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Performance-Related Material Properties of Asphalt Mixture Components (Second Edition)

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: 10 June 2024 | Viewed by 7731

Special Issue Editors

College of Civil Science and Engineering, Yangzhou University, Yangzhou 225009, China
Interests: pavement structure and performance; multi-scale mechanical response of asphalt pavement; pavement recycling technology; advanced pavement materials
Special Issues, Collections and Topics in MDPI journals
School of Civil Engineering, Jiulidi Campus, Southwest Jiaotong University, Chengdu, China
Interests: pavement cracking; thermoreversible aging; wax in asphalt; performance characterization
Special Issues, Collections and Topics in MDPI journals
School of Transportation and Logistics Engineering, Wuhan University of Technology, Wuhan, China
Interests: asphalt pavement; jointed concrete pavement; long-term pavement performance; mechanistic-empirical model; machine learning
Special Issues, Collections and Topics in MDPI journals
School of Civil and Transportation Engineering, Beijing University of Civil Engineering and Architecture, Beijing, China
Interests: asphalt pavements; oxidative aging; fracture mechanics; numerical modeling; artificial neural networks
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Each component of an asphalt mixture (e.g., asphalt binder, aggregate, recycled materials and additives) directly affects the performance of the asphalt mixture and asphalt pavement, including fractures, permanent deformation, aging and moisture. Different damage modes are induced by different mechanisms and/or under different environmental conditions, and the contribution of each component to resist different types of damage is different. Therefore, it is vital to accurately evaluate the effects of the fundamental properties of asphalt mixture components and the component interactions that are related to damage performance, which are critical to develop performance models for asphalt mixtures. The assessment of material properties becomes essential when recycled materials and/or additives are involved.  

The Special Issue “Performance-Related Material Properties of Asphalt Mixture Components (Second Edition)” aims to publish original research articles to determine the fundamental properties of asphalt mixture components that are related to the distress/performance of asphalt mixtures and asphalt pavements.

Topics include, but are not limited to, the following:

  1. Influence of the viscoelastic properties of asphalt mixture components on performance;
  2. Influence of the morphological properties of asphalt mixture components on performance;
  3. Influence of the chemical properties of asphalt binders on the durability of asphalt pavements;
  4. Evaluation of asphalt binders and aggregate interactions;
  5. Numerical modeling of asphalt mixture components and their interactions;
  6. Environmental effects on asphalt mixture components and performance;
  7. Performance of asphalt mixtures with recycled materials.

It is our pleasure to invite you to submit a manuscript to this Special Issue. Research articles, reviews and communication are all welcome.

Dr. Yao Zhang
Dr. Haibo Ding
Dr. Yu Chen
Dr. Meng Ling
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • asphalt binder
  • asphalt mixtures
  • asphalt pavement
  • aggregate
  • recycled materials
  • distress
  • material properties
  • numerical modelling

Published Papers (11 papers)

