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1 1 Report on the 10 th International Conference on Asphalt Pavements, Quebec, Canada, August Introduction The 10 th ICAP was attended by Co van der Vusse (B&O huis) and Sandra Erkens (IW). In this report we relay our impressions, both in general and (in the Appendices) in more detail. These impressions are based on the sessions and presentations actually attended and discussions with other participants. For a more complete overview, we refer to the proceedings. 1.2 History International Conference on Asphalt Pavements, a series of conferences initiated in 1962 as the An Arbor conference series in order to disseminate research findings and new developments in the asphalt world. In 1972 the conference was held outside An Arbor, in London, for the first time, when it was in London to stress the international aim. The International Society for Asphalt Pavements became the sponsor in 1978, leading to a change in the conference name but continuity in aim. From 1962 to 2002 there has th been a conference once every five years, but at the 9 conference in 2002 in Copenhagen it was decided to change to a four yearly schedule, with a symposium on a dedicated topic in between. The first symposium of that kind was held in 2004 on accelerated pavement testing, the next on pavements and th environment will be held in 2008 in Zurich. The change in pace has led to the 10 ICAP conference in 2006 in Quebec, Canada. 1.3 Participation th The 10 ICAP in numbers: there were about 200 papers, in 1 key note lecture, 4 plenary sessions of 4 papers each and 45 parallel sessions on a wide variety of topics. The conference was attended by over 400 participants (350 pre-registered) from 32 countries. The proceedings of the previous ICAP conferences are now all available on CD s which are sold by the ISAP Scociety. 1.4 General impression The conference was well organised and both attendance and contributions came from all over the world. There is a shift from the purely road engineering to a more general outlook, where related environmental and maintenance strategies are also being considered. The average level of the contributions is high, although particularly in the classic road engineering topics there is often lack of intend, appearing as if find one just randomly started testing and hopes to find results that will be useful, rather than devising a research plan beforehand and finding the proper approach for the questions at hand. 1.5 Dutch representation, position & reputation There where 10 Participants from Dutch organisations, 6 from the Delft University of Technology (3 from Road engineering, 3 from structural mechanics), 2 from DWW (Co van der Vusse from B&O huis & Sandra Erkens from I), 1 from CROW and 1 from the R&D department of a contractor. Other contractors, engineering firms and road laboratories did not attend the conference. 1

2 Besides the direct contribution from the Dutch or Dutch based participants, contributions and activities from the Netherlands were also referenced in various sessions and Dutch representatives played a role in the conference. Egbert Beuving (EAPA) held a plenary lecture on the developments in Europe, outlining the developments in standards and highlighting innovations. Especially the photo s he showed on the roll pave principle resulted in reactions from the audience. Andre Molenaar (TUD) was chairman of another plenary session and his work on cracking was mentioned in the key note lecture by Reynaldo Rogue. The work done by the combination of his group and Tom Scarpas structural mechanics group on constitutive modelling was mentioned by various speakers like Chuck Schwarz (Univ Maryland) and Andy Collop (Nottingham pavement centre). The structural mechanics group more recent work was also referenced in moisture damage sessions. The IPG programme was mentioned several times in relation to noise reduction research efforts and ravelling in porous asphalt. 1.6 Topics targeted by ICAP ICAP targeted five main themes, each of which had several sub-themes. The division of contributions over the five main themes is shown in the Figure underneath. The historical focus on Asphalt Pavement Materials and within this theme on the topic of in situ and laboratory characterization and modeling of pavement materials can still be recognized, however, broadening the scope of the conference by including other topics appears to work out nicely. 12% 8% 43% Developments in Asphalt Pavement Materials Structural Design for New and Existing Pavements Pavement Performance 20% Pavement Investigation and Analysis 17% Highway Operations FIGURE: Percentage of the total number of papers that deals with a specific theme The complete list of main and sub-topics is shown on the next page. The subtopics in this list were also the themes on which papers were invited. The number of contributions on the subtopics varied from 27 to 1 while some were even omitted from the final programme because no papers were received (or at least not accepted). In the following sections the general observations per main theme are summarised, please note that these impressions are based on the presentations we attended, for a more complete overview we refer to the proceedings. These can be accessed via the CD on the V-drive (V:\I\Congressen verslag\icap2006) or Kennisplein. In the appendices, you find additional observations from Sandra en Co concerning the sessions each of us attended. 2

3 1 Developments in Asphalt Pavement Materials 1.1 Asphalt mix design 1.2 Low-cost surfacing materials 1.3 In situ and laboratory characterization and modeling of pavement materials 1.4 Improving the performance of granular base materials 1.5 Improving the performance of asphalt binders 1.6 Reuse and recycling 1.7 Utilization of process materials and by-products 1.8 Foamed mix 1.9 Water damage in asphalt 1.10 Asphalt cracking 1.11 Asphalt reinforcement 2 Structural Design for New and Existing Pavements 2.1 Development of long-lasting pavements 2.2 Validation and implementation of the 2002 Pavement Design Guide 2.3 Effects of European standardization of truck weights and dimensions 2.4 Pavement-vehicule interaction 2.5 Low-volume road design 2.6 Accounting for frost action and seasonal effects 2.7 Life-cycle cost analysis 3 Pavement Performance 3.1 Long-term performance studies 3.2 Full-scale and accelerated pavement testing 3.3 Measuring pavement performance 3.4 Pavement instrumentation 3.5 Modeling pavement deterioration 4 Pavement Investigation and Analysis 4.1 New developments in backcalculation of pavement layer moduli 4.2 Innovative approaches to the interpretation of deflection data 4.3 Developments in non-destructive pavement analysis 4.4 Pavement profile analysis 4.5 Collection and analysis of distress data 4.6 Characteristics of safe pavements 4.7 Pavement noise 4.8 Measurement and analysis of other surface characteristics 5 Highway Operations 5.1 Partnership in pavement construction and maintenance 5.2 Performance-based contracts and specifications 5.3 Risk management in pavement construction 5.4 Quality systems 5.5 Advancement in construction techniques 5.6 Reduction of user disturbance 5.7 Preventative maintenance 5.8 Pavement preservation tools 5.9 Sustainable development List of topics addressed at 10 th ICAP DEVELOPMENTS IN ASPHALT PAVEMENT MATERIALS This main topic was by far the largest theme of the conference and as such it covered a wide variety of sub-topics. An interesting observation mentioned by several people was the spin-off of the SUPERPAVE mix design system in the US. Although the system itself may have its drawbacks, the fact that the same tests are used throughout the US provides a common starting point. They feel that this facilitates sharing of knowledge and experience and thereby speeds up developments. This is an interesting observation with regard to the implementation of the European standards for AC in In interesting contribution in this respect dealt with an attempt to integrate these standards in a 3

