| 1. |
- Abed, Ahmed, et al.
(author)
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Uncertainty analysis of life cycle assessment of asphalt surfacings
- 2024
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 25:2, s. 219-238
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Journal article (peer-reviewed)abstract
- The Life Cycle Assessment (LCA) of asphalt pavements are associated with significant uncertainty resulting from variability in the quantity and impact of individual components, the quality of data for each component, and variability of asphalt durability. This study presents a framework to quantify and incorporate the uncertainty of LCA and asphalt durability data into LCA of asphalt surfacings. The suggested framework includes: estimating the uncertainty of asphalt production processes by the pedigree matrix method, conducting a deterministic LCA, applying Monte Carlo Simulation (MCS) to estimate the probability density functions (PDFs) of the considered impacts using the uncertainty data, deterministic solution, and asphalt durability. This framework was applied to six asphalt mixtures; the results show that there is significant uncertainty in the processes that contribute to the environmental impacts. They also showed that considering asphalt durability and its uncertainty is critical and can significantly change the results and interpretation of LCA.
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| 2. |
- Ahmed, Abubeker W., 1981-, et al.
(author)
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Evaluation of a permanent deformation model for asphalt concrete mixtures using extra-large wheel-tracking and heavy vehicle simulator tests
- 2015
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In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 16:1, s. 154-171
-
Journal article (peer-reviewed)abstract
- This paper evaluates a mechanistic–empirical permanent strain model for asphalt concrete mixtures. The evaluation was carried out based on two different types of tests: an extra-large wheel-tracking (ELWT) test and a full-scale accelerated pavement test using a heavy vehicle simulator (HVS). Asphalt slabs from three different types of asphalt mixtures were prepared for the ELWT test and tested at several pavement temperatures and tyre inflation pressures. Lateral wandering was also incorporated.The measured permanent deformations in the asphalt slabs were thereafter modelled using the permanent strain model from the US Mechanistic-Empirical Pavement Design Guide and model parameters were estimated for the three types of mixes. For validation, data from an HVS tested pavement structure consisting of the same asphalt mixtures as those tested using the ELWT were used. A set of calibration factors for the three mixtures were therefore obtained between the two tests. In all cases, the calibration factors were within ±20% from unity. Differences in geometry, scale, wheel loading configuration as well as the speed of loading between the two test devices could be the possible reasons for the differences in observed calibration factors.
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| 3. |
- Ahmed, Abubeker W., et al.
(author)
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Evaluation of permanent deformation models for unbound granular materials using accelerated pavement tests
- 2013
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In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 14:1, s. 178-195
-
Journal article (peer-reviewed)abstract
- Mechanistic-empirical (M-E) pavement design methods have become the focus of modern pavement design procedure. One of the main distresses that M-E design methods attempt to control is permanent deformation (rutting). The objective of this paper is to evaluate three M-E permanent deformation models for unbound granular materials, one from the US M-E pavement design guide and two other relatively new models. Two series of heavy vehicle simulator (HVS) tests with three different types of base material were used for this purpose. The permanent deformation, wheel loading, pavement temperature, and other material properties were continuously controlled during the HVS tests. Asphalt concrete layers were considered as linear elastic where stress-dependent behaviour of unbound materials was considered when computing responses for the M-E permanent deformation models with a nonlinear elastic response model. Traffic wandering was also accounted for in modelling the traffic by assuming it was normally distributed and a time-hardening approach was applied to add together the permanent deformation contributions from different stress levels. The measured and predicted permanent deformations are in general in good agreement with only small discrepancies between the models. Model parameters were also estimated for three different types of material.
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| 4. |
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| 5. |
- Arraigada, M, et al.
(author)
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Determination of Road Deflections from Traffic Induced Accelerations
- 2007
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In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 8:3, s. 399-421
-
Journal article (peer-reviewed)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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| 6. |
- Bagampadde, Umaru, et al.
(author)
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Classical and contemporary aspects of stripping in bituminous mixtures
- 2004
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In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 5:1, s. 7-45
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Journal article (peer-reviewed)abstract
- Stripping or removal of bitumen from an aggregate because of water penetrating into the interface causes many pavements to fail. Stripping has been existent since the advent of paving technology. It causes functional weakening of pavements leading to costly repairs. This state-of-the-art paper deals with important concepts of stripping as, bitumen chemistry and rheology, aggregate properties (chemical and mineralogical composition, surface texture, morphology, porosity, etc), traffic, water properties, construction practices (mixing, placement and in-service drainage) and nature of antistripping additives. Adhesion of bitumen onto aggregate is explained based on theories like mechanistic tenacity, molecular orientation, chemical reaction, and thermodynamic balance of interfacial forces. Stripping is elucidated using several mechanisms namely, displacement, detachment, spontaneous emulsification, bitumen film rupture, water pore pressure, hydraulic scouring, chemical disbanding, microbial activity, osmosis; and blistering and pitting. Attendant theories to the mechanisms are explained. Moisture sensitivity test methods emerged are described and discussed. The large number of tests that have evolved shows the importance of the phenomenon of stripping. Remedial measures which include use of antistripping additives, careful selection of hot mix component materials, good construction practice, and others have been proposed for use in practice.
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| 7. |
- Balieu, Romain, et al.
(author)
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Life Cycle Sustainability Assessment of Electrified Road Systems
- 2019
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In: ROAD MATERIALS AND PAVEMENT DESIGN. - Abingdon, UK : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 20:sup1, s. S19-S33
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Journal article (peer-reviewed)abstract
- The widespread use of Electric Vehicles (EVs) has been one of the main directionsfor pursuing a sustainable future of road transport in which, the deployment ofthe associated charging infrastructures, static or dynamic, has been included as oneof the main cornerstones for its success. Different electrified road (eRoad) systemswhich allow for dynamic charging of EVs by transferring electrical power from theroad to the vehicle in-motion, either in a conductive or contactless way, are underactive investigation. One of the important tasks in feasibility analysis of suchinfrastructure is to quantitatively assess its environmental performance and, thus,the consequential influences to the sustainability of road electrification as a whole.Having this concern in mind, in this study, a systematic LCA study is carried out in which the environmental impacts from the different life cycle stages have beencalculated and compared among several promising eRoad systems. In a next step,suitable strategies can be accordingly made to minimize these impacts in a most effectiveway; and more importantly, the LCA results of this study can serve as one ofthe important bases for conducting a more comprehensive and objective evaluationof the potential environmental benefits EVs could bring.
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| 8. |
- Biligiri, Krishna Prapoorna, et al.
