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  • 1.
    Abdi, Adel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Choice of Appropriate Tyres as an Asset to Traffic Safety on Winter Roads: Compilation and Evaluation of Some Winter Tyre Tests in Sweden2011Ingår i: International Journal of Civil & Environmental Engineering, ISSN 2077-1258, Vol. 11, nr 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Winter tyres must be able to cope with the slipperiness which occurs on the surface of the roads during winter. The slipperiness is generated by water vapour in the atmosphere, precipitating and transforming into a solid form i.e. in ice form, either directly or after refrigeration or cooling. Many experimental studies e.g. winter tyre tests have been carried out by many companies and authorities independently from each other to determine if there are any types of tyres which have the best grip on different road surface conditions in the winter. The purpose of this study is to compile, analyse, compare and evaluate the obtained results of some winter tyre tests which have been performed in Sweden during years 2007-2010. The study aims further to find out which types of these tyres are most appropriate as an asset and increase the traffic safety on Swedish winter roads. Both studded tyres and non-studded tyres, socalled friction tyres or all season tyres were used in the tests. The method of the study is partly based on a theoretical study by reviewing some literature in this area and furthermore studying some practical cases i.e. winter tyre tests. The results of the tests are given in tables and figures showing the function of different types of the studded and nonstudded tyres on different road conditions. All test-tyres have been supplied by several tyre manufacturers. The study is only limited to compare the grip and effectiveness of different type of winter tyres on different kind of road conditions. The study does not take the impact of the tyres on the environment into consideration. The study shows that currently there are several types of winter tyres on the market but there is no tyre that is ideal or works best under all winter conditions.

  • 2.
    Abdi, Adel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Lind, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Fastigheter och byggande.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap.
    Designing appropriate contracts for achieving efficient winter road and railway maintenance with high performance quality: A survey of the state of practice in Sweden2014Ingår i: International Journal of Quality and Service Sciences, ISSN 1756-669X, E-ISSN 1756-6703, Vol. 6, nr 4, s. 399-415Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose - For a long time, the winter maintenance of the Swedish road and railway network had been performed in-house by Swedish Transport Administration, Swedish local authorities i.e. municipalities and Stockholm public transport. During the last 15 years the winter operation and maintenance of these state infrastructures have been performed by public procurement and contracting from independent contractors, where in practice the lowest price is the dominating selection criteria. The aim of this paper is to investigate and identify how these contracts are designed and how satisfied the parties are with the contract and the quality of the performed work during the winter and point our directions for improvement. Design/methodology/approach - The study was conducted by a literature review and followed by semi-structured interviews and electronic questionnaire. Findings - The results of the study which are based on the interviews and the online questionnaire show that there is widespread dissatisfaction with the contracts among both clients and contractors. Practical implications - The article prepares a basis showing how a contract affects the quality of the performed winter road and railway maintenance services. Originality/value - The findings lead to a number of suggestions about how to improve the contracts, e.g. having a separate winter maintenance contract to increase the quality of performed winter maintenance measures, a more partnering-like structure where consultations and adjustment can be made during the contract period. A partnering structure also makes it less important to get all the details right in the contract.

  • 3.
    Abdi, Adel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Lind, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Fastigheter och byggande, Bygg- och fastighetsekonomi.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Effective Winter Highway Maintenance through Applicationof Partnering Concept2013Ingår i: International Journal of Engineering Management and Economics (IJEME), ISSN 1756-5154, E-ISSN 1756-5162, Vol. 3, nr 3, s. 112-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inmany countries winter road maintenance is outsourced to private contractors. Selecting appropriate contract for performance of winter highway maintenance and implementing it in an efficient way is then very important for both results and costs. Writing contracts concerning winter road maintenance is however difficult as weather conditions are hard to describe in an exact way and as what is rational to do in a certain situation, depends on expected future conditions. Problems during recent harsh winters in Sweden have clearly illustrated this. The study argues, with reference both to theoretical and empirical studies, that a partnering concept can improve efficiency in outsourced winter road maintenance. A detailed model of how partnering can be implemented is presented for winter road maintenance contracts together with systems for information supply such as International Roughness Index –surface unevenness measurement and Road Weather Information System.

  • 4.
    Abdi, Adel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Lind, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Fastigheter och byggande, Bygg- och fastighetsekonomi.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Payment mechanisms for winter road maintenance services2013Ingår i: Australasian Journal of Construction Economics and Building, ISSN 1835-6354, Vol. 13, nr 4, s. 18-31Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In countries with severe winters, a major portion of the annual budget for road maintenance is allocated to winter road maintenance. Thus it is important to identify an appropriate basis for the remuneration of the entrepreneurs who carry out the maintenance tasks, one that minimises or eliminates disputes and that satisfies both client organisations and contractors. The objective of this study is to investigate and evaluate the payment models applied in Sweden for winter road maintenance services and suggest possible improvements. Inadequate reimbursement models lead either to unnecessary cost overruns that affect the client's annual budget or cause cash flow problems for the contractor, which can result in safety issues. To solve the problems associated with paying for just-in-time road maintenance, cold region countries such as Sweden have developed various remuneration models, including some based on what is known as the Weather Index. The study uses a domestic questionnaire survey, analysis of a number of current contract documents, a series of meetings with project managers followed by an international benchmarking investigation. The study identified four winter maintenance remuneration models of which one is based on weather data. The study reveals that the payment model based on weather data statistics is applied only to roads with higher traffic flow and generates the most uncertainty about costs. Possible improvements should include more reliable weather data obtained from weather stations and bonuses related to customer satisfaction.

