Showing papers on "Asphalt concrete published in 2016"

Analysis of Adhesive Characteristics of Asphalt Based on Atomic Force Microscopy and Molecular Dynamics Simulation

Abstract: Asphalt binder is a very important building material in infrastructure construction; it is commonly mixed with mineral aggregate and used to produce asphalt concrete. Owing to the large differences in physical and chemical properties between asphalt and aggregate, adhesive bonds play an important role in determining the performance of asphalt concrete. Although many types of adhesive bonding mechanisms have been proposed to explain the interaction forces between asphalt binder and mineral aggregate, few have been confirmed and characterized. In comparison with chemical interactions, physical adsorption has been considered to play a more important role in adhesive bonding between asphalt and mineral aggregate. In this study, the silicon tip of an atomic force microscope was used to represent silicate minerals in aggregate, and a nanoscale analysis of the characteristics of adhesive bonding between asphalt binder and the silicon tip was conducted via an atomic force microscopy (AFM) test and molecular dynam...

Linking asphalt binder fatigue to asphalt mixture fatigue performance using viscoelastic continuum damage modeling

Abstract: Fatigue cracking is a major form of distress in asphalt pavements. Asphalt binder is the weakest asphalt concrete constituent and, thus, plays a critical role in determining the fatigue resistance of pavements. Therefore, the ability to characterize and model the inherent fatigue performance of an asphalt binder is a necessary first step to design mixtures and pavements that are not susceptible to premature fatigue failure. The simplified viscoelastic continuum damage (S-VECD) model has been used successfully by researchers to predict the damage evolution in asphalt mixtures for various traffic and climatic conditions using limited uniaxial test data. In this study, the S-VECD model, developed for asphalt mixtures, is adapted for asphalt binders tested under cyclic torsion in a dynamic shear rheometer. Derivation of the model framework is presented. The model is verified by producing damage characteristic curves that are both temperature- and loading history-independent based on time sweep tests, given that the effects of plasticity and adhesion loss on the material behavior are minimal. The applicability of the S-VECD model to the accelerated loading that is inherent of the linear amplitude sweep test is demonstrated, which reveals reasonable performance predictions, but with some loss in accuracy compared to time sweep tests due to the confounding effects of nonlinearity imposed by the high strain amplitudes included in the test. The asphalt binder S-VECD model is validated through comparisons to asphalt mixture S-VECD model results derived from cyclic direct tension tests and Accelerated Loading Facility performance tests. The results demonstrate good agreement between the asphalt binder and mixture test results and pavement performance, indicating that the developed model framework is able to capture the asphalt binder’s contribution to mixture fatigue and pavement fatigue cracking performance.

Durability of Asphalt Concrete Subjected to Deteriorating Effects of Water and Frost

Abstract: The paper presents testing of the detrimental effects of water and frost on asphalt pavements. It included laboratory testing of fatigue life of asphalt concrete that was subjected to action of water and frost and field testing of damages caused by water and frost on existing asphalt pavements, such as stripping, raveling, and potholes. Laboratory simulation of water and frost action was based on the original AASHTO T283 method and its modification. The original method was modified in such a way that instead of a single freeze-thaw cycle, 50 and 150 cycles were applied. Fatigue life was measured in the indirect tensile fatigue test in the Nottingham Asphalt Tester (NAT) apparatus. The asphalt concrete specimens were prepared in laboratory. Some specimens contained liquid adhesive agent—namely, fatty amine—and others did not. The detrimental effect of water and frost was clearly identified. Also, the results of field investigation—condition survey of existing pavements and the results of laboratory...

Superhydrophobic Coatings on Asphalt Concrete Surfaces: Toward Smart Solutions for Winter Pavement Maintenance

Abstract: Millions of dollars are annually spent for ice or snow removal from the roadways and airport paved surfaces in cold regions. The presence of snow or ice on paved areas can cause traffic accidents and financial loss because of flight cancellations or delays. For mitigating winter pavement maintenance issues, the use of superhydrophobic (super-water-repellent) coating techniques is gaining attention as a smart and cost-effective alternative to traditional snow and ice removal practices. This study focuses on creating, characterizing, and evaluating innovative superhydrophobic coatings on asphalt concrete surfaces for ice- and snow-free flexible pavement applications. The layer-by-layer (LBL) method was used to create an asphalt concrete surface coating with polytetrafluoroethylene (PTFE) as a well-known super-ice- and super-water-repellent material. Superhydrophobicity and skid resistance of the coated asphalt concrete surface were characterized by the water contact angle, the work of adhesion, and the coef...

