Research

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29 pages, 13794 KiB

Open AccessArticle

Study of Decay Mechanisms and Rules of Recycled Asphalt Pavement via a Full-Scale Experiment

by Quanping Xia, Jiangping Gao, Qigong Zhang, Bin Xu, Qiang Sun, Ke Sun and Zhaodi Yuan

Coatings 2023, 13(11), 1955; https://doi.org/10.3390/coatings13111955 - 16 Nov 2023

Viewed by 721

Under the influence of long-term vehicle loads and large attenuation degrees, asphalt pavement performance gradually decreases, which leads to failure in fulfilling the appropriate requirements and, in turn, may affect driving safety. The purpose of this paper was to study the attenuation mechanism [...] Read more.

Under the influence of long-term vehicle loads and large attenuation degrees, asphalt pavement performance gradually decreases, which leads to failure in fulfilling the appropriate requirements and, in turn, may affect driving safety. The purpose of this paper was to study the attenuation mechanism and rule of styrene–butadiene–styrene (SBS)-modified recycled asphalt pavement, so as to determine the applicable position and rational utilization of recycled asphalt mixture. To achieve this goal, two structures were designed, and full-scale experiments were carried out. The performance of the field test road based on accelerated loading testing (ALT) was analyzed through field monitoring data. The fatigue characteristics of stone matrix asphalt-13 (SMA-13) and asphalt concrete-20 (AC-20) mixtures before and after accelerated loading were studied via the trabecular bending fatigue test and dynamic modulus test. The microscopic components in the asphalt mixtures were determined via thin-layer chromatography on chromarods with flame ionization detection (TLC-FID). The results showed that the fatigue properties of recycled asphalt mixture can meet the requirements of ordinary asphalt mixtures and meet the technical standards of asphalt pavement design. With the increase in loading times, the British pendulum number (BPN) value of the two structures tended to be stable, and the BPN of Plan 2 was six less than that of Plan 1. Under the same test conditions, the fatigue life sequence of the recycled asphalt mixture under different loading frequencies was 20 Hz > 10 Hz > 5 Hz. The contents of four components in the reclaimed asphalt mixture were similar to those in the ordinary asphalt mixture. The light component of the reclaimed asphalt mixture of SMA-13 was reduced by 11.69%, and the light component of the ordinary asphalt mixture of SMA-13 was reduced by 15.29% through the full-scale test. In summary, recycled asphalt mixture should not be applied to the upper layer of pavement but can be rationalized in the middle layer and the bottom layer of pavement. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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19 pages, 5106 KiB

Open AccessArticle

Research on Flexural and Freeze–Thaw Properties of Polypropylene-Fiber-Reinforced Pavement Concrete Containing Waterborne Epoxy

by Li Wang, Bing Zhang, Hongliang Zhang, Bendong Zhao, Biao Wang, Quanman Zhao and Min Sun

Coatings 2023, 13(6), 1035; https://doi.org/10.3390/coatings13061035 - 02 Jun 2023

Viewed by 1172

Abstract

In order to further enhance the reinforcing effectiveness of polypropylene (PP) fibers on pavement concrete, waterborne epoxy (WBE) was introduced in this research and its effect on the flexural properties and freeze–thaw resistance of PP-fiber-reinforced concrete was evaluated. Compressive-strength tests, flexural-strength tests, three-point [...] Read more.