  • 5.
    Abdi, Adel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Lind, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Fastigheter och byggande, Bygg- och fastighetsekonomi.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Public Procurement of Winter Road Maintenance Services Based on EU Procurement Directive: Lessons from Sweden2013Ingår i: Journal of Investment and Management, ISSN 2328-7721, Vol. 2, nr 4, s. 70-86Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Public procurement of road maintenance services, particularly in cold regions is not an easy task in order to satisfy road-users during winter. Road-users’ dissatisfaction, complaint and pressure can usually be considered as major factors for having more accessible and safe roads during winter. These pressures have contributed and led to an increasing critical approach focusing on public procurement of these services after some harsh winters in the recent years in Sweden with traffic disruption and delay as consequence i.e. an increasing focus on the way in which the Swedish state authorities and local governments procure winter road maintenance services. The present study which is part of a larger research project investigating efficient winter road maintenance through procurement, tendering and contract aimed at extending this knowledge base with regard to procurement and socioeconomic factors with focus on the winter maintenance of the Swedish road network. The study reveals that even the Swedish winter road maintenance services are procured and outsourced in accordance with EU directive and public procurement rules transposed into the Swedish act on public procurement, the act has been interpreted in a manner that all the process has led to great dissatisfaction of end-users during winter due to improper bundling of winter related services. The lack of economic motivation in current contracts concerning winter road maintenance in the form of incentives has led to an inefficient performance of winter road measures. The study suggests a number of proposals in order to make forthcoming contracts more effective through proper bundling of winter services and create incentives for contractors to improve the performance of winter road maintenance services.

  • 6.
    Abdi, Adel
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Lind, Hans
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Fastigheter och byggande, Bygg- och fastighetsekonomi.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Use of Road Weather Information System (RWIS) as Assistive Tool for Effective Winter Road Maintenance: Technical andContractual Interactions2012Ingår i: International Journal of Engineering and Technolgy, ISSN 2049-3444, Vol. 2, nr 12, s. 2002-2012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Winter highway operation and maintenance in the northern periphery is a challenge, a broad and complex area. Understanding about this area and its effect on winter traffic performance is far from complete. During the last forty years since Swedish Transport Administration (former Swedish National Road Administration) began attempting of the use of Road Weather Information System -RWIS on the Swedish road network, the repair and maintenance methods of this assistive tool has dramatically changed. Changing of the methods have been due to the progress and development of the technology within this area i.e. from simple stations that could be connected via telephone network for icy road warning to amore sophisticated and modern internet based technology. The main objective of this study was to investigate and find the importance and effectiveness of using weather data collected from RWIS by road agencies as an assistive tool for effective performance of winter road maintenance, and how these tools are currently maintained without influencing the delay of winter road maintenance.The study also attempts to find possible interactions between technical and contractual issues that may affect winter road maintenance. The method of the study was partly based on a theoretical study by reviewing some internationally published articles and reports in this area and furthermore a domestic questionnaire survey, an internationalbenchmarking and a follow-up study within a selected region in Sweden. The results of the study reveal that even if the weather stations are normally placed on roads where the risk of icy roads is greatest, there are indirect factors which influence the planned maintenance of these tools which subsequenly cause delay of winter road maintenance.

  • 7.
    Bekele, Abiy
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap. KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vägtekniks laboratorium.
    Rydén, Nils
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Gudmarsson, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Slow dynamic diagnosis of asphalt concrete specimen to determine level of damage caused by static low temperature conditioning2017Ingår i: 43rd Annual Review of Progress in Quantitative Nondestructive Evaluation, American Institute of Physics (AIP), 2017, Vol. 1806, artikel-id 080012Konferensbidrag (Refereegranskat)
    Abstract [en]

    The phenomenon of slow dynamics has been observed in a variety of materials which are considered as relatively homogeneous that exhibit nonlinearity due to the presence of defects or cracks within them. Experimental realizations in previous work suggest that slow dynamics can be in response to acoustic drives with relatively larger amplitude as well as rapid change of temperature. Slow dynamics as a nonlinear elastic response of damaged materials is manifested as a sharp drop and then recovery of resonance frequency linearly with logarithmic time. In this work, slow dynamics recovery is intended to be used as a means of identifying and evaluating thermal damage on an asphalt concrete specimen. The experimental protocol for measuring slow dynamics is based on the technique of nonlinear resonance spectroscopy and is set up with non-contact excitation using a loud speaker and the data acquisition tool box of Matlab. Sweeps of frequency with low amplitude are applied in order to probe the specimen at its linear viscoelastic state. The drop and then recovery in fundamental axially symmetric resonance frequency is observed after the specimen is exposed to sudden temperature change. The investigation of the viscoelastic contribution to the change in resonance frequency and slow dynamics can help identify micro-damage in asphalt concrete samples.

  • 8.
    Birgisson, Bjorn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Beatty, C.L.
    Nanomodified Concrete Additive and High Performance Cement Past and Concrete Therefrom2006Patent (Övrig (populärvetenskap, debatt, mm))
  • 9.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik (stängd 20110301).
    Foreword2010Ingår i: Transportation Research Record: Journal of the Transportation Research Board, ISSN 0361-1981, nr 2141, s. VII-VIIIArtikel i tidskrift (Refereegranskat)
  • 10.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik (stängd 20110301).
    Nanotechnology in Cement and Concrete VOLUME 2 Foreword2010Ingår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, nr 2142, s. IX-XArtikel i tidskrift (Övrigt vetenskapligt)
  • 11.
    Birgisson, Björn
    et al.
    University of Florida.
    Darku, D.
    Roque, R.
    Page, G.
    The Need for Inducing Shear Instability to Obtain Relevant Parameters for HMA Rut-Resistance2004Ingår i: 2004 JOURNAL OF THE ASSOCIATION OF ASPHALT PAVING TECHNOLOGISTS: FROM THE PROCEEDINGS OF THE TECHNICAL SESSIONS, Association of Asphalt Paving Technologists , 2004, Vol. 73, s. 23-52Konferensbidrag (Refereegranskat)
    Abstract [en]