(author)
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Confined E * testing on poroelastic road surface mixtures
- 2012
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 13:2, s. 385-395
-
Journal article (peer-reviewed)abstract
- In Europe, poroelastic road surface (PERS) material is being tested to a level at which it can be applied on different types of roads as a noise-reducing pavement. Traffic noise reductions of around 10–12 dB have been achieved using PERS in comparison to a conventional dense asphalt concrete. The PERS material is designed as an open-graded mix to have at least 20% air voids by volume.The objective of this research study was to evaluate the effect of six different confinement levels on the E * dynamic modulus testing of PERS mixtures. The major aim of utilising confinement on PERS materials was specifically to simulate and assess field performance characteristics of those mixes in the laboratory. Furthermore, the choice for confinement is essential in order to obtain realistic test results for a porous or open-graded aggregate structure of the PERS mix. AASHTO TP 62-07 was utilised for dynamic modulus E * testing; for confined tests, a lateral air pressure was provided that simulated confining effect on the samples. Confined tests were conducted only on the two variants of the PERS mixtures that had about 50% or greater amount of aggregates by volume of the mix. Moduli (E *) and phase angle (φ) master curves were established using the test results.
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| 9. |
- Birgisson, Björn, et al.
(author)
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A new algorithm for determination of crack growth path in HMA materials
- 2007
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In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 8:1, s. 47-60
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Journal article (peer-reviewed)abstract
- In this paper, a new algorithm is presented for determination of the crack growth path in hot mix asphalt (HMA) materials. In a newly developed fracture simulator, the pavement structure is modeled with a viscoelastic boundary element method, which provides an attractive alternative to finite element-based methods for modeling crack initiation and growth. According to the HMA fracture mechanics, a fundamental energy-based threshold is used to determine crack growth and the direction of crack growth, and viscoelastic mixture properties are used to determine the rate of crack growth. To determine where a crack propagates, a grid in the critical zone is defined to cover a range of possible crack growth directions and locate the direction of the maximum dissipated creep strain energy (DCSE). The crack will propagate in the direction of the maximum DCSE when the DCSE in this direction reaches the damage threshold. The fracture simulator is shown to predict top-down crack growth patterns in hot mix asphalt pavements observed in the field.
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| 10. |
- Birgisson, Björn, et al.
(author)
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A viscoelastic displacement discontinuity method for analysis of pavements with cracks
- 2006
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In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 7:4, s. 417-455
-
Journal article (peer-reviewed)abstract
- This paper presents a development of the displacement discontinuity boundary element method for modeling the linear viscoelastic behavior of asphalt mixtures and simulating crack propagation in asphalt pavements. The viscoelastic formulation is based on the correspondence principle, involving Laplace transformation of the constitutive equations and the associated boundary conditions. The time-dependent behavior of the asphalt mixtures is characterized by the Burger's or power law model. The associated transformed problem is solved in an analogous way to using the linear-elasticity-based displacement discontinuity method. The corresponding time-dependent viscoelastic solution is obtained using an efficient and robust algorithm for numerical Laplace inversion. A substructuring approach is employed to construct the layered formulation and higher order elements are used to capture the bending effect in the pavement structure. With incorporation of the hot mix asphalt (HMA) fracture mechanics, which is based on the concept that there is a dissipated creep strain energy (DCSE) threshold to cracking, the numerical framework can efficiently simulate crack onset and growth in asphalt pavements. Several examples are presented to verify the accuracy and efficiency of the numerical method and to demonstrate its application in modeling pavement cracking.
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| 11. |
- Birgisson, Björn, et al.
(author)
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Influence of Mixture Properties on Fracture Mechanisms in Asphalt Mixtures
- 2010
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In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 11, s. 61-88
-
Journal article (peer-reviewed)abstract
- This paper reports a research study aimed at providing insight into key mechanisms and mixture properties that influence fracture in asphalt concrete. The experimental analysis was based on the Hot Mix Asphalt (HMA) Fracture Mechanics visco-elastic crack growth law. HMA cracking mechanism was investigated using multiple laboratory test configurations on both unmodified and polymer modified mixtures. A Digital Image Correlation (DIC) was employed to more accurately capture localized or non-uniform stress distributions in asphalt mixtures and as a tool for detecting first fracture. Crack initiation and crack growth were predicted effectively using a Displacement Discontinuity (DD) boundary element method.
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| 12. |
- Birgisson, Björn, et al.
(author)
-
Numerical implementation of a strain energy-based fracture model for HMA materials
- 2007
-
In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 8:1, s. 7-45
-
Journal article (peer-reviewed)abstract
- This work combines a new strain energy-based fracture criterion with a viscoelastic displacement discontinuity boundary element method to investigate crack growth in hot mix asphalt (HMA) materials. The study employs a fundamental crack growth threshold and simulates crack growth by accumulation of the dissipated creep strain energy (DCSE) below this threshold, only healable micro-damage develops, and non-healable crack initiation or growth occurs, otherwise. A critical zone is introduced ahead of the crack tip to represent the portion of the material being damaged. Once the cumulative micro-damage inside the critical zone reaches the cracking threshold, the crack extends by the length of the critical zone. An HMA fracture simulator is developed by incorporating the DCSE threshold concept into a numerical framework based on a viscoelastic displacement discontinuity method, which has proven its convenience and efficiency in crack modeling. Numerical analyses are performed to predict piecewise crack propagation in asphalt mixtures using the HMA fracture simulator, and laboratory experiments are also conducted to verify and validate the numerical model.
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| 13. |
- Bjurström, Henrik, et al.
(author)
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Non-contact rolling surface wave measurements on asphalt concrete
-
In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402.
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Journal article (other academic/artistic)abstract
- Rolling surface wave measurements on a single, thin asphalt concrete (AC) layer arepresented to investigate their use in rapid nondestructive field tests. An array of 47 micro-electromechanicalsensor (MEMS) microphones is mounted on a trailer together with an automated impactsource. Multichannel recordings from single impacts are obtained at 80 equally spaced positions as thetrailer moves at a constant speed. The complete battery-powered data acquisition system enables largescaletesting of newly built pavements. Multiple sets of test results show good repeatability for theassessed shear wave velocity and demonstrate the strong temperature dependency of AC. The presentedresults indicate a possible application for quality assurance of AC using rolling surface wavemeasurements.
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| 14. |
- Bjurström, Henrik, 1983-, et al.
(author)
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Non-contact rolling surface wave measurements on asphalt concrete
- 2019
-
In: International Journal on Road Materials and Pavement Design. - : TAYLOR & FRANCIS LTD. - 1468-0629 .- 2164-7402. ; 20:2, s. 334-346
-
Journal article (peer-reviewed)abstract
- Rolling surface wave measurements on a single, thin asphalt concrete (AC) layer are presented to investigate their use in rapid nondestructive field tests. An array of 47 micro-electro-mechanical sensor (MEMS) microphones is mounted on a trailer together with an automated impact source. Multichannel recordings from single impacts are obtained at 80 equally spaced array positions as the trailer moves at a constant speed. The complete battery-powered data acquisition system enables large-scale testing of newly built pavements. Multiple sets of test results show good repeatability for the assessed shear wave velocity and demonstrate the strong temperature dependency of AC. The presented results indicate a possible application for quality assurance of AC using rolling surface wave measurements.
