Special Issue "Achievements and Prospects of Functional Pavement: Materials and Structures"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials".

Deadline for manuscript submissions: closed (31 December 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Jian-long Zheng

School of Traffic and Transportation Engineering, Changsha University of Science and Technology (CSUST), Changsha 410004, China
Website | E-Mail
Interests: asphalt mixture mechanical property; asphalt pavement design; special soil subgrade; road maintenance
Guest Editor
Prof. Dr. Zhanping You

Civil & Environmental Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA
Website | E-Mail
Interests: transportation materials; pavement; asphalt
Guest Editor
Dr. Xueyan Liu

Pavement Engineering Section, Faculty of Civil Engineering and Geosciences, Delft University of Technology (TUDelft), the Netherlands
Website | E-Mail
Interests: constitutive modeling; numerical modeling; material experimental characterization of pavement materials; static and dynamic response of reinforcing systems

Special Issue Information

Dear Colleagues,

In order to further promote the development of functional pavement technology, summarize the research results of functional pavement, and determine future development directions, this SCI-indexed journal has launched a Special Issue of carefully selected and invited articles, on the topic of “Achievements and Prospects of Functional Pavement: Materials and Structures”. The following topics are considered to be included in the scope of this journal:

The theme of this conference is "The Achievements and Prospects of Functional Pavement", which is divided into the following topics:

1. Green roads

1) Pavement design and construction technology based on carbon emission

2) Pavement material can be replaced with application technology

3) Low noise, low pollution and other low impact road application technology

2. Safety pavement

1) Design and construction technology of durable drainage pavement

2) New materials and new technologies for road snow removal

3) Evaluation and optimization of anti-skid performance of pavement

3. Intelligent roads

1) Pavement state intelligent monitoring technology

2) Power generation, temperature control, and other functional roads

3) Pavement intelligent management application technology

4. Durable roads

1) New theory and new method of durability pavement structure design

2) Study on decay regularity and prediction model of pavement performance

3) A new design method for high performance asphalt mixture

All the papers will be peered reviewed. This journal is an open access journal and therefore a fee setup by the publisher will be charged which is not related to the guest editors.

Prof. Dr. Jian-long Zheng
Prof. Dr. Zhanping You
Dr. Xueyan Liu
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 papers will be 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. Applied Sciences 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 1500 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

  • Functional Pavement
  • Green road;
  • Safety pavement
  • Intelligent road
  • Durable road
  • Pavement materials
  • Asphalt pavements

Published Papers (18 papers)

