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11 pages, 2607 KiB

Open AccessFeature PaperArticle

A Study of Rubber-REOB Extender to Produce Sustainable Modified Bitumens

by Giulia Tarsi, Paolino Caputo, Michele Porto and Cesare Sangiorgi

Appl. Sci. 2020, 10(4), 1204; https://doi.org/10.3390/app10041204 - 11 Feb 2020

Cited by 11 | Viewed by 2768

Abstract

Thanks to greater attention to the environment and the depletion of non-renewable resources, the sustainability and the circular economy have become crucial topics. The current trend of pavement engineering is to reduce the use of standard bitumen by replacing it with more sustainable [...] Read more.

Thanks to greater attention to the environment and the depletion of non-renewable resources, the sustainability and the circular economy have become crucial topics. The current trend of pavement engineering is to reduce the use of standard bitumen by replacing it with more sustainable materials such as industrial residues and by-products. In this regard, the present study aims to characterize innovative extended bitumen using recycled materials. Due to promising preliminary results as bitumen modifiers, the powdered rubber from end-of-life tires and the re-refined engine oil bottom (REOB) have been investigated as feasible components of bitumen extenders. Nevertheless, several variables strongly affect the performance of the resulting binder, which cannot be neglected. Hence, this research focuses on the rubber–REOB interaction in order to evaluate their optimum ratio, which may maximize the use and advantages of both recycled materials as suitable partial replacements for bitumen. Various rubber–REOB ratios were considered and investigated by means of low and high frequency nuclear magnetic resonance (NMR) spectrometers and scanning electron microscope (SEM). Full article

(This article belongs to the Special Issue Asphalt Materials)

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11 pages, 5203 KiB

Open AccessArticle

Synthetic Microstructure Generation and Multiscale Analysis of Asphalt Concrete

by Marek Klimczak and Witold Cecot

Appl. Sci. 2020, 10(3), 765; https://doi.org/10.3390/app10030765 - 21 Jan 2020

Cited by 7 | Viewed by 2638

Abstract

In this paper, we present an enhanced framework for the synthetic asphalt concrete (AC) microstructure generation for the numerical analysis purposes. It is based on the Voronoi tessellation concept with some necessary extensions that allow for the reliable generation of the aggregate particles [...] Read more.

In this paper, we present an enhanced framework for the synthetic asphalt concrete (AC) microstructure generation for the numerical analysis purposes. It is based on the Voronoi tessellation concept with some necessary extensions that allow for the reliable generation of the aggregate particles of the given size distribution. The synthetic microstructure generation allows for faster numerical modeling of the novel materials. It can partially replace the X-ray computed tomography approach, which is frequently used in such analysis. Our framework is a kind of compilation of the known techniques with the enhancements applied to expedite the microstructure modeling process. Therefore, the generated microstructure is used in the numerical upscaling to model the macroscale asphalt concrete properties. We restrict ourselves (in this paper only) to the 2D elastic computations. We also assume the perfect bonding between these two materials and the static load for the sake of simplicity. The upscaling is performed by the multiscale finite element method (MsFEM). A short recapitulation of the MsFEM foundations as well as the numerical test comparing the overkill mesh solution with the upscaled one is provided in the paper. The test results confirm that the whole presented methodology can serve as a fast and reliable tool for the tests on novel asphalt mixtures and other heterogeneous materials. It can reduce the cost of the design process substituting some of the laboratory experiments, giving the opportunity to test the developed constitutive models and expedite the numerical analysis itself. Full article

(This article belongs to the Special Issue Asphalt Materials)

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18 pages, 3734 KiB

Open AccessArticle

Exploring the Possibility of Using Ionic Copolymer Poly (Ethylene-co-Methacrylic) Acid as Modifier and Self-Healing Agent in Asphalt Binder and Mixture

by Yuefeng Zhu, Reyhaneh Rahbar-Rastegar, Yanwei Li, Yaning Qiao and Chundi Si

Appl. Sci. 2020, 10(2), 426; https://doi.org/10.3390/app10020426 - 7 Jan 2020

Cited by 7 | Viewed by 2681

Abstract

It is well-accepted that the ionic copolymer poly (ethylene-co-methacrylic) acid (also named EMAA) is one type of self-healing material. This particular capability has great potential for extending the service life of infrastructures. In order to improve the rheological, mechanical, and self-healing [...] Read more.

It is well-accepted that the ionic copolymer poly (ethylene-co-methacrylic) acid (also named EMAA) is one type of self-healing material. This particular capability has great potential for extending the service life of infrastructures. In order to improve the rheological, mechanical, and self-healing properties of asphalt binder and asphalt mixtures, EMAA and styrene butadiene rubber (SBR) were selected as the additives. In this study, the effects of EMAA and SBR on the performance of bitumen and asphalt mixtures were examined and characterized using various parameters including rheological indices, Glover–Rowe parameter, ductility self-healing rate, fluorescence microscopy, and scanning electron microscope (SEM) test on binders, and different testing methods such as complex modulus, thermal stress-restrained specimen test (TSRST), disk-shaped compact tension (DCT), and fatigue–healing–fatigue test on the mixtures. The results showed that EMAA can significantly improve the stiffness and self-healing capacity of virgin and SBR modified binders and mixtures. Moreover, the cracking resistance of EMAA/SBR compound modified binder and mixture showed a significant improvement. However, EMAA is not recommended to be added as a modifier to virgin binders and mixtures due to its poor cracking resistance. Some novel tests and parameters mentioned in this paper are recommended for characterizing binders and mixtures in the future. Full article

(This article belongs to the Special Issue Asphalt Materials)

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20 pages, 4511 KiB

Open AccessArticle

A New Type of Crumb Rubber Asphalt Mixture: A Dry Process Design and Performance Evaluation

by Feng Ma, Jiasheng Dai, Zhen Fu, Jenny Liu, Wenhao Dong and Zhen Huang

Appl. Sci. 2020, 10(1), 372; https://doi.org/10.3390/app10010372 - 3 Jan 2020

Cited by 11 | Viewed by 4152

Abstract

To obtain a crumb rubber asphalt mixture with excellent performance, this study combined trans-polyoctenamer rubber (TOR), crumb rubber, and other additives to establish a new type of crumb rubber (CRT). The objective of this study was to design and evaluate the road performance [...] Read more.

To obtain a crumb rubber asphalt mixture with excellent performance, this study combined trans-polyoctenamer rubber (TOR), crumb rubber, and other additives to establish a new type of crumb rubber (CRT). The objective of this study was to design and evaluate the road performance of the new type of crumb rubber asphalt mixture (CRTAM) with a skeleton dense texture through a dry process. First, the skeleton intrusion compact volume method was used to optimize the grading of coarse and fine aggregates, and the design of the CRTAM gradation was carried out through the same and unequal volume replacement grading method. Then, three types of road performance were analyzed: high-temperature stability, low-temperature crack resistance, and water stability. The results showed that 2% and 2.5% CRT met a low-temperature index with equal volume substitution, and the six gradations obtained by unequal volume replacement with 2% CRT complied with the requirements of a skeleton dense texture. When the substitution ratio was 1.5 and 0.5, the high-temperature performance was better. In addition, when the substitution ratio was 0.5, the flexural strain energy density was the highest and the low-temperature performance was the best. Including considerations of economic benefits, it is recommended that the CRT content be 2% and the substitution ratio be 0.5. Full article

(This article belongs to the Special Issue Asphalt Materials)

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14 pages, 5333 KiB

Open AccessArticle

Degradation Prediction Model for Friction of Road Pavements with Natural Aggregates and Steel Slags

by Bruno Crisman, Giulio Ossich, Paolo Bevilacqua and Roberto Roberti

Appl. Sci. 2020, 10(1), 32; https://doi.org/10.3390/app10010032 - 19 Dec 2019

Cited by 19 | Viewed by 2890

Abstract

Steel production wastes (steel slags) are used more often in asphalt concrete pavements as a valuable replacement for natural aggregates, which are becoming increasingly rare. In this paper authors investigate the polishing characteristics of aggregates, and in particular of steel slags, used in [...] Read more.