    Instability rutting is a major distress mode in hot mix asphalt pavements, which occurs when the structural properties of the compacted mix cannot resist near surface critical stress conditions caused by traffic loads. The critical stress conditions for rutting instability include high near surface shear stresses and low confinement. On the mixture level, instability rutting is manifested in a rearrangement of the aggregate structure. This paper illustrates that it may be necessary to induce instability in mixtures to determine parameters that are relevant to mixture rut resistance. The Superpave(TM) gyratory compactor with shear measurements and the option of changing the compaction angle during compaction was used in this study. Mixtures were compacted to a density that is consistent with the air voids of field pavements immediately after construction, namely 7 percent (+/- 0.5) percent air voids. The subsequent application of high shear stresses by increasing the gyratory angle from 1.25 degrees to 2.5 degrees results in the rearrangement of the aggregate structure during which parameters can be measured that define clear differences in mixtures. Based on the testing of 31 mixtures with different void structure and aggregate characteristics, three distinctive responses were observed: a) brittle response, b) plastic response, under which once the mixtures loose strength due to rearrangement they never regain another stable rearrangement, and c) optimal response, which is bracketed by the plastic and brittle types of responses. Key parameters were identified that are relevant to the rut-resistance of mixtures. Using these new parameters, a framework for the evaluation of mixture rutting potential is developed. Based on a comparison of predicted rutting potential to APA rut depth measurements, as well as a statistical analysis of results, the validity of the proposed framework is established. The results show that the proposed framework has may have the potential for becoming an index test for evaluating the rutting potential of mixtures. Based on the findings of this paper, the proposed approach for evaluating mixture rut-potential should be studied further and validated for an even larger variety of asphalt mixtures.

  • 12.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Dham, M.
    Optimization of Clay Addition for Enhancement of Pozzolanic Reaction in Nanomodified Cement Paste2011Ingår i: Nanotechnology in Civil Infrastructure: A Paradigm Shift / [ed] Kasthurirangan Gopalakrishnan, Bjorn Birgisson, Peter Taylor, Nii O. Attoh-Okine, Springer Berlin/Heidelberg, 2011Kapitel i bok, del av antologi (Refereegranskat)
  • 13.
    Birgisson, Björn
    et al.
    University of Florida.
    Montepara, A
    Napier, J
    Romeo, E
    Roncella, R
    Tebaldi, G
    Measurement and Prediction of HMA Fracture Energy using Micromechanical Analyses2006Konferensbidrag (Refereegranskat)
  • 14.
    Birgisson, Björn
    et al.
    University of Florida.
    Montepara, A.
    Napier, J.
    Romeo, E.
    Tebaldi, G.
    Evaluation of aggregate size-dependent of asphalt mixtures in cracking behavior2005Konferensbidrag (Refereegranskat)
  • 15.
    Birgisson, Björn
    et al.
    Department of Civil and Coastal Engineering, University of Florida, United States.
    Montepara, A.
    Romeo, E.
    Roncella, R.
    Napier, J.
    Tebaldi, G.
    Determination and prediction of crack patterns in hot mix asphalt (HMA) mixtures2008Ingår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 75, nr 3-4, s. 664-673Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a comparison between predicted and measured crack patterns developing in hot mix asphalt (HMA) mixtures during common fracture tests. A digital image correlation (DIC) System was applied to obtain displacement/strain fields and for detecting crack patterns. The resulting cracking behavior was predicted using a displacement discontinuity boundary element method to explicitly model the microstructure of HMA. The predicted fracture initiation and crack propagation patterns are consistent with observed cracking behavior. The results imply that fracture in mixtures can be modeled effectively using a micro-mechanical approach and that crack propagation patterns can be captured using the DIC System.

  • 16.
    Birgisson, Björn
    et al.
    University of Florida.
    Montepara, A
    Romeo, E
    Roncella, R
    Roque, R
    Tebaldi, G
    Determination and Prediction of Crack Patterns in Asphalt Mixture under Static Loading2006Ingår i: International Conference on CRACK PATHS (CP 2006), 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a comparison between predicted and measured crack patterns developing in asphalt mixtures during static loading. Two different state configuration were investigated performing the Indirect Tensile Test (IDT) and the Semi-Circular Bending Test (SCB). A Digital Image Correlation System was applied to obtain a dense and accurate displacement/strain field of asphalt mixtures and for describing the cracking behavior. The resulting fracture behavior in the tests was predicted using a displacement discontinuity boundary element method to explicitly model the microstructure of asphalt mixtures. The predicted crack initiation and crack propagation patterns are consistent with observed cracking behavior. The results also imply that fracture in mixtures can be modeled effectively using a micromechanical approach that allows for crack growth both along aggregate surfaces, as well as through aggregates. 

  • 17.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik (stängd 20110301).
    Montepara, A.
    Romeo, E.
    Roncella, R.
    Tebaldi, G.
    Roque, R.
    The use of digital image correlation for accurate determination of fracture energy density in Hot Mix Asphalt (HMA)2008Ingår i: PAVEMENT CRACKING: MECHANISMS, MODELING, DETECTION, TESTING AND CASE HISTORIES / [ed] AlQadi IL, Scarpas T, Loizos A, BOCA RATON: CRC PRESS-TAYLOR & FRANCIS GROUP , 2008, s. 811-820Konferensbidrag (Refereegranskat)
    Abstract [en]