4 mixture design method by a Norwegian cooperation of highway agency, material suppliers and research institutes. Concerning response modelling and classical damage types, a lot of Dutch work is still mentioned as state of the art, but where concerning newer materials (half warm mixes, highly modified mixes) most of the contributions are from non-european participants (South Africa and Asia). The keynote lecture was on pavement cracking, showing that the approach in the US is still focussed quite strongly on separating the various damage mechanisms. It provided a nice overview, but limited new insights. The current focus is on energy approaches, but this doesnot really present anything new either STRUCTURAL DESIGN FOR NEW AND EXISTING PAVEMENTS The key issue here is the mechanistic-empirical desing approach, the heart of the AASTHO 2002 guide. It is not generally applied, but it is clearly gaining momentum. The most interesting aspect is that they try to combine material, climate, structural and traffic data in one over-all approach. We do not yet have something like it, so despite all the problems and uncertainties raised in various presentations (how to get your data, how to calibrate the models), it is an interesting starting point for the increasing demand for a Euro-design code to go with the European standars for AC. Because the ME approach requires traffic spectra rather than ESALS, it triggers contributions in the area of pavement-vehicle interaction. These are of varied quality, from attempts to somehow summarize those spectra to get back to ESALS to WIM-like systems and simulations of trucks to assess the most important influences on the dynamic load PAVEMENT PERFORMANCE Pavement performance is partially dominated by Accelerated Pavement stories, but most of them stress the need to bridge the gap between the APT and field data. An interesting topic was based on the claim that since road users care only for comfort, which is smoothness, pavement performance indicators should be related to this parameter. It is an interesting approach, but it neglects aspects like splash&spray and rutting, also mentioned as important for comfort by our users, and skid resistance which is linked to safety. With regard to pavement deterioration, the focus appears to shifting from practice-like tests to modelling. This doesnot mean that there aren t still a number of contributions on simple performance tests or pavement-like tests, but these are mainly variation on the well-known themes. Some interesting work on rutting is presented by LCPC and OCW/Nynas (France, resp. Belgium). Several American groups are working on simulating various deterioration mechanisms like rutting and cracking. The limiting factor in these approaches appears to be the material modelling, with the input limited to tension (cracking) or compression (rutting) tests. However, these limits are acknowledged and they all claim to work towards general models PAVEMENT INVESTIGATION AND ANALYSIS An interesting observation is that, where there would appear to be a close link between this topic and the previous, this is does not appear to be the case. Where the contributions in the previous section focus on testing and modelling from a material-based point of view, those in this section aim at pavement inspection and the link to management systems. Using Pavement inspection data for the ultimate validation or the identification of necessary modification of pavement performance models is not addressed. Another observation is that our standardized inspection routine appears to be fairly advanced. Several contributions address feasibility studies into such routines and the development of network condition databases. Concerning the registration of construction parameters, however, especially the Americans appear to have rather elaborate quality control and data storage systems. The impression 4

5 obtained is that they use these also in there innovative contracts, which could be interesting for our current developments HIGHWAY OPERATIONS (CO VAN DER VUSSE) Vooraf: Deelname vanuit het BOH is ingegeven door het thema Highway Operations waaronder wordt verstaan a. management models - partnership in pavement construction and maintenance - performance based contracts and specification - risk management in pavement construction - quality systems b. technical and organizational issues, including topics as - reducing of user disturbance - preventative maintenance - pavement preservation tools - sustainable development - safety issues. Deze onderwerpen zijn min of meer terug te vinden in de papers/presentaties. Daarnaast heb ik onder meer aandacht geschonken aan onderwerpen die te maken hadden met longlife pavement, performance/eigenschappen van verhardingen (stroefheid, geluid), dunne deklagen, zeer open asfaltbeton en recycling. Als waardevol zijn mij opgevallen de papers/presentaties over - het reconstrueren van een drukke autosnelweg (M4) in het verkeer door P.Scott (UK). Er is veel aandacht geschonken aan de informatie aan de gebruikers en omwonenden en dat het komt overeen met de aanpak van de reconstructie van de A10 west. Opmerkelijk was de verkeersoplossing. Overdag s was hetzelfde aantal rijstroken (versmald) beschikbaar voor het verkeer. In de nacht werd het verkeer naar 1 rijbaan geleid en de 2 verkeersstromen (1-1) werden gescheiden door kegels. Dat is volgens de RWSrichtlijnen ondenkbaar. Toch was het aantal ongevallen niet opvallend. - innovatie en performance contracten door S.Brown (UK). Highways Agency is ruim 10 jaar geleden overgegaan op een andere werkwijze (en forse reorganisatie) waarbij meer aan de markt wordt overgelaten. Het functioneren van de weg is vastgelegd in functionele specificaties/eisen en het is een lange termijn benadering met partnership oa om de veiligheid te verbeteren. De bedrijven zijn niet snel geneigd om nieuwe werkwijzen/oplossingen te introduceren die ze nog niet goed beheersen maar wel het risico van dragen. Ze denken nu aan bdfo(peration) contracten met een duur van 30jaar. Ook wordt de aannemer in een zeer vroeg stadium betrokken bij de voorbereiding van het contract dus nog voor de inschrijving. Kwaliteit wordt zwaar meegewogen, bij nieuwbouw contracten is de verhouding 70 30% (kwaliteit prijs) en voor onderhoud is dat zelfs 80 20%. Dit is voor RWS een belangrijk thema. - eigenschappen van het wegdek in relatie tot het gebruik is belicht door: Brillet (FR). Dat heeft bij de Fransen geleid tot het niet meer toepassen van een bepaald mengsel (SCAC) op de snelwegen ivm stroefheidsproblemen. Bovendien gebruiken zij voor een hogere stroefheidswaarde materiaal met een hoge PSV en polymeer bitumen. Fernandez ( PORT). De Portugezen overwegen om de eisen voor stroefheid te verhogen. Dit is interessant knoppen materiaal. - beperking van geluid is belicht door Tighe (CAN, proefvakken oa rubberasfalt), Carter (CAN, theorie ontstaan van geluid). Zie ook dunne deklagen. - analyse van de onderhoudsfrequenties irt de schade (Brillet, FR). Uitkomst van het onderzoek is inzicht in de maatgevende schade (thermal cracking 37%, stroefheid 31%). Dat inzicht heeft er toe geleid dat er nu meer VTAC/dunne deklagen worden toegepast. - interessant voor diegenen die duurzaamheid een warm hart toedragen is de paper van L. Uzarowski (CAN). Hij geeft een interessante beschouwing over duurzaamheid en pleit oa voor beperking van afval, beperking van nieuwe materialen, beperking van zware transporten en een life cycle benadering. 5