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Research

17 pages, 6136 KiB  
Article
Calculation of and Key Influencing Factors Analysis on Equivalent Resilient Modulus of a Submerged Subgrade
by Junyao Tang, Siyu Chen, Tao Ma, Binshuang Zheng and Xiaoming Huang
Materials 2024, 17(4), 949; https://doi.org/10.3390/ma17040949 - 18 Feb 2024
Viewed by 458
Abstract
To calculate and analyze the equivalent resilient modulus of a submerged subgrade, a constitutive model considering the effect of saturation and matrix suction was introduced using ABAQUS’s user-defined material (UMAT)subroutine. The pavement response under falling weight deflectometer (FWD) load was simulated at various [...] Read more.
To calculate and analyze the equivalent resilient modulus of a submerged subgrade, a constitutive model considering the effect of saturation and matrix suction was introduced using ABAQUS’s user-defined material (UMAT)subroutine. The pavement response under falling weight deflectometer (FWD) load was simulated at various water levels based on the derived distribution of the resilient modulus within the subgrade. The equivalent resilient modulus of the subgrade was then calculated using the equivalent iteration and weighted average methods. Based on this, the influence of the material and structural parameters of the subgrade was analyzed. The results indicate that the effect of water level rise on the tensile strain at the bottom of the asphalt layer and the compressive strain at the top of the subgrade is obvious, and its trend is similar to an exponential change. The equivalent resilient modulus of the subgrade basically decreases linearly with the rise in the water level, and there is high consistency between the equivalent iteration and weighted average methods. The saturated permeability coefficient and subgrade height have the most significant effect on the resilient modulus of the subgrade, which should be emphasized in the design of submerged subgrades, and the suggested values of the resilient modulus of the subgrade should be proposed according to the relevant construction conditions. Full article
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17 pages, 5268 KiB  
Article
Investigation of Phenolic Resin-Modified Asphalt and Its Mixtures
by Lieguang Wang, Lei Wang, Junxian Huang, Mingfei Wu, Kezhen Yan and Zirui Zhang
Materials 2024, 17(2), 436; https://doi.org/10.3390/ma17020436 - 16 Jan 2024
Viewed by 529
Abstract
This study comprehensively examines the influence of phenol-formaldehyde resin (PF) on the performance of base asphalt and its mixtures for road applications, emphasizing its innovative use in enhancing pavement quality. Optimal PF content was determined through the evaluation of standard indicators and rotational [...] Read more.
This study comprehensively examines the influence of phenol-formaldehyde resin (PF) on the performance of base asphalt and its mixtures for road applications, emphasizing its innovative use in enhancing pavement quality. Optimal PF content was determined through the evaluation of standard indicators and rotational viscosity. In-depth analyses of PF-modified asphalt’s high- and low-temperature rheological properties and viscoelastic behavior were conducted using dynamic shear rheometers and bending beam rheometers. Aging resistance was assessed through short-term aging and performance grade (PG) grading. Moreover, Marshall and water stability tests were performed on PF-modified asphalt mixtures. Findings indicate that the uniform dispersion of PF particles effectively inhibits asphalt flow at high temperatures, impedes oxygen penetration, and delays the transition from elasticity to viscosity. These unique properties enhance the high-temperature stability, rutting resistance, and aging resistance of PF-modified asphalt. However, under extremely low temperatures, PF’s brittleness may impact asphalt flexibility. Nonetheless, the structural advantages of PF-modified asphalt, such as improved mixture density and stability, contribute to enhanced high-temperature performance, water stability, adhesion, and freeze–thaw cycle stability. This research demonstrates the feasibility and effectiveness of using PF to enhance the overall performance of base asphalt and asphalt mixtures for road construction. Full article
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17 pages, 5634 KiB  
Article
Experimental Investigation of the Size Effect on Roller-Compacted Hydraulic Asphalt Concrete under Different Strain Rates of Loading
by Xiao Meng, Yunhe Liu, Zhiyuan Ning, Jing Dong and Gang Liang
Materials 2024, 17(2), 353; https://doi.org/10.3390/ma17020353 - 10 Jan 2024
Viewed by 490
Abstract
Asphalt concrete is widely used in hydraulic structure facilities as an impermeable structure in alpine cold regions, and its dynamic mechanical properties are influenced by the strain rate and specimen size. However, the specimen size has an important effect on mechanical properties; few [...] Read more.