In order to further enhance the reinforcing effectiveness of polypropylene (PP) fibers on pavement concrete, waterborne epoxy (WBE) was introduced in this research and its effect on the flexural properties and freeze–thaw resistance of PP-fiber-reinforced concrete was evaluated. Compressive-strength tests, flexural-strength tests, three-point bending tests, freeze–thaw cycling tests and a scanning electron microscopic observation were carried out to analyze mainly the influence of WBE on the flexural properties and freeze–thaw resistance of PP-fiber-reinforced concrete. WBE contents of 0, 5%, 10%, 15% and 20% by weight of the cement were employed. The experimental results indicated that WBE was beneficial to improving the flexural properties of PP-fiber-reinforced concrete. With increasing content of WBE, the flexural strength and the peak load showed significant increases. Although a slight degradation in the abovementioned flexural parameters was observed when the WBE content was above 15%, the deflection at the peak, the fracture energy and the fracture toughness still showed an upward trend. In addition, the freeze–thaw resistance of PP-fiber-reinforced concrete was improved remarkably with the increasing addition of WBE content, leading to smaller mass loss and higher residual flexural strength. Moreover, microstructural images revealed that with the addition of WBE, the PP fiber/concrete interfacial bonding was effectively improved, and the concrete matrix tended to be denser as well, which provided higher resistance for crack initiation and propagation. In consideration of maximally improving the flexural properties of PP-fiber-reinforced pavement concrete, and while ensuring the compressive strength and meeting the freeze–thaw requirements, it was recommended that the content of WBE in PP-fiber-reinforced concrete should be 15%. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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18 pages, 10295 KiB

Open AccessArticle

Structural Fault Diagnosis Based on Static and Dynamic Response Parameters

by Qiuwei Yang, Fengjiang Qin and Xi Peng

Coatings 2023, 13(5), 920; https://doi.org/10.3390/coatings13050920 - 14 May 2023

Cited by 1 | Viewed by 881

Abstract

Structural fault diagnosis is an important subject for ensuring the normal use of structures. More test data will help to improve the accuracy and reliability of structural fault diagnosis. Therefore, a structural fault detection algorithm based on static–dynamic mixed sensitivity analysis is proposed. [...] Read more.

Structural fault diagnosis is an important subject for ensuring the normal use of structures. More test data will help to improve the accuracy and reliability of structural fault diagnosis. Therefore, a structural fault detection algorithm based on static–dynamic mixed sensitivity analysis is proposed. The vibration parameters used were the vibration modes of some of the nodes in the structure measured by the vibration test system. The static response parameter used was the vertical displacement of the structure under the gravity load measured by the static test system. In particular, the gravity load and the structure were connected rigidly to form a new added-mass system. The vibration mode of the additional-mass system was measured again to obtain more equations for fault evaluation. Based on the static and dynamic measurement data, the failure coefficients of all components in the structure were calculated through the mixed sensitivity of the static displacement and vibration-mode shape. According to the calculated value of the failure coefficient, the failure state of all components in the structure could be finally evaluated. The main innovation of the proposed method was the use of the static load as a part of the new added-mass system to obtain more vibration parameters for the defect diagnosis. The implementation process and effect of this method were verified using a numerical truss structure and an experimental steel beam structure. Moreover, the defect diagnosis results of the proposed hybrid method were compared with those of a pure static algorithm and a pure dynamic algorithm to illustrate the advantages of the hybrid method. The research results showed that this method has the advantages of simple implementation and high diagnosis accuracy. Especially for symmetric structures, the proposed method can successfully avoid the possible missed diagnoses of the pure static algorithm and pure dynamic method. The algorithm provides a simple and feasible method for structural defect identification. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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15 pages, 3794 KiB

Open AccessArticle

Mechanical Strengths of Alkali-Activated Blast Furnace Slag Powder with Different Alkali Activators and Plant Fibers

by Jing Zhu, Lizhuo Song, Zijian Qu, Xiaopeng Wang, Zijie Wen, Xiaodong Liu and Hui Wang

Coatings 2023, 13(3), 664; https://doi.org/10.3390/coatings13030664 - 22 Mar 2023

Cited by 1 | Viewed by 1395

Abstract

In this paper, the influence of water glass types, the modulus of water glass, the alkali content, the water consumption, and plant fibers on the mechanical strengths of alkali-activated blast furnace slag powder (BFS) is investigated. Moreover, the fiber types and pretreatment on [...] Read more.