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| 15. |
- Chen, Feng, et al.
(author)
-
A study on dielectric response of bitumen in the low-frequency range
- 2015
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 16, s. 153-169
-
Journal article (peer-reviewed)abstract
- From the current state of literature, the dielectric property of bitumen has not been understood extensively, nor its relation with other properties such as polarity and rheology. In this study, dielectric spectroscopy measurement in a low-frequency range (10−2–106 Hz) was performed on both pure bitumen in different grades and wax-modified bitumen (WMB). From the performed tests we found the following: (i) the dielectric response of base bitumen is strongly temperature and frequency dependent, which is also highly linked to the rheology of the system. (ii) No remarkable differences in the dielectric constant (Formula presented.) among different grades of bitumen from the same crude oil source can be seen. (iii) Regular changes of dielectric loss tangent (tan δ) among the different grades of bitumen can be observed, which can be a good indicator for the linkage between the dielectric and rheological responses. In addition, it can also be perceived that the dielectric spectroscopy may have the potential to become a new approach for the multi-scale characterisation of road infrastructure materials.
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| 16. |
- Chen, Feng, 1987-, et al.
(author)
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Experimental and numerical analysis of asphalt flow in a slump test
- 2019
-
In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 20, s. S446-S461
-
Journal article (peer-reviewed)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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| 17. |
- Das, Prabir Kumar, et al.
(author)
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Atomic force microscopy to investigate asphalt binders : a state-of-the-art review
- 2016
-
In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 17:3, s. 693-718
-
Journal article (peer-reviewed)abstract
- Atomic force microscopy (AFM) is a non-destructive imaging tool, which is capable of qualitative and quantitative surface analysis with sub-nanometer resolution. Simultaneously with the topology at the micro-scale, AFM is capable of acquiring micro-mechanical information such as relative stiffness/Young's modulus, stickiness/adhesion, hardness, energy loss and sample deformation quantitatively. This paper presents an extensive review on the applications of AFM to investigate different physiochemical properties and performances of asphalt binder. AFM techniques and principles, different sample preparation techniques and its effect on observed micro-structures, chemical origin, surface or bulk phenomenon and temperature sensitivity of these micro-structures are also discussed in this paper. All of the studies conducted on this topic clearly indicated that AFM can successfully be utilised as a tool to better understand how the surface morphology and its physicochemical properties are interlinked and related to the binder performances.
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| 18. |
- Das, Prabir Kumar, et al.
(author)
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Coupling of oxidative ageing and moisture damage in asphalt mixtures
- 2015
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 16, s. 265-279
-
Journal article (peer-reviewed)abstract
- In this paper, a possible way to capture the combined effect of oxidative ageing and moisture damage on mixture performance has been proposed. The formulations that are needed for finite element (FE) modelling of oxygen and moisture diffusion process have been established. The proposed model should be able to link the in-time changes to the mastic as function of mixture morphology, ageing propensity and the moisture diffusion properties to the physical properties of the asphalt mixture due to the loss of adhesive and/or cohesive bonding. Such an FE model can help find the trends and relationships that can assist in the development of predictive pavement performance model. Also, from this, one can figure out the key parameters that are mainly responsible for ageing-moisture-induced premature damage of asphalt pavements.
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| 19. |
- Das, Prabir Kumar, et al.
(author)
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Evaluation of fracture and moisture damage performance of wax modified asphalt mixtures
- 2012
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 13:1, s. 142-155
-
Journal article (peer-reviewed)abstract
- In this study the fracture and moisture damage characteristics of wax modified asphalt mixtures were evaluated. Two types of commercial waxes (FT-paraffin and Asphaltan B) were added to bitumen of penetration grade 70/100. Using this wax modified and unmodified bitumen; total 48 specimens were produced from two sources of aggregates and two levels of gradation. Bitumen properties were determined by conventional test methods, Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) testing. Thermal Stress Restrained Specimen Test (TSRST) was used to evaluate low temperature cracking resistance and cracking behavior of asphalt mixture was investigated at 0 degrees C using Superpave Indirect Tensile Test (IDT). The influence of wax on the asphalt mixture resistance to cracking and moisture damage performance has been evaluated using Hot Mix Asphalt (HMA) fracture mechanics and Superpave IDT test results. The addition of FT-paraffin and Asphaltan B showed better cracking and moisture damage resistance of the asphalt mixture compared to unmodified mixture, but FT-paraffin showed the largest effect on cracking resistance while Asphaltan B showed highest resistance to moisture damage. In BBR test results, mixtures modified with FT-paraffin showed lower limit m value (LmT) which implies minor negative effect in stress relaxation. However, according to TSRST results, the mixtures with both waxes had nearly same fracture temperature as mixture with unmodified bitumen.
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| 20. |
- Das, Prabir Kumar, et al.
(author)
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Micromechanical investigation ofphase separation in bitumen bycombining atomic force microscopywith differential scanning calorimetryresults
- 2013
-
In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 14:S1, s. 25-37
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Journal article (peer-reviewed)abstract
- The thermo-rheological behaviour of bitumen depends largely on its chemical structure and intermolecular microstructures. Bitumen is a complex mixture of organic molecules of different sizes and polarities for which the micro-structural knowledge is still rather incomplete. Knowledge at that level can have great implications for behaviour at a larger scale and will help to optimise the bitumen in its production stage. The present study is focused on understanding the fundamental mechanisms behind the micro-structural phase appearance and the speed or mobility at which they change. To do so, atomic force microscopy was utilised at different temperatures to investigate the phase separation behaviour for four different types of bitumen and co-relate it with the differential scanning calorimetry measurements. Based on the experimental evidences, it was found that the observed phase separation is mainly due to the wax/paraffin fraction presence in bitumen and that the investigated bitumen behaves quite differently. Recommendations are made to continue this research into qualitative information to be used on the asphalt mix design level.
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| 21. |
- Dinegdae, Yared, 1981-, et al.
(author)
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Evaluation of ERAPave PP permanent deformation models using APT
- 2023
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402.
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Journal article (peer-reviewed)abstract
- Permanent deformation is one of the failure modes considered in the analysis and design of flexible pavements. ERAPave performance prediction (PP) which is a mechanistic empirical (ME) pavement design tool utilises two distinct models for the prediction of permanent deformation in the bound and unbound granular layers including subgrade. This paper aims to calibrate these models using pavement response and performance data from accelerated pavement testing (APT) structures. Material properties such as layer modulus were established through an optimisation that involves both falling weight deflectometer (FWD) and pavement response measurements. Based on the predicted performance results, a separate set of calibration was performed for permanent deformation development in moist and wet moisture conditions. The calibrated models have resulted in predictions that are in good agreement with observed performances. Furthermore, the model parameters successfully captured the initial densification behaviour and the associated sensitivity with axle load level.
