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Materials, Structure, and Modeling for Smart and Resilient Roads

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

Deadline for manuscript submissions: closed (10 March 2023) | Viewed by 22491

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Special Issue Editors

Prof. Dr. Xu Yang

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Guest Editor

1. School of Highway, Chang’an University, Xi’an, China
2. Department of Civil Engineering, Monash University, Melbourne, Australia
Interests: construction materials; paving materials; bituminous materials; cement; composite materials; thermal plastic materials
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Filippo Giustozzi

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Guest Editor

Department of Civil and Infrastructure Engineering, RMIT University, Melbourne, Australia
Interests: recycling; circular economy; waste plastics; crumb rubber; bitumen; asphalt; polymers

Dr. Lingyun You

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Guest Editor

School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology, Wuhan, China
Interests: pavement mechanics; sustainable road materials; foamed and emulsified asphalt; analytical solution; finite element approach; molecular dynamics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The smartness and resilience of infrastructures are becoming increasingly ubiquitous. As important components of infrastructure, roads play an important role to achieve the goal for the entire infrastructure system. The large-scale construction of transportation infrastructure has increased the demand for its sustainability. Currently, road construction bears important responsibilities for the use of natural resources and energy, the generation of waste, the emission of greenhouse gases, and the intensification of urban heat island effects. At the same time, the aging and wear phenomenon of road materials will lead to a reduction in service life and further consume resources and energy. To reduce the negative effects, the road structure needs to be more durable and smarter. For example, as asphalt mixture is the most commonly used road material, improving the durability of asphalt pavement is an important goal in this regard. To obtain this enhanced durability and sustainability, in the few past decades, some smart admixtures have been developed to make this material more intelligent. Thermochromic materials have been used in asphalt due to the advantages of the dynamic conversion of optical and thermal properties, which reversibly change color according to temperature, thereby dynamically adjusting the reflectivity of the asphalt to solar radiation. Ultraviolet blocking materials can enhance the anti-ultraviolet aging ability of asphalt. Induction heating is used to enhance the engineering healing ability of asphalt mixture. The warm and cold mixing technologies can reduce greenhouse gas emissions, thereby, saving energy. Recycling technology and regeneration technology play an important role in realizing long-life pavement structures. In this Special Issue, the latest developments in these smart and durable road surfaces are discussed. The compatibility of smart admixtures with traditional pavement materials and the influence on the properties and structure of pavement materials are considered. It is also critical to simulate the long-life structure formation, the activation of intelligent performance, the service life in a specific environment, and the environmental impact of new durable pavement structures.

The purpose of this Special Issue of the Materials is to attract manuscripts about new materials and innovative technologies for smart and resilient roads. The topics cover, but are not limited to, the following:

Advanced functional materials to improve road resilience;
Intelligent materials that enhance the road environment (smart roads);
Innovative computational methods to solve road problems;
High-performance and recycled road materials to enhance durability and sustainability;
Incorporation of smart road principles into the design of cities;
Advanced technologies for road construction and maintenance.

Prof. Dr. Xu Yang
Prof. Dr. Filippo Giustozzi
Prof. Dr. Lingyun You
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

transportation infrastructures
sustainable materials
durable structures
smart and resilient roads
multiscale modeling
road resilience

Published Papers (12 papers)

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Research

10 pages, 2206 KiB

Open AccessArticle

Discrete Element Modeling of the Meso-Mechanical Response of Asphalt Pavement under Vehicle Load

by Dong Zhang, Chunying Wu, Lili Cai, Jiang Bian and Chaoen Yin

Materials 2022, 15(21), 7808; https://doi.org/10.3390/ma15217808 - 05 Nov 2022

Cited by 1 | Viewed by 1178

Abstract

Numerical simulation is an effective way to study the mechanical response of asphalt pavement, which is very important for the pavement structural design. In this study, a three-dimensional meso-structure discrete element model of asphalt pavement was generated with the FISH programming language and its meso-mechanical response under vehicle load was analyzed. The contact forces within the asphalt pavement, in asphalt mastic, in coarse aggregates and between asphalt mastic and coarse aggregates were studied. The results of the study show that the contact forces within the asphalt mixture are highly uneven. The number of contact points in coarse aggregates account only for about 10% of all contact points while the sum of the contact forces in coarse aggregates contributes to over 50% of all contact forces. This demonstrates that the coarse aggregates bear most of the vehicle load. The average normal contact force in coarse aggregates is about 5 N and the average tangential contact force in coarse aggregates is about 2 N. The modeling results provide a quantitative understanding of the distribution of loading in asphalt pavement. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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13 pages, 3387 KiB