Steel production wastes (steel slags) are used more often in asphalt concrete pavements as a valuable replacement for natural aggregates, which are becoming increasingly rare. In this paper authors investigate the polishing characteristics of aggregates, and in particular of steel slags, used in bituminous road surfacing, are a major factor in determining the resistance to skidding. The main purpose of the study is the identification of a suitable degradation model, based on friction indicators, in the laboratory, as well as the comparison of in-situ pavement skid resistance with the cumulative number of passing vehicles over the years. The model predicts the expected resistance to skidding of the road surface based on the knowledge of the polished stone value (PSV) of the aggregates and the expected traffic on the road. In this study, several types of aggregates were compared: steel slag, limestone, limestone and slag mixture, diabase, Criggion stone and basalt. Using a standard PSV test, it was found that the aggregates did not reach the lower value of skid resistance (equilibrium value). The analysis of the British Portable Number (BPN) data versus polishing time allowed to empirically derive a regression model for each investigated aggregate. Hence, it appears possible to define both an investigatory level and threshold level to predict the actual residual life of the pavement from the examination of skid resistance. Full article

(This article belongs to the Special Issue Asphalt Materials)

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11 pages, 1968 KiB

Open AccessArticle

Evaluation of Chicken Feather and Styrene-Butadiene/Chicken Feather Composites as Modifier for Asphalts Binder

by Leslie Mariella Colunga-Sánchez, Beatriz Adriana Salazar-Cruz, José Luis Rivera-Armenta, Ana Beatriz Morales-Cepeda, Claudia Esmeralda Ramos-Gálvan and María Yolanda Chávez-Cinco

Appl. Sci. 2019, 9(23), 5188; https://doi.org/10.3390/app9235188 - 29 Nov 2019

Cited by 7 | Viewed by 2788

Abstract

In the present work, the evaluation of chicken feather particles (CFP) and styrene-butadiene/chicken feather (SBS-CF) composites as modifiers for asphalt binder is presented. It is well known that elastomers are the best asphalt modifiers, because their thermoplastic behavior assists asphalts in improving the [...] Read more.

In the present work, the evaluation of chicken feather particles (CFP) and styrene-butadiene/chicken feather (SBS-CF) composites as modifiers for asphalt binder is presented. It is well known that elastomers are the best asphalt modifiers, because their thermoplastic behavior assists asphalts in improving the range of their mechanical properties at both low and high temperatures. Nowadays, the use of natural products and byproducts as fillers for polymer matrices has been a matter of research, and the field of asphalt modification is not the exception. Chicken feather particles (CFP) is a waste material whose main component is keratin, which offers remarkable properties. In the present work, CFP was used as a filler of a styrene-butadiene rubber matrix (SBS) with radial structure, to obtain a composite intended as an asphalt modifier. Besides, raw CFP was also tested as an asphalt modifier. Physical, thermal and rheological properties of the modified asphalts were evaluated in order to determine their degree of modification with respect to the original asphalt. The results show that the addition of raw CFP improves some physical properties as penetration and decreases the phase separation; furthermore, the asphalt modified with CFP displayed similar rheological properties to those shown by the asphalt modified with SBS, while some other properties resulted in being even better, like the phase separation, with the advantage that the CFP comes from a natural waste product. Full article

(This article belongs to the Special Issue Asphalt Materials)

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Graphical abstract

11 pages, 1305 KiB

Open AccessArticle

Silane Modification of Crumb Rubber on the Rheological Properties of Rubberized Asphalt

by Yunbao Zhang, Zhaohui Liu and Juan Peng

Appl. Sci. 2019, 9(22), 4831; https://doi.org/10.3390/app9224831 - 12 Nov 2019

Cited by 10 | Viewed by 2484

Abstract

Because there is a lack of studies on rubberized asphalt based on silane coupling agent modification, KH-550 modified crumb rubber and rubberized asphalts incorporating normal rubber and modified rubber were prepared, respectively. The rheological properties of asphalt samples were evaluated by a dynamic [...] Read more.

Because there is a lack of studies on rubberized asphalt based on silane coupling agent modification, KH-550 modified crumb rubber and rubberized asphalts incorporating normal rubber and modified rubber were prepared, respectively. The rheological properties of asphalt samples were evaluated by a dynamic shearing rheometer and a bending beam rheometer; then, mechanisms of KH-550 on rubber surface and functional group changes were analyzed by a Brunauer–Emmett–Teller specific surface area measurement and a Fourier transform infrared spectroscopy. The results imply that: (i) rubber surface area rises and chemical reactions accrue between rubber and asphalt; (ii) modified rubber achieves a more stable state within asphalt, which helps to enhance the mechanical properties of asphalt; (iii) modified rubber helps asphalt to dissipate stress so as to resist the formation of cracks and deformation under low temperature conditions. Full article

(This article belongs to the Special Issue Asphalt Materials)

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15 pages, 1419 KiB

Open AccessArticle

Effect of Characteristics of Different Types of Bauxite Clinker on Adhesion

by Xirong Wu, Nanxiang Zhen and Fansheng Kong

Appl. Sci. 2019, 9(22), 4746; https://doi.org/10.3390/app9224746 - 7 Nov 2019

Cited by 4 | Viewed by 2201

Abstract

Based on the fact that bauxite clinker has minor thermal conductivity and better skid resistance and wear-resisting property, it can be used in HFST (high friction surface treatment) or the abrasion layer of asphalt mixture to replace or partly replace the existing aggregate. [...] Read more.

Based on the fact that bauxite clinker has minor thermal conductivity and better skid resistance and wear-resisting property, it can be used in HFST (high friction surface treatment) or the abrasion layer of asphalt mixture to replace or partly replace the existing aggregate. Bauxite clinker is classified into mainly six types according to different chemical composition contents. The selection of bauxite clinker as aggregate is not only for the economic value, but also for improving the adhesion between aggregate and asphalt, which has a certain blindness This study evaluated the characteristics of different types of bauxite clinker. The adhesion of different types of bauxite clinker with asphalt was evaluated by means of agitating hydrostatic adsorption method and surface free energy theory. The effect of characteristic parameters of bauxite clinker on adhesion was evaluated by grey correlation entropy analysis. The results show that Type B and D bauxite clinker aggregates have the best adhesion to asphalt. The outcome of grey entropy correlation analysis shows that the parameters which characterize the structural indexes of bauxite clinker, such as porosity, water absorption and apparent density, have the greatest effect on the adhesion. The results of study can provide some reference for the selection of bauxite clinker, which is used in different types of highway construction, and a theoretical reference for the applicability research of bauxite clinker in asphalt mixture and the improvement of skid resistance and durability of pavement. Full article

(This article belongs to the Special Issue Asphalt Materials)

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22 pages, 8039 KiB

Open AccessArticle

Improvement Methods for Reduction of the High Stress of Ultra-High Asphalt Concrete Core Dams

by Jun Gao, Faning Dang, Zongyuan Ma, Yi Xue and Jie Ren

Appl. Sci. 2019, 9(21), 4618; https://doi.org/10.3390/app9214618 - 30 Oct 2019

Cited by 8 | Viewed by 3127

Abstract

With the rapid development of asphalt concrete core rockfill dams (ACCRDs), the construction of ultra-high asphalt concrete core rockfill dams (UACCRDs) has been improved significantly. However, the security problems of asphalt concrete core (ACC) become very prominent with the increase of dam height. [...] Read more.

With the rapid development of asphalt concrete core rockfill dams (ACCRDs), the construction of ultra-high asphalt concrete core rockfill dams (UACCRDs) has been improved significantly. However, the security problems of asphalt concrete core (ACC) become very prominent with the increase of dam height. The shear failure control standard and tensile failure control standard of ACC are suggested. The mechanisms of ACC that generate high shear stress and high tensile stress are investigated. Based on the definition of stress level and the transmission mechanism of arch structures, the improvement methods that reduce the high shear stress and high tensile stress of ultra-high asphalt concrete core (UACC) are proposed and investigated. The results show that the stress level of ACC can be reduced significantly by the increase of the strength parameters of ACC (failure ratio, cohesion, and internal friction angle). The following value ranges of the failure ratio, cohesion, and internal friction angle of ACC for the suitable construction of UACCRDs are recommended: R_f ≥ 0.75, C ≥ 0.30 MPa, and φ ≥ 28.5° (h = 150 m), with the growth gradient adjusted by 5%, 15%, and 5%/25 m. The tensile stress and tensile stress area can be reduced obviously by the new type of dams (curved asphalt concrete core rockfill dams (CACCRDs)). The value ranges of the curvature of CACC (k ≥ 1.0 × 10⁻³) for the suitable construction of UACCRDs are recommended. Full article

(This article belongs to the Special Issue Asphalt Materials)

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17 pages, 3163 KiB

Open AccessArticle

Viscoelastic Properties of Asphalt Mixtures with Different Modifiers at Different Temperatures Based on Static Creep Tests

by Yongchun Cheng, He Li, Liding Li, Yuwei Zhang, Haitao Wang and Yunshuo Bai

Appl. Sci. 2019, 9(20), 4246; https://doi.org/10.3390/app9204246 - 11 Oct 2019

Cited by 21 | Viewed by 4476

Abstract

To obtain the viscoelastic parameters of asphalt mixtures and analyze the effect of temperatures and modifiers on viscoelastic properties of asphalt mixtures, the creep compliances of the neat asphalt mixture (AM), compound diatomite and basalt fibers reinforced asphalt mixture (DBFAM), and styrene-butadiene-styrene modified [...] Read more.