6 - opmerkelijk is de aandacht voor preventief (klein) onderhoud aangestipt door Hein (CAN) welke het systematisch benaderd en Yilderim (USA) die inzicht gaf in het cursusprogramma van zijn door 2 universiteiten gestichte instituut voor preventief onderhoud. De cursus is bestemd voor beleidsfunctionarissen en uitvoerenden. Beide onderbouwden het nut met de stelling dat het achterwege laten van preventief onderhoud leidt een veelvoud van meerkosten later. (1$ nu ipv 4 a 10 $ later). - aan longlife benaderingen is door diverse personen aandacht geschonken: Lane (CAN). Zij legde relatie met contracten en ging in op hoe een langere levensduur bevorderd kan worden door middel van specificaties (per jaar). Zij zoeken het overigens vooral in de contract/garantieduur. Deze is nu 7 jaar. Zij streven naar 10 jaar. Haas belichtte return on investment met een interessante theorie geïllustreerd met een praktisch voorbeeld van een weg (DBFM) in Canada met een contractduur van 99 jaar. Rada (USA) ging in op het long term pavement programma (ontwerp en kwaliteitsborging). Overige onderwerpen: - dunne deklagen zijn door diverse personen (Ertman Larsen DK, Pretorius SA) belicht. De Denen doen onderzoek overigens in samenwerking met IPG (DWW) en Pretorius heeft onderzoek gedaan naar betrouwbare criteria voor dunne deklagen. - zeer open asfalt beton is door de Zwitsers onderzocht met zelfs een proefvak voor 2zoab. Ze melden belangrijke daling van het aantal ongevallen. - aan rap ofwel recycled asphalt is ruim aandacht geschonken oa in de plenaire sessie (zie Sandra) oa vanwege de voordelen voor het milieu: geen of minder nieuwe materialen, minder transportkosten, het asfalt wordt ter plaatste vernieuwd hetgeen vooral aantrekkelijk is in gebieden met een lage dichtheid van asfaltwegen ofwel zonder vaste asfaltmolens. Hosokawa (JAP) bracht een spectaculaire produktiemethode waarin in een arbeidsgang de bovenlaag werd gerecycled en een nieuwe toplaag werd aangebracht. Bij de samenvattingen is nog meer informatie te vinden. 1.7 Specific questions asked by DWW-colleagues MARKTBENADERING, DE WIJZE VAN SPECIFICEREN EN TOETSEN IN D&C - CONTRACTEN Zou vallen onder thema 5.2, Higway Operations-performance based contracts and specifications en 5.4 Quality systems. Brown is ingegaan op de performance contracten (zie highway operations) maar ook in andere papers is er iets van gezegd (Lane) DE WIJZE WAAROP (DAARIN) MET CE - NORMEN WORDT OMGEGAAN Een Noors initiatief om via de CE-normen tot een ontwerpprocedure te komen, uitgewerkt door wegbeheerder, onderzoeksinstellingen en leveranciers kwam nog een beetje in deze richting (paper nr 1.1-3) EUROPESE STANDAARDISERING VAN NOISE PERFORMANCE VAN PAVEMENTS. PAVEMENT NOISE, THEMA 4.7, had wel enige bijdragen die behandeld zijn in combinatie met andere onderwerpen oa dunne deklagen (zie highway operations). 6

7 1.7.4 KLIMAAT EN WEGDEKKEN Meest relevante bijdragen die ik heb gehoord gingen over cold-in place recycling, maar dat was niet vanuit milieu oogpunt maar pragmatisch: afgelegen wegen, lang vervoer en hoge kosten leiden tot het ter plaatse met de aanwezige materialen her-paven. Er was wel een firma aanwezig (Green ARM) die een en ander vertelden over het in een arbeidsgang recyclen van de bestaande bovenlaag en het aanbrengen van een nieuwe toplaag EFFECTS OF EUROPEAN STANDARDIZATION OF TRUCK WEIGHTS AND DIMENSIONS Thema 2.3 had geen bijdragen. De nadruk in dit hoofdthema lag op de AASHTO-design guide met zijn mogelijkheden om aslast spectra in te voeren en de worsteling hoe hier mee om te gaan en wegdek-voertuig interactie. In die laatste categorie liepen de benaderingen uiteen van uitgebreide simulaties met truckmodellen om de meest belangrijke aspecten die tot verhoging van de belasting leiden te komen (kwam toch uit op vlakheid), via WIM-inputs tot equivalente aslast beschouwingen zoals we die klassiek gebruiken PAVEMENT VEHICLE INTERACTION Zie genoemde onder STILLE VOEGOVERGANGEN (I.E. THORMA JOINTS) Er was een presentatie over joints maar die ging over het dichtingsmateriaal en niet over stille voegovergangen. 1.8 th List of upcoming events highlighted during the 10 ICAP Theme/topic organisation date location Advanced characterization of pavement 4 th 3D FEM in June Athens, Greece and soil engineering materials Pavements Consolidating Best Practice 9 th CAPSA: sept Gaborone, Botswana Int. conf. On heavy vehicle ISHVWD 10 & may Paris, France ICWIM 5 Managing Pavement Assets ICMPA June Calgary, Canada Pavements & Environment ISAP symposium Aug Zurich, Switzerland Int conf on Asphalt Pavements 11 th ICAP 2010 Japan 7