Asphalt concrete is widely used in hydraulic structure facilities as an impermeable structure in alpine cold regions, and its dynamic mechanical properties are influenced by the strain rate and specimen size. However, the specimen size has an important effect on mechanical properties; few systematic studies have investigated on the size effect of hydraulic asphalt concrete (HAC) under dynamic or static loading rates. In the present study, four sizes of cylindrical roller-compacted hydraulic asphalt concrete (RCHAC) specimens with heights of 50 mm, 100 mm, 150 mm, and 200 mm were prepared and tested under different loading rates ranging from 10−5 s−1 to 10−2 s−1 to investigate the size effects of mechanical properties and failure modes at the temperature of 5 °C. The effect of strain rate on the size effects of the compressive strength and the elastic modulus of RCHAC have also been explored. These tests indicate that when the specimen size increases, the compressive strength and failure degree decrease, while the elastic modulus increases. When the height increases from 50 mm to 200 mm, the compressive strength at different strain rates decreased by more than 50%. Furthermore, the elastic modulus increased by about 211.8% from 0.51 GPa to 1.59 GPa at a strain rate of 10−5 s−1, and increased by 150% from 5.08 GPa to 12.71 GPa at a strain rate of 10−2 s−1. As the strain rate increases, the variation trends with the size of the compressive strength, elastic modulus, and failure degree are distinctly intensified. A modified dynamic size effect law, which incorporates both the specimen size and strain rate, is proposed and verified to illustrate the dynamic size effect for the RCHAC under different loading rates. Full article
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21 pages, 1810 KiB  
Article
Effects of the Mixing Process on the Rheological Properties of Waste PET-Modified Bitumen
by Grzegorz Mazurek, Przemysław Buczyński, Marek Iwański, Marcin Podsiadło, Przemysław Pypeć and Artur Kowalczyk
Materials 2023, 16(23), 7271; https://doi.org/10.3390/ma16237271 - 22 Nov 2023
Viewed by 551
Abstract
This paper analyses the key findings of a study devoted to PET-modified bitumen. The research program was run according to the D-optimal experimental plan based on a factorial design. Five factors, i.e., the type of polymer (source), the type of bitumen (qualitative factors), [...] Read more.
This paper analyses the key findings of a study devoted to PET-modified bitumen. The research program was run according to the D-optimal experimental plan based on a factorial design. Five factors, i.e., the type of polymer (source), the type of bitumen (qualitative factors), PET amount, mixing rate, and mixing temperature (quantitative factors), controlled the bitumen–polymer mixing process. The experiment included a series of determinations of bitumen’s rheological characteristics obtained by MSCR (Jnr, R) and G*/sin(δ) at 50 °C, 60 °C, and 70 °C. The low-temperature properties of the composite (critical temperature) were evaluated using a BBR test. The findings showed that bitumen modification with PET primarily reduced the creep susceptibility of the bituminous–polymer mixture. The low-temperature characteristics of the modified bitumen played a secondary but essential role. The amount of polymer and the mixing rate interacted with the temperature, significantly reducing the stiffness of the composite, while the type and amount of bitumen had a substantial effect on the results obtained in the BBR test. It is worth noting that when combining bitumen and plastomer, special attention should be paid to ensuring a high level of homogeneity of the mixture by controlling the parameters of the mixing process accordingly. The tests and analyses provided crucial models (GLM), which allowed for the prediction of the plastomer-modified bitumen’s low- and high-temperature properties. The resulting relationships between factors and the identification of their impact on the bitumen properties enable a better understanding of the process of bitumen modification with PET. The conclusions presented here serve as a basis for future optimisation of the modified bitumen composition. The performed studies indicate that the use of >3% plastomer in bitumen 70/100 allows for a reduction in its susceptibility (MSCR) to below 0.5 kPa−1, making it suitable for bituminous mixtures for high-traffic roads. No significant increase in critical temperature (BBR) was observed. Full article
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23 pages, 7060 KiB  
Article
Effect of Basalt Fiber Diameter on the Properties of Asphalt Mastic and Asphalt Mixture
by Bo Li, Minghao Liu, Aihong Kang, Yao Zhang and Zhetao Zheng
Materials 2023, 16(20), 6711; https://doi.org/10.3390/ma16206711 - 16 Oct 2023
Cited by 3 | Viewed by 675
Abstract
In this study, basalt fiber having two types of diameters (16 μm and 25 μm) was selected and added to asphalt mastic and asphalt mixtures using different fiber proportions. The influences of fiber diameters and proportions on the properties of asphalt mastic and [...] Read more.