To obtain the viscoelastic parameters of asphalt mixtures and analyze the effect of temperatures and modifiers on viscoelastic properties of asphalt mixtures, the creep compliances of the neat asphalt mixture (AM), compound diatomite and basalt fibers reinforced asphalt mixture (DBFAM), and styrene-butadiene-styrene modified asphalt mixture (SBSAM) were tested and calculated by the static creep tests. And the creep compliances of the three asphalt mixtures at −20 °C, −10 °C, and 0 °C are deducted by the time–temperature equivalence principle (TTEP) and Arrhenius equation. Further, the relaxation modulus of the three asphalt mixtures from −20 °C to 50 °C at 10 °C increments are calculated by the convolution integral and Simpson method. Subsequently, the Burgers model, the generalized Kelvin model, and the generalized Maxwell model are applied to analyze the viscoelastic properties of the three asphalt mixtures at different temperatures. The results show that the generalized Kelvin model and the generalized Maxwell model are superior to the Burgers model in describing the variation of viscoelastic properties of asphalt mixtures with loading time. At low temperatures, asphalt mixtures have excellent properties in resisting permanent deformation and releasing internal stress. Besides, the addition of SBS modifier and compound diatomite and basalt fibers modifier can significantly raise the viscosity η₁ and the elastic modulus E₁ of the asphalt mixture, respectively. Full article

(This article belongs to the Special Issue Asphalt Materials)

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15 pages, 4752 KiB

Open AccessArticle

Characterization of Air Voids Distribution in the Open-Graded Asphalt Mixture Based on 2D Image Analysis

by Guangji Xu, Xiao Chen, Xiaoming Huang, Tao Ma and Wei Zhou

Appl. Sci. 2019, 9(19), 4126; https://doi.org/10.3390/app9194126 - 2 Oct 2019

Cited by 7 | Viewed by 2786

Abstract

The air voids distribution has a significant effect on the pavement performance related distresses such as rutting, cracking, moisture damage and permeability. However, most studies only quantified the air voids by average content, ignoring the heterogeneity inside the materials. This study focuses on [...] Read more.

The air voids distribution has a significant effect on the pavement performance related distresses such as rutting, cracking, moisture damage and permeability. However, most studies only quantified the air voids by average content, ignoring the heterogeneity inside the materials. This study focuses on the heterogeneity of air voids distribution inside the open-grade asphalt mixture based on 2D image analysis. Equivalent aperture is proposed to measure the area of each air void. Results showed that along both vertical and horizontal sections inside the open-grade asphalt mixture, the number of voids with 0~2 mm equivalent aperture would have a great impact on the total number of voids, while large amounts of small voids would not significantly affect the total voids number. Additionally, voids with 0~4 mm equivalent aperture account for the largest proportion, and when the equivalent aperture is beyond 4 mm, the number of voids would decrease as the equivalent aperture increases, regardless of the void areas. Furthermore, in both vertical and horizontal sections, as the equivalent aperture increases, the speed to accumulate voids area would firstly increase and then decrease. As the equivalent aperture increases, the contribution to the total voids area would increase accordingly, and it would approach the peak when the equivalent aperture reaches about 8 mm. Full article

(This article belongs to the Special Issue Asphalt Materials)

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15 pages, 4450 KiB

Open AccessArticle

Effects of Cement–Mineral Filler on Asphalt Mixture Performance under Different Aging Procedures

by Zhenyang Fan, Xuancang Wang, Zhuo Zhang and Yi Zhang

Appl. Sci. 2019, 9(18), 3785; https://doi.org/10.3390/app9183785 - 10 Sep 2019

Cited by 15 | Viewed by 7229

Abstract

Cement-containing mineral powder can effectively improve the moisture stability of an asphalt mixture; therefore, this study systematically summarizes the research status of cement–mineral fillers on the performance of an asphalt mixture and determines the limitations of related studies. In this study, long-term performance [...] Read more.

Cement-containing mineral powder can effectively improve the moisture stability of an asphalt mixture; therefore, this study systematically summarizes the research status of cement–mineral fillers on the performance of an asphalt mixture and determines the limitations of related studies. In this study, long-term performance tests of styrene-butadiene-styrene- (SBS)-modified asphalt mixtures are designed and evaluated with different blending ratios of the cement–mineral powder under three aging conditions. Moreover, the effect of the cement–mineral composite filler on long-term performance of the asphalt mixture using different blending ratios is determined. Cement improves the high-temperature performance and water stability of asphalt mixtures, but only for certain aging conditions. Considering the regulations for the road performance of asphalt mixtures for three aging conditions, as well as long-term performance considerations, the results indicated that the mass ratio of Portland cement to mineral powder must not exceed 2:2. Low-temperature bending and splitting tensile tests confirmed that an excessive amount of cement filler will embrittle the modified asphalt mixture during long-term aging, thereby deteriorating the tensile properties. The mechanism by which the filler influences the performance of the asphalt mixture should be further studied from the perspective of microscopic and molecular dynamics. Full article

(This article belongs to the Special Issue Asphalt Materials)

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16 pages, 2229 KiB

Open AccessArticle

Durability Evaluation Study for Crumb Rubber–Asphalt Pavement

by Xuancang Wang, Zhenyang Fan, Li Li, Hongyao Wang and Minghui Huang

Appl. Sci. 2019, 9(16), 3434; https://doi.org/10.3390/app9163434 - 20 Aug 2019

Cited by 21 | Viewed by 4487

Abstract

In this study, the failure mechanism of crumb rubber–asphalt pavement was analyzed under the combined effects of low temperature, water, and traffic load. The investigation was carried out based on the mechanical and deformational properties of crumb rubber–asphalt mixture and the typical environmental [...] Read more.

In this study, the failure mechanism of crumb rubber–asphalt pavement was analyzed under the combined effects of low temperature, water, and traffic load. The investigation was carried out based on the mechanical and deformational properties of crumb rubber–asphalt mixture and the typical environmental and load conditions such pavement is typically exposed to. A method was proposed for objective evaluation of the interfacial adhesion between rubber crumbs and asphalt through consideration of the effects of the characteristics of the materials and the working environment. The main evaluation method used herein included the indirect tensile strength test under freeze–thaw–boiling cycle, and the Cántabro abrasion test under water-immersion was adopted as an auxiliary method. The evaluation system has the advantages of simple implementation, realistic simulation of the actual working state of the mixture, and reliable results. Moreover, it is a durability evaluation method that can be specifically applied to asphalt mixtures with some special aggregates or stone mastic asphalt (SMA) mixtures. Full article

(This article belongs to the Special Issue Asphalt Materials)

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14 pages, 7235 KiB

Open AccessFeature PaperArticle

Microtexture Performance of EAF Slags Used as Aggregate in Asphalt Mixes: A Comparative Study with Surface Properties of Natural Stones

by Rosolino Vaiana, Filippo Balzano, Teresa Iuele and Vincenzo Gallelli

Appl. Sci. 2019, 9(15), 3197; https://doi.org/10.3390/app9153197 - 6 Aug 2019

Cited by 26 | Viewed by 3905

Abstract

Steelmaking industries produce a large amount of solid wastes that need to be adequately managed in order to ensure environmental sustainability and reduce the impact of their disposal on earth pollution. Electric arc furnace (EAF) slags are those wastes deriving from secondary steelmaking [...] Read more.