Open AccessArticle

Mechanical Behavior of Shape Memory Alloy Fibers Embedded in Engineered Cementitious Composite Matrix under Cyclic Pullout Loads

by Zhao Yang, Yalong Du, Yujia Liang and Xiaolong Ke

Materials 2022, 15(13), 4531; https://doi.org/10.3390/ma15134531 - 27 Jun 2022

Cited by 10 | Viewed by 1348

Abstract

The incorporation of superelastic shape memory alloy (SMA) fibers into engineered cementitious composite (ECC) materials can provide high seismic energy dissipation and deformation self-centering capabilities for ECC materials. Whether the SMA fibers can be sufficiently bonded or anchored in the ECC matrix and whether the mechanical properties of the SMA fibers in the ECC matrix can be effectively utilized are the key scientific issues that urgently need to be studied. In order to study the mechanical behavior of SMA fiber embedded in ECC matrix, four groups of semi-dog-bone pullout specimens were fabricated, and the cyclic pullout tests were conducted in this paper. The pullout stress, displacement, and self-centering capability were analyzed, and different influencing factors were discussed. The results show that the knotted ends can provide sufficient anchorage force for SMA fibers, and the maximum pullout stress of SMA fiber can reach 1100 MPa, thus the superelasticity can be effectively stimulated. The SMA fibers show excellent self-centering capability in the test. The minimum residual deformation in the test is only 0.29 mm, and the maximum self-centering ratio can reach 0.93. Increasing bond length can increase the ultimate strain of SMA fibers with knotted ends, but reduce the maximum pullout stress. Increasing fiber diameter can increase both the ultimate strain and the maximum stress of knotted end SMA fibers. While neither bond length nor fiber diameter has significant effect on the self-centering ratio. This paper provides a theoretical basis for further study of the combination of SMA fibers and ECC materials. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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21 pages, 7102 KiB

Open AccessArticle

Prediction Models for Evaluating Resilient Modulus of Stabilized Aggregate Bases in Wet and Dry Alternating Environments: ANN and GEP Approaches

by Kaffayatullah Khan, Fazal E. Jalal, Mohsin Ali Khan, Babatunde Abiodun Salami, Muhammad Nasir Amin, Anas Abdulalim Alabdullah, Qazi Samiullah, Abdullah Mohammad Abu Arab, Muhammad Iftikhar Faraz and Mudassir Iqbal

Materials 2022, 15(13), 4386; https://doi.org/10.3390/ma15134386 - 21 Jun 2022

Cited by 10 | Viewed by 1514

Abstract

Stabilized aggregate bases are vital for the long-term service life of pavements. Their stiffness is comparatively higher; therefore, the inclusion of stabilized materials in the construction of bases prevents the cracking of the asphalt layer. The effect of wet–dry cycles (WDCs) on the resilient modulus (M_r) of subgrade materials stabilized with CaO and cementitious materials, modelled using artificial neural network (ANN) and gene expression programming (GEP) has been studied here. For this purpose, a number of wet–dry cycles (WDC), calcium oxide to SAF (silica, alumina, and ferric oxide compounds in the cementitious materials) ratio (CSAFRs), ratio of maximum dry density to the optimum moisture content (DMR), confining pressure (σ₃), and deviator stress (σ₄) were considered input variables, and M_r was treated as the target variable. Different ANN and GEP prediction models were developed, validated, and tested using 30% of the experimental data. Additionally, they were evaluated using statistical indices, such as the slope of the regression line between experimental and predicted results and the relative error analysis. The slope of the regression line for the ANN and GEP models was observed as (0.96, 0.99, and 0.94) and (0.72, 0.72, and 0.76) for the training, validation, and test data, respectively. The parametric analysis of the ANN and GEP models showed that M_r increased with the DMR, σ₃, and σ₄. An increase in the number of WDCs reduced the M_r value. The sensitivity analysis showed the sequences of importance as: DMR > CSAFR > WDC > σ₄ > σ₃, (ANN model) and DMR > WDC > CSAFR > σ₄ > σ₃ (GEP model). Both the ANN and GEP models reflected close agreement between experimental and predicted results; however, the ANN model depicted superior accuracy in predicting the M_r value. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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15 pages, 4314 KiB