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| 22. |
- Dinegdae, Yared H., et al.
(author)
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Effects of truck traffic on top-down fatigue cracking performance of flexible pavements using a new mechanics-based analysis framework
- 2018
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 19:1, s. 182-200
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Journal article (peer-reviewed)abstract
- The mechanics-based analysis framework predicts top-down fatigue cracking initiation timein asphalt concrete pavements by utilising fracture mechanics and mixture morphology-basedproperty. To reduce the level of complexity involved, traffic data were characterised and incorporatedinto the framework using the equivalent single axle load (ESAL) approach. There isa concern that this kind of simplistic traffic characterisation might result in erroneous performancepredictions and pavement structural designs. This paper integrates axle load spectraand other traffic characterisation parameters into the mechanics-based analysis framework andstudies the impact these traffic characterisation parameters have on predicted fatigue crackingperformance. The traffic characterisation inputs studied are traffic growth rate, axle load spectra,lateral wheel wander and volume adjustment factors. For this purpose, a traffic integrationapproach which incorporates Monte Carlo simulation and representative traffic characterisationinputs was developed. The significance of these traffic characterisation parameters wasestablished by evaluating a number of field pavement sections. It is evident from the resultsthat all the traffic characterisation parameters except truck wheel wander have been observedto have significant influence on predicted top-down fatigue cracking performance.
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| 23. |
- Dinegdae, Yared H., et al.
(author)
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Mechanics-based Topdown Fatigue Cracking Initiation Prediction Framework for Asphaltic Pavements
- 2015
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 16:4
-
Journal article (peer-reviewed)abstract
- In this paper, a new mechanics-based top-down fatigue cracking analysis framework is presented for asphalt pavements. A new mixture morphology-based set of material sub-models is presented for characterising key mixture properties and their change over time. Predicting the load induced top-down fatigue crack initiation (CI) time by utilising comprehensive mixture properties creates the possibility of optimising the mixture morphology while taking into account its subsequent effect on long-term pavement performance. The new framework was calibrated and subsequently validated against a number of field pavement sections with varying traffic levels that are representative for current practices and which have a wide range in material properties. The framework accounts the change in key mixture properties due to ageing and mixture-healing effect on damage accumulation while determining the overall effect of design inputs on cracking performance. Model calibration and validation were achieved based on the healing potential of the asphalt mixture. It was found out that the CI predictions for all the sections are in general agreement with the observed performance in the field, thus giving credibility for the framework.
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| 24. |
- Dinegdae, Yared Hailegiorgis, et al.
(author)
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Reliability-based calibration for a mechanics-based fatigue cracking design procedure
- 2016
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In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 17:3, s. 529-546
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Journal article (other academic/artistic)abstract
- This paper presents a new reliability-based code calibration in load resistance factor design (LRFD) format for the mechanics-based fatigue cracking analysis framework. The pavement design procedure incorporates an appropriate failure criterion and design period. Moreover, it provides uniform performance at the desired level of reliability while considering the inherent variabilities and uncertainties involved. A number of field pavement sections with well documented performance histories and high quality field and laboratory data were used for this purpose. Moreover, a reliability computation methodology that incorporates a central composite design (CCD) response surface approach (RS) is proposed. Appropriate statistical characterization of the dominant design parameters was performed considering its key role in reliability analysis. A first order reliability method (FORM) was used to compute pavement performance reliability and to establish the partial safety factors of the design procedure. Illustrative examples based on the developed LRFD procedure have demonstrated clearly its capacity of delivering designs with uniform reliability.
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| 25. |
- Edvardsson, Karin, et al.
(author)
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Gravel Roads and Dust Suppression
- 2009
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In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 10:3, s. 439-469
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Journal article (peer-reviewed)abstract
- This review paper deals with the field of dust generation on gravel roads, dust suppressant performance and evaluation techniques. By applying the proper dust suppressant, matching the gravel road condition specific to the site, dust emission can be reduced, thereby providing a healthier ambient air environment, increasing road safety and ride comfort while reducing the need and cost of vehicle repair, road maintenance activities, and aggregate replacement. By applying the proper application rate of the dust suppressant, the cost of annual dust control as well as the environmental impact can be significantly reduced. Suitable measuring techniques for evaluating dust suppressant efficiency will facilitate the choice of the most appropriate dust suppressant and its optimal application rate.
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| 26. |
- Edvardsson, Karin, et al.
(author)
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Methods for Quantification of Lignosulphonate and Chloride in Gravel Wearing Courses
- 2010
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In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 11:1, s. 171-185
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Journal article (peer-reviewed)abstract
- Due to oxidation, breakdown, and leaching, dust suppressants will be lost from the gravel road surface. Methods for residual dust suppressant concentration supervision are a valuable tool for estimating life-length and optimal application rates, and, hence, efficiency of different products. The objective of this study was to identify methods for quantitative analyses of lignosulphonate and chloride, develop and adapt the methods for application on a gravel matrix, and validate the methods using samples collected in-situ. Results strongly suggest that the reliability and repeatability of the developed methods (23% for lignosulphonate and 30% for chloride, respectively) are acceptable for determination of relative variations in residual concentrations of dust suppressed gravel wearing courses.
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| 27. |
- Edwards, Ylva
(author)
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Influence of Waxes on Bitumen and Asphalt Concrete Mixture Performance
- 2009
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In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 10:2, s. 313-335
-
Journal article (peer-reviewed)abstract
- This paper deals with scientific work carried out to study the influence of different kinds of wax on bitumen and asphalt concrete mixture properties. Experimental parts involve base bitumens from different sources, isolated bitumen waxes and commercial waxes. Asphalt concrete slabs, containing base or wax modified bitumen were prepared and tested. Binder properties were evaluated using different types of laboratory equipment, such as dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimeter (DSC), as well as equipment for determining more conventional parameters. Asphalt concrete properties were evaluated at low temperatures using the tensile strain restrained specimen test (TSRST) and creep test at -25 degrees C At higher temperatures, dynamic creep testing was performed at 40 degrees C, and complex modulus tests between 0 and 20 degrees C Binder test results indicated that the magnitude and type of effect on bitumen rheology depend on the bitumen itself hype of crystallizing fraction in the bitumen and for type and amount of additive used. Adding polyethylene wax, showed no or positive effects on the rheological behaviour at low temperatures (decrease in stiffness) as well as medium and high temperatures (increase in complex modulus and decrease in phase angle). However, the corresponding positive effects could not be shown in dynamic creep testing (at 40 degrees C) of asphalt concrete mixtures containing these modified binders. Adding FT-paraffin decreased the physical hardening index (obtained using BBR) for all bitumens. Also polyethylene war and montan wax showed this effect for some bitumens. Slack wax showed a large increasing effect on physical hardening. No correlation between physical hardening index (PHI) and wax content by DSC was found in this study. Addition of commercial waxes used showed no or marginally positive influence on bitumen ageing properties for bitumens and test conditions used. Asphalt mixture test results were compared to the corresponding binder test results, and found to be less evident. Significant physical hardening by BBR could not be confirmed by TSRST.