In this study, basalt fiber having two types of diameters (16 μm and 25 μm) was selected and added to asphalt mastic and asphalt mixtures using different fiber proportions. The influences of fiber diameters and proportions on the properties of asphalt mastic and mixtures were studied. The adhesion behavior of the fiber-asphalt mastic (FAM) interface was evaluated by a monofilament pullout test, and the rheological properties of FAM were evaluated by temperature sweep, linear amplitude sweep, and bending beam rheological tests. In addition, the high-temperature stability, intermediate and low-temperature cracking resistance, and water stability of fiber-modified mixtures were studied by wheel tracking, ideal cracking, a low-temperature bending beam, and a water-immersed Marshall test. The results showed that the interface adhesion behavior between 16 μm fiber and asphalt mastic was more likely in the fiber failure mode at both −12 °C and 25 °C. Adding basalt fiber can significantly improve the high-temperature and fatigue properties of asphalt mastics. Moreover, 16 μm fiber had a better modifying effect on asphalt mastic than 25 μm fiber. The same enhancement trend can be observed in asphalt mixtures. Basalt fibers with 16 μm diameters can improve the high-temperature performance of asphalt mixtures more significantly. In addition, 16 μm fiber could sharply enhance the cracking performance of the mixtures at intermediate and low temperatures, while the enhancing effect of 25 μm fiber on the mixture is insignificant, though both diameters of the fibers have a minor effect on the water stability. Full article
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17 pages, 4946 KiB  
Article
Probing the Effect of Linear and Crosslinked POE-g-GMA on the Properties of Asphalt
by Yujuan Zhang, Pei Qian, Peng Xiao, Aihong Kang, Chenguang Jiang, Changjiang Kou, Zhifeng Wang and Yuqing Li
Materials 2023, 16(19), 6564; https://doi.org/10.3390/ma16196564 - 05 Oct 2023
Viewed by 721
Abstract
The copolymer ethylene–octene (POE) has good aging resistance and is an inexpensive asphalt additive compared to the styrene–butadiene–styrene copolymer (SBS). However, POE is easy to segregate in asphalt during storage at high temperatures. Grafting glycidyl methacrylate (GMA) onto the molecular backbone of POE [...] Read more.
The copolymer ethylene–octene (POE) has good aging resistance and is an inexpensive asphalt additive compared to the styrene–butadiene–styrene copolymer (SBS). However, POE is easy to segregate in asphalt during storage at high temperatures. Grafting glycidyl methacrylate (GMA) onto the molecular backbone of POE (i.e., POE-g-GMA) may solve this problem, for the epoxy groups in GMA can react with the active groups in asphalt. Asphalt modified with linear and crosslinked POE-g-GMA were prepared, and the hot storage stability, physical properties and thermal oxidation aging properties were discussed in detail. The results show that linear and low-degree crosslinked POE-g-GMA-modified asphalts are storage-stable at high temperatures via measurements of the difference in softening points and small-angle X-ray scattering (SAXS) characterizations from macro and micro perspectives. The difference in softening points (ΔSP) between the upper and lower ends is no more than 3.5 °C for modified asphalts after 48 h of being in an oven at 163 °C. More importantly, the crosslinking modification of POE-g-GMA can further increase the softening point and reduce the penetration as well as rheological properties via conventional physical property, dynamic shear rheometer (DSR) and multiple-stress creep recovery (MSCR) tests. Furthermore, asphalt modified with crosslinked POE-g-GMA reveals better aging resistance via measurements of the performance retention rate and electron paramagnetic resonance (EPR) characterizations after a rolling thin film oven test (RTFOT). This work may provide further guidelines for the application of polymers in asphalt. Full article
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18 pages, 3201 KiB  
Article
A Fractional Creep Constitutive Model Considering the Viscoelastic–Viscoplastic Coexistence Mechanism
by Jia Zhao, Weigang Zhao, Kaize Xie and Yong Yang
Materials 2023, 16(18), 6131; https://doi.org/10.3390/ma16186131 - 08 Sep 2023
Cited by 1 | Viewed by 654
Abstract
In order to improve the accuracy and universality of the nonlinear viscoelastic-plastic mechanical behavior characterization method of asphalt mixture, a new criterion for the division of the creep process of materials was established based on the strain yield characteristics, and the coexistence mechanism [...] Read more.