8 Appendix A Notes Sandra Note: the section number equals the topic number +1 (because of the automatic numbering of word), theme number and a chronological sequence, i.e. section concerns the first main theme (1+1=2), first sub theme (1) and the first presentation attended on that topic (1). Titles are paper titles and the numbers in brackets behind third-level headers are the paper numbers on the CD. If no third level titles are given, I did not attend sessions on that topic, the titles are included to maintain the topic-related numbering. 2 Developments in Asphalt Pavement Materials 2.1 Asphalt mix design NORTH AMERICAN SHIFTS IN HOT MIX ASPHALT TECHNOLOGY (42) He presents the history of hot mix asphalt technology as something strongly related to changes in vehicle technology. Presents an overview of developments in time, with rules of thumb as the initial approach, followed by Hubbard system of design after tior to the mid-1900s most asphalt mixtures were formulated using recipes although some early mix design methods were being developed. In the latter 1900s HMA design was dominated by the Marshall method of design, a method adopted in many countries throughout e 1920 s where void percentage and something equivalent to void in mineral aggregates was used. Then the Marshall design after the 1940 (no mention of the Hveem tests and design method). He also states that SHRP was basically a reaction to a rutting epidemic in the 80 s. SUPERPAVE s performance grades include the time and temperature effects on bitumen and mix performance, allowing rut mix design. Part of SUPERPAVE s importance is claimed to be the acceptance throughout the US of the same design method. This paved the way for the 2002 ASTHO mechanistic empirical design guide, but the general acceptance thereof is not yet at SUPERPAVE levels. An idea that is garnering general acceptance is the perpetual pavement approach, where high strains yield short life times and low strains yield perpetually lasting pavements (R: in material mechanics terms: stresses and strains in the initial response envelop do not cause damage). An approach of just replacing the top layer becomes wide spread (R: something we already do in our maintenance approach). There is a lot of attention on practical aspects like paver segregation, joint quality and construction effects (like a truck driver spraying diesel in his truck to prevent the asphalt load from sticking to it..). Most of these topics are addressed in the Netherlands as well, but from what I hear here, we are generally a bit further ahead DEVELOPMENTS IN EUROPE AND IN THE EUROPEAN ASPHALT AND BITUMEN STANDARDS (43) Egbert presents an overview of the existing European standards, the reasons for establishing them and the route to arrive there. He relates his presentation strongly to the bitumen specs and the initiation thereof in 1990, because they are still under development. HE stresses that it takes this long because all stakeholders are part of the process. Goes on to explain thart the standards for AC will be mandatory for all Europan member states starting january 2008 (R: hopefully it will have similar benefits as SUPERPAVE, shared standard allowing more cross reference of experience and shared research). As an aim for the future he describes standards that use only functional requirements, which does not include any compositional requirements. Ideally, one standard would than be sufficient. He stresses the importance of environmental issues on the European agenda and it s effects on mixtures via warm, half warm etc techniques. Presents two-layer laying techniques as a successful innovation (Q: our results have not been so good, weren t they?). Finally, he also shows rollpave, quite elaborately with many photo s (reaction in the room is incredulous), unfortunately he doesnot mention it is a Dutch initiative. 8

9 2.1.3 DEVELOPMENTS IN HOT MIX ASPHALT IN ASIA (44) The presentation consists of an overview n numbers (length of roads, percentage PA) of pavement developments in Asia, followed by an overview of the tests used, which are well know tests like wheel tracking (for rutting), Cantabro (for ravelling) and four point bending (for cracking). The Cantabro test and steered wheel tracking test in laboratory have been adapted to evaluate the raveling resistance of porous asphalt concrete spec. for intersections. Then it goes on to microscopic pictures of SBS modified asphalt, where they aim at high SBS contents to improve rut resistance and reduce water sensitivity. This is followed by field tests for friction, a dynamic friction tester which uses a spinning disk, similar to Wehner-Schulze, that is part of the ASTM (ASTM E ) and an acousrtic field measurement with a microphone on the axle (road acoustic checker car). Basically, they seem to be vartiations on tests known and used in Europe and/or the US TRENDS AND CALLENGES IN HOT MIX ASPHALT (45) Presentation on environmental issues in road engineering. He starts with the use of recycled asphalt, where use is driven by financial incentives (cheaper than new material), with the challenge of providing the same quality. Air quality criteria also result in an increase of warm (versus hot) mix asphalt, specifically alonf the east and west coast. The problem of run of water during heavy rain fall (because of paving/covering of most of the surface in populated areas, which limits infiltration. They look into PA to solve this for roads and parking lots, with sublayers with 40% voids which seem to work really well even in cold climates. Noise is also becoming an issue, for the approach here he refers to the Netherlands, with open surfaces rather han soundbarriers. For perpetual pavement design her refers to the website of the asphalt alliance where there is a free Monte Carlo and Wesly based design program available EVALUATION AND CHALLENGES OF THE FLOW NUMBER SIMPLE PERFORMANCE TEST (1.1-2) Presents the old flow number test (where a differentiated fitted polynomial was used to determine the actual flow number from the test curve) and the new one, which is quite different. It looks like a triaxiaal set-up and can be run both with and without confinement. They use specimens 150mm (!) high and 100mm diameter and friction reduction between the plates (which look to be of equal or slightly smaller D than the specimen?). Because of the rather complex set-up they started out to simplify the set-up. Simplification includes simpler deformation measurements. They make flownumber mastercurves, by running tests at various temperatures and stress levels and shifting the results (exact procedure unclear, check paper). They checked the sensitivity to volumetric parameters specifically air voids and bitumen content. They used over 1000 asphalt specimens, including both DOT mixtures and mixtures from field validation studies, to compare the materials Flow Number property against the actual field performance. The results showed that the Flow Number test has potential for ranking the relative performance of asphalt mixtures, determining the performance history of asphalt mixtures (in terms of deformation resistance), determining the optimal binder content of asphalt mixtures, and examining the effects of air voids on asphalt performance, but both confined and unconfined tests did not respond as strongly as expected to low void percentages (<3%). They claim that that locally based criteria could be established to determine local performance in rutting DEVELOPMENT OF A NEW ASPHALT MIX DESIGN SYSTEM IN NORWAY (1.1-3) Based on PROKAS project aimed at developing functional specifications, ran from 1998 to It was a combined effort of road authorities, contractors, material suppliers etc. One objective was to develop performance-based specifications for Norwegian asphalt mixtures. During the project, new test methods were tried out and useful experience regarding properties of typical Norwegian asphalt mixes was gained. A new mix-design procedure has been sketched based on the results from the project. In this procedure, a new asphalt binder selection system for mix design is used. The system is based on local climate conditions and traffic loadings. The method focuses on material selection and particularly binder selection. For binder content selection, they use the gyrator. For performance tests they used the Indirect Tensile Stiffness Modulus (ITSM) test and the Indentation Repeated Load Axial Test to assess the elastic modulus and deformation properties respectively. It correlates well with SUPERPAVE for conventional mixtures. 9

