performance, healing performance and road performance of SSAM were investigated by laboratory experiments. Finally, the SSAM was scanned using X-ray CT for 3D reconstruction and quantitative analyses. The results show that steel slag has obvious magnetic loss characteristics; the surface temperature of SSAM designed by composition is higher under microwave heating to obtain a better healing rate, and the road performance of SSAM meets the specification requirements. The damage-healing process mainly affects voids in SSAM, and microwave healing can reduce the fractal dimension of voids to reduce the proportion of fissures; from the healing index based on voids, self-healing can reduce the average coordination number and throat number of connected voids, thereby improving the performance of SSAM by reducing permeability. The self-healing performance of SSAM is improved through its compositional design; the mesoscopic model based on void characteristics helps to refine the theory of self-healing of asphalt mixtures under microwave heating.

Effect of printing patterns on pore-related microstructural characteristics and properties of materials for 3D concrete printing using in situ and ex situ imaging techniques

3D printed samples have the unique feature of being layered and laminated to form a structure. The pore distribution characteristics around layers and filaments differ from cast specimens and significantly affect the mechanical properties. To produce high-quality 3D printed elements in terms of structural integrity and long-term performance, it is essential to understand their microstructural characteristics both during the printing process and after curing. In this paper, an in situ imaging analysis technique is proposed to examine the effects of printing patterns on pore-related characteristics and their correlation with the mechanical properties of 3D printed concrete. The interfilament voids of fresh 3D printed specimens, one of the most important factors affecting the mechanical properties, are investigated using in situ images obtained during the printing process and through an ex situ image analysis using X-ray micro-computed tomography. Additionally, the spatial distributions of pores in entire printed prisms after one-day curing are obtained by ex situ imaging analysis. Through combining in situ and ex situ analyses, it was found that the changes in pore distribution during hardening are different depending on the printing patterns. The characteristics of interfilament voids significantly impact the performance of the printed sample, resulting from the anisotropy of the pore distributions. The obtained results provide insight into a real-time image-based microstructural monitoring technology for 3D concrete printing, which can be utilized to suggest the optimal printing patterns for the purpose.

Effect of type and aggregate gradation on the functional properties of porous asphalt (case study of Iran)

Porous asphalt mixtures are gaining popularity due to their ability to effectively drain surface water and mitigate traffic noise in regions with high rainfall. However, compared to conventional asphalt pavements, these types of pavements with high void content necessitate specific guidelines for achieving an optimal mix design. The performance characteristics of porous asphalt mixtures are notably influenced by the grading and composition of materials, especially with regards to their resistance to moisture damage. This study aimed to investigate the properties of porous asphalt mixtures using limestone and siliceous aggregates with varying gradations, while maintaining bitumen contents of 5% and 6%. In accordance with the regulations set forth by the National Center for Asphalt Technology, the findings indicate that siliceous-based aggregates exhibit improved void characteristics (increased by 3%) and permeability (increased by 11%). However, they also display reduced resistance to moisture-induced failures (decreased by 4%). On the other hand, adhering to the gradation recommendations provided by the National Asphalt Pavement Association guidelines, except for a slight decrease of 3% in moisture sensitivity, yields an overall enhancement of 25% in other performance characteristics. To analyze the data, statistical methods were employed, resulting in regression models with a minimum R2 value of 0.97. These models helped determine the optimal binder percentage for different aggregate types and gradations, providing valuable insights for practical implementation.