    Knowledge of the conditions governing the initiation and propagation of cracks in Hot Mix Asphalt (HMA) mixtures is a prerequisite for a comprehensive understanding of HMA cracking mechanisms. According to the "HMA Fracture Mechanics" pavement cracking model recently developed at the University of Florida, fundamental tensile failure limits of mixtures (fracture energy density and tensile strength) are identified as key parameters in defining the cracking resistance of HMA mixes. A Digital Image Correlation (DIC) system, developed for the purpose of investigating the cracking behavior of HMA mixtures, has been applied to accurately determine fundamental tensile failure limits of SBS polymer modified mixes. The effect of modification on crack localization and crack growth was also investigated. One unmodified and four SBS polymer modified HMA mixes were tested performing both the Superpave IDT test and the Semi-Circular Bending (SCB) test. Tensile failure limits and cracking behavior of two of these mixes (the unmodified and a heavily SBS linear modified) were evaluated also from the Three Point Bending Beam (3PB) test. Full field strain maps indicate that the addition of SBS polymers in mixtures leads to more homogeneous stress states during tensile loading condition, resulting in high strains strongly localized up to the location of impending fracture.

  • 18.
    Birgisson, Björn
    et al.
    University of Florida, United States.
    Montepara, A.
    Romeo, E.
    Roque, R.
    Roncella, R.
    Tebaldi, G.
    Determination of fundamental tensile failure limits of mixtures2007Ingår i: Asphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions, 2007, Vol. 71, s. 303-344Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cracking is one of the most influential distresses that governs the service life of asphalt concrete pavements. Acquiring more insight into the fracture behavior of asphalt mixtures is essential to improve the cracking resistance of asphalt pavements. Recent work at University of Florida (1,2) has focused on the development of a new visco-elastic fracture mechanics-based crack growth law which identified the fracture energy density of mixtures as a fundamental crack growth threshold. The work that led to the development of the HMA fracture mechanics framework was based solely on Superpave IDT test results, therefore, it is of considerable interest to evaluate the existence of a fundamental fracture threshold for other laboratory test configurations. The work presented in this paper focuses on the identification and evaluation of fundamental tensile failure limits of hot mix asphalt mixtures (HMA) from multiple laboratory test configurations. Fracture energy densities and tensile strengths were evaluated for three different mixtures, including unmodified and heavily polymer modified mixtures, from the Superpave IDT, the Semi-Circular Bending Test (SCB) and the Three Point Bending Beam Test (3PB). Experimental analyses were complemented by a Digital Image Correlation System capable of providing dense and accurate full field strain estimations and thus suitable for describing the cracking behavior of the material at crack initiation. Tensile failure limits and the resulting fracture behavior in the three test configurations were predicted using a displacement discontinuity boundary element method with tessellations. Both experimental and numerical results indicate that fundamental HMA tensile failure properties can be determined from different test methods when appropriate analysis and interpretation methods are used. It was found that significant damage and first fracture occur locally in specimens associated with all test methods prior to peak loading, while analysis based on peak load and approximate analysis may lead to erroneous results.

  • 19.
    Birgisson, Björn
    et al.
    University of Florida.
    Montepara, A
    Romeo, E
    Roque, R
    Tebaldi, G
    The Displacement Discontinuity Method for Predicting HMA Fracture Energy in the Bending Beam Test2007Ingår i: ADVANCED CHARACTERISATION OF PAVEMENT SOIL ENGINEERING MATERIALS, VOLS 1 AND 2, 2007, s. 69-77Konferensbidrag (Refereegranskat)
    Abstract [en]

    The displacement discontinuity method has been used previously to assess the mechanics of fracture in the SuperPave (TM) Indirect Tension Test and in the Semi-Circular Bending Test. In order to further verify the independence of the test method from the test configuration, this paper investigates the possibility of using the same method (i.e. the displacement discontinuity method) to predict hot mix asphalt fracture energy density in a Bending Beam Test. The predicted stress-strain curves were shown to compare well to the experimental results. The predicted crack initiation and propagation patterns are also consistent with observed cracking behavior. The results show that the displacement discontinuity method is capable of characterizing the fracture behavior of asphalt mixtures at intermediate to low temperatures, regardless of the particular testing setup used in the investigation and that it consistently provides reasonable predictions of HMA Fracture Energy Density.

  • 20.
    Birgisson, Björn
    et al.
    University of Florida.
    Montepara, A
    Romeo, E
    Roque, R
    Tebaldi, G
    The Effect of SBS Asphalt Modifiers on Hot Mix Asphalt (HMA) Mixture Cracking Resistance2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a laboratory investigation conducted to evaluate the effect ofboth radial and linear SBS modifiers on the cracking resistance of Hot Mix Asphalt(HMA) mixtures. Three types of asphalt mixtures composed by the same aggregate typeand gradation but different asphalt binders (one unmodified and the others obtained byadding linear and radial SBS polymers to the unmodified one) were produced in thelaboratory. The cracking performances of the mixtures were evaluated using a crackingmodel developed at the University of Florida called “HMA Fracture Mechanics Model”,based on the principles of visco-elastic fracture mechanics. The model requires onlyfive tensile asphalt mixture properties which are obtained using the Superpave IDT:resilient modulus, creep compliance power law parameters, tensile strength, fractureenergy and dissipated creep strain energy to failure.All the results presented show the benefit of SBS modifiers to mixture’s crackingresistance in terms of reduced rate of damage accumulation (m-value) and increasedtensile limits to failure (tensile strength, fracture energy and dissipated creep strainenergy to failure). No influence was observed in the elastic response but rather on thetime-dependent response. Finally, SBS linear polymers have shown to better improvecracking performances of HMA mixes than SBS radial ones.