Laboratory investigation of the performances of cement and fly ash modified asphalt concrete mixtures

Abstract: The influence of filler materials on volumetric and mechanical performances of asphalt concrete was investigated in this study. The AC60/70 asphalt binder incorporating with cement and fly ash as filler materials was mixed with limestone following the Marshall mix design method. The filler contents of cement and/or fly ash were varied. The non-filler asphalt concrete mixtures of the AC60/70 and the polymer modified asphalt were prepared for the purpose of comparison. The investigation programme includes the indirect tensile test, the resilient modulus test and the dynamic creep test. The tests are conducted under the humid temperate environments. All tests were then carried out under standard temperature (25 °C) and high temperature (55 °C) by using a controlled temperature chamber via the universal testing machine. The wet-conditioned samples were prepared to investigate the moisture susceptibility. Results show that cement and/or fly ash were beneficial in terms of improved strength, stiffness and stripping resistance of asphalt mixture. In addition, the combined use of cement and fly ash can enhance rutting resistance at wet and high temperature conditions. The results indicate that the strength, stiffness and moisture susceptibility performances of the asphalt concrete mixtures improved by filler are comparable to the performance of the polymer modified asphalt mixture.

Use of the Multiple Stress Creep Recovery (MSCR) Test Method to Characterize Polymer-Modified Asphalt Binders

Abstract: Use of polymer-modified binder has become much more important in recent years to enhance the durability and strength of asphalt concrete (AC) pavements in order to sustain higher traffic volumes, heavier loads, and extreme weather conditions. Unlike neat (unmodified) asphalt binders, polymer-modified binders are sensitive to the applied stress levels and show a nonlinear response in rutting factor and phase angle. The widely used dynamic shear rheometer (DSR) test (AASHTO T315) is not sufficient to capture viscoelastic properties of polymer modified-asphalt binders. Thus, state transportation agencies often need to conduct additional expensive and time consuming “PG Plus” tests (e.g., elastic recovery (ER), force ductility, toughness, and tenacity) for characterizing polymer-modified binders. Multiple stress creep recovery (MSCR), a recently introduced test method (AASHTO TP 70) for measuring high temperature properties of an asphalt binder, is expected to replace the existing AASHTO T315 for short-term aged binder. In the current study, MSCR and Superpave tests were conducted on three commonly used performance grade (PG) binders (PG 64-22, PG 70-28, and PG 76-28) from 12 different sources throughout Oklahoma. Based on expected traffic loads and service temperatures, the tested binder samples were graded in accordance with the MSCR grading system. The non-recoverable creep compliance (Jnr) and MSCR % recovery values obtained from the MSCR tests were then analyzed using the polymer curve and quadrant methods to assess the feasibility of the adoption of the MSCR test method for conditions prevailing in Oklahoma. Findings of this study reveal that the MSCR test method can be used to characterize polymer-modified binders without penalizing suppliers or risking the users.

Investigation of factors affecting dynamic modulus and phase angle of various asphalt concrete mixtures

Abstract: This study investigated the dynamic response of various asphalt concrete (AC) mixtures subjected to sinusoidal loading. Eight AC mixtures (four wearing and four base course) were selected including (but not limited to): superpave, asphalt institute manual series, and dense bituminous macadam. The uniaxial dynamic modulus (|E*|) test at various temperatures (4.4–54.4 °C) and frequencies (0.1–25 Hz) was conducted using asphalt mixture performance tester. Statistical analysis of two-level factorial was employed to regulate the factors affecting the AC mixtures. The results revealed that an increase in temperature (from 21.1 to 37.8 °C), translated into 45 and 43 % drop in |E*| values on average while 80 and 67 % decrease in |E*| values was attributed to the sweep of frequency (from 25 to 0.1 Hz) for wearing and base course mixes, respectively. Non-linear regression model was developed to express the dynamic modulus as a function of test temperature, loading frequency and mixture volumetric parameter. Furthermore, Witczak model of dynamic modulus prediction was evaluated and the results indicated a close fit with an average under prediction error of 0.20. The study characterized and ranked the representative AC mixtures that could help in selecting the material/gradation for mechanistic-empirical pavement design approach.