AOR: Adaptive opportunistic routing based on reinforcement learning for planetary surface exploration

Planetary surface exploration mobile ad-hoc networks (PSEMANET) show the characteristics of routing void caused by craters and electromagnetic interference, relatively high dynamics caused by node heterogeneity, and small node capacity caused by load constraints, which is the reason for the increase of communication delay and packet loss. Adaptive opportunistic routing based on reinforcement learning (AOR) is an opportunistic routing protocol that determines the forwarding node based on the current coordinates, queue length, and the number of neighbors. The full forwarding areas are used to avoid routing void, and the dual competition mechanism is designed to avoid the node hidden problem. The Q-value obtained by reinforcement learning is used to design the dynamic delay cost (DDC) so that nodes in the forwarding areas can compete to achieve adaptive path switching to the environment. Compared with representative proactive routing OLSR, reactive routing AODV, geographic routing GPSR and opportunistic routing BLR, AOR and AOR with memory(AOR-M) have high packet delivery ratio (PDR) and low end-to-end delay in planetary surface exploration scenarios implemented by our simulation system. And the AOR-M protocol shows the lowest expected end-to-end delay and highest channel utilization in both high and low speed scenarios. The result shows that the AOR-M provides efficient and robust routing in planetary surface exploration mobile ad-hoc networks with a complex environment, highly dynamic nodes, and performance constraints.

Interface Leakage Theory of Mechanical Seals Considering Microscopic Forces

The fluid flow in the small pore throat is a nonlinear flow, and the microscopic force between the fluid and the wall cannot be ignored. However, the previously established theories about the leakage between sealing interfaces have not considered the influence of microscopic forces. Based on contact mechanics and percolation theory, the void characteristics of the sealing interface were clarified, and the influence of microscopic force on fluid flow in porous medium was analyzed. Combined with the capillary force, the concept of a critical void radius between the mechanical seal interfaces is proposed. The fluid flow resistance model and leakage rate calculation equation of the sealing interface considering the van der Waals force are established, and the leakage judgment criterion of the sealing interface is provided. Through numerical calculation and experiments, the effect of microscopic force is verified in terms of the fluid flow law and macroscopic leakage rate. The results show that van der Waals forces have an important influence on the fluid flow between the sealing interfaces. As the microchannel size decreases, the van der Waals forces between solid and liquid increase, and the influence of these van der Waals forces on the fluid flow between the sealing interfaces cannot be ignored. The calculation model of the sealing interface leakage rate proposed in this paper shows little difference with the results of the Persson model, and is in good agreement with the experimental results; the maximum relative error is 8.7%, the minimum relative error is only 3.8%.

Study on the influence mechanism of recycled concrete aggregate on strength of asphalt mixtures

Recycled concrete aggregate (RCA) has great potential use in pavement. However, unclear characteristics of RCA and its relationship with the properties of asphalt mixture hinder severely its promotion. The objective of this study is to characterize the microscopic morphology and structure of RCA, further investigate its impact on the strength of asphalt mixture and associated mechanisms, by means of various test method. Results showed that cement mortar was the vital factor to affect the properties of RCA. Hence, the asphalt mixtures with RCA had characteristics of higher air voids (VV) and voids in the mineral aggregate (VMA), lower asphalt saturation (VFA), compared with conventional asphalt mixtures (CAM). In addition, according to the results of Micro-Scratch (MS) test, the compression depths of aggregate, interfacial transition zone (ITZ) and asphalt mortar in RAM are larger than that in CAM. Therefore, the influence of RCA on the performance of asphalt mixture is mainly in the following two aspects: reducing the strength of asphalt mortar; decreasing the skeleton strength of asphalt mixtures.

THE INFLUENCE OF DEICING SALT ON AIR VOIDS OF ASPHALT MIXTURE UNDER FREEZE-THAW CYCLE

The extensive use of deicing salt has not only solved the problem of road icing but also had a serious impact on the pavement, reducing its lifespan. In order to deeply understand the impact of deicing salt on the air voids of asphalt mixture in the northwest climate of China, this paper conducted freeze-thaw cycle tests on AC-13 and AC-16 asphalt mixtures under three different deicing salt solutions and three different low-temperature environments, and analyzed the changes in air voids, meanwhile, the Logistic prediction model was used to evaluate the change characteristics of the air voids. The experimental results showed that the air voids of asphalt mixture increased to varying degrees after multiple freeze-thaw cycles; when the temperature was above its freezing point, no frost heave damage occurred, and the air voids increased slowly; when the temperature was below the freezing point, frost heave damage occurred, causing rapid growth and connection of voids in the mixture, and the air voids increased rapidly; the Logistic model showed a good fit with the observed changes in air voids.