  • 21.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Montepara, A.
    Romeo, E.
    Tebaldi, G.
    Characterization of Asphalt Mixture Cracking Behavior using the Three-Point Bending Beam Test2011Ingår i: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 12, nr 6Artikel i tidskrift (Refereegranskat)
  • 22.
    Birgisson, Björn
    et al.
    University of Florida.
    Montepara, A.
    Roque, R.
    Romeo, E.
    Tebaldi, G.
    The displacement discontinuity method for modeling fracture in the semi-circular bending test2005Ingår i: 3rd M.I.T. Conference on Computational Fluid and Solid Mechanics, Elsevier Science Ltd., Boston , 2005, s. 79-82Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the capability of a displacement discontinuity boundary element method, which was already used to assess the mechanics of fracture in the SuperPave™ Indirect Tension Test, to model the microstructure of asphalt mixtures. The paper presents a semicircular bending test simulation in order to verify the independence of the method from the testing setup application. The predicted stress-strain curves were shown to compare well to the experimental results, as well as the cracking behaviour. The results imply that the method is able to characterize asphalt mixtures properties regardless of the particular testing setup used in the investigation. It has also shown promise as a tool for studying the mechanism of crack growth and propagation in hot mix asphalt (HMA) during every kind of testing setup.

  • 23.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik.
    Montepara, Antonio
    Romeo, Elena
    Roncella, Riccardo
    Roque, Reynaldo
    Tebaldi, Gabriele
    An optical strain measurement system for asphalt mixtures2009Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 42, nr 4, s. 427-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge of the conditions governing the initiation and propagation of cracks in hot mix asphalt (HMA) mixtures is a prerequisite for a comprehensive understanding of HMA cracking mechanisms. Traditional strain measurement sensors have proved to be not completely adequate in the sense that they do not provide pointwise measurements, thus not pinpointing the location of crack initiation, and not accounting for non-uniform strain distributions. This paper presents a digital image correlation (DIC) system for non-contact and full strain field measurements, conceived for the purpose of investigating the cracking behavior of HMA mixtures. The whole system was developed so as to account for the special nature of typical HMA testing configurations. An image matching technique (least squares matching) was employed for providing matches with sub-pixel accuracy. The performance of the method was investigated by several tests. The DIC system was shown to overcome the shortcomings of traditional on-specimen strain measurement devices achieving satisfactory accuracy compared to strain gauges.

  • 24.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik (stängd 20110301).
    Montepara, Antonio
    Romeo, Elena
    Roque, Reynaldo
    Tebaldi, Gabriele
    Influence of Mixture Properties on Fracture Mechanisms in Asphalt Mixtures2010Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 11, s. 61-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 25.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Montepara, Antonio
    Department of Civil and Environmental Engineering and Architecture, University of Parma.
    Romeo, Elena
    Department of Civil and Environmental Engineering and Architecture, University of Parma.
    Tebaldi, Gabriele
    Department of Civil and Environmental Engineering and Architecture, University of Parma.
    Characterisation of asphalt mixture cracking behaviour using the three-point bending beam test2011Ingår i: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 12, nr 6, s. 569-578Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of a three-point bending beam (3PB) test was investigated to characterise hot mix asphalt (HMA) cracking behaviour. Fundamental HMA fracture properties, identified as tensile strength and fracture energy density at first fracture, were determined for six different asphalt mixtures (two natural and four SBS polymer modified) applying the HMA Fracture Mechanics framework. Full-field strain maps obtained from an in-house developed digital image correlation-based method were observed to better understand the crack initiation and propagation mechanisms in the 3PB specimen. The resulting fracture behaviour was predicted using a displacement discontinuity boundary element method to model the microstructure of the six asphalt mixtures and to predict their fracture properties. Both numerical and experimental results indicate that the fracture mechanism of asphalt mixtures can be properly described from 3PB test results when appropriate interpretation models are used.

  • 26.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Ovik, J
    Newcomb, David
    Predictions of Seasonal Variations in Flexible Pavements at the MN/ROAD Site2002Ingår i: Transportation Research Record, Vol. 1730Artikel i tidskrift (Refereegranskat)
  • 27.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Roberson, R
    Drainage of Pavement Material: Design and Construction Issues2000Ingår i: Transportation Research Record, Vol. 1709Artikel i tidskrift (Refereegranskat)
  • 28.
    Birgisson, Björn
    et al.
    University of Florida.
    Roque, R.
    Evaluation of Gradation Effects on Dynamic Modulus2005Ingår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, nr 1929, s. 193-199Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The importance of aggregate characteristics has been emphasized in the Superpave (R) asphalt mixture design procedure. However, criteria for guidelines for the selection of suitable aggregate gradations-other than gradation limits for different nominal maximum size aggregate blends, including the restricted zone-have been neglected. With the move toward mechanistic-empirical pavement design, the dynamic modulus is used to account for mixture properties in the pavement design. It is of significant importance to mix designers to possess a framework for determining how to optimize a mixture for ensuring an adequate dynamic modulus. This paper presents the results from a study of the effects of gradation characteristics on the dynamic modulus. Power law-based gradation factors are obtained for 13 aggregate gradations (coarse and fine graded) composed of limestone and granite aggregates. These gradation factors were used to identify and evaluate relationships between gradation factors and the dynamic modulus at higher temperature (40 degrees C). Subsequently, a tentative framework was established for optimizing mixture gradations for dynamic modulus values. Findings illustrate that gradation factors based on power law parameters can be used to optimize mixture gradations for key mixture properties, such as the dynamic modulus. Results also demonstrate the critical nature of aggregate gradation in achieving desired mixture properties.