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| 28. |
- Edwards, Ylva, et al.
(author)
-
Wax in bitumen : Part 1: Classifications and General Aspects
- 2005
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 6:3, s. 281-309
-
Journal article (peer-reviewed)abstract
- Wax in bitumen has for a long time been of great interest, particularly regarding effects on bitumen quality and methods for determining wax content. Opinions about wax in bitumen have varied over the years and sometimes been contradictory. The findings of a literature study are presented in two companion papers. The main intention of the study was to give an extensive description ofthe field of knowledge concerning wax in bitumen. In this paper, classifications and general aspects on effects of wax in crude oil and bitumen are described. Theories behind possible mechanisms are also discussed, and commercial wax as additive to bitumen for different purposes described. Effects of wax are influenced by chemical composition and rheological properties of the bitumen, amount of wax in the bitumen as well as chemical composition and crystalline structure of the wax. The effect of wax on bitumen is linked to its crystallinity and melting properties. The temperature range of application as well as the definition of wax in bitumen is also of great importance. The presence of large wax crystals (macrocrystalline wax) in bitumen is considered to be most problematic. However, waxes in bitumen generally are microcrystalline and/or amorphous and can contain branched, alicyclic and aromatic components with heteroatoms, which renders crystallization considerably more difficult.
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| 29. |
- Edwards, Ylva, et al.
(author)
-
Wax in bitumen : Part II: Characterization and Effects
- 2005
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 6:4, s. 439-468
-
Journal article (peer-reviewed)abstract
- A large number of different methods for isolating and characterizing wax in bitumen, as well as for determination of wax content, have been used over the years. The methods used for determining wax content all give different results for one and the same bitumen, which has caused problems for many years. Through different types of phase transition, wax in bitumen influences bitumen properties to a larger or minor extent. In some cases, such an influence may give rise to negative effects like increased sensitivity to cracking or plastic deformation in asphalt concrete pavements. In other cases, wax may even show positive effects on bitumen, such as increased stiffness at higher temperatures, leading to improved resistance to rutting. This paper is the second of two companion papers discussing the field of knowledge concerning wax in bitumen. In the first paper, classifications and general aspects on effects of wax in crude oil and bitumen are described.
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| 30. |
- Ekblad, Jonas, et al.
(author)
-
Causes of rutting in flexible and semi-rigid test sections after 14 years of service
- 2018
-
In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 19:4, s. 878-897
-
Journal article (peer-reviewed)abstract
- Rutting is a major distress and is commonly targeted in design-build contracts as a key requirement, but at the same time, contemporary design methods usually provide scarce information on evolution in absolute terms. The objective of this paper is to investigate and analyse rutting results from a large full-scale road test. The analyses concerned magnitudes and the causes of rutting with a main focus on flexible and semi-rigid structures: one Reference, one high-performance asphalt (HPA) and one asphalt on a lean concrete (LC) base. Field measurements and sampling for the current study comprised acquiring transversal profiles and coring pavement samples. The results suggest that for the HPA and the LC base pavements, rutting is mainly caused by studded tyre wear and densification of the asphalt layers. For the conventional reference pavement additional rutting, most likely in the lower layers, was noted.
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| 31. |
- Ekblad, Jonas, et al.
(author)
-
Influence of water on resilient properties of coarse granular materials
- 2006
-
In: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 7:3, s. 369-404
-
Journal article (peer-reviewed)abstract
- The objective of this work was to investigate influence of water on resilient properties of a coarse (maximum particle size 90 mm) granular material using various gradings. Triaxial testing, using large-size samples (diameter 500 mm and height 1000 mm) and constant confining pressures, was performed at varying water content up to practically full saturation. Time Domain Reflectometry (TDR) was used to monitor transient in-sample water contents. Evaluation comprised resilient modulus and Poisson ratio in terms of total stresses, although the results were also discussed in the context of effective stresses. The coarsest grading experienced only a small reduction in resilient modulus when brought close to saturation, while specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared that, as water content increased, the specimens became more dilative (increase in Poisson ratio).
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| 32. |
- Erlingsson, Sigurdur, et al.
(author)
-
Fast layered elastic response program for the analysis of flexible pavement structures
- 2013
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 14:1, s. 196-210
-
Journal article (peer-reviewed)abstract
- One of the key components in analysing pavement structural behaviour is the response model which is used to estimate the stresses, strains and displacements of the pavement structure subjected to the existing traffic, taking into account the material properties and prevailing environmental conditions. Multilayer elastic theory (MLET) is often preferred over other methods such as the finite element method, due to its computational performance for repeated applications. A new elastic response analysis program has been developed based on the Burmister MLET theory to calculate the response of flexible pavement structures. In the development of the program, the time-consuming part of MLET processes was optimised. To improve the convergence and accuracy of responses in the vicinity of the surface of the top layer, an approach based on Richardson's extrapolation was employed. Moreover, an iterative approach to model stress dependency of unbound granular materials was incorporated. A comprehensive comparison of the program with two frequently used programs demonstrated an excellent agreement and improved performance.
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| 33. |
- Erlingsson, Sigurdur
(author)
-
Impact of Water on the Response and Performance of a Pavement Structure in an Accelerated Test
- 2010
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 11:4, s. 863-880
-
Journal article (peer-reviewed)abstract
- An accelerated load test using a Heavy Vehicle Simulator (HVS) was performed with the objective of investigating the response behaviour and performance of a commonly used pavement structure in Sweden. The structure consists of 10 cm asphalt bound layers, divided into surface course and bitumen base, over granular base and subbase resting on sandy subgrade. The structure was instrumented to register stresses, strains and deflections during loading.In the test more than 1,000,000 load cycles were applied. After applying the first 500,000 load cycles the water table was raised and a further 500,000 loading cycles were applied. Raising the groundwater table increased the rate of rutting developed in the structure in all unbound layers. A numerical analysis has been carried out to simulate the results.First the response was simulated to get a general overall agreement of the pavement response and the parameters of the model. Thereafter the permanent deformation behaviour in the main test was simulated using a simple three-parameter work hardening model with two sets of parameters for the unbound layers, before and after the groundwater table was raised. The permanent deformation behaviour of all layers was thereafter modelled separately for the two steps.Generally good agreement was established between the permanent deformation measurements and the calculations for all layers.