Open AccessArticle

Experimental Study on Self-Centering Performance of the SMA Fiber Reinforced ECC Composite Beam

by Zhao Yang, Tingyu Deng, Jiankun Li and Chengxiang Xu

Materials 2022, 15(9), 3062; https://doi.org/10.3390/ma15093062 - 22 Apr 2022

Cited by 8 | Viewed by 1385

Abstract

The combination of superelastic shape memory alloy fibers and ECC materials can form a new SMA fiber reinforced ECC composite material (SMAF-ECC) with good self-centering performance. In order to study the self-centering performance of the new composite material, 6 groups of pre-notch beam specimens were made for three-point bending cyclic loading tests, and the failure phenomenon, hysteresis curve, self-centering effect and influencing factors of the specimens were analyzed. The research results show that when the SMA fibers are effectively anchored in the ECC matrix, the SMA fibers can exert the superelastic properties to provide the ECC beams with recoverying force, and realize the crack self-closure and deflection self-recovery function for the beams, with the minimum residual crack width and deflection is only 0.9 mm and 1.3 mm respectively. Increasing fiber content can cause a small increase in the self-centering ability of the beams. However, only when the fiber diameter is appropriate, better self-centering effect can be achieved, but the difference caused by fiber diameter in the test was only 5%. SMA Fiber end forms have significant influence on self-centering performance. The knotted end beam can get a more than 70% self-centering ratio, while the straight end beams and bended end beams have no self-centering ability. The research results provide important reference for the research and application of this new self-centering materials and their structures. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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26 pages, 12392 KiB

Open AccessArticle

Discrete Element Modeling of Instability Mechanisms of Unbound Permeable Aggregate Base Materials in Triaxial Compression

by Yuanjie Xiao, Xiaoming Wang, Qunding Yu, Juanjuan Ren, Wenjun Hua, Ralina Mustafina, Fuguang Zhang, Huaiping Feng and Tongwen Zhang

Materials 2022, 15(8), 2716; https://doi.org/10.3390/ma15082716 - 07 Apr 2022

Cited by 2 | Viewed by 1512

Abstract

Unbound permeable aggregate base (UPAB) materials with strong load-transmitting skeleton yet adequate inter-connected pores are desired for use in the sponge-city initiative. However, the micro-scale fabric evolution and instability mechanism of macroscopic strength behavior of such UPAB materials still remain unclear. In this study, virtual monotonic triaxial compression tests were conducted by using the discrete element method (DEM) modeling approach on specimens with different gradations quantified by the parameter of gravel-to-sand ratio (G/S). The realistic aggregate particle shape and inter-particle contact behavior were properly considered in the DEM model. The micromechanical mechanisms of the shearing failure of such UPAB materials and their evolution characteristics with G/S values were disclosed from contact force chains, microstructures, and particle motion. It was found that the proportion of rotating particles in the specimens decreased and the proportion of relative sliding between particles increased as the content of fine particles decreased. The plastic yielding of the specimens originated from the failure of contact force chains and the occurrence of the relative motion between particles, while the final instability was manifested by the large-scale relative motion among particles along the failure plane (i.e., changes in the internal particle topology). By comparing the macroscopic strength, microstructure evolution, and particle motion characteristics of the specimens with different G/S values, it was found that the specimens with G/S value of 1.8 performed the best, and that the G/S value of 1.8 could be regarded as the threshold for separating floating dense and skeletal gap type packing structures. The variation of Euler angles of rotating particles was significantly reduced in the particle size range of 4.75 mm to 9.50 mm, indicating that this size range separates most of the particles from rolling and sliding. Since particle rolling and sliding behavior are directly related to shear strength, this validates the rationality of the parameter G/S for controlling and optimizing gradations from the perspective of particle movement. The findings could provide theoretical basis and technical guidance for the effective design and efficient utilization of UPAB materials. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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31 pages, 2539 KiB