10 Field samples are taken and tested to assess their performance with respect to the functional requirements as follow-up to the actual mix design. They started testing the design method and produced a number of sections with different mixtures in2005, obviously evaluation will still some time. A remark with respect to the CE- guide is made, but it is not quite clear how this fits in. NOTE: They show a table of mixture properties where PA performs more poorly that AC on permanent deformation! Check definition AGGREGATE QUALITY AND THE INFLUENCE ON THE RUTTING IN ASPHALT PAVEMENTS (1.1-4) Conclusion is that modified binders respond better with respect to rutting (tsja), research mainly based on determining the effect of aggregate on resistance to studded tyres and that is what most of the presentation is about as well. The relation to rutting is sketchily at best. Mostly he mixes up rutting and damage due to studded tyres (might explain the weird ranking from previous speaker) COMPARISON OF FIELD AND LABORATORY COMPACTED ASPHALT MIXTURES (1.1-5) A presentation on an approach that involved image analyses and mechanical tests to asses the most representative lab compaction method. They used several compaction methods, gyratory compaction, vibratory compaction (kango hammer), slab compaction and field compaction with dead weight rollers, wheel rollers (?) and vibrating rollers and various aggregate and binder types. They analysed 4 horizontal planes per core. They focussed on the orientation of the particles in those planes (so not the 3D structure or pores). In terms of aggregate orientation, slab compacted specimens tend to mimic field compaction better than gyratory and vibratory compaction. Where moulds are used, tendency to preferential orientation was stronger. The mechanical properties of slab compacted specimens were in some cases also closer to those of field cores than those from the other compaction techniques, but the stiffness modulus and permanent deformation resistance of field cores are still considerable lower than those of any laboratory specimens. R: it appears that this was almost literally the same presentation as given at CAPSA last year??? 2.2 Low-cost surfacing materials DETERMINATION OF MATERIAL PROPERTIES OF BITUMEN STABILIZED MATERIALS USING TRI- AXIAL TESTING (1.3-22) Presentation on a program to characterize the behaviour of bitumen stabilized materials for use in cold in-place recycling for numerous reasons. Focuses on the results of the monotonic and long duration dynamic tri-axial tests on various mixtures with crushed rock (limestone) and millings (RAP) which were treated with two types of bitumen emulsion, as well as with foamed bitumen. It was found that for the blends with mainly RAP, the bitumen emulsion produces a mix with a slightly higher shear resistance than foamed bitumen. For the blends with less RAP the use of foamed bitumen resulted in more shear resistance than emulsion. The friction angle appears to be mainly influenced by the aggregate used and not by the type of binder. He established a transition between secondary and tertiary type response at a ratio of deviator over normal stress of 0.4/0,5 he actual level differs per mix composition and binder type. Also, there are differences between mixtures in the sense that some mixtures can deal with higher strain levels before getting into tertiary flow than others. (R:This may help to establish the usefulness of various test conditions and/or failure criteria for various materials.) THREE-DIMENSIONAL VISCOPLASTIC CHARACTERIZATION OF ASPHALT CONCRETE UTILIZING PERZYNA AND HISS METHODOLOGIES (1.3-22) Description of nn enhanced viscoplastic model for irrecoverable deformations of asphalt concrete. They moved to Perzyna type plasticity after the independent validations tests couldnot be describd with the simpler model they used. They se (and state it) a ACRe like approach, but visco-plastic rather then strain rate dependent, the adaptation the Scarpas group made shortly after finishing the original ACRe project.their initial model did not include hardening, the more advanced model does. Incorporation of temperature and loading rate effects is via an extended time-temperature superposition principle. Model calibration was based on cyclic creep tests with full recovery under two different loading historiesthey have now predicted monotonic (i.e. constant strainrate) tests that they did not use fr model calibration and those look good. 10

11 They aim to use it for rutting analyses, but it is still only based on compression tests so it remains to be seen of it will work. Intensions are to also incorporate tension and such OVERLAY TESTER: A SIMPLE AND RAPID SCREENING TEST FOR CHARACTERIZING CRACK RESISTANCE OF HMA MIXES (1.3-24) Presentation on the feasibility of using the Overlay Tester (OT) as a simple test for characterizing crack resistance of an stone skeleton asphalt mixes, to prevent rut resistance design from compromising crack resistance. The OT can be run on standard size samples, typically 150 mm long by 75 mm wide by 38 mm high, which are glued on to a set of steel plates with an opening between them. The plates are moved apart repeatedly, resulting in cracking of the asphalt above. Result is a crack length versus nr of load repetitions. He states that in a series of tests, it was found that asphalt absorption by aggregate appears to have a major impact on crack resistance of asphalt mixes. Q: do we have experience with that? They claim a good correlation with both fatigue bending tests and filed performance. R: instrumentation appeared rather limited, so it appears a simple empirical performance test. Check the correlations from the paper THE PERMANENT DEFORMATION LAW OF ASPHALT MIXTURES: INVESTIGATION OF THE EFFECT OF MIX COMPOSITION AND MATERIAL PROPERTIES (1.3-46) In the presentation first Franckens early work on large triaxial specimens is summarized, than the new EU test is described and the differences are addressed. They try to establish if they can still use the old results hen interpreting the new results. As expected, they cannot simply use the A and B values from Frankens power law for permanent deformation, because the deformation in the new test is approximately 4 times as high as predicted with the formula. Their analysis is complicated by a rather high variability in the intercept value. The power is more reproducible and showed a reasonable correlation with binder characteristics. They find logical rankings in B for variation in binder type and mix type. They excluded the gyratory compactor as a method for specimen preparation because of the variability, instead they used slab compaction FRACTURE BEHAVIOR OF ASPHALT MIXTURES USING THE DISK-SHAPED COMPACT TENSION TEST AND DISCRETE ELEMENT METHOD (1.3-47) The presentation deals with fracture in hot-mix asphalt, using a micromechanical modeling approach that of the materials heterogeneous microstructure via the discrete element method. They simulate the disk-shaped compact tension (DCT) using a clustering technique that realistically portrays the heterogeneous structure over the depth of the specimen is excluded. Butt you still need to assess the properties of the constituent materials that result in the cohesion and adhesion that is exhibited. They hope to use the approach for understanding and accounting for size effects in fracture tests and the modeling of cracking in hot-mix asphalt pavements CREEP MODULUS OF ASPHALT MIXES DETERMINED IN UNIAXIAL CYCLIC COMPRESSION TEST WITH SOME CONFINEMENT (1.3-48) Presentation on the effect of several variables on the value of the Creep Modulus determined in the Uniaxial Cyclic Compression Test with some confinement, according to EN standards. Using the Nottingham Asphalt Tester they studied the following variables: stress level, loading time, rest period, curing period, testing temperatures and sample size. The purpose was also to compare the some confinement procedure with the traditional unconfined uniaxial cyclic compression test, which is not included in the standard. The results of this study indicate that the some confinement procedure could have a different influence on the Creep Modulus depending on the volumetric properties of the mix being studied and the testing conditions. He presents results on SMA and PA (but he talks about dense and pourous mixtures, where I suppose PA is porous and SMA is considered dense), where PA is more sensitive to creep, both with and without confinement. Also, the creep in both mixtures increased with test frequency. They conclude that adding some confinement is necessary to prevent underestimating the resistance to rutting. The confinement here is introduced by a restraint rather than by applying pressure and this would result in different confinement levels due to 11