  • 29.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Roque, R
    Page, G
    Evaluation of Water Damage Using Hot Mix Asphalt Fracture Mechanics2003Ingår i: Journal of Asphalt Paving Technologists, Vol. 72Artikel i tidskrift (Refereegranskat)
  • 30.
    Birgisson, Björn
    et al.
    University of Florida.
    Roque, R.
    Page, G.
    Performance-based fracture criterion for evaluation of moisture susceptibility in hot-mix asphalt2004Ingår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, nr 1891, s. 55-61Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The laboratory testing procedures currently available for testing hot-mix asphalt moisture susceptibility all evaluate the effects of moisture damage in the laboratory by measuring the relative change of a single parameter before and after conditioning (i.e., tensile strength ratio, resilient modulus ratio). The use of a single parameter to evaluate moisture damage must be questioned. Instead, a single unified framework that accounts for changes in key mixture properties is needed to evaluate the effects of moisture damage in mixtures effectively. The use of a new performance-based fracture parameter, the energy ratio (ER), for quantifying the effects of moisture damage on the fracture resistance of mixtures is evaluated here. ER is used to determine the effects of moisture damage on changes in the fracture resistance of six granite mixtures prepared with and without the use of an antistripping additive. The granite aggregate used is a known stripping aggregate. In addition, one limestone mixture with a known high resistance to stripping was used. The results indicate that not only is the ER capable of detecting the effects of moisture damage on the fracture resistance of mixtures, it is also shown to detect the presence of antistripping agents in mixtures. Results indicate that the ER may form the basis of a promising combined performance-based fracture criterion for evaluating the effects of moisture damage in mixtures as well as the overall resistance to fracture.

  • 31.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Roque, R
    Page, G
    Ultrasonic Pulse Wave Velocity Test as a Tool for Monitoring Changes in HMA Mixture Integrity due to Exposure to Moisture2003Ingår i: Transportation Research Record, Vol. 1832Artikel i tidskrift (Refereegranskat)
  • 32. Birgisson, Björn
    et al.
    Roque, Reynaldo
    Page, Gale C.
    Wang, Jianlin
    Development of new moisture-conditioning procedure for hot-mix asphalt2007Ingår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, nr 2001, s. 46-55Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The presence of pore water in mixtures can cause premature failure of hot-mix asphalt pavements. The processes typically associated with moisture damage are complex and occur over a long period of time in the field. Short of being able to simulate each of the possible mechanisms of moisture damage directly, the ideal laboratory-based conditioning system should accelerate the penetration of moisture through the asphalt film and at the same time minimize complicating effects. This paper presents the results of an experiment conducted to determine whether it was possible to use cyclic pore pressures to induce enough damage to distinguish between mixtures known to be highly resistant from mixtures known to be susceptible to moisture damage. Experimental constraints included requirements that conditioning be accomplished within a reasonable length of time and that typical laboratory equipment be used. Evaluation of the resulting effects of moisture damage included the use of the Superpave (R) indirect tension test and the energy ratio parameter. Findings show that cyclic pore pressures can be used to accelerate moisture damage enough to distinguish between mixtures known to be strippers and those known to be highly resistant to moisture damage. The use of cyclic pore pressures to accelerate moisture damage in mixtures may minimize the introduction of other confounding damage effects on the mixtures.

  • 33.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Ruth, B
    Development of Tentative Guidelines for the Selection of Aggregate Gra¬dations in Hot-Mix Asphalt2002Ingår i: Journal of ASTM International, Vol. 1412Artikel i tidskrift (Refereegranskat)
  • 34.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Ruth, B
    Improved Performance by Consideration of Terrain Conditions: Soils, Drainage, and Climate2003Ingår i: Transportation Research Record, Vol. 1819Artikel i tidskrift (Refereegranskat)
  • 35.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Sangpetngam, B
    Roque, R
    Prediction of the Viscoelastic Response and Crack Growth in Asphalt Mixtures Using the Boundary Element Method2002Ingår i: Transportation Research Record, Vol. 1789Artikel i tidskrift (Refereegranskat)
  • 36. Birgisson, Björn
    et al.
    Sholar, G.
    Roque, R.
    Evaluation of a predicted dynamic modulus for Florida mixtures2005Ingår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, nr 1929, s. 200-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The new 2002 AASHTO guide for the design of pavement structures is based on mechanistic principles and requires the dynamic modulus as input to compute stress, strain, and rutting and cracking damage in flexible pavements. The 2002 AASHTO guide has three different levels of analysis; the level used depends on the importance of the pavement structure in question. Dynamic modulus testing is required for Level 1 pavement analysis, whereas no laboratory test data are required for Level 2 and Level 3 pavement analysis. Instead, a predictive dynamic modulus equation is used to generate input values. It is of significant importance to state agencies to understand how well the dynamic modulus for locally available materials compares with the predicted dynamic modulus. This paper presents the results of a study by the Florida Department of Transportation and the University of Florida that focused on the evaluation of the dynamic modulus predictive equation used in the new AASHTO 2002 guide for mixtures typical to Florida. The resulting research program consisted of dynamic modulus testing of 28 mixtures common to Florida. Results showed that on average the predictive modulus equation used in the new AASHTO 2002 flexible pavement design guide appeared to work well for Florida mixtures when used with a multiptier to account for the uniqueness of local mixtures. Results of the study also identified optimal viscosity-temperature relationships that result in the closest correspondence between measured and predicted dynamic modulus values.