In this paper, the influence of water glass types, the modulus of water glass, the alkali content, the water consumption, and plant fibers on the mechanical strengths of alkali-activated blast furnace slag powder (BFS) is investigated. Moreover, the fiber types and pretreatment on the plant fibers and the measuring temperature on the performance of alkali-activated BFS are further considered. Results indicate that BFS activated by potassium silicate shows higher mechanical strengths than that activated by sodium silicate. The alkali-activated BFS with alkali treatment on fibers is the most advantageous. The modulus of alkali leads to decreasing the compressive strength. A total of 35% water consumption is the most beneficial to the specimens’ flexural and compressive strengths. Samples with 14% potassium silicate show the maximum mechanical strength. Alkali-activated BFS with 1% wheat straw fibers in addition by total volume represents the maximum mechanical strength. The alkali-activated BFS with alkali treatment on fibers is the most advantageous. The addition of potassium silicate can improve the flexural and compressive strengths by the maximum values of 30.4% and 16.8% compared to specimens with sodium silicate. A total of 35% water consumption can increase the flexural and compressive strengths by 33.8% and 32.7%. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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16 pages, 2462 KiB

Open AccessArticle

Mathematical Model for Early-Aged UHPFRC Compressive Strength Changes

by Xi Peng, Qiuwei Yang, Hongfei Cao and Haozhen Wang

Coatings 2023, 13(3), 525; https://doi.org/10.3390/coatings13030525 - 27 Feb 2023

Cited by 5 | Viewed by 1488

Abstract

Compressive strength is the most important mechanical index of ultra-high performance fiber-reinforced concrete (UHPFRC). The rule of changes in compressive strength in early-aged UHPFRC is of great significance to guide concrete curing, formwork removal, and prestress stretching. Therefore, it is very necessary to [...] Read more.

Compressive strength is the most important mechanical index of ultra-high performance fiber-reinforced concrete (UHPFRC). The rule of changes in compressive strength in early-aged UHPFRC is of great significance to guide concrete curing, formwork removal, and prestress stretching. Therefore, it is very necessary to study an accurate mathematical model to describe the change in compressive strength of UHPFRC at an early age. For this purpose, a new mathematical model of compressive strength age is proposed in this work for predicting the long-term strength of UHPFRC according to a few test data from early-aged UHPFRC. This new model can overcome the shortcomings of the existing models, such as the exponential model, logarithmic model, and polynomial model. The proposed model is first demonstrated by using four groups of compressive strength test data compiled from previous research studies. Subsequently, an experiment of early-aged UHPFRC compressive strength was carried out to further verify the proposed mathematical model. The mixed proportion used in the UHPFRC compressive strength test was 10.87:0.82:1 (powder:steel fiber:water), and the design strength grade was 120 MPa. Based on the UHPFRC experimental data, it was shown that the average fitting error and standard deviation of the new model were about 10%~20% of that of the logarithmic model and the polynomial model. The proposed model can precisely predict the compressive strength of UHPFRC, with a determination coefficient (R²) of 0.9974. The research results show that the average fitting error and standard deviation of this new model were significantly reduced when compared to the existing models, and the predicted compressive strength by the new model on the 60th day is the closest to the actual design strength grade of concrete. The greatest advantage of the proposed method lies in its simple formula, fast implementation, and no need for complex mathematical operations. It has been shown that the proposed model is superior to the existing models due to its higher fitting accuracy and prediction accuracy, and it can be better used to predict the later strength of UHPFRC by using only a few compressive strength test data taken at the early age stage. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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15 pages, 2989 KiB

Open AccessArticle

The Influence of Assembly Unit of Fibers on the Mechanical and Long-Term Properties of Reactive Powder Concrete

by Zhangjie Cai, Jie Ren, Guangming Shen, Changhong Jin, Xingqing Gu, Wenjie Cheng and Hui Wang

Coatings 2023, 13(2), 412; https://doi.org/10.3390/coatings13020412 - 11 Feb 2023

Cited by 6 | Viewed by 1246

Abstract

The corrosion of concrete structures by chloride salt is very significant in coastal environments. In order to improve the durability of marine concrete structures, cement-based materials with high durability need to be developed. In this investigation, the influence of NaCl freeze–thaw cycles (FT-C) [...] Read more.