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Research

Open AccessArticle Optimization of the Calcium Alginate Capsules for Self-Healing Asphalt
Appl. Sci. 2019, 9(3), 468; https://doi.org/10.3390/app9030468
Received: 3 December 2018 / Revised: 15 January 2019 / Accepted: 28 January 2019 / Published: 30 January 2019
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Abstract
It has been demonstrated that calcium alginate capsules can be used as an asphalt healing system by pre-placing rejuvenator (healing agent) into the asphalt mix and releasing the rejuvenator on demand (upon cracking). This healing mechanism relies on the properties of capsules which [...] Read more.
It has been demonstrated that calcium alginate capsules can be used as an asphalt healing system by pre-placing rejuvenator (healing agent) into the asphalt mix and releasing the rejuvenator on demand (upon cracking). This healing mechanism relies on the properties of capsules which are determined by the capsule preparation process. In this study, to optimize the calcium alginate capsules, capsules are prepared using varying Alginate/Rejuvenator (A/R) ratios. Light microscope microscopy and Environmental Scanning Electron Microscope (ESEM) are employed to characterize the morphology and microstructure of these capsules. Thermal stability and mechanical property are investigated by thermogravimetric analysis (TGA) and compressive tests. The testing results indicate that higher alginate content results in smaller diameter and lower thermal resistance, but higher compressive strength. The optimum A/R ratio of calcium alginate capsules is found to be 30/70. To prove the effectiveness of the optimized capsules, the capsules are embedded in asphalt mortar beams and a bending and healing program is carried out. The effect of capsule shell material on the mechanical response of asphalt mixture is evaluated through three-point bending on the mortar beams embedded with blank capsules (without the healing agent). Aged mortar beams containing alginate capsules encapsulating rejuvenator demonstrate a higher strength recovery after bending tests, which indicates effective healing due to the release of the rejuvenators from the capsules. Full article
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Open AccessArticle Dynamic Response Analysis of Rutting Resistance Performance of High Modulus Asphalt Concrete Pavement
Appl. Sci. 2018, 8(12), 2701; https://doi.org/10.3390/app8122701
Received: 21 October 2018 / Revised: 5 December 2018 / Accepted: 12 December 2018 / Published: 19 December 2018
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Abstract
In order to systematically study the rutting resistance performance of High-Modulus Asphalt Concrete (HMAC) pavements, a finite element method model of HMAC pavement was established using ABAQUS software. Based on the viscoelasticity theory of asphalt, the stress and deformation distribution characteristics of HMAC [...] Read more.
In order to systematically study the rutting resistance performance of High-Modulus Asphalt Concrete (HMAC) pavements, a finite element method model of HMAC pavement was established using ABAQUS software. Based on the viscoelasticity theory of asphalt, the stress and deformation distribution characteristics of HMAC pavement were studied and compared to conventional asphalt pavement under moving loads. Then, the pavement temperature field model was established to study the temperature variation and the thermal stress in HMAC pavement. Finally, under the condition of continuous temperature variation, the creep behavior and permanent deformation of HMAC pavement were investigated. The results showed that under the action of moving loads, the strain and displacement generated in HMAC pavement were lower than those in conventional asphalt pavement. The upper surface layer was most obviously affected by outside air temperature, resulting in maximum thermal stress. Lastly, under the condition of continuous temperature change, HMAC pavement could greatly reduce the deformation of asphalt material in each surface layer compared to conventional asphalt pavement. Full article
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Open AccessArticle Induction Heating-Assisted Compaction in Porous Asphalt Pavements: A Computational Study
Appl. Sci. 2018, 8(11), 2308; https://doi.org/10.3390/app8112308
Received: 29 September 2018 / Revised: 28 October 2018 / Accepted: 1 November 2018 / Published: 20 November 2018
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Abstract
Low temperature asphalt (LTA) technologies, such as warm-mixed asphalt mixes, are utilized in the paving industry to lower energy demands and greenhouse gas emissions during asphalt mixing and pavement construction. However, the asphalt mixes developed that incorporate LTA additives are more sensitive than [...] Read more.
Low temperature asphalt (LTA) technologies, such as warm-mixed asphalt mixes, are utilized in the paving industry to lower energy demands and greenhouse gas emissions during asphalt mixing and pavement construction. However, the asphalt mixes developed that incorporate LTA additives are more sensitive than hot-mixed asphalts to temperature reduction during compaction, which leads to inadequate compaction and subsequent poor pavement performance. The induction heating-assisted compaction of pavement structures appears to be an effective way to ameliorate such issues and to improve mix compactability at lower temperatures. Considering that induction-assisted compaction is a complex process, a computational methodology is proposed in this paper. A porous asphalt concrete mix was considered as case material. For the pavement compaction analyses after induction, the temperature field generated by electromagnetic induction was predicted and the material parameters of asphalt mortar were adjusted. The effect of induction heating on asphalt compaction effectiveness, the tendency of mix density changing, the increase in compactor passes, and the influence of temperature on compaction at different locations in the pavement were studied as well. Full article
