| 1. |
- Abd-Alla, E. S. M ., et al.
(författare)
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New wheel tracking test to analyze movements of aggregates in multi-layered asphalt specimens
- 2006
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Ingår i: Journal of the Japan Petroleum Institute. - : Japan Petroleum Institute. - 1346-8804 .- 1349-273X. ; 49:5, s. 274-279
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a new wheel tracking test for analyzing movements of aggregates in mixtures. The test device is conducted using as examples four-layered specimens taken from two Swiss national motorways, where severe rutting (G section) and longitudinal cracking (H section) were observed. This test method was developed by Moriyoshi. Tests can be carried out under temperature distributions similar to field situation. Two-dimensional movements and strains between aggregates for four-layered specimens due to the moving wheel loads were analyzed by right angle for direction of wheel pass. For this purpose, the cross section of the slabs with a width of 30 cm was divided optically into 5 vertical subsections. The transverse permanent surface deformations, the area changes in the transversal subsections as well as the maximum deformation of the surface and layer-interface through the centerline of the applied wheel load were determined. Strain distributions between aggregates in mixtures at high temperature (45 degrees C) under 600 passes were also measured by photo analysis. Test results show consolidation of the asphalt mixtures and material flow on the surface near the wheel load. The results also demonstrate that the aggregates (size of aggregate: 2 mm or larger) in each mixture move mainly in vertical direction. Large strains (40% or larger) between aggregates at summer condition were measured in the surface mixture near wheel track after 600 passes.
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| 2. |
- Arraigada, M, et al.
(författare)
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Determination of Road Deflections from Traffic Induced Accelerations
- 2007
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Ingår i: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 8:3, s. 399-421
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Tidskriftsartikel (refereegranskat)abstract
- Vertical elastic pavement deflections from moving vehicles provide valuable information for assessing the structural behaviour of a road under real loads. Various types of sensors can be installed in a road for deflection monitoring. This paper explores the use of accelerometers. It discusses the problems involving the calculation of deflections from measured acceleration by double integration due to the amplification of measurement errors in the acceleration signal. It proposes a simple algorithm to correct integration errors and obtain deflections from acceleration measurements. It also presents a laboratory testing method to evaluate the performance of two accelerometers for their suitability in road applications. In addition, using a selected accelerometer, pavementdeflections at a wheel tracking test site are calculated and discussed.
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| 3. |
- Arraigada, M, et al.
(författare)
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Evaluation of Accelerometers to Determine Pavement Deflections under Traffic Loads
- 2008
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 42:6, s. 779-790
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work was to study the use of accelerometers to measure pavement deflections due to traffic loads. To this end, accelerometers were embedded in two sites: the full scale load simulator Circular Test Track (CTT) and the A1 motorway in Switzerland. Deflections were derived from acceleration measurements using an algorithm that double integrates the measured signal and corrects any errors derived from the procedure. In the motorway, deflections were monitored using a set of three magnetostrictive deflectometers. Additionally, the pavement's material viscoelastic parameters determined in the laboratory were incorporated in Finite Element (FE) models to estimate the theoretical deflections. The calculated deflections were then compared to the measured and to the theoretical deflections. Deflections calculated from acceleration showed a reasonable qualitative correlation to those measured by magnetostrictive deflectometers. In addition, the FE models revealed the inability of the accelerometers to measure very slow or quasi-static motion.
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| 4. |
- Bressi, S., et al.
(författare)
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A new laboratory methodology for optimization of mixture design of asphalt concrete containing reclaimed asphalt pavement material
- 2016
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Ingår i: Materials and Structures. - : Kluwer Academic Publishers. - 1359-5997 .- 1871-6873. ; 49:12, s. 4975-4990
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Tidskriftsartikel (refereegranskat)abstract
- The reduction of virgin bitumen added to asphalt mixtures containing Reclaimed Asphalt Pavement (RAP) is based on the typical assumption that all the aged binder function in the same way as the virgin binder. However, recent studies conducted by the authors for a specific case show that a blend or mobilization of RAP binder are negligible. The aged bitumen becomes softer acting as glue facilitating cluster formation between small-size RAP particles. The reduction of small-size particles causes changes in the target grading curve and in the voids-fill, affecting the compactability of RAP mixtures. Therefore the target grading curve of RAP mixtures needs to be readjusted, using different proportions of virgin aggregates and taking into account the cluster phenomenon. The objective of this paper is to develop a new mix design approach for RAP mixtures, taking into account the cluster phenomenon and the contribution of the aged bitumen in the compactability. The virgin aggregates, filler and RAP are investigated and individually included in the calculation. 3D images of the virgin aggregates allowed the determination of new surface area factors; the concept of critical filler concentration led to the definition of the minimum bitumen quantity required to maintain the mastic in a diluted state and fill the voids. A RAP clustering model was introduced to predict the agglomeration of small-size RAP particles. The readjustment of the target grading curve was analytically calculated, allowing the correct estimation of the amount of virgin bitumen to be added to asphalt mixtures. Finally, a first verification of the entire process was carried out performing laboratory tests. These promising results enable the challenge of a new mix design optimization for HMA with high RAP content to be addressed.