12 the different response of the materials, thus creating a difference. It is unclear whether that matches with reality or not PERMANENT DEFORMATION CHARACTERISTICS OF AGGREGATE SKELETON IN ASPHALT MIXES (1.3-67) Presentation on a project that aims to characterize rutting resistance of asphalt mixes by characterising the performance of the bitumen, mastic and aggregates respectively. On the basis of this, models will be developed for the behaviour of each component (Q: how will you put them together for overall reponse prediction?). Mixes selected are ZOAB 0/16, SMA 0/11 and DAB 0/16, the aggregates skeletons are in some cases compacted with some water. He did not check whether the aggregate skeleton achieved is comparable to those in the asphalt mixtures. This presentation deals with characterisation and model development for the aggregate skeletons. The characterization was performed by means of triaxial testing involving both stress controlled monotonic failure tests conducted at constant confinement and permanent deformation tests conducted under cyclic and constant confinement. He shows failure tests where DAB exhibits a peak,but both SMA and ZOAB look more elsto-plastic, in all cases the deformation was dilational (i.e.: volume increase R:something that will be constrained in AC by the binder, loading it in tension). The permanent deformation of aggregate skeleton under cyclic confinement was higher than the permanent deformation under constant confinement. He also states that the stresses at 10% permanent deformation in the cyclic tests (plotted on I1- sqrtj2) for ZOAB and SMA are close to those at failure in the monotonic test, for DAC they are much lower? REPEATED AND UNIAXIAL TENSILE CREEP TESTING OF ASPHALT CONCRETE (1.3-68) Presentation on results from laboratory testing undertaken to characterize the tensile behaviour of two generic types of asphalt mixture (bitumen macadam and???). Uniaxial tensile creep testing and repeated load creep testing have been undertaken over a range of conditions. For both mixtures, increasing the stress level and/or increasing the temperature was found to reduce the time to failure. The elastic moduli of both mixtures was found to be independent of stress level and the steady state viscous behaviour was found to be non-linear. Both approach and results are in line with the ACRe project results, this is a next step, where cyclic loading is being included. They do not yet state modelling or simulation results RUTTING PREDICTION OF ASPHALT CONCRETE MATERIALS USING A MULTI-CRITERIA VISCOPLASTICITY MODEL (1.3 87) During the past few years, many efforts have been devoted to the study of rutting problems. Under high traffic loadings together with extreme environmental conditions, permanent deformations of asphalt pavements appear and become more and more severe, requiring more efforts with regard to developing suitable predictive models. In this paper, a three-dimensional elasto-viscoplastic model is developed and applied to describe the behaviour of asphalt concrete materials under cyclic loadings. The model is based on a double-criteria visco-plasticity model and focuses on the coupling of a Drucker-Prager type criterion with a customized quadratic criterion. This is in order to take into account the evolution of volumetric deformations and the role of the shear strains on the establishment of permanent deformations. The kinematic hardening law is introduced following the continuum thermodynamics framework together with Koiter's evolution law for plasticity followed by an extension to viscoplasticity using a Duvaut-Lions type formulation. The model is validated using experimental results of dynamic creep tests. A numerical method for high-cycles calculation will also be presented. 12

13 2.3 In situ and laboratory characterization and modeling of pavement materials 2.4 Improving the performance of granular base materials 2.5 Improving the performance of asphalt binders 2.6 Reuse and recycling PAVEMENT RECYCLING THE USAGE OF ASPHALT PAVEMENT RECYCLING TO ACHIEVE TECHNICAL, ECONOMICAL AND ENVIRONMENTAL SUSTAINABILITY IN ROAD SERVICEABILITY (169) In this presentation an overview of the techniques (quite fast, little detail) for recycling is given along with the general advantages, cost benefit, environmental benefits and such. According to him, road owners nearly always choose to use it for financial reasons (Q: is it short time benefit or also for LCA?). He highlights the growing interest in the energy consumption of construction processes, where recycling has benefits over HMA, and cold over warm recycling. He stresses that recycling offers these energy and cost benefits with no compromise on quality. (Q:does that match with experience? For cold recycling as well as warm?). The high quality of current day recycled pavements is mainly due to advances in equipment accuracy and quality, according to the speaker. He expects recycling to increase further due to budget constraints at the road owners and the focus on environment WHAT DO WE EXPECT FROM RECYCLING IN A ROAD CONSTRUCTION COMPANY? (170) Starts by introducing the emulsion conference in France in octobre In his opinion recycling will grow mainly due to lack of materials, boh binder and aggregates are getting scarce, which makes recycling interesting. In the US they use >10% RAP, in France they have purchased a moblile plant to use 50% RAP. The standards in FRnce allow 10 % RAP in binder courses, 15 % in ( lower layers??). He believes that the performance is the key to get more recycling accepted by road owners DEVELOPMENT AND PERFORMANCE OF ASPHALT PAVEMENT RECYCLING TECHNIQUES IN THE AMERICAS (171) In this presentation a standard rehabilitation/overlay job on a major Ontario highway was flanked by a cold in place recyling of the original pavement, overlayed with a superpave mixture with modified binder. The standard job shows reflective cracks after a few years, but the other is still looking very good (R: uclear if anything was done to stop the cracks from coming through in the standard case, nor if polymers were used there. If not, comparison is rather unfair.) On foamed bitumen he mentions that mixing is essential for quality, not high tech foaming equipment. He states that this is the reason that the strength achieve in the field can be considerable higher than those in the lab if it wasnot mixed properly in the latter. For this reason, he pleads for using strength achieved instead of target water content as criteria, since the water content necessarily is in equilibrium with the surrounding moisture conditions and thus situation dependent. He shows data where eventually the stiffness of foamed asphalt exceeds that of HMA and claims this could be used in the design (R: it can, but only f the strength is also higher!!). A limiting factor on foamed ad other recycling techniques according to the speaer is the road authorities fixation on the cheapest bids, rather than LCA approaches EVOLUTION OF FLEXIBLE PAVEMENT RECYCLING IN ONTARIO AN AGENCY S PERSPECTIVE (172) This presentation provides an overview of recycling use in Ontario from 1989 to now. Initially, central hot recycling was the key method, gradually giving way to hot in place recycling and currently a shift towards full depth cold in place recycling, often with foamed asphalt. Some quality (IRI an such) data presented shows that most CIR pavement last for at least 11 years, against 15 years for full depth reclamation, with similar performance up to 7 years of life, after that on smoothness FDR performs better than CIR, which starts to deteriorate more rapidly. As an essential factor in success, the pre-project evaluation in order to assess the suitabilityof various recycling approaches for that work is mentioned, but it is not clear what criteria they use for this assessment. The province of Ontario has a series of design manuals for these techniques, which are available trough their website (). A leading role in the implementation is attributed to the contractors in the Ontario region. 13