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Open AccessArticle The Effect of Ageing on Chemical and Mechanical Properties of Asphalt Mortar
Appl. Sci. 2018, 8(11), 2231; https://doi.org/10.3390/app8112231
Received: 8 October 2018 / Revised: 8 November 2018 / Accepted: 9 November 2018 / Published: 13 November 2018
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Abstract
Asphalt mortar is a mixture of bitumen, filler, and sand. Mortar plays an important role in asphalt mixtures as it serves as the adhesive between the coarser aggregates. Due to the effect of bitumen ageing, the chemical and mechanical properties of asphalt mortar [...] Read more.
Asphalt mortar is a mixture of bitumen, filler, and sand. Mortar plays an important role in asphalt mixtures as it serves as the adhesive between the coarser aggregates. Due to the effect of bitumen ageing, the chemical and mechanical properties of asphalt mortar evolve with time. The mortar becomes more brittle and prone to cracking, thus leading to inferior pavement performance. In this study, Fourier transform infrared (FTIR) spectrometry was used to quantify changes in the chemical functional groups related to ageing and to calculate the carbonyl and sulfoxide indices. In addition, frequency sweep tests and uniaxial tension tests were performed by means of dynamic shear rheometer (DSR) tests to determine evolution of the stiffness and strength due to ageing. Two different oven ageing protocols were used to evaluate the effect of fine mineral particles on bitumen ageing. The protocols differed with respect to the order of ageing and mixing of the constituents. The results showed that both the chemical and mechanical properties of mortars significantly changed with ageing. Specifically, the carbonyl index, stiffness, and strength of the mortar increased. Under the same ageing conditions, a higher ageing level was observed for mortars produced by first mixing and then ageing compared to the mortars produced by mixing aged bitumen with filler and sand. This could be due to the presence of sand and filler particles, which resulted in an increased length of diffusion paths and consequently a slower ageing process. Full article
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Open AccessArticle Influence of Surface Texture Characteristics on the Noise in Grooving Concrete Pavement
Appl. Sci. 2018, 8(11), 2141; https://doi.org/10.3390/app8112141
Received: 4 September 2018 / Revised: 26 October 2018 / Accepted: 30 October 2018 / Published: 2 November 2018
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Abstract
To thoroughly explore the relationship between concrete pavement texture characteristics and tire/pavement noise of grooving concrete pavement, the surface texture, i.e., roughness, macrotexture, and microtexture, was investigated in numerous highway pavements. The On-Board Sound Intensity (OBSI) method was used to test the pavement/tire [...] Read more.
To thoroughly explore the relationship between concrete pavement texture characteristics and tire/pavement noise of grooving concrete pavement, the surface texture, i.e., roughness, macrotexture, and microtexture, was investigated in numerous highway pavements. The On-Board Sound Intensity (OBSI) method was used to test the pavement/tire noise. The statistical correlation between concrete pavement texture characteristics and tire/pavement noise was quantitatively described by two correlation analysis methods for highway concrete pavement: origin of linear regression and the Pearson two-sided test method. The results indicate that the effect of pavement roughness on tire/pavement noise is significant, while the noise level is minor for the flat pavement. The macro texture depth also has a marked impact on the tire/pavement noise. In addition, a large grooving depth of concrete pavement could cause a high tire/pavement noise level; however, there is no clear correlation between side-way force coefficient (SFC) and tire/pavement noise. Full article
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Open AccessArticle Analysis of the Fatigue Crack Propagation Process of the Stress-Absorption Layer of Composite Pavement Based on Reliability
Appl. Sci. 2018, 8(11), 2093; https://doi.org/10.3390/app8112093
Received: 25 August 2018 / Revised: 23 October 2018 / Accepted: 25 October 2018 / Published: 30 October 2018
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Abstract
The stress-absorption layer in cement concrete pavement delays the development of reflection cracks and is good at fatigue resistance. Laboratory investigations of the anti-crack performance of the high viscous asphalt sand stress-absorption layer (HVASAL) and rubber asphalt stress-absorption layer (RASAL) were carried out [...] Read more.