Steelmaking industries produce a large amount of solid wastes that need to be adequately managed in order to ensure environmental sustainability and reduce the impact of their disposal on earth pollution. Electric arc furnace (EAF) slags are those wastes deriving from secondary steelmaking production; these slags can be re-used and recycled in many industrial applications such as the production of asphalt mixes. In this paper authors investigate the surface performance of EAF slags used as second-hand aggregate in asphalt mixes. In particular, slags behavior under polishing is compared to other types of aggregate commonly used for asphalt concrete such as limestone, basalt, and kinginzite. Several devices (skid tester, laser profilometer, polishing machine) were used to collect experimental data; the analysis of microtexture was carried out by comparing aggregate surface performance before and after polishing. Results show that EAF slags are positively comparable to basalt as concerns the polishing behavior; good correlations between skid resistance and some microtexture indicators are also carried out. Full article

(This article belongs to the Special Issue Asphalt Materials)

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16 pages, 8013 KiB

Open AccessArticle

Effect of Thermo-Oxidative Ageing on Nano-Morphology of Bitumen

by Wengang Zhang, Ling Zou, Zhirong Jia, Fang Wang, Ying Li and Ping Shi

Appl. Sci. 2019, 9(15), 3027; https://doi.org/10.3390/app9153027 - 26 Jul 2019

Cited by 19 | Viewed by 3032

Abstract

In recent years, the research on bitumen has reached the nanometer level, but there are still some problems in the study of the relationship between the atomic force microscope (AFM) nano-morphology and ageing of bitumen. The purpose of this paper is to find [...] Read more.

In recent years, the research on bitumen has reached the nanometer level, but there are still some problems in the study of the relationship between the atomic force microscope (AFM) nano-morphology and ageing of bitumen. The purpose of this paper is to find out the effect of thermal oxygen ageing on the nano-morphology of bitumen. Atomic force microscope (AFM) test sample of bitumen was prepared in this paper. Area ratio of bee-like structure, roughness, and maximum amplitude were selected as the nano-morphological parameters of the bitumen. The calculation method of nano-parameters was also proposed. Bitumen with different ageing degrees was prepared by thin film oven test (TFOT). Nano-morphological parameters of bitumen with different ageing degrees were obtained by AFM and analyzed with NanoScope Analysis, and the relationships between nano-morphological parameters and bitumen technical indexes after ageing, such as penetration, ductility, softening point, and viscosity were analyzed. The test results show that the wave crests and wave troughs of the bee-like structure on the surface of the bitumen alternate, while the other areas are relatively flat. The bee-like structure continues to develop as the ageing time prolongs, and the number of bee-like structures decreases, but the volume and the undulation degree increase. With the ageing time prolonging, the nano-parameters of bitumen, such as the area ratio of bee-like structure, roughness, and maximum amplitude, show a trend of increasing gradually, but the increasing rates become smaller and smaller. During the ageing process of bitumen, with the increase of nano-morphological parameters (area ratio of bee-like structure, roughness, and maximum amplitude), penetration at 25 °C and ductility at 15 °C of the bitumen decrease, and softening point and viscosity at 60 °C increase. AFM testing technology and image analysis method in this paper can be used for a reference in the nano-scale study of bitumen. Full article

(This article belongs to the Special Issue Asphalt Materials)

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13 pages, 4400 KiB

Open AccessArticle

Performance and Reinforcement Mechanism of Modified Asphalt Binders with Nano-Particles, Whiskers, and Fibers

by Xiangyang Xing, Jianzhong Pei, Chenchen Shen, Rui Li, Jiupeng Zhang, Jianyou Huang and Dongliang Hu

Appl. Sci. 2019, 9(15), 2995; https://doi.org/10.3390/app9152995 - 26 Jul 2019

Cited by 22 | Viewed by 3273

Abstract

The asphalt binders could be modified to improve road perfo rmances by using various methods, and the reinforcement mechanisms are obviously different and quietly affect the road performances. According to the composite reinforcement theory, nano-CaCO₃ particles, CaCO₃ whiskers, and aramid fibers [...] Read more.

The asphalt binders could be modified to improve road perfo rmances by using various methods, and the reinforcement mechanisms are obviously different and quietly affect the road performances. According to the composite reinforcement theory, nano-CaCO₃ particles, CaCO₃ whiskers, and aramid fibers were used as reinforcements to prepare modified asphalt binders, and the conventional technical performances and dynamic shear rheometer (DSR) rheological properties were measured and investigated. In addition, scanning electron microscopy (SEM) was applied to observe the interfaces between reinforcements and asphalt matrixes and the different reinforcement mechanisms were analyzed. The test results showed that the use of nano-CaCO₃ particles, CaCO₃ whiskers, and aramid fibers can improve the high-temperature stability of modified asphalt binders by different reinforcement mechanisms. The nano-CaCO₃ particles were still effective under high-temperature conditions and could last for a long time through the principle of dispersion enhancement. The CaCO₃ whiskers segregate easily and cannot be well dispersed in asphalt binders. The aramid fibers played an important role of stress transmission and fiber reinforcement in asphalt binders, and 2 mm-aramid fibers hold the best reinforcement effects. The conclusions can provide a reference for the selection and application of modifiers in the preparation of modified asphalt in laboratory and engineering projects. Full article

(This article belongs to the Special Issue Asphalt Materials)

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13 pages, 1570 KiB

Open AccessArticle

Blistering Mechanism Analysis of Hydraulic Asphalt Concrete Facing

by Zhengxing Wang, Jutao Hao, Zhiheng Sun, Baodong Ma, Shifa Xia and Xiulin Li

Appl. Sci. 2019, 9(14), 2903; https://doi.org/10.3390/app9142903 - 19 Jul 2019

Cited by 7 | Viewed by 3140

Abstract

Two years after the Zhanghewan Pumped-Storage Power Station was put into operation, more than 500 blisters appeared in the asphalt concrete facing of the upper reservoir, and nearly half of them ruptured at the surface. The blistering mechanism of the asphalt concrete facing [...] Read more.

Two years after the Zhanghewan Pumped-Storage Power Station was put into operation, more than 500 blisters appeared in the asphalt concrete facing of the upper reservoir, and nearly half of them ruptured at the surface. The blistering mechanism of the asphalt concrete facing was studied in this paper. Through on-site inspection and coring inspection, it was found that the blistering was caused by the vapor pressure formed by the water enclosed in the middle of the impervious layer during high temperatures. Numerical analysis showed that the temperature 5 cm below the surface could reach 50–60 °C. Through numerical analysis and model tests, the internal water at this temperature may form a vapor pressure of 20 kPa. Finally, the blister size of the asphalt concrete facing at this temperature and pressure was studied with a model test. The possible sources of moisture inside the impervious layer were also analyzed through a core test, which found that moisture was most likely to be introduced by water spraying during rolling. Full article

(This article belongs to the Special Issue Asphalt Materials)

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12 pages, 4538 KiB

Open AccessArticle

Investigation of Crack Propagation and Healing of Asphalt Concrete Using Digital Image Correlation

by Navid Hasheminejad, Cedric Vuye, Alexandros Margaritis, Bart Ribbens, Geert Jacobs, Johan Blom, Wim Van den bergh, Joris Dirckx and Steve Vanlanduit

Appl. Sci. 2019, 9(12), 2459; https://doi.org/10.3390/app9122459 - 16 Jun 2019

Cited by 21 | Viewed by 3784

Abstract

The fatigue performance and healing ability of asphalt pavements are important for mixture design, rehabilitation, and maintenance of the roads. By analyzing these parameters in an asphalt mixture, it is possible to predict the crack formation and propagation in asphalt pavements and healing [...] Read more.

The fatigue performance and healing ability of asphalt pavements are important for mixture design, rehabilitation, and maintenance of the roads. By analyzing these parameters in an asphalt mixture, it is possible to predict the crack formation and propagation in asphalt pavements and healing of these cracks during the rest periods. The healing effect in asphalt mixtures has been observed and verified by many researchers and different methods exist to evaluate this phenomenon. However, current methods are still inadequate to fully observe and quantify the healing phenomenon in asphalt mixtures. In this study, a digital image correlation (DIC) method is used to calculate the strain map on the surface of cylindrical asphalt specimens during the indirect tensile fatigue test. This strain map is used to detect the location of crack initiations and development of the microcracks during the experiments. Next, the specimens are unloaded and the temperature of the climate chamber is increased to 60 °C for 18 h to investigate the healing phenomenon on the surface of the specimens. It is observed that the strain reduces near the microcrack areas especially at the tip of the microcracks. Furthermore, using DIC it is possible to observe the healing rate and the minimum time required to heal the microcracks on the surface of the specimens. Full article

(This article belongs to the Special Issue Asphalt Materials)

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17 pages, 5579 KiB

Open AccessArticle

Experimental Study on Hydraulic Fracturing of High Asphalt Concrete Core Rock-Fill Dam

by Zhengxing Wang, Jutao Hao, Jian Yang, Yan Cao, Xiulin Li and Shijia Liu

Appl. Sci. 2019, 9(11), 2285; https://doi.org/10.3390/app9112285 - 3 Jun 2019

Cited by 7 | Viewed by 3159

Abstract

In this paper, we experiment on the hydraulic fracturing of asphalt concrete with a voids content higher than 3%, which has arisen from the possible local shear dilatancy of Quxue asphalt’s core wall of concrete core dam, the highest one of the sort [...] Read more.