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| 5. |
- Bueno, M., et al.
(författare)
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Low temperature characterization of bituminous binders with a new cyclic shear cooling (CSC) failure test
- 2014
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 58, s. 16-24
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Tidskriftsartikel (refereegranskat)abstract
- Low temperature cracking of asphalt pavements is associated to the thermal stresses created when asphalt binder changes from a ductile into a brittle state during cooling. Under repetitive traffic loads, this change of properties can become a significant problem, resulting in the formations of large cracks on the driving surface, thus requiring early pavement repair. Nevertheless, the conventional test methods for assessing low temperature properties of bitumen are often insufficient and subject to low reproducibility. Therefore, a reliable method is necessary to characterize the performance of bituminous binders at low temperature. This work presents the cyclic shear cooling failure test (CSC-failure test) as an alternative method based on a failure test with the dynamic shear rheometer (DSR) at decreasing temperature until fracture occurs. Operational parameters, like shear strain amplitude or loading frequency, have been analysed in order to develop a reproducible procedure applicable for different types of bituminous binders. Moreover, a failure criterion has been defined by analysing the different characteristic temperatures from the failure curves obtained in the test.
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| 6. |
- Canestrari, F., et al.
(författare)
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Mechanical testing of interlayer bonding in asphalt pavements
- 2013
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Ingår i: Advances in Interlaboratory Testing and Evaluation of Bituminous Materials. - Dordrecht : Springer Netherlands. - 9789400751033 ; , s. 303-360
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Bokkapitel (refereegranskat)abstract
- Steadily increasing requirements on pavement performance properties, in terms of bearing capacity and durability, as well as new innovative developments regarding pavement materials and construction, are observed worldwide. In this context interlayer bonding at the interfaces of multi-layered bituminous systems is recognized as a key issue for the evaluation of the effects, in terms of stress-strain distribution, produced by traffic loads in road pavements. For this reason a correct assessment of interlayer bonding is of primary importance, and research efforts should be addressed in order to improve the lack of correlation and/or harmonization among test methods. Following this principle RILEM TG 4 organized an interlaboratory test in order to compare the different test procedures to assess the interlayer bonding properties of asphalt pavement. The results of the experimental research are presented with a preliminary overview of basic elements, test methods and experimental investigations on interlayer bonding. Then the RILEM TG 4 experimental activities, based on the construction of three real- scale pavement sections, are presented in detail. Each pavement section was composed of two layers, and three different interface conditions were chosen. The first pavement was laid without interface treatment and the others with two different types of emulsion. Fourteen laboratories from 11 countries participated in this study and carried out shear or torque tests on 1,400 cores. The maximum shear or torque load and the corresponding displacement were measured, and the shear or torque strength was calculated as a function of the following parameters: diameter, test temperature, test speed, stress applied normal to the interface and age of the specimen. The results of this study are presented in terms of precision and correlations regarding the parameters which results in useful information on asphalt pavement interlayer bond tests.
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| 7. |
- Chen, Feng, 1987-, et al.
(författare)
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Experimental and numerical analysis of asphalt flow in a slump test
- 2019
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Ingår i: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 20, s. S446-S461
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical behaviour of uncompacted asphalt mixtures is still not well understood,threatening directly to the pavement practices such as control of mixture’s workability andsegregation. This situation may become even worse due to the gradually increasing complexityand advances in paving materials and technologies. This study adopts a slump flow testbased on concrete technology and a Discrete Element (DE)-based numerical tool to investigatethe mechanical behaviour of uncompacted asphalt mixture from a microstructural point ofview, particularly focusing on the bituminous binder effects. The combined experimental andnumerical analysis indicates that bitumen distinctly influences the contact interactions withinthe mixture and thus its macroscopic flow, which can be physically interpreted as a combinedeffect of lubricated friction and bonding force. Additional case studies demonstrate that the DEmodel is capable of simulating the flow response of asphalt mixtures under changed particlecontact conditions and driven force.