The stress-absorption layer in cement concrete pavement delays the development of reflection cracks and is good at fatigue resistance. Laboratory investigations of the anti-crack performance of the high viscous asphalt sand stress-absorption layer (HVASAL) and rubber asphalt stress-absorption layer (RASAL) were carried out by force-controlled fatigue crack propagation tests, for which three types of overlay structures with three types of pre-crack (i.e., the middle crack, the side crack, and the 45° inclined crack) were designed. A probability model was established to describe the propagation of the fatigue cracks. The fatigue crack propagation, the fatigue life, the crack propagation rate, and the crack propagation mechanism of the three types of overlay structure were compared and analyzed. The results show that the stress-absorption layers have good anti-crack fatigue performance, and that the RASAL is better than the HVASAL. The crack propagation patterns of the three types of overlay structure were found. In the double logarithmic coordinate, the curves of the three types of cracks are straight lines with different intercepts and slopes. The probability model quantifies the relationship between the crack propagation rate and ∆K. The influences of the three types of crack on the fatigue properties of the asphalt overlays are different. Full article
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Open AccessArticle Preparation Technique and Properties of Nano-TiO2 Photocatalytic Coatings for Asphalt Pavement
Appl. Sci. 2018, 8(11), 2049; https://doi.org/10.3390/app8112049
Received: 17 September 2018 / Revised: 20 October 2018 / Accepted: 22 October 2018 / Published: 25 October 2018
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Abstract
According to the characteristics of asphalt pavement, a kind of nano-TiO2 photocatalytic coating was prepared by using the emulsified asphalt as the carrier. All of its properties met the technical requirements. An exhaust gas degradation test device and its test steps were [...] Read more.
According to the characteristics of asphalt pavement, a kind of nano-TiO2 photocatalytic coating was prepared by using the emulsified asphalt as the carrier. All of its properties met the technical requirements. An exhaust gas degradation test device and its test steps were developed. The evaluation indexes, cumulative degradation rate, and degradation efficiency, were put forward. From the two aspects of the nano-TiO2 content in photocatalytic coatings and the spraying amount of photocatalytic coatings in the surface of slabs (300 mm × 300 mm), the exhaust gas degradation effects, the performances of skid resistance, and the water permeability of asphalt mixture were analyzed. The test results showed that the cumulative degradation rate of exhaust gas was better when nano-TiO2 content was increased in the range of 0–8% and the spraying amount was changed in the range of 0–333.3 g/m2. In practical engineering applications, the anti-skid performance of asphalt pavement can be satisfied when the spraying amount of photocatalytic coating was limited to under 550 g/m2. The spraying amount of nano-TiO2 photocatalytic coating had little effect on the water permeability of the asphalt mixture. Therefore, 8% nano-TiO2 content in the coating and a 400 g/m2 spraying amount were finally recommended based on the photocatalytic properties, as well as for economic reasons. Full article
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Open AccessArticle The Effect of Intermediate Principal Stress on Compressive Strength of Different Cement Content of Cement-Stabilized Macadam and Different Gradation of AC-13 Mixture
Appl. Sci. 2018, 8(10), 2000; https://doi.org/10.3390/app8102000
Received: 17 September 2018 / Revised: 14 October 2018 / Accepted: 17 October 2018 / Published: 22 October 2018
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Abstract
Since the effect of intermediate principal stress on the strength of pavement materials is not entirely clear so far, a proprietary true triaxial apparatus was developed to simulate the spatial status of principal stresses to conduct compressive strength tests on different gradations of [...] Read more.
Since the effect of intermediate principal stress on the strength of pavement materials is not entirely clear so far, a proprietary true triaxial apparatus was developed to simulate the spatial status of principal stresses to conduct compressive strength tests on different gradations of AC-13, different cement contents of cement-stabilized macadam. With the same minimum principal stress, the triaxial compressive strengths of cube specimens under different intermediate principal stresses were compared. The results indicate that, as the intermediate principal stress increases, the compressive strength of the specimen increases and then decreases; different gradations of AC-13 do not show much difference in triaxial compressive strength while different cement contents of cement-stabilized macadam indicate considerable difference. Analysis results suggest significant effect of intermediate principal stress on the compressive strength of pavement materials: for AC-13, the coarser the gradation, the greater the effect of intermediate principal strength on its strength; for cement-stabilized Macadam, the higher the cement content, the greater the effect of intermediate principal stress. Strength model analysis results suggest that Double-Shear-Corner Model is more suitable to characterize cement-stabilized macadam’s strength performance compared to the Mohr–Coulomb model and Double-Shear Model. Full article
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Open AccessArticle Fatigue Performance and Model of Polyacrylonitrile Fiber Reinforced Asphalt Mixture
Appl. Sci. 2018, 8(10), 1818; https://doi.org/10.3390/app8101818