In order to improve the accuracy and universality of the nonlinear viscoelastic-plastic mechanical behavior characterization method of asphalt mixture, a new criterion for the division of the creep process of materials was established based on the strain yield characteristics, and the coexistence mechanism of Viscoelastic–Viscoplastic strain was proposed in the subsequent yield phase; then, a viscoelastic element was constructed in the form of a parallel connection of two fractional viscoelastic elements based on fractional calculus theory, and its mathematical equations were derived; with novel viscoelastic elements, a constitutive model characterizing the whole creep process of asphalt mixtures was developed and its analytical expression was derived. The laboratory short-term creep test of Cement and Asphalt Mortar (CA mortar) and the simulation test data of asphalt mixtures from the references were used to verify the constitutive model. The results show that the creep constitutive model of asphalt mixture established in this paper has excellent fitting accuracy for different phases of the creep process of asphalt mixture under different stress levels, where the minimum fitting correlation values R2 for CA mortar, asphalt mixture (applied to pavement engineering), and asphalt sand are 0.9976, 0.981, and 0.979, respectively. Therefore, this model can be used to provide a theoretical reference for the study of the characterization of the mechanical behavior of asphalt materials. Full article
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20 pages, 6518 KiB  
Article
Aging Behavior and Mechanism Evolution of Nano-Al2O3/Styrene-Butadiene-Styrene-Modified Asphalt under Thermal-Oxidative Aging
by Zhiyuan Ji, Xing Wu, Yao Zhang and Gabriele Milani
Materials 2023, 16(17), 5866; https://doi.org/10.3390/ma16175866 - 27 Aug 2023
Viewed by 672
Abstract
The goal of this paper is to analyze the aging behavior and the mechanism evolution of nano-Al2O3 (NA)-reinforced styrene-butadiene-styrene (SBS) asphalt under different thermal-oxidative aging conditions. First, NA/SBS-modified asphalt and SBS-modified asphalt with different aging levels were prepared. Second, the [...] Read more.
The goal of this paper is to analyze the aging behavior and the mechanism evolution of nano-Al2O3 (NA)-reinforced styrene-butadiene-styrene (SBS) asphalt under different thermal-oxidative aging conditions. First, NA/SBS-modified asphalt and SBS-modified asphalt with different aging levels were prepared. Second, the viscosity and high temperature rheological performance of the specimens were tested and the property-related aging indexes were calculated and compared. Third, a Fourier transform infrared (FTIR) test of the specimen was conducted and the chemical group-related aging indexes were calculated and analyzed. Fourth, gel permeation chromatography (GPC) was used to analyze the molecular weight of the specimens under different aging levels. Then, an atomic force microscope (AFM) was adopted to analyze the microsurface morphology of different specimens. Finally, correlation analysis between property-related indexes and chemical group indexes was conducted. The results show that NA can enhance the thermal-oxidative aging resistance of SBS asphalt. NA can inhibit the increase in sulfoxide groups and the degradation of the SBS polymer with the increase in aging. NA can slow down the formation of large molecule during the aging process. The degree of change in both the bee structures and micromorphological roughness of NA/SBS asphalt is lower than that of SBS asphalt under different aging levels. Full article
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16 pages, 11606 KiB  
Article
Evaluation of the Adhesion between Aggregate and Asphalt Binder Based on Image Processing Techniques Considering Aggregate Characteristics
by Min Li, Jian Wang, Zibao Guo, Jingchun Chen, Zedong Zhao and Jiaolong Ren
Materials 2023, 16(14), 5097; https://doi.org/10.3390/ma16145097 - 19 Jul 2023
Viewed by 654
Abstract
Aggregate–asphalt adhesion plays an important role in the water stability of asphalt concrete. In various test standards of different countries, it is evaluated via the subjective judgment of testers using the boiling water test. The subjective judgment in the test method is detrimental [...] Read more.
Aggregate–asphalt adhesion plays an important role in the water stability of asphalt concrete. In various test standards of different countries, it is evaluated via the subjective judgment of testers using the boiling water test. The subjective judgment in the test method is detrimental to the accuracy of the adhesion evaluation. However, there is no quantitative evaluation method for the aggregate–asphalt adhesion in existing studies. Moreover, the effects of aggregate shape on adhesion are also not discussed and stipulated. Hence, an innovative method based on the Chinese boiling water test and image processing technique is put forward to quantificationally evaluate the aggregate–asphalt adhesion. Moreover, the effects of aggregate shapes on adhesion are also investigated via the proposed method from a view of aspect ratio and homogeneity. Results show that the peeling of the asphalt membrane on the aggregate surface is more serious as the complexity of the aggregate shape increases after the boiling water tests, while the effect degree gradually decreases. The effect of aspect ratio on the peeling status of asphalt membrane is lower than that of aggregate homogeneity. Full article
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15 pages, 3706 KiB  
Article