In this paper, we experiment on the hydraulic fracturing of asphalt concrete with a voids content higher than 3%, which has arisen from the possible local shear dilatancy of Quxue asphalt’s core wall of concrete core dam, the highest one of the sort constructed in the world. The model test has shown that under the sole water pressure 0.13 MPa—relevant to the pressure where the dilatancy could appear at core wall of Quxue dam—the asphalt concrete with a voids content of 3.5% underwent hydraulic fracturing. Furthermore, the asphalt concrete with a voids content of 3.0% was tested for nearly 500 h and no sign of hydraulic fracturing was found, which again confirmed the threshold requirement for a 3% voids content to the impervious asphalt concrete to the hydraulic fracture concern. According to the analysis of the test result, the theory of fracture mechanics could be applied to the hydraulic fracture of asphalt concrete with a voids content between 3.4~4.0%, which behaved during hydraulic fracturing like a quasi-brittle material, similar to concrete. Because the hydraulic fracturing could occur in the shear dilatant asphalt concrete, a proper mix proportion of asphalt concrete to a project with adverse stress state should be carefully designed to rule out the possibility of shear dilatancy. Full article

(This article belongs to the Special Issue Asphalt Materials)

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17 pages, 3054 KiB

Open AccessArticle

Influence of Ultraviolet Aging on Adhesion Performance of Warm Mix Asphalt Based on the Surface Free Energy Theory

by Bo Li, Yu Wang, Xiaoyu Ren, Xuqiu Teng and Xiuli Su

Appl. Sci. 2019, 9(10), 2046; https://doi.org/10.3390/app9102046 - 17 May 2019

Cited by 23 | Viewed by 3392

Abstract

To explore the effect of ultraviolet (UV) aging on the adhesion properties of warm mix asphalt (WMA), WMA binders were prepared by adding Evotherm M1 and Sasobit into base asphalt. The base asphalt and two WMA binders were aged using a self-made UV [...] Read more.

To explore the effect of ultraviolet (UV) aging on the adhesion properties of warm mix asphalt (WMA), WMA binders were prepared by adding Evotherm M1 and Sasobit into base asphalt. The base asphalt and two WMA binders were aged using a self-made UV aging box after a rolling thin-film oven test (RTFOT). As a comparison, pressure aging vessel (PAV) tests were performed for asphalt binders after RTFOT. The contact angles between the WMA binder and distilled water, glycerol, and formamide, before and after UV aging, were measured using the sessile drop method. On the basis of the surface free energy (SFE) theory, the SFE and its components, cohesion work, adhesion work, peeling work, and compatibility rate, before and after the UV aging of WMA, were obtained. The results show that the contact angle between WMA and water gradually increases with the degree of UV aging, which indicates that the aging increases the hydrophobicity of asphalt. After the RTFOT aging, UV aging at different times, and PAV aging, the SFE and its component, as well as cohesion work for all asphalt binders were reduced. The attenuation was severe after UV aging, followed by PAV aging and RTFOT aging. With the extension of UV aging time, the adhesion work, hot mix asphalt, and limestone aggregate compatibility rate gradually reduced, the peeling work increased, and the overall adhesion performance became poor. Under the aging effect of RTFOT and PAV, the Evotherm M1 WMA had the strongest anti-peeling ability, better compatibility, and the best adhesion. When the UV aging time of Sasobit WMA reached 100 h, the adhesion performance increased. Full article

(This article belongs to the Special Issue Asphalt Materials)

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22 pages, 3909 KiB

Open AccessArticle

A Study on the Design Method for the Material Composition of Small Particle-Size Asphalt Mixture for Controlling Cracks in Asphalt Pavement

by Jiyu Xin, Jianzhong Pei, Mitsuyoshi Akiyama, Rui Li, Jiupeng Zhang and Libo Shao

Appl. Sci. 2019, 9(10), 1988; https://doi.org/10.3390/app9101988 - 15 May 2019

Cited by 10 | Viewed by 3797

Abstract

Generally, various kinds of cracks are the main type of distresses during the service period of asphalt pavements. To save maintenance costs and improve the crack resistance of asphalt pavements effectively, this paper presents a unique design method for the material composition of [...] Read more.

Generally, various kinds of cracks are the main type of distresses during the service period of asphalt pavements. To save maintenance costs and improve the crack resistance of asphalt pavements effectively, this paper presents a unique design method for the material composition of small particle-size (SPS) asphalt mixture for controlling cracks in asphalt pavement. First, Stone Mastic Asphalt (SMA)-II was designed as a basic gradation according to the A.N. Talbot curve and SMA-II-1, SMA-II-2 and SMA-II-3 were designed according to the Superpave mix design method, the Bailey method and the Particle interference theory, respectively. Second, based on Marshall test results, the optimal fiber content and optimal asphalt content of three gradations were determined. Then, the influence of the passing rate of 1.18-mm sieve and 0.075-mm sieve on the air voids of SMA-II and the influence of the filler-asphalt ratio on the performance of SMA-II were investigated, and an appropriate range of filler-asphalt ratio was obtained. Finally, a high-temperature performance test, a water stability test, and a skid resistance test demonstrate that the overall performance of SMA-II can satisfy the specifications. A low-temperature bend test and analysis of bending strain energy density show that SMA-II with a crumb rubber modifier and a polymer fiber has better crack resistance performance than SMA-I (SBS-modified mixture). Life-cycle cost analysis shows the economic advantage of SPS asphalt thin overlays over traditional AC-13 thin overlays. Full article

(This article belongs to the Special Issue Asphalt Materials)

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13 pages, 4026 KiB

Open AccessArticle

Timely and Durable Polymer Modified Patching Materials for Pothole Repairs in Low Temperature and Wet Conditions

by Sen Han, Mengmei Liu, Weigong Shang, Xiang Qi, Zhuang Zhang and Shihao Dong

Appl. Sci. 2019, 9(9), 1949; https://doi.org/10.3390/app9091949 - 12 May 2019

Cited by 16 | Viewed by 4373

Abstract

Aiming to solve the contradiction between the workability and performance of pothole patching using cold mixtures, this paper proposed new patching materials based on the microcapsule technique and polymer reinforcement, namely cold mixtures with polymer modified asphalt and dense graded (DG) of aggregates [...] Read more.

Aiming to solve the contradiction between the workability and performance of pothole patching using cold mixtures, this paper proposed new patching materials based on the microcapsule technique and polymer reinforcement, namely cold mixtures with polymer modified asphalt and dense graded (DG) of aggregates (PADG) mixtures. Laboratory tests were conducted to compare the PADG mixtures with commonly used DG mixtures and open graded (OG) mixtures concerning workability, storability, cohesion, stability, and durability of each mixture. The results found that the PADG mixtures were satisfactory in their workability and storability and were as satisfactory as the OG mixtures. Meanwhile, stability and durability of the PADG mixtures was better than the DG mixtures and OG mixtures, i.e., the PADG mixtures showed stability in the conditions of the timeliness, low temperature, and immersion, as well as the freeze-thaw resistance and wear resistance in wet conditions. Therefore, it can be concluded that PADG mixtures are applicable in timely and durable pothole repairs in low temperatures and wet conditions. Full article

(This article belongs to the Special Issue Asphalt Materials)

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18 pages, 4637 KiB

Open AccessArticle

Effects of Vehicular Speed on the Assessment of Pavement Road Roughness

by Giuseppe Loprencipe, Pablo Zoccali and Giuseppe Cantisani

Appl. Sci. 2019, 9(9), 1783; https://doi.org/10.3390/app9091783 - 29 Apr 2019

Cited by 44 | Viewed by 5715

Abstract

Good ride quality is a fundamental requirement for all road networks in modern countries. For this purpose, it is essential to monitor and evaluate the effect of irregularities on road pavement surfaces. In the last few decades, many roughness indices have been proposed, [...] Read more.