The corrosion of concrete structures by chloride salt is very significant in coastal environments. In order to improve the durability of marine concrete structures, cement-based materials with high durability need to be developed. In this investigation, the influence of NaCl freeze–thaw cycles (FT-C) and NaCl dry-wet alternations (DW-A) on the flexural and compressive strengths of reactive powder concrete (RPC) with an assembly unit of basalt fibers and steel fibers is studied. Additionally, the mass loss rate, the relative dynamic modulus of elasticity (RDEM), the chloride ion migration coefficient (CMC) and the impact toughness are measured after the NaCl FT-C and DW-A action. Our findings show that the RDEM, mass loss, and mechanical strength loss of RPC are increased by the ascending NaCl FT-C and DW-A. Meanwhile, the RDEM and the impact toughness are decreased by the NaCl FT-C and DW-A. The RPC with 0.5% basalt fibers and 1.5% steel fibers by volume of RPC shows the optimum mechanical performance and resistance to NaCl FT-C and DW-A. However, RPC with 3% steel fibers shows the worst resistance to NaCl erosion. The maximum mass loss rates, RDEM, flexural strength loss rate, compressive strength loss rate, CMC and impact toughness of all specimens after 300 NaCl FT-C and 30 NaCl DW-A are 4.5%, 91.7%, 28.1%, 29.3%, 3.2 × 10⁻¹² (m²/s) and 2471 J. Meanwhile, the corresponding minimum values are 1.62%, 83.2%, 20.4%, 15.7%, 1.1 × 10⁻¹² (m²/s) and 625 J. The researching findings will provide an optimum mix ratio of RPC with an assembly unit of basalt fibers and steel fibers, which can be applied in the marine engineering environment. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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15 pages, 4419 KiB

Open AccessArticle

Reusing Fine Silty Sand Excavated from Slurry Shield Tunnels as a Sustainable Raw Material for Synchronous Grouting

by Rui Wang, Haoqing Xu, Yi Liu, Pengming Jiang and Aizhao Zhou

Coatings 2023, 13(2), 398; https://doi.org/10.3390/coatings13020398 - 09 Feb 2023

Cited by 1 | Viewed by 1057

Abstract

Using the Nanjing Dinghuaimen Yangtze River Tunnel project as a case study, we proposed a method to reuse the excavated silty-fine sand by adjusting the proportion of the waste sand to replace the commercial sand. This would address the issue of recycling the [...] Read more.

Using the Nanjing Dinghuaimen Yangtze River Tunnel project as a case study, we proposed a method to reuse the excavated silty-fine sand by adjusting the proportion of the waste sand to replace the commercial sand. This would address the issue of recycling the significant amount of waste sand generated when the slurry shield passes through the silty-fine sand stratum. Moreover, we have evaluated grout indicators such as density, fluidity, consistency, bleeding rate, volumetric shrinkage, setting time, and unconfined compressive strength and examined how the particle size and distribution of the sand affected the grout’s performance. The findings show that as the replacement ratio increases, the grout’s density, fluidity, consistency, and bleeding rate gradually increase; meanwhile, the volumetric shrinkage increases initially before decreasing; the setting time decreases gradually; the unconfined compressive strength initially decreases before increasing. The key factor altering the grout’s performance when the replacement ratio is less than 50% is the weakening of the adsorption effect of fine sand particles on water due to the increase in the sand’s fineness modulus. When it is greater than 50%, the particle size of the sand tends to be distributed nonuniformly and fine particles fill the voids between larger particles, thus contributing to the changes in grout properties. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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13 pages, 3559 KiB

Open AccessArticle

The Influence of Aspect Ratio of Steel Fibers on the Conductive and Mechanical Properties of Compound Cement Reactive Powder Concrete

by Zhao Liang, Xi Peng and Hui Wang

Coatings 2023, 13(2), 331; https://doi.org/10.3390/coatings13020331 - 01 Feb 2023

Cited by 4 | Viewed by 1223

Abstract

The performance of steel fibers reinforced RPC has a great relationship with the aspect ratio of the fibers. It is necessary to systematically study the relationship between the aspect ratio and the mechanical properties of RPC and the force-electricity response. In this paper, [...] Read more.