Open AccessArticle

Correlation between Rheological Fatigue Tests on Bitumen and Various Cracking Tests on Asphalt Mixtures

by Muhammad Aakif Ishaq and Filippo Giustozzi

Materials 2021, 14(24), 7839; https://doi.org/10.3390/ma14247839 - 17 Dec 2021

Cited by 5 | Viewed by 2769

Abstract

Accurate characterisation and appropriate binder selection are essential to increase the load-induced cracking resistance of asphalt mixtures at an intermediate temperature. Hence, the primary goal of this study was to correlate the cracking resistance exerted by the binder with the cracking performance of asphalt mixtures. The laboratory-based experimental plan covered various types of laboratory tests specified by various agencies and road authorities to study the correlation of a neat bitumen and five polymer-modified binders with their corresponding asphalt mixtures. The fatigue life of the binders was assessed through a Linear Amplitude Sweep (LAS) test and statistically correlated with various load-induced cracking parameters from the indirect tensile test, semi-circular bending (SCB) test, and four points bending beam test (FPBB) of asphalt mixtures at 25 °C. Binders and mixes were further grouped depending on their polymeric family (i.e., modified with a particular type of polymer) to validate their statistical correlation. The indicator that mostly correlated the binder properties with the asphalt mixture properties is the secant modulus from the SCB test. Fatigue parameters obtained through LAS better explain the asphalt fatigue performance obtained through FPBB; specifically, asphalt tests at high strain levels (e.g., 400 micro strain) better correlate to the LAS fatigue parameter (Nf). Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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33 pages, 7119 KiB

Open AccessArticle

An Attempt to Track Two Grades of Road Bitumen from Different Plants Using Fourier Transform Infrared Spectroscopy

by Serge-Bertrand Adiko, Alexey A. Gureev, Olga N. Voytenko and Alexey V. Korotkov

Materials 2021, 14(19), 5870; https://doi.org/10.3390/ma14195870 - 07 Oct 2021

Cited by 2 | Viewed by 1620

Abstract

This study aimed to evaluate the possibility of using Fourier Transform Infrared (FTIR) spectroscopy to track binders produced by three different plants: plants A, B, and C. The work included the quality assessment of 80 bituminous materials graded as BND 70/100 and 100/130 according to GOST 33133 (Russian interstate standard) and chemical analyses using FTIR spectroscopy. FTIR analyses were conducted before and after short-term ageing in a Rolling Thin Film Oven Test (RTFOT). Thus, the number of binder samples was multiplied by two (2) for a final total of 160 infrared (IR) spectra. All infrared spectra were normalised to ensure the reliability of results, and the standard deviation and variance coefficient were included. The principal purpose of the present work was to track the origin and the ageing extent of the bituminous binders under study. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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20 pages, 4755 KiB

Open AccessArticle

Experimental Study on Consolidation-Creep Behavior of Subgrade Modified Soil in Seasonally Frozen Areas