14 2.7 Utilization of process materials and by-products FATIGUE BEHAVIOUR OF BITUMEN-FILLER MASTICS (1.8 99) Purpose of the project is to develop or select a standard testr for fatigue in binders and/or mastics. They used a series of fillers, among which a sewage residue, in various quantities. Tests included direct tension at various strain rates and temperatures. In the test both cylindrical and hemispherical geometries were used (between flat plates and between rounded plates). The third test used was the DSR. Increase in filler content for a given filler results in both an increase in stiffness and an increase in fatigue life. For a stress criterion you see stiffening from bitumen to mastic to mixture, for strain criteria bitumen and mastic are almost the same. They did the DSR at low temperatures in order to ensure that failure was purely in fatigue, without flow. They found that various grade bitumens from a single crude source wen tested at equi-stiffness conditions showed comparable fatigue response, while the same grades from different sources tended to show different response. The fatigue tests were performed using oscillatory shear loading in the DSR at 10 C and 20 C at a frequency of 10 Hz and it shows that the fatigue is influenced by filler concentration but not by filler type. Also, no stress or strain dependency (criterion) for pure bitumen or bitumen-filler mastics was apparent in the results. 2.8 Foamed mix 2.9 Water damage in asphalt DETERMINATION OF BOND STRENGTH AS A FUNCTION OF MOISTURE CONTENT AT THE AGGREGATE-MASTIC INTERFACE (1.9 72) Moisture infiltration into asphalt mixes can have a negative effect on the material characteristics of the individual components and damages the bond between the components, leading to separation of the aggregates from the asphalt mixture (i.e. stripping). The phenomenon of stripping is a complicated process involving a combination of physical, chemical and mechanical processes. This paper s focus is on damage to the aggregate-mastic bond caused by a weakening of the interface due to diffusion of moisture. The adhesive tensile strength of the interface between thin film asphalt mastic and a diabase aggregate substrate is determined via a modified version of ASTM D 4541 Pull-Off Strength of Coatings Using Portable Adhesion Testers. Experimental results of the pull-off test are linked to moisture diffusion simulations via the finite element analysis tool RoAM (Raveling Of Asphaltic Mixtures) developed at Delft University of Technology. On the basis of this combination of experimental measurements and computational analyses, for the first time, bond strength degradation as a function of the amount of moisture at the mastic-aggregate interface is established. The paper extensively describes the proposed methodology and identifies future research on the topic EVALUATION AND CORRELATION OF TENSILE STRENGTH RATIO (TSR) AND PERFORMANCE OF ASPHALT PAVEMENTS IN WISCONSIN (1.9 73) The Wisconsin Department of Transportation (WisDOT) has been using the Tensile Strength Ratio (TSR) test (ASTM D-4867) to predict the potential susceptibility of asphalt mixture to moisture damage and other associated pavement deterioration. The objectives of this paper are to evaluate the relationship between the performance of asphalt pavements in the field and the TSR values measured in laboratory on the original asphalt mixtures used in constructing pavements, and to evaluate the effect of anti-stripping additives on field performance. To assess the moisture damage problem in the field, 21 existing WisDOT pavement sections built prior to adoption of the TSR parameter requirement were selected to cover a wide range of locations and aggregate sources. The TSR and the pavement performance data (Pavement Distress Index or PDI) for these projects were collected from the WisDOT Pavement Management Database. The results indicated no relationship between TSR and field pavement performance as measured by the PDI, and no relationship between TSR and specific pavement distresses related to moisture damage (surface raveling and rutting). To evaluate the effect of using anti-stripping additive, a database study was conducted. The database showed that antistripping additives do have an effect on pavement performance. 14