The performance of steel fibers reinforced RPC has a great relationship with the aspect ratio of the fibers. It is necessary to systematically study the relationship between the aspect ratio and the mechanical properties of RPC and the force-electricity response. In this paper, the flexural strength, the compressive strength and the flexural toughness and AC electrical resistance and AC impedance spectroscopy of reactive powder concrete are investigated. The flexural strength, compressive strength, and flexural toughness with the curing age of 1 day and 28 days are tested. The cement is the compound cement in this study, and the mass ratio of ordinary portland cement and sulphoaluminate cement is 1:1, and two kinds of steel fibers with aspect ratios of 30(AR-30) and 75(AR-75) are used. The fiber content is 2% of the concrete volume. Scanning electron microscope (SEM) and scanning electron microscope energy spectrum analysis (EDS) are investigated to analyze the composition of the hydration products. It can be obtained from the research results that the flexural strength and the compressive strength of reactive powder concrete decrease with the increase of steel fibers content with an aspect ratio of 30. The decreasing rates of the flexural strength and the compressive strength with the curing age of 1 d and 28 d are 14.93%~83.26% and 0.40%~46.36% with the incorporation of steel fibers with an aspect ratio of 30. The flexural toughness decreases in the form of a quadratic function with the mass ratio of steel fibers with an aspect ratio of 30. The electrical resistance of reactive powder concrete increases with the increase of steel fibers with an aspect ratio of 30. The maximum decreasing rate of electrical conductivity is 91.16%. The AC impedance spectrum is obtained, and the electric circuit of reactive powder concrete accords with the series conduction model, which parallel electrical resistance and capacitance of pore solution, rapid strength RPC and steel fibers respectively connect with a contact resistance of the electrode and specimens. It is found that the steel fibers network with an aspect ratio of 75 is closer by studying the equivalent circuit diagram. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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14 pages, 4635 KiB

Open AccessArticle

Influence of CO₂ Curing on the Alkali-Activated Compound Mineral Admixtures’ Corrosion Resistance to NaCl Dry–Wet Alternations

by Houchao Sun, Wenjie Cheng, Haoxin Xu, Zhangjie Cai, Minggan Yin and Feiting Shi

Coatings 2023, 13(1), 67; https://doi.org/10.3390/coatings13010067 - 30 Dec 2022

Cited by 3 | Viewed by 1218

Abstract

In this study, the influence of CO₂ curing on the corrosion resistance of reinforced alkali-activated compounds is investigated. Fly ash (FA) and blast furnace slag powder (BFS) are used as mineral admixtures. The specimens were subjected to dry–wet alternations with 3% NaCl, [...] Read more.

In this study, the influence of CO₂ curing on the corrosion resistance of reinforced alkali-activated compounds is investigated. Fly ash (FA) and blast furnace slag powder (BFS) are used as mineral admixtures. The specimens were subjected to dry–wet alternations with 3% NaCl, used to simulate a concrete structure under a corrosion environment. The ultrasonic velocity, mass loss rate, and electrical characteristics (such as electrical resistance, AC impedance spectra, and corrosion area rates determined by Tafel curves) are utilized to determine the degree of corrosion. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to analyze the corrosion mechanism. Results show that the corrosion resistance is decreased by the addition of FA but improved by CO₂ curing. When CO₂ curing is provided, the addition of BFS shows a higher enhancing effect on the corrosion resistance than that of FA. The equivalent circuit diagram of reinforced alkali-activated compound mineral admixtures obtained by AC impedance spectra is composed of three electrical elements (electrical resistance and capacitance in parallel) in series. The X-ray diffraction results show that adding BFS and CO₂ curing can decrease the rust’s iron oxides on the steel bars’ surface. Finally, as found in the SEM photos, BFS and CO₂ curing can effectively improve the compactness of specimens. Meanwhile, the roughness of hydration is increased by CO₂ curing. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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11 pages, 2996 KiB