Separate and joint clustering characteristics of large-Stokes-number sprays subjected to turbulent co-flows

Separate and joint droplets, clusters, and voids characteristics of sprays injected in a turbulent co-flow are investigated experimentally. Simultaneous Mie scattering and interferometric laser imaging for droplet sizing along with separate hotwire anemometry are performed. The turbulent co-flow characteristics are adjusted using zero, one or two perforated plates. The Taylor-length-scale-based Reynolds number varies from 10 to 38, and the Stokes number estimated based on the Kolmogorov time scale varies from 3 to 25. The results show that the mean length scale of the clusters normalized by the Kolmogorov length scale varies linearly with the Stokes number. However, the mean void length scale is of the order of the integral length scale. It is shown that the number density of the droplets inside the clusters is approximately 7 times larger than that in the voids. The ratios of the droplets number densities in the clusters and voids to the total number density are independent of the test conditions and equal 5.5 and 0.8, respectively. The joint probability density function of the droplets diameter and clusters area shows that the droplets with the most probable diameter are found in the majority of the clusters. It is argued that intensifying the turbulence broadens the range of turbulent eddy size in the co-flow which allows for accommodating droplets with a broad range of diameters in the clusters. The results are of significance for engineering applications that aim to modify the clustering characteristics of large-Stokes-number droplets sprayed into turbulent co-flows.

Numerical study on thermal-hydro coupling characteristics of underground coal combustion under heterogeneous void fraction

Coal seam mining will lead to the movement and fissures of the overlying strata, which makes a complex void condition between the mining area and the ground surface. The void condition plays a key role in the occurrence and expansion of underground coal fires. In this study, the void rate model and the coupled thermal-hydro model of the underground coal fire were constructed. The COMSOL Multiphysics was used to study the coupling law of the temperature field and gas flow field of coal seam spontaneous combustion. By setting different oxygen content and inlet gas velocity, the influence of the external environmental parameters on the expansion law of underground coal fire is analyzed. The results show that the void characteristics of the mining area and the overlying strata have an obvious influence on the expansion of underground coal fire, and there is also a two-way coupling effect of the temperature field and gas flow field. The analyses of the influencing parameters show that reducing the oxygen content or increasing the inlet gas velocity will have a certain inhibitory effect on the expansion of underground coal fires, which can reduce the risk of spontaneous combustion.

Engineering properties and air void characteristics of cold recycled mixtures with different compaction methods

Cold recycled mixtures (CRM) offer advantages in terms of resource conservation and reduced CO2 emissions. This paper utilizes the vertical vibration testing method (VVTM), Marshall compaction (MC), Superpave Gyratory Compactor (SGC), and field core samples to analyze the effects of different compaction methods on the engineering properties of CRM. The study begins by discussing the volumetric and mechanical parameters of CRM with different compaction methods, followed by an analysis of fatigue performance. Additionally, CT scanning technology is used to study the effect of different compaction methods on the void characteristics of CRM. The results demonstrate that VVTM specimens offer better mechanical properties compared to MC and SGC specimens. Furthermore, the RT (splitting tensile strength), MS (dry-wet tensile strength ratio), and TSR (freeze-thaw splitting strength ratio) of VVTM specimens exhibit the highest correlation with field core samples, reaching 97%, 97%, and 95%, respectively. The VVTM specimens also exhibit the biggest fatigue, which is similar to that of the field core sample. The Weibull distribution model is utilized to predict the fatigue life of CRM with different compaction methods, with the fatigue equation indicating that VVTM specimens have better fatigue performance. In addition, the number of voids, diameter of voids, and fractal dimension of VVTM specimens along the longitudinal direction are closer to those of field cores. The fractal dimension of CRM specimens with different compaction methods is between 1.2 and 1.4, indicating that the complex shape of voids may alter stress concentration and impact the performance of CRM.