Received: 1 September 2018 / Revised: 28 September 2018 / Accepted: 29 September 2018 / Published: 3 October 2018
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Abstract
Fatigue is considered a major pavement structural distress and an important part of a performance-based mix design. Currently, the fatigue model of asphalt mixture, especially the mixture incorporated with fibers, is not perfect. In this paper, the central-point bending fatigue test was conducted [...] Read more.
Fatigue is considered a major pavement structural distress and an important part of a performance-based mix design. Currently, the fatigue model of asphalt mixture, especially the mixture incorporated with fibers, is not perfect. In this paper, the central-point bending fatigue test was conducted by constant strain mode with MTS apparatus. The fatigue performance and model of polyacrylonitrile (PAN) fiber-reinforced asphalt mixture produced with different fiber contents and asphalt contents were reported. The results indicated that the fatigue life of fiber reinforced mixture was higher than the reference one. The effects of fiber contents and asphalt contents on fatigue life were discussed. The mechanism of an optimum fiber content for the fatigue life in the fiber reinforced asphalt mixture was explained. The statistical analysis of variance (ANOVA) method and regression method were used to evaluate the effects of fiber content, strain level, and volumetric parameters, etc. on the fatigue life of an asphalt mixture. This paper presents a new fatigue performance model of a PAN fiber-reinforced asphalt mixture, including the fiber content, tensile strain, mixture initial flexural stiffness, and voids filled with asphalt (VFA). Compared to the earlier fatigue equations, the accuracy of the new fatigue model with the fiber content is improved significantly according to the statistical analysis results. Meanwhile, the model can preferably reveal the effect of fiber content, strain level, initial stiffness, and VFA on fatigue life. Full article
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Open AccessArticle Non-Newtonian Behaviors of Crumb Rubber-Modified Bituminous Binders
Appl. Sci. 2018, 8(10), 1760; https://doi.org/10.3390/app8101760
Received: 27 August 2018 / Revised: 13 September 2018 / Accepted: 26 September 2018 / Published: 29 September 2018
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Abstract
Crumb rubber-modified bitumen (CRMB) has been utilized in the asphalt paving industry for decades due to its various benefits. The complex interaction between bitumen and crumb rubber as well as the addition of warm-mix additives makes the typical laws of Newtonian fluids insufficient [...] Read more.
Crumb rubber-modified bitumen (CRMB) has been utilized in the asphalt paving industry for decades due to its various benefits. The complex interaction between bitumen and crumb rubber as well as the addition of warm-mix additives makes the typical laws of Newtonian fluids insufficient to describe the behaviors of highly modified bituminous binders. To systematically explore the non-Newtonian behaviors of CRMB, a dynamic shear rheometer was utilized to apply shear loading on the samples at various temperatures and shear rates. Results show that the viscosity of different binders are highly temperature- and shear rate-dependent, while highly modified binders exhibit more obvious shear-thinning behaviors at certain temperatures. With the help of zero shear viscosity and yield stress, the shear-thinning behaviors of non-Newtonian binders can be sufficiently characterized. The Arrhenius equation is invalid to describe viscosity-temperature characteristics of bitumen in the non-Newtonian region. A second-order polynomial function was proposed to characterize the viscosity-temperature dependence with a high correlation degree. Full article
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Open AccessArticle Rheological Performance of Bio-Char Modified Asphalt with Different Particle Sizes
Appl. Sci. 2018, 8(9), 1665; https://doi.org/10.3390/app8091665
Received: 25 August 2018 / Revised: 11 September 2018 / Accepted: 13 September 2018 / Published: 15 September 2018
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Abstract
To improve the performance of petroleum asphalt, bio-char was used as a modifier for a petroleum asphalt binder, in this study. The rheological properties of bio-char modified asphalt binders were compared with different particle sizes and contents, with one control and one flake [...] Read more.
To improve the performance of petroleum asphalt, bio-char was used as a modifier for a petroleum asphalt binder, in this study. The rheological properties of bio-char modified asphalt binders were compared with different particle sizes and contents, with one control and one flake graphite modified asphalt binder. Specifically, the bio-char modifiers with two particle sizes (ranging from 75 μm–150 μm and less than 75 μm) and three contents of 2%, 4%, and 8% were added into the asphalt binder. A flake graphite powder with particle sizes less than 75 μm was used as a comparison modifier. The Scanning Electron Microscopy (SEM) image showed the porous structure and rough surface of bio-char as well as dense structure and smooth surface of flake graphite. A Rotational Viscosity (RV) test, Dynamic Shear Rheometer (DSR) test, aging test, and Bending Beam Rheometer (BBR) test were performed to evaluate the properties of bio-char modified asphalt in this study. Both modifiers could improve the rotational viscosities of the asphalt binders. The porous structure and rough surface of bio-char lead to larger adhesion interaction in asphalt binder than the smooth flake graphite. As a result, the bio-char modified asphalts had better high-temperature rutting resistance and anti-aging properties than the graphite modified asphalt, especially for the binders with the smaller-sized and higher content of bio-char particles. Furthermore, the asphalt binder modified by the bio-char with sizes less than 75 μm and about 4% content could also achieve a better low-temperature crack resistance, in comparison to other modified asphalt binders. Thus, this type of bio-char particles is recommended as a favorable modifier for asphalt binder. Full article