Open AccessArticle

The Influence of CO₂ Curing on the Mechanical Performance and the Corresponding Chloride Ion Resistance of Alkali-Activated Compound Mineral Admixtures

by Ling Peng, Junchao Yang, Hui Wang and Xiaoqing Jin

Coatings 2022, 12(12), 1920; https://doi.org/10.3390/coatings12121920 - 07 Dec 2022

Cited by 4 | Viewed by 915

Abstract

In this paper, the mechanical properties (the flexural strength, compressive strength and the drying shrinkage rate) of CO₂-cured alkali-activated compound mineral admixtures (blast furnace slag powder (BFS) and fly ash (FA)) are investigated. In addition, the corresponding chloride ion mobility coefficient [...] Read more.

In this paper, the mechanical properties (the flexural strength, compressive strength and the drying shrinkage rate) of CO₂-cured alkali-activated compound mineral admixtures (blast furnace slag powder (BFS) and fly ash (FA)) are investigated. In addition, the corresponding chloride ion mobility coefficient is measured. Additionally, the freeze–thaw cycles with an NaCl concentration of 3% is studied. Thermogravimetric analysis and scanning electron microscopy are applied in analyzing the mechanical properties. The curing ages of the alkali-activated compound mineral admixtures are 1 day, 3 days and 28 days. Results show that the mechanical strengths are decreased by the addition of FA and increased by the increasing curing age and CO₂ curing. The maximum reducing rates of flexural and compressive strengths by FA are 47.6% and 42.3%. Meanwhile, the corresponding increasing rates by CO₂ curing are 26.5% and 23.1%, respectively. The improving effect of alkali-activated BFS by CO₂ curing is higher than that of FA. Furthermore, the drying shrinkage rate is increased by the increasing dosages of BFS, the increasing curing ages and CO₂ curing. Additionally, CO₂ curing and the increasing dosage of BFS leads to decreasing the chloride ion mobility coefficient. Finally, CO₂ curing and the addition of BFS can effectively improve the resistance of NaCl freeze–thaw cycles. The compactness of the hydration products is improved by the addition of BFS and the roughness of hydration products is increased by CO₂ curing. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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Review

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24 pages, 12364 KiB

Open AccessReview

Review of Research on Tire–Pavement Contact Behavior

by Zhenlong Gong, Yinghao Miao and Claudio Lantieri

Coatings 2024, 14(2), 157; https://doi.org/10.3390/coatings14020157 - 24 Jan 2024

Viewed by 868

Abstract

This article presents the latest progress in research on tire–pavement contact behavior. Firstly, the tire–pavement contact characteristics and their influencing factors are summarized. Then, the measurement methods and theoretical research on tire–pavement contact behavior are reviewed, and the advantages and shortcomings of different [...] Read more.

This article presents the latest progress in research on tire–pavement contact behavior. Firstly, the tire–pavement contact characteristics and their influencing factors are summarized. Then, the measurement methods and theoretical research on tire–pavement contact behavior are reviewed, and the advantages and shortcomings of different methods are compared and analyzed. Finally, analysis in the field of pavement engineering is summarized based on contact behavior. This article suggests a few key research directions: Tire–pavement contact behavior is influenced by multiple factors; therefore, multi-physical field-coupling analyses need to be carried out. Tire–pavement contact tests are mostly static and non-standardized, and it is a future trend to develop high-precision, low-cost, and standardized instruments that can measure dynamic contact. Theoretical research models rarely involve environmental factors; a contact model of the tire, pavement, and environment needs to be constructed that can truly describe the contact process. There is a relationship between contact characteristics and pavement performance; pavement performance evaluation indexes need to be established based on tire–pavement contact characteristics in the future. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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