Good ride quality is a fundamental requirement for all road networks in modern countries. For this purpose, it is essential to monitor and evaluate the effect of irregularities on road pavement surfaces. In the last few decades, many roughness indices have been proposed, with the aim to represent shortly the pavement surface characteristics and the relative performances, using a single number and a correspondent scale of values. In this work, a comparison between three different evaluation methods (International Roughness Index, ISO 8608 road profile classification and frequency-weighted vertical acceleration a_wz according to ISO 2631) was carried out, applying these methods to some real road profiles. The similarities and differences between the obtained results are described, evaluating the effect of the road characteristic speed on the roughness thresholds. In fact, the specific aim of the analyses is to underline the need to use different thresholds depending on the speed at which the vehicular traffic can travel on the road sections. In this way, it will be possible to identify appropriate thresholds for the various types of roads, having for each of them a specific range of design or operating speed. Full article

(This article belongs to the Special Issue Asphalt Materials)

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19 pages, 6099 KiB

Open AccessArticle

Labeling Strategy for Evaluating the Performance of Thin Asphalt Wearing Courses

by Lívia Garcia-Gil and Rodrigo Miró

Appl. Sci. 2019, 9(8), 1694; https://doi.org/10.3390/app9081694 - 24 Apr 2019

Cited by 3 | Viewed by 2861

Abstract

Traditional design procedures of asphalt mixtures are based on volumetric parameters and the compliance with the mechanical performance, while functional properties receive less attention. Additionally, even though the potential of sustainable technologies is proven, this is not sufficiently reflected in the technical specifications [...] Read more.

Traditional design procedures of asphalt mixtures are based on volumetric parameters and the compliance with the mechanical performance, while functional properties receive less attention. Additionally, even though the potential of sustainable technologies is proven, this is not sufficiently reflected in the technical specifications and their use is not widely spread. In order to face these challenges, the development of a useful tool that allows infrastructure managers an easy evaluation of the mechanical, functional, and environmental performance and the pursuit of balance between properties will encourage the optimization of road surfaces. The aim of this research is to develop a multi-labeling scheme for asphalt mixtures for thin wearing courses according to their mechanical, functional, and environmental attributes. In particular, the study focuses on the Spanish case, because all the collected data belong to the Spanish road network; however, the approached methodology is flexible enough to be adjusted to the requirements of individual countries. The findings in this research show promise because the developed labeling scheme allows not only the assignation of performance labels to any asphalt mixture based on its properties, but also the comparison of features between different asphalt mixtures. Full article

(This article belongs to the Special Issue Asphalt Materials)

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20 pages, 4199 KiB

Open AccessArticle

Assessment of Thermal Stresses in Asphalt Mixtures at Low Temperatures Using the Tensile Creep Test and the Bending Beam Creep Test

by Marek Pszczola, Mariusz Jaczewski and Cezary Szydlowski

Appl. Sci. 2019, 9(5), 846; https://doi.org/10.3390/app9050846 - 27 Feb 2019

Cited by 19 | Viewed by 4801

Abstract

Thermal stresses are leading factors that influence low-temperature cracking behavior of asphalt pavements. During winter, when the temperature drops to significantly low values, tensile thermal stresses develop as a result of pavement contraction. Creep test methods can be suitable for the assessment of [...] Read more.

Thermal stresses are leading factors that influence low-temperature cracking behavior of asphalt pavements. During winter, when the temperature drops to significantly low values, tensile thermal stresses develop as a result of pavement contraction. Creep test methods can be suitable for the assessment of low-temperature properties of asphalt mixtures. To evaluate the influence of creep test methods on the obtained low-temperature properties of asphalt mixtures, three point bending and uniaxial tensile creep tests were applied and the master curves of stiffness modulus were analyzed. On the basis of creep test results, rheological parameters describing elastic and viscous properties of the asphalt mixtures were determined. Thermal stresses were calculated and compared to the tensile strength of the material to obtain the failure temperature of the analyzed asphalt mixtures. It was noted that lower strain values of creep curves were obtained for the Tensile Creep Test (TCT) than for the Bending Beam Creep Test (BBCT), especially at lower temperatures. Results of thermal stress calculations indicated that higher reliability was obtained for the viscoelastic Monismith method based on the TCT results than for the simple quasi-elastic solution of Hills and Brien. The highest agreement with the TSRST results was also obtained for the Monismith method based on the TCT results. No clear relationships were noted between the predicted failure temperature and different methods of thermal stress calculations. Full article

(This article belongs to the Special Issue Asphalt Materials)

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13 pages, 2402 KiB

Open AccessArticle

Evaluating the Role of Aggregate Gradation on Cracking Performance of Asphalt Concrete for Thin Overlays

by Lívia Garcia-Gil, Rodrigo Miró and Félix E. Pérez-Jiménez

Appl. Sci. 2019, 9(4), 628; https://doi.org/10.3390/app9040628 - 13 Feb 2019

Cited by 23 | Viewed by 3512

Abstract

Thin asphalt concrete overlays are a maintenance technique that mainly restore the functional properties of pavements. One of the main issues in thin overlays is reflective cracking that can cause early deterioration and reduce their service life. For this reason, the purpose of [...] Read more.

Thin asphalt concrete overlays are a maintenance technique that mainly restore the functional properties of pavements. One of the main issues in thin overlays is reflective cracking that can cause early deterioration and reduce their service life. For this reason, the purpose of this investigation is to evaluate the effect of material selection on cracking performance of asphalt concrete mixtures for thin overlays. In particular, this paper evaluates the role of aggregate skeleton gradation. The study of the effect of aggregate gradation was divided into two stages: (1) fine fraction content and (2) maximum nominal aggregate size. Based on this, up to seven asphalt mixture gradations were designed and evaluated through the Fénix test at different test temperatures. The results showed a significant correlation between the fine fraction content, and maximum nominal aggregate size, and the cracking performance of the asphalt concrete mixtures. Mixtures manufactured with a low content of fine aggregates, as well as small nominal maximum size, experienced a further improvement of their toughness. These results reflected the importance of considering not only the effect of asphalt binder and environmental conditions but also aggregate gradation in the design of asphalt concrete mixtures in order to achieve a desirable cracking performance. Full article

(This article belongs to the Special Issue Asphalt Materials)

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18 pages, 7231 KiB

Open AccessFeature PaperArticle

Effect of Freeze-Thaw Cycles on Mechanical Characteristics of Bitumens and Stone Mastic Asphalts

by Bagdat B. Teltayev, Cesare O. Rossi, Galiya G. Izmailova and Erik D. Amirbayev

Appl. Sci. 2019, 9(3), 458; https://doi.org/10.3390/app9030458 - 29 Jan 2019

Cited by 25 | Viewed by 3445

Abstract

The present article investigates in laboratory conditions the effect of cyclic freezing and thawing (CFT) on characteristics of the neat bitumen and bitumens modified with different polymers, as well as stone mastic asphalt concretes prepared with the use of the neat and the [...] Read more.

The present article investigates in laboratory conditions the effect of cyclic freezing and thawing (CFT) on characteristics of the neat bitumen and bitumens modified with different polymers, as well as stone mastic asphalt concretes prepared with the use of the neat and the modified bitumens. Maximal and minimal temperature in cycles of freezing and thawing (FT) is accepted equal to +20 °C and −18 ± 2 °C respectively. Characteristics of low temperature resistance of bitumens (stiffness S and m-value) have been determined on bending beam rheometer at the temperatures of −24 °C, −30 °C, and −36 °C. Strength at direct tension of the stone mastic asphalt concretes has been evaluated in the device TRAVIS (Infratest Ltd., Brackenheim, Germany) at the temperatures of 0 °C, −10 °C, −20 °C, and −30 °C. Resistance of stone mastic asphalt concretes to rutting has been determined on a Hamburg wheel tracking machine. The characteristics of the bitumens have been determined in the initial condition and after 25 and 50 cycles of FT, and the characteristics of stone mastic asphalt concretes, in the initial condition and after 50 cycles of FT. The results obtained experimentally have shown that CFT impacts essentially on the investigated characteristics of bitumens and stone mastic asphalt concretes. Modification with polymers improves the mechanical characteristics of the bitumens and decreases the effect of CFT. It is also found out that when selecting a bitumen for specific climatic conditions it is necessary to take into account both the number of cycles of FT and the characteristic low temperature. Full article

(This article belongs to the Special Issue Asphalt Materials)

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19 pages, 6595 KiB

Open AccessArticle

Dynamic Responses of Asphalt Concrete Waterproofing Layer in Ballastless Track

by Jie Zhou, Xianhua Chen, Qinghong Fu, Gang Xu and Degou Cai

Appl. Sci. 2019, 9(3), 375; https://doi.org/10.3390/app9030375 - 22 Jan 2019

Cited by 26 | Viewed by 3873

Abstract

The application of asphalt concrete waterproofing layer (ACWL) for the subgrade has been a trend in Chinese high-speed railway. The purpose of this research is to discuss the dynamic characteristics of full cross-section ACWL in the ballastless track structure under the train loads. [...] Read more.