  • 37.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Sjölander, Peta White
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap, Ergonomi.
    Snickars, Folke
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Urbana och regionala studier.
    Kjellberg, Peter
    KTH.
    Perhson, Susanna
    KTH.
    Eriksson, Thomas
    KTH.
    Reitberger, Göran
    KTH.
    RAE2012: KTH Research Assessment Exercise 20122012Bok (Övrig (populärvetenskap, debatt, mm))
  • 38. Birgisson, Björn
    et al.
    Soranakom, C.
    Napier, J. A. L.
    Roque, R.
    Microstructure and fracture in asphalt mixtures using a boundary element approach2004Ingår i: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 16, nr 2, s. 116-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes the use of the displacement discontinuity boundary element method to model the microstructure of asphalt mixtures. The problem of indirect tension test (IDT) was used to demonstrate the application of the method in the modeling of the cracking behavior of asphalt mixtures. An IDT sample was modeled by three sets of displacement discontinuity boundary elements based on location and function: (1) on the periphery of the specimen, (2) inside the specimen to represent the aggregate structure, and (3) internal fracture path elements inside the aggregate structure. The mastic was modeled by a nonlinear failure law. The simulation of the cracking behavior of the IDT test with this method showed a good agreement with laboratory observations. The predicted stress-strain curves matched the experimental results for both vertical compressive stress and horizontal tensile stress. Crack patterns from these simulations were also similar to the patterns observed visually in the laboratory. In summary, explicit fracture modeling has shown promise as a tool for studying the crack growth and localization of asphalt mixtures.

  • 39.
    Birgisson, Björn
    et al.
    University of Florida.
    Soranakom, C.
    Napier, J.
    Roque, R.
    Numerical simulation of the cracking behavior of asphalt mixtures2004Ingår i: Recent Advances In Materials Characterization And Modeling Of Pavement Systems / [ed] Tutumluer, E; Najjar, YM; Masad, E, American Society of Civil Engineers (ASCE), 2004, Vol. 123, s. 46-64Konferensbidrag (Refereegranskat)
    Abstract [en]

    An understanding of the cracking behavior of hot mix asphalt mixtures provides an important basis for the development of mixtures with improved cracking resistance and pavement cracking perfonnance models. This paper describes the use of random assemblies of displacement discontinuity boundary elements to model the behavior of asphalt mixtures. These random assemblies of boundary elements form particles of varying sizes, which are arranged to simulate the discrete nature of mixtures. To account for the aggregate and mastic properties, each particle is connected to other particles by specifying the cohesion, friction, and tensile properties of the material between particles. The crack initiation and crack growth are simulated using two distinct crack growth laws, based on sequential and parallel crack growth rules. Cracks are allowed to grow along particle boundaries. A series of simulations were performed of the load-deformation and cracking behavior of a typical 19.0-mm nominal maximum aggregate size mixture commonly used by the Florida Department of Transportation. The effects of crack growth rules, particle size, and localization to geometric effects were studied. In summary, the method presented appears to provide a valuable tool for studying the mechanistic behavior of asphalt mixtures.

  • 40.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Soranakom, C
    Napier, J
    Roque, R
    Simulation of Fracture Initiation in Hot Mix Asphalt Mixtures2003Ingår i: Transportation Research Record, Vol. 1849Artikel i tidskrift (Refereegranskat)
  • 41.
    Birgisson, Björn
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Väg- och banteknik.
    Taylor, Peter
    Armaghani, Jamshid
    Shah, Surendra P.
    American Road Map for Research for Nanotechnology-Based Concrete Materials2010Ingår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, nr 2142, s. 130-137Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanical behavior of concrete materials depends to a large extent on structural elements and phenomena that are effective on micro- and nanoscales. The nanomodification of concrete materials has the potential to open up new uses and classes of concrete materials, with wide-ranging implications for the concrete transportation infrastructure. The development of nanotechnology-based concrete materials will require a multidisciplinary approach, consisting of teams of civil engineers, chemists, physicists, and materials scientists. To help develop nanotechnology-based concrete materials, a concentrated effort was undertaken in the United States to develop a national road map for research in this area. This effort included two National Science Foundation (NSF) workshops held in August 2006 and September 2007. In addition to NSF, the Portland Cement Association, the Defense Threat Reduction Agency, the Florida Concrete and Products Association, the Army Corps of Engineers, TRB, and the International Union of Testing and Research Laboratories for Materials and Structures sponsored this effort. The road map for nanotechnology-based concrete materials charts a path beginning with current nanotechnology capabilities to advanced materials and systems. The road map details key milestones and step-by-step short-term, intermediate, and long-term courses of development that must take place to reach these key milestones. The road map also serves as a tool to identify the gap between the basic concrete materials of today and the potential of nanosystems and nanomaterials interacting in concrete nano-houses, nano-bridges, and nano-pavements. The national road map for nanotechnology-based concrete is described and discussed.

  • 42. Birgisson, Björn
    et al.
    Wang, Jianlin
    Roque, Reynaldo
    A new algorithm for determination of crack growth path in HMA materials2007Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 8, nr 1, s. 47-60Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 43.
    Birgisson, Björn
    et al.
    University of Florida.
    Wang, Jianlin
    Roque, Reynaldo
    Sangpetngam, Boonchais
    A viscoelastic displacement discontinuity method for analysis of pavements with cracks2006Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 7, nr 4, s. 417-455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 44. Birgisson, Björn
    et al.
    Wang, Jianlin
    Roque, Reynaldo
    Sangpetngam, Boonchais
    Numerical implementation of a strain energy-based fracture model for HMA materials2007Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 8, nr 1, s. 7-45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 45.
    Bjurström, Henrik
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Rydén, Nils
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Non-contact surface wave testing of pavements: comparing a rolling microphone array with accelerometer measurements2016Ingår i: Smart Structures and Systems, ISSN 1738-1584, E-ISSN 1738-1991, Vol. 17, nr 1, s. 1-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rayleigh wave velocity along a straight survey line on a concrete plate is measured in order to compare different non-destructive data acquisition techniques. Results from a rolling non-contact data acquisition system using air-coupled microphones are compared to conventional stationary accelerometer results. The results show a good match between the two acquisition techniques. Rolling measurements were found to provide a fast and reliable alternative to stationary system for stiffness determination. However, the non-contact approach is shown to be sensitive to unevenness of the measured surface. Measures to overcome this disadvantage are discussed and demonstrated using both forward and reverse rolling measurements.