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Open AccessArticle Properties Analysis of Oil Shale Waste as Partial Aggregate Replacement in Open Grade Friction Course
Appl. Sci. 2018, 8(9), 1626; https://doi.org/10.3390/app8091626
Received: 2 August 2018 / Revised: 27 August 2018 / Accepted: 10 September 2018 / Published: 12 September 2018
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Abstract
Open graded friction course (OGFC) is a high permeable mixture used to reduce noise, improve friction. However, limitations with the use of OGFC are due to the relatively low strength and stiffness. Therefore, investigating environmental and economic benefits, as well as service life [...] Read more.
Open graded friction course (OGFC) is a high permeable mixture used to reduce noise, improve friction. However, limitations with the use of OGFC are due to the relatively low strength and stiffness. Therefore, investigating environmental and economic benefits, as well as service life of OGFC technology is the future of the pavement. In this study, a new modified OGFC (SM-OGFC) was prepared by replacing the fine aggregate below 4.75 mm in OGFC with the oil shale waste (OSW), and the silane coupling agent modifier was used to assist modification. The preparation process of SM-OGFC was optimized by central composite design, to obtain an SM-OGFC with the best mechanical properties. The Marshall test, rutting test, −15 °C splitting test, −10 °C beam bending test, immersion Marshall test, spring-thawing stability test, Cantabro test and permeability test were conducted to evaluate the properties of SM-OGFC. The results prove that SM-OGFC has excellent overall performance in comparison with OGFC and styrene-butadiene-styrene (SBS) modified OGFC. Furthermore, Scanning Electron Microscopy (SEM) observation illustrates that the unique laminar columnar connected structure and cell-like structure antennae of OSW could be the main reasons why SM-OGFC obtained excellent performance. Furthermore, economic analysis indicated that the SM-OGFC mixture had higher cost effectiveness. Full article
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Open AccessArticle Laboratory Evaluation on Performance of Compound-Modified Asphalt for Rock Asphalt/Styrene–Butadiene Rubber (SBR) and Rock Asphalt/Nano-CaCO3
Appl. Sci. 2018, 8(6), 1009; https://doi.org/10.3390/app8061009
Received: 11 May 2018 / Revised: 11 June 2018 / Accepted: 18 June 2018 / Published: 20 June 2018
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Abstract
As a natural modifier of asphalt, rock asphalt has been widely used to improve its thermal stability and aging resistance. However, the thermal cracking resistance of asphalt modified by rock asphalt is unsatisfactory. In order to improve the thermal cracking resistance in low [...] Read more.
As a natural modifier of asphalt, rock asphalt has been widely used to improve its thermal stability and aging resistance. However, the thermal cracking resistance of asphalt modified by rock asphalt is unsatisfactory. In order to improve the thermal cracking resistance in low temperature, two kinds of modifiers—styrene–butadiene rubber (SBR) and nano-CaCO3—were selected as the compound modifiers, and then implemented to improve the low-temperature performance of the binder. Then, compound asphalt modified by Buton rock asphalt (BRA) was chosen as the study subject. The thermal stability and aging resistance of asphalt modified by BRA, compound-modified asphalt by BRA/SBR, and compound-modified asphalt by BRA and nano-CaCO3 were determined to identify whether the compound modifiers in the asphalt would have a negative effect on the thermal stability and aging resistance of the asphalt. The dynamic shear rheometer (DSR) test was employed to evaluate the thermal stability. The thin film oven test (TFOT) and pressure aging vessel (PAV) were adopted to determine the aging resistance. The viscoelastic characteristics of asphalt with and without modifiers were revealed to evaluate the low-temperature crack resistance of asphalt modified by compound modifiers. The bending beam rheometer (BBR) creep test was conducted in three test temperatures in order to determine the creep stiffness modulus of the BRA compound-modified asphalt. The viscoelastic model considering the damage caused by loading was established; then, the creep compliance and parameters of the viscoelastic damage model were implemented to evaluate the low-temperature performance of the compound-modified asphalt. The results show that the compound modifiers have little negative effects on the thermal stability and aging resistance of asphalt. The thermal crack resistance of the compound-modified asphalt by BRA/SBR was the best, followed by the compound-modified asphalt by BRA and nano-CaCO3 within the three materials. The accuracy of forecasting the characteristics of compound-modified asphalt was improved by using the viscoelastic model and considering the damage effect. Full article