by Fuyu Wang, Weichen Pang, Ziqi Li, Haibin Wei and Leilei Han

Materials 2021, 14(18), 5138; https://doi.org/10.3390/ma14185138 - 07 Sep 2021

Cited by 2 | Viewed by 1927

Abstract

Frost heaving and boiling are the most common road disorders due to the special climatic conditions in a seasonal frozen area. From the perspective of controlling road disorders in seasonally frozen areas and making effective use of industrial waste residue, two kinds of subgrade modified soil—crumb rubber modified fly ash soil (CRFS) and oil shale waste residue modified fly ash soil (OSFS)—were proposed by the research group. The research results proved that the two new subgrade fillers both have excellent engineering characteristics in cold areas, such as high strength and low thermal conductivity, and both have the function of waste utilization, giving them broad application prospects. In road engineering, the instability of slopes and retaining walls and the uneven settlement of the subgrade are closely related to soil creep, which are problems that cannot be ignored in road design and use. As a new material to treat road disorders in seasonally frozen areas, more attention should be paid to the continuous deformation property of modified soil under long-term load. The study on the creep characteristics of the modified soil can provide reliable parameters for the design of the modified soil subgrade and predict the settlement of the subgrade after construction, which is of great significance to the stability of the subgrade. In this paper, an experimental study on the consolidation–creep characteristics of two kinds of subgrade modified soil in a seasonal frozen region was carried out, the relationship between modified soil deformation and time is discussed, and the effects of different moisture contents and compaction degrees on the creep characteristics of modified soil were analyzed. The test results provide parameters for the engineering design of modified soil subgrade and provide data support for the popularization and application of modified soil in seasonally frozen subgrade. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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19 pages, 5164 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study on Solidification and Stabilization of Heavy-Metal-Contaminated Soil Using Cementitious Materials

by Xiaojun Li, Ruizhi Yang, Hao Li, Hao Yi and Hongjun Jing

Materials 2021, 14(17), 4999; https://doi.org/10.3390/ma14174999 - 01 Sep 2021

Cited by 13 | Viewed by 2147

Abstract

In order to solve the shortcomings of the traditional curing agent in the treatment of composite heavy-metal-contaminated soil with the solidification and stabilization method, a new type of cementing material A was used as a curing agent, and the Pb, Cd, Cu composite heavy-metal-contaminated soil was artificially prepared to carry out an experimental study on solidification and stabilization (SS) restoration by the mechanical properties test, leaching performance test, and microscopic test. The results show that in the range of test dosage, with the increase in the curing agent content, the unconfined compressive strength of the solidified body increased, and the resistance to deformation was enhanced. From the perspective of leaching characteristics, the new curing agent A had an excellent curing effect on the composite heavy-metal-contaminated soil. To achieve safe disposal, a curing agent content of 10% applies only for the soil heavily contaminated by heavy metals. The curing agent A could significantly reduce the content of acid-extractable heavy metals after solidifying the heavy metal Pb, Cd, and Cu composite contaminated soil and effectively converted it into a residue state. The solidified phase contained hydrated products such as calcium silicate hydrate (CSH) and ettringite (AFt). These hydrated products can inhibit the leaching performance of heavy metal ions through adsorption, encapsulation, and ion exchange. The study provides a feasible method and reference for the solidification, restoration, and resource utilization of heavy-metal-contaminated soil in the subgrade. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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14 pages, 5362 KiB

Open AccessEditor’s ChoiceArticle

Evaluation Approach of Fracture Behavior for Asphalt Concrete with Different Aggregate Gradations and Testing Temperatures Using Acoustic Emission Monitoring

by Liuxu Fu, Yubo Jiao, Xianhua Chen and Mengsu Zhang

Materials 2021, 14(16), 4390; https://doi.org/10.3390/ma14164390 - 05 Aug 2021

Cited by 4 | Viewed by 1528

Abstract

Different aggregate gradations of asphalt concrete possess dissimilar skeleton structures, leading to diverse macroscopic and mechanical characteristics. Acoustic emission (AE) technology can realize real-time monitoring of the whole damage evolution process of materials. The objective of the present investigation was to demonstrate the fracture characteristics of asphalt concrete with three types of aggregate gradations, including dense-graded asphalt concrete (AC), stone mastic asphalt (SMA), and open-graded friction course (OGFC) under indirect tensile load on account of the acoustic emission (AE) technique. The Marshall compaction method was used to prepare specimens, and the indirect tensile test (IDT) and AE monitoring were conducted simultaneously at different temperatures. The corresponding AE parameters containing energy, cumulative energy, count, and cumulative count were adopted to characterize the fracture process of asphalt concrete with different aggregate gradations. The impact of temperature on the damage characteristics of asphalt concrete was also assessed. Test results indicated that the AE parameters could effectively classify the damage stages of asphalt concrete, and specimens with different aggregate gradations exhibited different AE characteristics during failure processes. The combination of AE parameters and cumulative AE parameters can accurately characterize the damage characteristics of asphalt concrete. SMA specimens possessed the best overall performance among these three types of asphalt concrete in terms of the variations in energy and cumulative energy at different temperatures. The findings obtained in this study can provide a practical AE-based evaluation approach for demonstrating the fracture mechanism of asphalt concrete with different aggregate gradations. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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29 pages, 15512 KiB