Influence of Morphological Characteristics of Coarse Aggregates on Skid Resistance of Asphalt Pavement
by Yuanshuai Dong, Zihao Wang, Wanyan Ren, Tianhao Jiang, Yun Hou and Yanhong Zhang
Materials 2023, 16(14), 4926; https://doi.org/10.3390/ma16144926 - 10 Jul 2023
Cited by 1 | Viewed by 912
Abstract
This research aims to improve the durability of skid resistance of asphalt pavement from the perspective of coarse aggregates based on on-site investigation. Firstly, the skid resistance of six representative actual roads was tested during two years by employing the Dynamic Friction Tester [...] Read more.
This research aims to improve the durability of skid resistance of asphalt pavement from the perspective of coarse aggregates based on on-site investigation. Firstly, the skid resistance of six representative actual roads was tested during two years by employing the Dynamic Friction Tester and the attenuation characteristics of skid resistance of different types of asphalt pavements were analyzed. Secondly, core samples were drilled onsite and coarse aggregates were extracted from the surface layer of the core samples. The morphological parameters of coarse aggregates were collected by a “backlighting photography” system and three-dimensional profilometer, and the variation rules of angularity and micro-texture of coarse aggregates were investigated. Finally, the correlation between the morphological characteristics of coarse aggregates and the pavement skid resistance was established based on the grey correlation entropy. The research results show that with the increase in service time, the attenuation rate of skid resistance of asphalt pavement gradually slows down; the angularity of coarse aggregates gradually decreases, and the micro-texture on the wearing surface gradually wears away. The grey correlation entropy between all the micro-texture indexes of coarse aggregates and dynamic friction coefficient, as well as between the roundness and skid resistance is more than 0.7, whereas the correlation between other evaluation indicators and the dynamic friction coefficient is poor, indicating that compared with the angularity of coarse aggregates, the micro-texture affects the skid resistance of actual asphalt pavement more greatly. In engineering applications, the use of coarse gradation, coarse aggregates with high roughness or high anti-wear performance can slow down the attenuation of pavement skid resistance, so that the pavement can maintain superior long-term anti-skidding performance. Full article
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15 pages, 3282 KiB  
Article
Mesoscopic Mechanical Properties of Aggregate Structure in Asphalt Mixtures and Gradation Optimization
by Jingchun Chen, Jian Wang, Min Li, Zedong Zhao and Jiaolong Ren
Materials 2023, 16(13), 4709; https://doi.org/10.3390/ma16134709 - 29 Jun 2023
Viewed by 679
Abstract
Particle media are widely used in engineering and greatly influence the performance of engineering materials. Asphalt mixtures are multi-phase composite materials, of which coarse aggregates account for more than 60%. These coarse aggregates form a stable structure to transfer and disperse traffic loads. [...] Read more.
Particle media are widely used in engineering and greatly influence the performance of engineering materials. Asphalt mixtures are multi-phase composite materials, of which coarse aggregates account for more than 60%. These coarse aggregates form a stable structure to transfer and disperse traffic loads. Therefore, knowing how to adjust the structural composition of coarse aggregates to optimize their performance is the key to optimize the performance of asphalt mixtures. In this study, the effects of different roughness and different sizes on the interlocking force and contact force of coarse aggregates were investigated through means of simulation (DEM), and then the formation-evolution mechanism of the coarse aggregate structure and the role of different sizes of aggregates in the coarse aggregate structure were analyzed. Subsequently, the optimal ratio of coarse aggregates was explored through indoor tests, and finally, the gradation of asphalt mixture based on the optimization of fine structure was formed and verified through indoor tests. The results showed that the major model can effectively reveal the role of different types of aggregates in the fine structure and the relationship between the strength of contact forces between them and clarify that the strength of the fine structure increases with the increase in aggregate roughness. Hence, the coarse aggregate structure can be regarded as a contact force transmission system composed of some strong and sub-strong contact forces. Their formation-evolution mechanism can be regarded as a process of the formation of strong and sub-strong contact forces and the transformation from sub-strong contact force to strong contact force. Moreover, the dynamic stability of the optimized graded asphalt mixture was increased by 30%, and the fracture toughness was increased by 26%. Full article
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