The application of asphalt concrete waterproofing layer (ACWL) for the subgrade has been a trend in Chinese high-speed railway. The purpose of this research is to discuss the dynamic characteristics of full cross-section ACWL in the ballastless track structure under the train loads. The laboratory tests were conducted to evaluate the performance of the asphalt mixtures for the ACWL and a test section of ACWL was constructed on the high-speed railway in north China. The linear viscoelastic behavior of the asphalt concrete obtained from the test section was characterized by the generalized Maxwell model according to the results of dynamic modulus test. Then a 3D finite element model for the interaction system of vehicle and ballastless track structure was presented and validated by field measured data. The results indicated that the tensile strain at the bottom of the ACWL was at a relatively low level and the vertical dynamic responses of each structural layer are obviously reduced due to the application of ACWL. Therefore, the full cross-section ACWL helps to reduce the vibration of the track structure and maintain the long-term stability of the subgrade. Full article

(This article belongs to the Special Issue Asphalt Materials)

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19 pages, 5478 KiB

Open AccessArticle

Investigation on Microstructural Damage Properties of Asphalt Mixture Using Linear and Damage-Coupled Viscoelastic Model

by Wenke Huang, Zhibin Ren, Xiaoning Zhang and Jiangmiao Yu

Appl. Sci. 2019, 9(2), 303; https://doi.org/10.3390/app9020303 - 16 Jan 2019

Cited by 4 | Viewed by 3789

Abstract

This paper presents an image-based micromechanical modeling approach for simulating the damage-couple viscoelastic response of asphalt mixture. Details of the numerical damage-couple viscoelastic constitutive formulation implemented in a finite element code are presented and illustrated by using the ABAQUS user material subroutine (UMAT). [...] Read more.

This paper presents an image-based micromechanical modeling approach for simulating the damage-couple viscoelastic response of asphalt mixture. Details of the numerical damage-couple viscoelastic constitutive formulation implemented in a finite element code are presented and illustrated by using the ABAQUS user material subroutine (UMAT). Then, an experimental procedure based on the Linear Amplitude Sweep test for obtaining the viscoelastic and damage parameters at a given temperature was conducted. An improved morphological multi-scale algorithm was employed to segment the adhesive coarse aggregate images. We developed a pixel-based digital reconstruction model of asphalt mixture with the X-ray CT image after being processed. Finally, the image-based FE model incorporated with damage-coupled viscoelastic asphalt mastic phase and elastic aggregates was used for the compressive test simulations successfully in this study. Simulation results showed that the damaged simulation results have a larger stress distribution compared with the undamaged simulation due to the irregularity of the coarse aggregates. The von Mises stress distribution is smaller as the loading time increases due to the viscoelastic behavior of asphalt mastic. It can also provide insight on the damaged mechanisms and the possible location in asphalt mixture where microscopic cracking would most likely occur. Full article

(This article belongs to the Special Issue Asphalt Materials)

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14 pages, 3385 KiB

Open AccessArticle

Quantitative Analysis of the Blending Degree of Virgin and RAP Binders in Recycled Asphalt Mixtures with a High RAP Content

by Zhen Yang, Guoyi Zhuang, Xiaoshu Wei, Jintao Wei, Huayang Yu and Wei Xu

Appl. Sci. 2018, 8(12), 2668; https://doi.org/10.3390/app8122668 - 18 Dec 2018

Cited by 17 | Viewed by 3463

Abstract

Recycled asphalt mixtures (RAM), which are prepared by blending reclaimed asphalt pavement (RAP), virgin bitumen and mineral additives, provide a variety of advantages, including resource recycling, reductions in costs, and reduced negative environmental impacts. However, multiple agencies have expressed concerns about the utilization [...] Read more.

Recycled asphalt mixtures (RAM), which are prepared by blending reclaimed asphalt pavement (RAP), virgin bitumen and mineral additives, provide a variety of advantages, including resource recycling, reductions in costs, and reduced negative environmental impacts. However, multiple agencies have expressed concerns about the utilization ratio of RAP; thus, a comprehensive understanding of the blending degree of virgin and RAP binders in RAM would be significantly helpful for promoting the application of RAP. This study aims to quantitatively analyze the blending degree of virgin and RAP binders in RAM with high RAP contents. Carboxyl-terminated butadiene acrylonitrile (CTBN) was utilized as a tracer to mark the virgin bitumen; in addition, Fourier transform infrared (FTIR) spectroscopy was used to develop the structural index of CTBN (I_CTBN). By establishing the standard curve between I_CTBN and the CTBN content, the blending degree of virgin and RAP binders at different locations within RAM can be determined quantitatively. The study results indicate that the RAP binder was completely blended with the virgin bitumen in the outer RAP layer. However, the blending degree decreased with an increase in the RAP depth, and the blending degree in the inner RAP layer was only approximately half that which was found in the case of complete blending. Full article

(This article belongs to the Special Issue Asphalt Materials)

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19 pages, 5370 KiB

Open AccessArticle

Pavement Performance Investigation of Nano-TiO₂/CaCO₃ and Basalt Fiber Composite Modified Asphalt Mixture under Freeze‒Thaw Cycles

by Yafeng Gong, Haipeng Bi, Zhenhong Tian and Guojin Tan

Appl. Sci. 2018, 8(12), 2581; https://doi.org/10.3390/app8122581 - 12 Dec 2018

Cited by 26 | Viewed by 3585

Abstract

The objective of this research is to evaluate the pavement performance degradation of nano-TiO₂/CaCO₃ and basalt fiber composite modified asphalt mixtures under freeze‒thaw cycles. The freeze‒thaw resistance of composite modified asphalt mixture was studied by measuring the mesoscopic void volume, [...] Read more.

The objective of this research is to evaluate the pavement performance degradation of nano-TiO₂/CaCO₃ and basalt fiber composite modified asphalt mixtures under freeze‒thaw cycles. The freeze‒thaw resistance of composite modified asphalt mixture was studied by measuring the mesoscopic void volume, stability, indirect tensile stiffness modulus, splitting strength, uniaxial compression static, and dynamic creep rate. The equal-pitch gray prediction model GM (1, 3) was also established to predict the pavement performance of the asphalt mixture. It was concluded that the high- and low-temperature performance and water stability of nano-TiO₂/CaCO₃ and basalt fiber composite modified asphalt mixture were better than those of an ordinary asphalt mixture before and after freeze‒thaw cycles. The test results of uniaxial compressive static and dynamic creep after freeze‒thaw cycles showed that the high-temperature stability of the nano-TiO₂/CaCO₃ and basalt fiber composite modified asphalt mixture after freeze‒thaw was obviously improved compared with an ordinary asphalt mixture. Full article

(This article belongs to the Special Issue Asphalt Materials)

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15 pages, 2342 KiB

Open AccessArticle

Comparison of Relaxation Modulus Converted from Frequency- and Time-Dependent Viscoelastic Functions through Numerical Methods

by Weiguang Zhang, Bingyan Cui, Xingyu Gu and Qiao Dong

Appl. Sci. 2018, 8(12), 2447; https://doi.org/10.3390/app8122447 - 1 Dec 2018

Cited by 30 | Viewed by 6406

Abstract

Due to the difficulty of obtaining relaxation modulus directly from experiments, many interconversion methods from other viscoelastic functions to relaxation modulus were developed in previous years. The objectives of this paper were to analyze the difference of relaxation modulus converted from dynamic modulus [...] Read more.