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| 34. |
- Erlingsson, Sigurdur
(author)
-
Numerical Modelling of Thin Pavements Behaviour in Accelerated HVS Tests
- 2007
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 8:4, s. 719-744
-
Journal article (peer-reviewed)abstract
- Two thin road structures have been tested in accelerated testing by using a Heavy Vehicle Simulator (HVS). Both were surface dressed structures, one with a target 20 cm thick unbound base course layer and the other with the base divided into a 10 cm bitumen stabilized base over 10 cm unbound base. The tested road structures were instrumented to estimate deflections, strains and stresses in various locations inside the structure.Numerical analyses, by using two different techniques, the multilayer elastic theory (MLET) and the finite element (FE) have been carried out to simulate the response behaviour of the tested structure and compared with the actual measurements. For both techniques linear and nonlinear behaviour of the base was assumed. For the FE method both 2D axisymmetric and a 3D analysis were carried out. The results have further been used to model the permanent deformation development in each layer. The main finding of the study was that induced vertical stresses were generally well predicted in both structures. Better agreement was generally found between the vertical stresses and the actual response with the non-linear response, especially for high loading conditions.The best prediction of surface deflections was obtained in a three dimensional linear elastic analysis where a rectangular loading area was used instead of a circular one in the two dimensional axisymmetric solutions. Generally, poor or moderate agreement was found between the strain measurements and the numerical estimations. The simple work hardening model used to model the accumulated deformation relied on results from repeated load triaxial test results and gave generally good agreement with the results from the testing.
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| 35. |
- Erlingsson, Sigurdur
(author)
-
On Forecasting the Resilient Modulus from the CBR Value of Granular Bases
- 2007
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 8:4, s. 783-797
-
Journal article (peer-reviewed)abstract
- The unbound granular materials (UGM), base and subbase layers, play an essential role in the overall structural performance of thin pavement structures. They show complex stress dependent elasto-plastic behaviour under external loading. Therefore the UGM are commonly tested using the Repeated Load Triaxial (RLT) testing method to estimate the stiffness of the material by applying haversine loading pulses.The RLT testing method represents the actual stress situation quite adequately and gives satisfactorily estimates of the stiffness characteristics of UGM. A simple test that has been used for a long time in structural design of flexible pavements is the CBR (California Bearing Ratio) test. In the CBR test, the load-deformation curve is acquired while a plunger is penetrated into the material at a constant rate. In the literature one can find a number of relationships for UGM where the CBR value is used to predict the stiffness. These connections usually do not take into account that stiffness of UGM is both stress and moisture dependent.To investigate if a relationship between the two tests exists, twenty materials have been tested with both methods and the test results compared. The materials were of varying quality and were tested at four different moisture contents. The results indicate that a simple power law can be used to forecast the stiffness if the CBR-value is known.
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| 36. |
- Fadil, Hassan, et al.
(author)
-
Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests
- 2019
-
In: International Journal on Road Materials and Pavement Design. - : TAYLOR & FRANCIS LTD. - 1468-0629 .- 2164-7402.
-
Journal article (peer-reviewed)abstract
- Reliable determination of material properties is a key component for modelling and performance prediction of asphalt pavements. This paper deals with the potential use of instrumented indentation tests for viscoelastic characterisation of asphalt mortar as a new alternative to existing techniques. The main focus lies on the potential of indentation tests for multi-scale measurement of the shear relaxation modulus. A three-dimensional finite element model of a rigid spherical indenter penetrating an asphalt mortar sample is developed and used to model indentation tests performed at different material scales. The asphalt mortar is modelled as an idealised fine aggregate composite with elastic spheres, suspended within a viscoelastic bitumen mastic matrix. Based on the obtained numerical results the scale-dependency of the shear relaxation modulus measured with the indentation test is investigated. It is shown that the measurement scale is effectively controlled by the size of the indenter-specimen contact area, while the effect of indentation depth is minimal. The minimum contact area size required for obtaining representative properties, measured at the mortar scale, is determined. The viscoelastic parameters obtained from the indentation model are compared to those obtained using a representative volume element (RVE) for the asphalt mortar. In this way, the paper provides a new impulse for linking the mortar and asphalt scales in the multiscale modelling of asphalt mixtures. Feasibility of the proposed testing technique is further evaluated experimentally. Viscoelastic indentation tests are performed on asphalt mastics and mortar at two different sizes of contact areas. Experimental results indicate that indentation tests allow reliable characterisation of mortars relaxation modulus on both macro-scale as well as on individual component level.
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| 37. |
- Fadil, Hassan, et al.
(author)
-
Predicting the master curves of bituminous mastics with micromechanical modelling
- 2021
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402.
-
Journal article (peer-reviewed)abstract
- The performance of asphalt mixtures is significantly affected by the viscoelastic properties of their mastic phase. The analytical approaches used to predict the properties of mastics from their constituents’ properties are limited in their accuracy and potential to handle non-linear material behaviour. An alternative micromechanical finite element modelling approach to calculate the master curves of mastics from the binder and filler phase properties is presented, where the representative volume elements of mastics consist of linear-viscoelastic bitumen matrices and elastic spherical filler particles. For validation, shear relaxation moduli of bitumen and bitumen-filler mastics are measured at (Formula presented.) °C (Formula presented.) °C. Additionally, the model is evaluated and compared with the existing analytical solutions. The results indicate that the proposed approach is advantageous as compared to the analytical solutions, as it allows predicting the mastics’ properties over wider temperature, frequency and material ranges at better agreement with the measurements while giving insight into the micromechanical behaviour.
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| 38. |
- Fadil, Hassan, et al.
(author)
-
The viscoelastic characterisation of asphalt mixtures using the indentation test
- 2021
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 22:sup1, s. S411-S424
-
Journal article (peer-reviewed)abstract
- Viscoelastic characterisation of asphalt mixtures is an important component for modelling and performance prediction of flexible pavements. In this study, using spherical indentation testing for measuring the viscoelastic properties of asphalt is explored. Indentation testing may provide an interesting alternative to existing experimental techniques, as it is capable of characterising small material volumes. Thus, it may become a useful tool for the characterisation of thin asphalt layers and for the measurement of binder phase properties in-situ in asphalt mixtures. Spherical indentation tests are performed on two mastic asphalt (MA) mixtures, prepared with different mastic types. The shear relaxation moduli obtained from the indentation tests are compared with the ones measured with seismic and SuperPave Indirect Tensile (IDT) tests. A new statistical analysis methodology is proposed for viscoelastic characterisation of the mastic phase with the indentation tests performed on MA mixtures. The accuracy and sensitivity of the developed method are examined.
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| 39. |
- Fladvad, Marit, et al.