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Open AccessArticle Initiation and Propagation of Top-Down Cracking in Asphalt Pavement
Appl. Sci. 2018, 8(5), 774; https://doi.org/10.3390/app8050774
Received: 5 April 2018 / Revised: 25 April 2018 / Accepted: 4 May 2018 / Published: 12 May 2018
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Abstract
Top-down cracking (TDC) alongside the wheel path is one of the commonly seen distress types on asphalt pavements, especially on heavy-duty asphalt pavements. It has been believed that TDC is caused by either tension stress or shear stress in the top asphalt layer(s). [...] Read more.
Top-down cracking (TDC) alongside the wheel path is one of the commonly seen distress types on asphalt pavements, especially on heavy-duty asphalt pavements. It has been believed that TDC is caused by either tension stress or shear stress in the top asphalt layer(s). In this paper, new initiation and propagation mechanisms of TDC are proposed and validated through both accelerated pavement testing in the field and uniaxial repeated loading penetration tests in the laboratory at different temperatures. The test results clearly show that the uniaxial repeated loading penetration test can simulate both initiation and propagation processes of TDC very closely. Based on these test results, the mechanisms for crack initiation and propagation are further investigated with the finite element (FE) program. The FE analysis results show that under repeated loading, shear damage will occur first in the asphalt layer, then extend horizontally and consequently result in a shear-damaged layer. The damaged layer then led to higher tensile strain in the upper mixture which caused tension cracks and finally propagated upwards to the pavement surface. The whole process of TDC initiation and propagation can be described as “shear damage, then tension propagation”, which is the new mechanism proposed in this paper. Full article
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Open AccessArticle Algorithm for Virtual Aggregates’ Reconstitution Based on Image Processing and Discrete-Element Modeling
Appl. Sci. 2018, 8(5), 738; https://doi.org/10.3390/app8050738
Received: 15 February 2018 / Revised: 9 April 2018 / Accepted: 3 May 2018 / Published: 7 May 2018
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Abstract
Based on the Aggregate Imaging Measurement System (AIMS) and the Particle Flow Code in Two Dimensions (PFC2D), an algorithm for modeling two-dimensional virtual aggregates was proposed in this study. To develop the virtual particles precisely, the realistic shapes of the aggregates were captured [...] Read more.
Based on the Aggregate Imaging Measurement System (AIMS) and the Particle Flow Code in Two Dimensions (PFC2D), an algorithm for modeling two-dimensional virtual aggregates was proposed in this study. To develop the virtual particles precisely, the realistic shapes of the aggregates were captured by the AIMS firstly. The shape images were then processed, and the morphological characteristics of aggregates were quantified by the angularity index. By dividing the particle irregular shape into many triangle areas and adjusting the positions of the generated balls via coordinate systems’ conversion within PFC2D, the virtual particles could be reconstructed accurately. By calculating the mapping area, the gradations in two-dimensions could be determined. Controlled by two variables (μ_1 and μ_2), which were drawn from the uniform distribution (0, 1), the virtual particles forming the specimens could be developed with random sizes and angular shapes. In the end, the rebuilt model of the SMA-13 aggregate skeleton was verified by the virtual penetration tests. The results indicated that the proposed algorithm can not only model the realistic particle shape and gradations precisely, but also predict its mechanical behavior well. Full article
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Open AccessArticle Fatigue Equation of Cement-Treated Aggregate Base Materials under a True Stress Ratio
Appl. Sci. 2018, 8(5), 691; https://doi.org/10.3390/app8050691
Received: 4 April 2018 / Revised: 26 April 2018 / Accepted: 26 April 2018 / Published: 29 April 2018
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Abstract
The objective of this article is to establish a fatigue equation based on the true stress ratio for cement-treated aggregate base materials. The true stress ratio herein means the ratio of the stress and the true strength of the cement-treated aggregate base materials [...] Read more.
The objective of this article is to establish a fatigue equation based on the true stress ratio for cement-treated aggregate base materials. The true stress ratio herein means the ratio of the stress and the true strength of the cement-treated aggregate base materials related to loading rates and curing times. The unconfined compressive strength tests and compressive resilience modulus tests were carried out under various loading rates and curing times of 3, 7, 14, 28, 60, 90 days, respectively. According to the test results, the relationship between the unconfined compressive strength (a mix design parameter in China) and the compressive resilience modulus (a structural design parameter and the construction quality control parameter in China) of the cement-treated aggregate base material with different curing times was established. However, it was found that the strengths varied with the loading rates, which is not reflected in the existing