Due to the difficulty of obtaining relaxation modulus directly from experiments, many interconversion methods from other viscoelastic functions to relaxation modulus were developed in previous years. The objectives of this paper were to analyze the difference of relaxation modulus converted from dynamic modulus and creep compliance and explore its potential causes. The selected methods were the numerical interconversions based on Prony series representation. For the dynamic to relaxation conversion, the time spectrum was determined by the collocation method. Meanwhile, for the creep to relaxation conversion, both the collocation method and least squares method were adopted to perform the Laplace transform. The results show that these two methods do not present a significant difference in estimating relaxation modulus. Their difference mostly exists in the transient reduced time region. Calculating the average of two methods is suggested to avoid great deviation of single experiment. To predict viscoelastic responses from creep compliance, the collocation method yields comparable results to the least squares method. Thus, simply-calculated collocation method may be preferable in practice. Further, the master curve pattern is sensitive to the Prony series coefficients. The difference in transient reduced time region may be attributed to the indeterminate Prony series coefficients. Full article

(This article belongs to the Special Issue Asphalt Materials)

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14 pages, 4548 KiB

Open AccessArticle

Microstructure Analysis of Modified Asphalt Mixtures under Freeze-Thaw Cycles Based on CT Scanning Technology

by Yafeng Gong, Haipeng Bi, Chunyu Liang and Shurong Wang

Appl. Sci. 2018, 8(11), 2191; https://doi.org/10.3390/app8112191 - 8 Nov 2018

Cited by 24 | Viewed by 3429

Abstract

The modifiers NTC (nano-TiO₂/CaCO₃) and BF (basalt fiber) were adopted to modify a base matrix asphalt mixture. The base matrix asphalt mixture and three kinds of modified asphalt mixture under F–T (freeze–thaw) cycles were scanned by computed tomography. The [...] Read more.

The modifiers NTC (nano-TiO₂/CaCO₃) and BF (basalt fiber) were adopted to modify a base matrix asphalt mixture. The base matrix asphalt mixture and three kinds of modified asphalt mixture under F–T (freeze–thaw) cycles were scanned by computed tomography. The air voids and morphological changes of asphalt mixture were summarized by image processing technology, and the development process of F–T damage to asphalt mixture was explained from a micro-view. The porosity of NTC-modified asphalt mixture changed little, and the void distribution between base matrix asphalt mixture and NTC-BF (nano-TiO₂/CaCO₃ and basalt fiber) composite modified asphalt mixture was more uniform. The macro-pores in the asphalt mixture under 15 F–T cycles began to connect gradually, and the pore characteristics also changed. The number and shape of the pores changed under 15 F–T cycles. According to the state characteristics, the change amplitude of the pore characteristics of matrix asphalt mixture and NTC-BF composite modified asphalt mixture were the most stable under F–T cycles. Full article

(This article belongs to the Special Issue Asphalt Materials)

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11 pages, 2800 KiB

Open AccessArticle

Fatigue Resistance Characterization of Warm Asphalt Rubber by Multiple Approaches

by Jiangmiao Yu, Xianshu Yu, Zheming Gao, Feng Guo, Duanyi Wang and Huayang Yu

Appl. Sci. 2018, 8(9), 1495; https://doi.org/10.3390/app8091495 - 31 Aug 2018

Cited by 46 | Viewed by 5318

Abstract

Warm asphalt rubber (WAR) mixture is a sustainable paving material with advantages including waste recycling and noise reducing. A comprehensive understanding of the fatigue performance of WAR specimens is helpful to its wide application. However, research on evaluating the fatigue performance of WAR [...] Read more.

Warm asphalt rubber (WAR) mixture is a sustainable paving material with advantages including waste recycling and noise reducing. A comprehensive understanding of the fatigue performance of WAR specimens is helpful to its wide application. However, research on evaluating the fatigue performance of WAR binder and mixtures is very limited. This paper applies five fatigue analysis approaches to evaluate the fatigue life of WAR samples with three different warm mix asphalt (WMA) additives. The conventional G*sinδ, linear amplitude sweep (LAS), indirect tensile fatigue test (ITFT), and four-point bending beam (4PB) test were conducted based on available standards. In addition, a novel shear fatigue test was performed on WAR mortars. Test results indicated that the incorporation of crumb rubber has a significantly positive effect on fatigue resistance. WAR with chemical and foaming additives exhibited a poorer performance than asphalt rubber (AR), but their fatigue performance was still greatly superior to the non-rubberized samples. Finally, LAS as well as mortar shear fatigue and 4PB tests provided the same prediction of fatigue resistance, while the results of G*sinδ and the ITFT were inconsistent. It is recommended to use LAS, the mortar shear fatigue test, and the 4PB test for the fatigue resistance evaluation of rubberized specimens. The validation of the findings with more materials and field performances is recommended. Full article

(This article belongs to the Special Issue Asphalt Materials)

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44 pages, 10434 KiB

Open AccessReview

A Review on Bitumen Rejuvenation: Mechanisms, Materials, Methods and Perspectives

by Valeria Loise, Paolino Caputo, Michele Porto, Pietro Calandra, Ruggero Angelico and Cesare Oliviero Rossi

Appl. Sci. 2019, 9(20), 4316; https://doi.org/10.3390/app9204316 - 14 Oct 2019

Cited by 50 | Viewed by 7780

Abstract

This review aims to explore the state of the knowledge and the state-of-the-art regarding bitumen rejuvenation. In particular, attention was paid to clear things up about the rejuvenator mechanism of action. Frequently, the terms rejuvenator and flux oil, or oil (i.e., softening agent) [...] Read more.

This review aims to explore the state of the knowledge and the state-of-the-art regarding bitumen rejuvenation. In particular, attention was paid to clear things up about the rejuvenator mechanism of action. Frequently, the terms rejuvenator and flux oil, or oil (i.e., softening agent) are used as if they were synonymous. According to our knowledge, these two terms refer to substances producing different modifications to the aged bitumen: they can decrease the viscosity (softening agents), or, in addition to this, restore the original microstructure (real rejuvenators). In order to deal with the argument in its entirety, the bitumen is investigated in terms of chemical structure and microstructural features. Proper investigating tools are, therefore, needed to distinguish the different mechanisms of action of the various types of bitumen, so attention is focused on recent research and the use of different investigation techniques to distinguish between various additives. Methods based on organic synthesis can also be used to prepare ad-hoc rejuvenating molecules with higher performances. The interplay of chemical interaction, structural changes and overall effect of the additive is then presented in terms of the modern concepts of complex systems, which furnishes valid arguments to suggest X-ray scattering and Nuclear Magnetic Resonance relaxometry experiments as vanguard and forefront tools to study bitumen. Far from being a standard review, this work represents a critical analysis of the state-of-the-art taking into account for the molecular basis at the origin of the observed behavior. Furnishing a novel viewpoint for the study of bitumen based on the concepts of the complex systems in physics, it constitutes a novel approach for the study of these systems. Full article

(This article belongs to the Special Issue Asphalt Materials)

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Open AccessFeature PaperReview

Bitumen and Bitumen Modification: A Review on Latest Advances

by Michele Porto, Paolino Caputo, Valeria Loise, Shahin Eskandarsefat, Bagdat Teltayev and Cesare Oliviero Rossi

Appl. Sci. 2019, 9(4), 742; https://doi.org/10.3390/app9040742 - 20 Feb 2019

Cited by 255 | Viewed by 34255

Abstract

This synthesis explores the state-of-the-knowledge and state-of-the-practice regarding the latest updates on polymer-modified bitumens (PmBs). The information in this study was gathered from a thorough review of the latest papers in the literatures related to modified bituminous materials, technologies, and advances. For this [...] Read more.

This synthesis explores the state-of-the-knowledge and state-of-the-practice regarding the latest updates on polymer-modified bitumens (PmBs). The information in this study was gathered from a thorough review of the latest papers in the literatures related to modified bituminous materials, technologies, and advances. For this purpose, the paper is presented in two principle sections. In the first part, the bitumen itself is investigated in terms of chemical structure and microstructural systems. In the second part, the paper focuses on bitumen modification from different aspects for assessing the effectiveness of the introduced additives and polymers for enhancing the engineering properties of bitumen in both paving and industrial applications. In conclusion, the knowledge obtained in this study has revealed the importance of the chemical composition of base bitumen for its modification. It can be declared that while some polymers/additives can improve one or some aspects of neat bitumen properties, they can lead to compatibility problems in storage and production. In this respect, several studies showed the effectiveness of waxes for improving the compatibility of polymers with bitumen in addition to some benefits regarding warm mix asphalt (WMA) production. Full article

(This article belongs to the Special Issue Asphalt Materials)

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