(author)
-
Modelling the response of large-size subbase materials tested under varying moisture conditions in a heavy vehicle simulator
- 2022
-
In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 23:5, s. 1107-1128
-
Journal article (peer-reviewed)abstract
- Pavement design methods must be able to predict the behaviour of pavement materials at increased moisture levels due to climate changes causing increased precipitation and more intense rainfall events. This paper intends to examine the influence of moisture and gradation on pavement response. An instrumented accelerated pavement test (APT) has been conducted on two thin flexible pavement structures with unbound base course and subbase materials using a heavy vehicle simulator (HVS). The two pavement structures were identical except for the gradation of the subbase material, where one had a 0/90 mm curve with a controlled fines content, and the other had an open-graded 22/90 mm curve. The APT was conducted using constant dual-wheel loading, and three different groundwater (GW) levels were induced in order to change the moisture content in the structures. The HVS was stopped regularly for carrying out response measurements from the instrumentation. The analysis is focussed on the response of the unbound aggregate layers to varying moisture levels in the pavement structure. The increased GW level causes a substantial increase in rutting. Conflicting results are found regarding the development of stresses and strains throughout the APT. Two models, linear elastic and non-linear elastic, is employed to model the responses from the pavement structures.
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| 40. |
- Fladvad, Marit, et al.
(author)
-
Permanent deformation modelling of large-size unbound pavement materials tested in a heavy vehicle simulator under different moisture conditions
- 2022
-
In: International Journal on Road Materials and Pavement Design. - : Taylor and Francis Ltd.. - 1468-0629 .- 2164-7402. ; 23:5, s. 1157-1180
-
Journal article (peer-reviewed)abstract
- Climate changes alter the environmental conditions which pavement design is based on, invalidating empirical design methods. Transition to mechanistic design requires the ability to model the behaviour of pavement materials under relevant environmental conditions. An accelerated pavement test (APT) is designed to test two instrumented pavement structures under moisture conditions which are altered by raising the groundwater table (GWT). Open-graded and well-graded subbase materials are used to investigate the effect of gradation on moisture dependency. Pavement response behaviour is modelled using a non-linear elastic (NLE) approach. Accumulation of permanent deformation under different moisture conditions is calculated by two models and compared to measured surface rutting. Moisture transport through the structures differs due to the subbase gradation. Increased GWT accelerates the accumulation of permanent deformations in both structures, identified by both models. One model provides a significantly better fit to the subgrade deformations and the width of the rutting profile.
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| 41. |
- Ghafoori Roozbahany, Ehsan, 1982-, et al.
(author)
-
Fracture testing for the evaluation of asphalt pavement joints
- 2013
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 14:4, s. 764-791
-
Journal article (peer-reviewed)abstract
- Asphalt joints are inevitable parts of every pavement. Although much attention is dedicated to the construction of such joints, reliable tools for assessing the mechanical properties of joints for design and performance assessment are still scarce. This is particularly true for cold joints when attaching a new hot pavement to a cold existing pavement as in the case of large patches for pavement repair. This paper intends to evaluate different new or modified static fracture testing methods for ranking existing joint construction techniques. Some of these testing methods, such as indirect tensile test, direct tensile test and 4-point bending test are familiar in the field of asphalt pavement characterisation, but have scarcely been used for assessing the quality of joints so far. These three test types were adopted and evaluated for joints and the test results were analysed with finite element (FE) software ABAQUS. Different joints for testing were prepared in the laboratory using a special specimen construction procedure. The results suggest that joints with inclined interfaces seem to show more promising behaviour than vertical joints. It was confirmed that starting compaction from the hot side of the joint generally produces better results than compaction starting from the cold side of the joint. Pre-heating of the joint surface and using a bond sealant appears to provide the best results.
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| 42. |
- Ghafoori Roozbahany, Ehsan, 1982-, et al.
(author)
-
Introducing a new method for studying the field compaction
- 2017
-
In: International Journal on Road Materials and Pavement Design. - : TAYLOR & FRANCIS LTD. - 1468-0629 .- 2164-7402. ; 18, s. 26-38
-
Journal article (peer-reviewed)abstract
- The flow of particles during compaction may have a prominent influence on the difference of field and laboratory results as recently demonstrated by the authors with their newly developed compaction flow test (CFT). This test with a simple compaction simulator was used for studying the flow behaviour and rearrangement of particles for mixtures with different structures and thicknesses. However, validating the CFT results for practical purposes requires field measurements that provide more insight into the compaction process and eventually allowing to adjust the CFT for further use as an evaluating in-site tool. This study presents a new method for conducting such measurements during field compaction. In this method, some representative particles are tracked inside asphalt specimens and the accuracy of the results is examined by X-ray computed tomography. The results of the feasibility tests show that this method has potential for further use in the field and for building up a comprehensive basis of knowledge on field compaction towards closing the gap between the field and laboratory results.
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| 43. |
- Ghafoori Roozbahany, Ehsan, 1982-, et al.
(author)
-
Investigation of asphalt joint compaction using discrete element simulation
- 2019
-
In: International Journal on Road Materials and Pavement Design. - : TAYLOR & FRANCIS LTD. - 1468-0629 .- 2164-7402.
-
Journal article (peer-reviewed)abstract
- Constructing high quality asphalt joints plays a vital role in preventing premature failures of pavements. Previous studies suggested that many construction parameters directly and indirectly influence the quality of asphalt joints. Due to uncertainties about the influence of each parameter on the quality of the finalised joints, closer and more detailed studies are still needed for achieving further improvements in this field. This study investigates the possible impacts of thickness, bottom layer roughness, joint interface geometries and compaction techniques on the particle flow of a coarse structured mixture during compaction. Therefore, discrete element method (DEM) was utilised to evaluate the influence of each construction parameter on the interlock between the cold and the hot side of an asphalt pavement joint. The results helped to explain earlier experimental findings about the joints and revealed potential for further laboratory and field investigations.
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| 44. |
- Gudmarsson, Anders, et al.
(author)
-
Precision of modal analysis to characterise the complex modulus of asphalt concrete
- 2019
-
In: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 20:sup 1, s. S217-S232
-
Journal article (peer-reviewed)abstract
- Modal analysis is an economic and efficient test method to characterise the complex modulus of asphalt concrete. In this paper, the precision of modal analysis was evaluated by performing testing at several laboratories on two cylindrical asphalt concrete specimens. In addition, the complex moduli characterised by modal analysis were compared to cyclic tension-compression testing. The results showed that the coefficient of variation was less than 3% at loading frequencies above 10 Hz for the complex modulus determined through modal analysis. The comparison of the complex modulus determined from modal analysis and tension-compression testing resulted in a coefficient of variation values not more than 9% for loading frequencies ranging from 0.1 to 10 9 Hz.
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| 45. |
- Gullberg, David, et al.