Permanent Deformation of Asphalt Mixtures

Abstract: This dissertation describes the results of a research that was conducted on the permanent deformation of asphalt mixtures. Central to this research was the separate characterization of the contribution of the aggregate skeleton and the bituminous mortar towards resistance to permanent deformation. The mixtures considered in this research included porous asphalt, stone mastic asphalt and dense asphalt concrete. The test program comprised of modulus testing as well as monotonic tension and compression tests on the asphalt mixtures, monotonic and repeated load triaxial tests on the aggregate skeletons along with dynamic shear and direct tension tests on the bitumen and the bituminous mortar. Prior to testing, the compaction homogeneity of the aggregate skeleton and asphalt mixture specimens was examined by means of X-ray tomography. The repeated load triaxial tests conducted on the aggregate skeleton included constant and cyclic confinement tests. The cyclic confinement tests offered a more realistic means of characterizing the permanent deformation behaviour of the aggregate skeleton in comparison to the constant confinement tests. In addition, the permanent deformation under cyclic confinement was higher than the permanent deformation under constant confinement. The approach developed in this research was based on the Desai plasticity model. In order to demonstrate the practical implications of this plasticity approach, two test pavements with a significant amount of permanent deformation were analysed. The analyses showed that the observed permanent deformation could be explained by the approach developed in this research.

Evaluation of Sunflower Oil as a Rejuvenator and Its Microencapsulation as a Healing Agent

Abstract: Self-healing microencapsulation in asphalt concrete is an emerging technology that would allow this particular material to resist cracking damage caused by vehicular and environmental loading. The objectives of this study were to evaluate the effects of asphalt rejuvenators on asphalt binder, to select a suitable healing agent for asphaltic materials, and to develop a synthesis procedure for the production of microencapsulation of asphalt rejuvenators. Produced microcapsules were characterized using scanning electron microscopy (SEM) to assess the effects of preparation parameters on the size and morphology of the microcapsules. Based on the results of the experimental program, it was concluded that the use of sunflower oil as a rejuvenator was effective in reversing the aging of asphalt binder and to positively affect both the high-temperature and low-temperature grades of the binder. In contrast, the use of PennzSuppress as a rejuvenator was not effective in reversing the aging of asphalt binder...

Strain transfer analysis of optical fiber based sensors embedded in an asphalt pavement structure

Abstract: Asphalt pavement is vulnerable to random damage, such as cracking and rutting, which can be proactively identified by distributed optical fiber sensing technology. However, due to the material nature of optical fibers, a bare fiber is apt to be damaged during the construction process of pavements. Thus, a protective layer is needed for this application. Unfortunately, part of the strain of the host material is absorbed by the protective layer when transferring the strain to the sensing fiber. To account for the strain transfer error, in this paper a theoretical analysis of the strain transfer of a three-layered general model has been carried out by introducing Goodman's hypothesis to describe the interfacial shear stress relationship. The model considers the viscoelastic behavior of the host material and protective layer. The effects of one crack in the host material and the sensing length on strain transfer relationship are been discussed. To validate the effectiveness of the strain transfer analysis, a flexible asphalt-mastic packaged distributed optical fiber sensor was designed and tested in a laboratory environment to monitor the distributed strain and appearance of cracks in an asphalt concrete beam at two different temperatures. The experimental results indicated that the developed strain transfer formula can significantly reduce the strain transfer error, and that the asphalt-mastic packaged optical fiber sensor can successfully monitor the distributed strain and identify local cracks.

Performance Characteristics of Silane Silica Modified Asphalt

Abstract: At present there are many kinds of fillers and modifier used for modified asphalt, but the effect of modifier differs in thousands of ways; most of them can increase the high temperature performance of asphalt, but the modified effect of low-temperature crack resistance, water stability, and antifatigue performance is different. Aiming at the subsistent problems, this paper innovatively puts forward the idea of taking the silane silica (nanosilica modified with silane coupling agent) as filler to develop one kind of modified asphalt concrete which has excellent comprehensive performance based on the idea of enhance the whole performance of asphalt concrete and interface consolidation strength between aggregate and asphalt at the same time. The best mixing amount of silane silica and the production process of modified asphalt were conducted by contrasting the test date as penetration, viscosity, and softening point; the aging of asphalt and modified asphalt was analyzed by TG test, the superiority of silane silica modified asphalt is more clearly understandable by chemical analysis results. Meanwhile it is proved that silane silica has positive effect to improve the mixture of high and low temperature performance, water stability, and aging resistance through a series of road performance tests.