fatigue equations. Therefore, it is questionable to obtain the stress ratio of fatigue tests with a fixed strength value obtained from the standard strength test where the loading rate is fixed (in China, the fixed loading rate is 1 mm/min for cement-treated aggregate base materials). Thus, in this paper, the four-point bending strength (i.e., flexural strength) test was carried out at different loading rates to resolve such deficiencies. Based on the strength test results at different loading rates, the true stress ratio of the fatigue test corresponding to the fatigue loading rate can be calculated. Then the four-point bending fatigue test was conducted to establish an improved fatigue equation characterized by the true stress ratio. The results show that the patterns of variation for unconfined compressive strength increasing with the curing time were similar to that of the compressive resilience modulus. The fatigue equation curve based on the true stress ratio can be extended to the strength failure point of (1, 1), where both the true stress ratio and the fatigue life value are one. The internal relationship between the strength failure and the fatigue failure was unified. This article provides a theoretical method and basis for unifying the mix design parameters and the construction quality control parameters. Full article
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Open AccessArticle Fatigue Resistance Evaluation of Modified Asphalt Using a Multiple Stress Creep and Recovery (MSCR) Test
Appl. Sci. 2018, 8(3), 417; https://doi.org/10.3390/app8030417
Received: 23 January 2018 / Revised: 23 February 2018 / Accepted: 1 March 2018 / Published: 12 March 2018
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Abstract
Fatigue resistance quantification of modified asphalt is typically time consuming and may not correlate well with mixture fatigue test results. In this paper, the applicability of a multiple stress creep and recovery (MSCR) test on asphalt binder’s fatigue resistance was evaluated. Six binder [...] Read more.
Fatigue resistance quantification of modified asphalt is typically time consuming and may not correlate well with mixture fatigue test results. In this paper, the applicability of a multiple stress creep and recovery (MSCR) test on asphalt binder’s fatigue resistance was evaluated. Six binder types with a variety of modifiers and different modifier contents were characterized. The MSCR test was conducted and its sensitivity to binder type and additive content under different aging durations was evaluated. Mixture fatigue tests including a semi-circular bending- Illinois flexibility index test and indirect tensile strength were conducted using control base asphalt and SBS modified asphalt. A ranking between the binder MSCR and mixture fracture test results was conducted to check if the MSCR result was representative of the mixture’s fatigue resistance. Results indicate that the MSCR test at intermediate temperatures (20 °C, 25 °C, and 30 °C) can be performed with good repetitions. It was also found that the MSCR test was sensitive enough to differentiate the fatigue resistance among different binder types and additive contents. The ranking analysis shows that the binder MSCR test at intermediate temperatures showed a similar ranking to the mixture’s fatigue tests, indicating that the binder MSCR test could be potentially utilized to represent a mixture’s fatigue resistance where binder selection is a major concern. It was also found that the SBS modified binder showed the best crack resistance and was less affected by aging. Full article
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Open AccessArticle Potential of Waste Oyster Shells as a Novel Biofiller for Hot-Mix Asphalt
Appl. Sci. 2018, 8(3), 415; https://doi.org/10.3390/app8030415
Received: 6 February 2018 / Revised: 5 March 2018 / Accepted: 8 March 2018 / Published: 11 March 2018
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Abstract
This paper reports the use of waste oyster shells as a novel biofiller for hot-mix asphalt (HMA) pavement applications. The effects of different fractions (e.g., 0, 5, 10, 15 wt %) of oyster shell powder (OSP) on the bitumen performance were investigated. The [...] Read more.
This paper reports the use of waste oyster shells as a novel biofiller for hot-mix asphalt (HMA) pavement applications. The effects of different fractions (e.g., 0, 5, 10, 15 wt %) of oyster shell powder (OSP) on the bitumen performance were investigated. The chemical properties of unfilled and OSP-filled asphalts were characterized by means of thin layer chromatography-ionization detection (TLC-FID), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Thermal characteristics were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Physical and rheological properties were assessed through penetration, softening point, ductility, and dynamic shear rheometer (DSR) tests. Results showed that OSP addition increased the resins content, as well as the stiffness of blends. No obvious reactions have occurred between the filler and the asphalt. A higher dose of OSP altered the morphology of the binder, whereas lower and intermediate doses improved its thermal stability and enhanced its low-temperature, rutting, and fatigue performances with respect to the plain asphalt. Overall, the waste oyster shells could be used as filler substitute, not only to improve the quality of road pavements but also to reduce the cost of their construction and solve the waste disposal problems. Full article
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