(author)
-
Evaluation of a novel calibrated-mechanistic model to design against fracture under Swedish conditions
- 2012
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 13:1, s. 49-66
-
Journal article (peer-reviewed)abstract
- Sweden has initiated the development of a new calibrated-mechanistic pavement design procedure to replace the current mechanical-empirical pavement procedure entitled “PMS Objekt.” The first phase was focused on the implementation and calibration of the vi scoelastic fracture mechanics framework entitled “HMA Fracture Mechanics”, developed at the University of Florida. This paper outlines the implementation and calibration of a new pavement design module for Sweden that is based on the HMA fracture mechanics framework. Both the developed design module, as well as the reference model used for calibration (PMS Objekt) are presented in this paper. The results in thickness design after calibration of the design module indicate that the framework is clearly applicable for common Swedish conditions and design standards.
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| 46. |
- Gullberg, David, et al.
(author)
-
Evaluation of the predictive models used in the new swedish mechanistic-empirical design module
- 2012
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 13:2, s. 300-311
-
Journal article (peer-reviewed)abstract
- In order to perform thickness design of flexible pavements based on the HMA fracture mechanics framework prior to construction, the tensile strength and creep power law parameters of the mixture has to be determined. As samples are normally not available in the design stage, these properties will have to be modelled rather than determined in a laboratory. This paper evaluates material models based on the relationship between dynamic (complex) modulus and creep compliance in order to predict tensile strength and creep power law parameters for a mixture. For this evaluation, fourteen field sections from the United States have been used for verification and the results indicate that the crack resistance of a mixture can indeed be estimated without a development of extensive empirical relations between mixture properties and crack-resistance.
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| 47. |
- Hailesilassie, Biruk Wobeshet, et al.
(author)
-
A closer scientific look at foam bitumen
- 2017
-
In: Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 18:2, s. 362-375
-
Journal article (peer-reviewed)abstract
- In the asphalt industry, a substantial interest is observed to find possibilities to reduce the production temperature of asphalt mixtures. In the context of this research, new methods for the visualisation of unstable bitumen foam, such as dynamic X-ray radiography, computed tomography (CT) and high-speed camera investigations, have been developed. Moreover, characterisation with empirical methods such as expansion ratio and half-life was determined accurately using ultrasonic measurements. This opens new possibilities to characterise bitumen foam (foaming process) for practical applications. Examination of the foam bitumen stream using a high-speed camera revealed that the foam bitumen contains fragmented pieces of bitumen, which resemble more a liquid than foam. This indicates that the foam is formed afterwards and not, as assumed, within the expansion chamber of the foam generator. In situ thermal imagery of the surface, during the hot foaming process, showed that the temperature distribution depends on the foaming water content (W.C.) and bubble size distribution. Higher W.C. results in more inhomogeneous temperature distribution as compared to lower W.C. (<2 wt%). The dynamic X-radiography results indicated that as the foam decays, the bubble size distribution becomes progressively larger with time for 160°C bitumen temperature. Furthermore, at the beginning of the foam formation, majority of the bubbles is small in cross-section size (0.2–10 mm2). At a later stage, the bubbles become polydisperse. Moreover, theoretical investigations based on the 3D X-ray CT scan data set of bubble merging show that the disjoining pressure increases as the foam film gets thinner with time and finally undergoes rupture. The speed of the bubbles also increases with time when the bubbles are getting closer to each other.
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| 48. |
- Hermansson, Åke, et al.
(author)
-
Prediction of Pavement Fatigue Life with Simulated Temperature Profile from Hourly Surface Temperatures
- 2003
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 4:3, s. 293-308
-
Journal article (peer-reviewed)abstract
- A typical model for predicting the fatigue life of an asphalt pavement involves mid-depth temperature and the elastic horizontal strains at the bottom of the asphalt layer. Strains are studied at the bottom of the asphalt layer as cracks are assumed to originate there. Pavement temperatures naturally experience daily fluctuations as a result of varying air temperature and solar radiation.The amplitude of the oscillation decreases with depth and maximum temperature is reached later in the day at greater depth. During warming up, strain levels under loading increase as stiffness decreases, while the bottom of the asphalt layer is rather cold and thus sensitive to strains. At cooling down, strain decreases and the bottom layer is warm and withstands strains more easily. It is therefore proposed in this paper to use the temperature at the bottom of the asphalt layer instead of the mid-depth temperature when calculating fatigue damage. It is also proposed to use the complete temperature profile to improve the calculation of strain levels under loading. As the fatigue damage caused each hour will vary with temperature during the course of the day, it is also pointed out that the calculations might be improved by relating the distribution of traffic to the distribution of incremental fatigue damage.A simulation model calculating the temperature profile and strain levels was developed and run for three different pavements with different thicknesses of asphalt layer. It was found that the distribution of incremental fatigue damage over a typical summer day could be completely different for different pavements.
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| 49. |
- Hermansson, Åke
(author)
-
Simulation of Asphalt Concrete (AC) Pavement Temperatures for use with FWD
- 2002
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 3:3, s. 281-297
-
Journal article (peer-reviewed)abstract
- A simulation model to be used primarily for falling weight deflectometer (FWD) testing has been developed to calculate temperatures of asphalt concrete (AC) layers. Input to the model is a series of measured temperatures at the surface of AC layer. The measuring series need to be started in the morning, before the sun has strongly heated up the AC layers. A start-up procedure is proposed to follow, if the measuring series lacks the early morning data. By means of a finite difference approximation of the heat transfer equation, the temperatures below the AC surface are calculated.Parameter values were adapted using data for 8 days during the period June 20 to June 27, 2001 from 3 different locations in Sweden. Two other locations in Sweden were used for validation. For the measuring data, the proposed model gives essentially better results than the commonly used BELLS method, as well as the improved version BELLS3 and a method recently proposed by researchers at the Michigan State University.Comparisons with measured temperatures, show that the proposed method calculates the temperature distribution of the AC layers with good accuracy. This includes cloudy as well as sunny days. The method also accurately handles the change between cloudy and sunny weather during the day.
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| 50. |
- Hesami, Ebrahim, et al.
(author)
-
A new protocol for measuring bituminous mastic viscosity as a function of its filler concentration
- 2014
-
In: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 15:2, s. 420-433
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Journal article (peer-reviewed)abstract
- In this contribution the development and results of a new test protocol for measuring the viscosity of bituminous mastics are presented. The paper describes the various considerations that need to be taken into account when dealing with mastics, gives a detailed description of the sample preparation, the test set-up and the actual test performance. A demonstration of the use of the test procedure is given by developing three types of mastics in which different filler types, but a similar bitumen base, were used. From the results it can be seen that the developed protocol is sensitive enough to allow for detailed studies of the effect of filler shape, chemistry and size distribution. In continuation of this work, more types of mastics will be investigated and the test results will be linked to additional chemical and mechanical test results to further enhance the fundamental understanding of mastics.
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