  • 46.
    Butt, Ali Azhar
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Assessment of the attributes based life cycle assessment framework for road projects2015Ingår i: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Number of life cycle assessment (LCA) tools has been suggested for pavements. However, very few have been adopted by the road authorities. Key reasons for this lack of implementation have been the tendency for very broad LCA analyses that include system boundaries considerably beyond the more natural system boundaries associated with road design, construction and maintenance as well as the lack of available LCA tools that have attributes that reflect key road properties. In this paper, a new attributesbased pavement LCA framework is evaluated for use on real road materials. Aggregates from two different sources and the effect of using a warm mix asphalt additive (WMAA) in asphalt mixtures were investigated in the laboratory. Different pavement design alternatives were generated using the laboratory data and analyzed using the road LCA framework. Asphalt production and material transportation were found to be the most energy consuming processes. The results presented showed that having actual pavement material properties as the key attributes in LCA enables a pavement focused assessment of environmental impacts associated with different design options and, LCA can help in decision support by evaluating environmental impacts of different design alternatives in a project planning/design stage.

  • 47.
    Butt, Ali Azhar
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Kringos, Nicole
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Considering the benefits of asphalt modification using a new technical LCA framework2016Ingår i: Journal of Civil Engineering and Management, ISSN 1392-3730, E-ISSN 1822-3605, Vol. 22, nr 5, s. 597-607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Asphalt mixtures properties can be enhanced by modifying it with additives. Even though the immediatebenefits of using polymers and waxes to modify the binder properties are rather well documented, the effects of suchmodification over the lifetime of a road are seldom considered. To investigate this, a newly developed open technical lifecycle assessment (LCA) framework was used to determine production energy and emission limits for the asphaltadditives. The LCA framework is coupled to a calibrated mechanics based computational framework that predicts the intimepavement performance. Limits for production energy of wax and polymers were determined for the hypotheticalcase studies to show how LCA tools can assist the additives manufacturers to modify their production procedures andhelp road authorities in setting ‘green’ limits to get a real benefit from the additives over the lifetime of a road. From thedetailed case-studies, it was concluded that better understanding of materials will lead to enhanced pavement design andcould help in the overall reduction of energy usage and emissions.

  • 48.
    Butt, Ali Azhar
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Kringos, Nicole
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Optimizing the Highway Lifetime by Improving the Self Healing Capacity of Asphalt2012Ingår i: Transport Research Arena 2012, 2012, Vol. 48, s. 2190-2200Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is of imminent urgency to optimize the lifetime of asphalt binders from the remaining available crude sources. This paper presents a recently developed model in which the self-healing capacity of bitumen is based on fundamental chemo-mechanical parameters. The implications of the enhanced bitumen healing rates are investigated by utilizing a newly developed Open Life Cycle Assessment framework. From the case study it was concluded that using bitumen with self-healing capacity can lead to a significant reduction in Greenhouse Gas emission and energy usage. Additionally, the importance of knowing the fuels and emission of bitumen modifiers on the highway sustainability was demonstrated.

  • 49.
    Butt, Ali Azhar
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Kringos, Nicole
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Using Life Cycle Assessment to Optimize Pavement Crack-Mitigation2012Ingår i: Scarpas et al. (Eds.), 7th RILEM International Conference on Cracking in Pavements: Vol. 1, Delft, The Netherlands, 2012, s. 299-306Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cracking is very common in areas having large variations in the daily temperatures and can cause large discomfort to the users. To improve the binder properties against cracking and rutting, researchers have studied for many years the behaviour of different binder additives such as polymers. It is quite complex, however, to decide on the benefits of a more expensive solution without looking at the long term performance. Life cycle assessment (LCA) studies can help to develop this long term perspective, linking performance to minimizing the overall energy consumption, use of resources and emissions. To demonstrate this, LCA of an unmodified and polymer modified asphalt pavement using a newly developed open LCA framework has been performed. It is shown how polymer modification for improved performance affects the energy consumption and emissions during the life cycle of a road. Furthermore, it is concluded that better understanding of the binder would lead to better optimized pavement design, hence reducing the energy consumption and emissions. A limit in terms of energy and emissions for the production of the polymer was also found which could help the polymer producers to improve their manufacturing processes, making them efficient enough to be beneficial from a pavement life cycle point of view.

  • 50.
    Butt, Ali Azhar
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Tasdemir, Yuksel
    Dept of Civil Engineering, Bozok University, 66100 Yozgat, Turkey.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    The Effect of Wax Modification on the Performance of Mastic Asphalt2010Ingår i: International Journal of Pavement Research and Technology (IJPRT), ISSN 1997-1400, Vol. 3, nr 2, s. 86-95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The scope of this study is to evaluate the mechanical performance of the polymer modified mastic asphalt with 4% montan wax (Asphaltan A) additive. The impact of wax modification on binder, binder/filler mixtures and mastic asphalt was investigated in the laboratory. Wax modified binder properties were determined using dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy and conventional tests (softening point, penetration, elastic recovery, breaking point, viscosity and storage stability). The bending beam rheometer (BBR) was used for determining low temperature creep compliance and the tensile stress restrained specimen test (TSRST) for determining low temperature fracture. The fatigue cracking behavior of mastic asphalt was investigated using Superpave Indirect Tensile Test (IDT). Based on HMA Fracture Mechanics the influence of wax on the asphalt mixture resistance to fatigue and brittle cracking has been evaluated. The addition of wax to the polymer modified binder resulted in a viscosity reduction at higher temperatures, indicating a possible lower production and laying temperature as compared to asphalt without wax additive. DMA and BBR results showed some increase in stiffness and a more elastic response of the wax modified binder at medium and low temperatures. The TSRST fracture temperature was higher for the mastic asphalt containing wax, indicating a certain negative impact of wax modification.

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