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| 8. |
- Chen, Feng, 1987-, et al.
(författare)
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Vibration-induced aggregate segregation in asphalt mixtures
- 2020
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Ingår i: Materials and Structures. - : SPRINGER. - 1359-5997 .- 1871-6873. ; 53:2
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Tidskriftsartikel (refereegranskat)abstract
- Aggregate segregation in asphalt mixture is a bothersome engineering issue during pavement construction. The practitioners have some measures to mitigate the segregation potential based on experiences which, however, can only reduce the risk to a certain extent. In this research, the authors aim to contribute to the discussion in a rational non-empirical way, by using novel experimental and numerical techniques. A case study is carried out to investigate the vibration-induced segregation in asphalt mixtures, corresponding to the circumstance arising during material transportation to the construction site. A novel experimental test is conducted for evaluating the segregation characteristics of asphalt mixtures under vertical vibration in laboratory conditions. A numerical investigation based on discrete element method is further performed to study the phenomenon from a micromechanical point of view. The obtained experimental and numerical results indicate that vibratory loading induces aggregate size segregation in asphalt mixtures, and the degree of segregation is influenced profoundly by the adhesive properties of bituminous binders and the aggregate gradation.
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| 9. |
- Etikan, M. Kaan, et al.
(författare)
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Experimental and numerical analyses of crushing resistance of unbound road materials
- 2024
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Ingår i: The international journal of pavement engineering. - : Taylor & Francis. - 1029-8436 .- 1477-268X. ; 25:1
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Tidskriftsartikel (refereegranskat)abstract
- Aggregate breakage in unbound pavement layers can lead to pavement distresses that affect their functionality and service life. Thus understanding the mechanics and clarifying the factors affecting materials breakage resistance are important for ensuring adequate performance of these layers. In this study, aggregate breakage in unbound granular materials (UGM) is investigated experimentally and numerically. Experimentally, aggregate breakage under uniaxial compression is examined for two UGMs prepared with the same aggregate type but different gradations. To capture the experimentally observed influence of gradation and load magnitude on aggregate breakage, a Discrete Element Method (DEM) model was developed, based on granular mechanics particle contact and failure laws. A simple procedure to identify the contact and failure law parameters from experiments is proposed. With those parameters, the model’s capability of capturing the effect of gradation and loading on the aggregate breakage in UGM is evaluated. Based on comparison with experimental findings, it is shown that the model can capture macro-scale properties of UGM, such as its deformation response under uniaxial compression, as well as the amount of aggregate breakage in the material.
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| 10. |
- Fadil, Hassan, et al.
(författare)
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A spherical indentation test for quasi-non-destructive characterisation of asphalt concrete
- 2024
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Ingår i: Materials and Structures. - : Springer. - 1359-5997 .- 1871-6873.
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Tidskriftsartikel (refereegranskat)abstract
- The indentation test is a promising technique for the viscoelastic characterisation of asphalt concrete (AC). Indentation measurements are primarily influenced by the material properties in the direct vicinity of the indenter-specimen contact point. Accordingly, it may become a useful alternative for the characterisation of thin asphalt layers as well as for a quasi-non-destructive AC characterisation in the field. In this study, the spherical indentation test is used to measure the linear viscoelastic properties of AC mixtures extracted from a road test section. The measured complex moduli are compared to those obtained by the shear box test and are found to exhibit a linear correlation. The measurements are further analysed using the Gaussian mixture model to assign each indentation test to either aggregate-dominated or mastic-dominated response. The measurements attributed to mastic-dominated response are found to be more sensitive to the temperature and AC’s binder properties as compared to the average measurements. Accordingly, the proposed test method may provide a promising tool to measure AC viscoelastic properties and monitor the changes in AC binder phase in a non-destructive manner. A finite element micromechanical model is used to identify a representative scale for the response measured in mastic-dominated tests as well as to quantify the effect of measured properties on the AC damage propensity.
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