Open AccessArticle

Evaluating Gyratory Compaction Characteristics of Unbound Permeable Aggregate Base Materials from Meso-Scale Particle Movement Measured by Smart Sensing Technology

by Yuanjie Xiao, Meng Wang, Xiaoming Wang, Juanjuan Ren, Weidong Wang and Xiaobin Chen

Materials 2021, 14(15), 4287; https://doi.org/10.3390/ma14154287 - 31 Jul 2021

Cited by 13 | Viewed by 2004

Abstract

The quality of compaction of unbound aggregate materials with permeable gradation plays a vital role in their field performance; however, there are currently few unanimously accepted techniques or quality control criteria available for ensuring adequate compaction of such materials in either laboratory or field applications. This paper presented testing results of a laboratory gyratory compaction study where the combinations of gyratory parameters were properly designed using the orthogonal array theory. Innovative real-time particle motion sensors were employed to record particle movement characteristics during the compaction process and provide a meso-scale explanation about compaction mechanisms. Particle abrasion and breakage were also quantified from particle shape digitized from the three-dimensional (3D) laser scanner before and after compaction. The optimal combination of gyratory parameters that yields the best compaction performance was determined from the orthogonal testing results with the relative importance of major influencing parameters ranked accordingly. Meso-scale particle movement at the upper center and center side positions of the specimen are promising indicators of compaction quality. The gyratory compaction process can be consistently divided into three distinct stages according to both macro-scale performance indicators and meso-scale particle movement characteristics. A statistically significant bi-linear relationship was found to exist between relative breakage index and maximum abrasion depth, whereas the quality of compaction and the extent of particle breakage appear to be positively correlated, thus necessitating the cost-effective balance between them. The results of this study could provide technical insights and guidance to field compaction of unbound permeable aggregates. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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14 pages, 4311 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Mixing Conditions on the Macro-Scale Homogeneity of Asphalt Mixtures Blended with Reclaimed Asphalt Pavement (RAP)

by Quan Liu and Markus Oeser

Materials 2021, 14(15), 4137; https://doi.org/10.3390/ma14154137 - 25 Jul 2021

Cited by 5 | Viewed by 1944

Abstract

The homogeneity of asphalt mixtures blended with reclaimed asphalt pavement (RAP) is affected by many factors. Due to the complicated compositions of recycled asphalt mixtures, the inhomogeneity issue might cause insufficient mechanical properties of asphalt mixtures, even though a design method was appropriately adopted. Therefore, it is of great significance to study the influence of mixing conditions on the homogeneity of asphalt mixtures blended with RAP materials. This study focused on the macro-scale homogeneity of produced asphalt mixtures. Specifically, asphalt mixtures incorporated with 40% RAP content were produced in a laboratory using different mixing times and mixing temperatures. A multi-direction indirect tensile stiffness modulus (ITSM) test was proposed to quantify the homogeneity of produced samples. In addition, the digital image processing (DIP) method was used to identify the distribution of aggregates and RAP binder. The results indicated that the influence of mixing time on the macro-homogeneity of asphalt mixtures indicated that a longer mixing time was favorable for the material dispersion. The influence of mixing temperature mainly rested on two perspectives. One was that the temperature variation induced the change of binder viscosity. The other was that the temperature influences the diffusion process between RAP binder and new bitumen, which further affected the mechanical performance of produced asphalt mixtures. Full article

(This article belongs to the Special Issue Materials, Structure, and Modeling for Smart and Resilient Roads)

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