15 2.9.3 NUMERICAL SIMULATION OF THE PHYSICAL PROCESSES INDUCING MOISTURE DAMAGE IN ASPHALTIC MIXES ( ) Very fast presentation, showing that the moisture and mechanical processes are now combined, giving damage in a moisture laden pavement which exceeds the damage by the same loads on the same material which is not influenced by moisture. She shows the ACRe constitutive data as well as data on the interface strength, have to check if this is actual test data or assumption. It was shown that based on the combination of properties a simulation could result in either adhesive or cohesive failure MOISTURE DAMAGE EVALUATION OF ASPHALT MIXTURES USING AASHTO T283 AND DC(T) FRACTURE TEST ( ) Bill Buttlar presents and he states that due to the rutting problems in the 80 s in the US their mixtures were made leaner, with the result that they now have a lot of cracking. Their assumption is that this is not just due to temperature and traffic stresses, but that their absorptive aggregates in combination with little binder also make the material sensitive to moisture and aging. They carried out fracture test (several types, among which ITT DSC, the disk shaped compact tension test) on dry and wetted specimens made with polymer modified and conventional binder. Visual observations and fracture test indicate more stripping in non-modified material, but TSR results contradict this. No clear overall conclusions SUITABLE TEST METHOD FOR PREDICTING EFFECT OF STRIPPING ON MECHANICAL PROPERTIES OF CANADIAN PAVEMENTS ( , SHOULD BE 1.9!) Presentation on a search for a simple test to evaluate moisture sensitivity of AC mixtures, claiming that the existing tests yield different rankings of the same mixtures. \they used standard road engineering tests like ITT, DSCT, Marshall etc on dry and moisture conditioned specimens from lab prepared and field cores. First goal is to differentiate between good and bad mixtures, second to distinguish between mixtures, third a correlation with other tests and finally simple testing. Shows what looks like an extensive statically analysis, but so fast that I m not sure. The best scoring (from the tests used) test was the Marshall stability Asphalt cracking PAVEMENT CRACKING: MECHANISMS, ANALYSIS, AND MITIGATION (KEYNOTE LECTURE) Rogue distinguishes classical bottom-up fatigue cracking and thermal and top down cracking. Causes are understood, mechanisms are not, and that is the missing link to get to more accurate predictions, as well as pavement design approaches and material specifications that more effectively mitigate this form of distress. (Q: if the mechanism is not known, how can you be sure that the causes are nown?). States that researchers have made important progress that has led to a general understanding of factors that affect asphalt pavement cracking and to the identification of mechanisms that may lead to fatigue, thermal, and top-down cracking. Reviews what is known about cracking mechanisms in asphalt pavement, what challenges remain to enhance our understanding, and how we might proceed to overcome these challenges. He lists a number of assumptions and simplifications that result in differences between lab and pavement repsons, like differnces in stress conditions, relaxation in practise, healing, avering effect over time and location in pavements. He observes that: Not all loads cause distress Most damage is healable Distesseis stepwise, not continuous Permanent damage requires presence of critical conditions Based on large and variable shift factors and reverse trends (lab ranking completely different than pavement performance) indicate that important factors are not (correctly) taken into account. Discusses endurance limit (no failure beneath microstrian) and postulates that this is not so much due to a threshold strin, but because under those levels the healing rate exceeds the damage rate. 15

16 Deals with the 50% stiffness limit as failure, claims gthat this is a non-fundamental criterion that introduces differences between lab and reality. Shows work from di \bennedetto from 2004 where it is clear that higher stiffeness materials tend to fail at S-values higher than 50%, approaching 100% for the very stiff ones (R: illustration of brittleness!!). Also, the stiffness at which fail;ure occurs depends on test conditions (strain/stress control, uniformity of strain field). Shows data where if fatigue threshold is not exceeded (no increase of deformation/ decrease of stiffness (R: couldnot reed vertical axis) where after rest the exact same response is observed. If the threshold is exceeded, after rest healing is observed, but to a lower level and with rapid decrease after loading is resumed. Rey claims that the threshold is a fundamental value, independent of mode of loading (strength, cyclic and creep were tried). Defines this as the Dissipated Creep Strain Energy (DCSE) as a more fundamental damage criterion, where this is the point at which macro cracking starts/rapid degradation commences. It is basically a transition of stable energy dissipation to rapidly increasing energy dissipation. R: I m not sure how the healing rate is taken into account, if at all. Does calim that for any mixture this approach yields a unique relation which can be used for any test, whether strain or stress controlled (if you know the energy dissipation therein?). Remarks on material and structural non-uniformities (cracks, stress redistribution etc) which coause actual situation to differ from assumed one in design. Shows figures from Kim, 2004 where you see damage move from bottom to top due to increasing layers thicknesses. (R: similar to what we showed in late nineties ). Suggests that fatigue cracks at the bottom of the pavement might not in fact occur and refers to a paper by Andre Molenaar from 2004? That also poses this question, proposing that bottom damage is more likely to be distributed in nature due to lack of stress concentrations (R: material weakness concentrations will still result in cracks, which cause their own stress concentrations). Another reason for cracking being top down rather than bottom up that he discusses is the more advanced ageing at the top, the larger and faster changing temperature at the top, causing the top to be more sensitive. So early on in a pavement l;ife distress will be due to faulty design, later on (after about 5 years) material damage might occur, with the top being most sensitive). He refers to field tests as the ultimate thruth, bu cautions that usually you don t know all the facts about it which limits the usability. From a selection of over twenty field sections the prediction (ranking) with respect to cracking damage three were predicted incorrectly, the others performed to prediction (R: he did not specify what they used as a criterion, check paper!) Asphalt reinforcement 3 Structural Design for New and Existing Pavements 3.1 Development of long-lasting pavements 3.2 Validation and implementation of the 2002 Pavement Design Guide DEVELOPMENTS AND CHALLENGES IN MECHANISTIC - EMPIRICAL PAVEMENT DESIGN METHODS (105) He refers to Monismith s lecture on the history of mechanistic-empirical design, which is placed on the ISAP website (check it out), as an important source for his presentation. He gives a historical overview, starting by Burmisters publications on multi-layer systems, on to the various computer codes for multi-layer analyses published through the years, among which he lists VEROAD (linked to TUD). This represents the mechanistic-component, the locally based (temperature, subgrade, traffic etc related) relations needed to go from there to the predicted pavement response/design criteria are the empirical part. He goes into more detail on OPAC 2000, a 2 layer equivalent ME code, which includes a 2 step calibration (for the local empirical component). It predicts / uses as input (?) the pavement service sate in time with separate degradation due to environmental and traffic components. Calibration involes design and evaluation by local experts, which is eventually made more ob.jective by regression analysis of predicted and actual response. The second ME-code discussed in detail is new AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG), referring to El- 16

17 BAsyouny&Witzac s 2005 AAPT contribution on the topic. As implementation challenges he identifies the necessary highway agency knowledge-to-apply-correctly, distribute budgets, assess and update pavement performance indicators, calibration of traffic, materials, environmental input and distress output data. 3.3 Effects of European standardization of truck weights and dimensions 3.4 Pavement-vehicule interaction CONCEPT FOR DEVELOPING A MECHANISTIC EMPIRICAL BASED CAN METHOD FOR NEW GENERATION AIRCRAFT ( ) Story on how ME is applied to assess potential damage by new aircrafts, uses FEM with \mohr Coulomb failure criterion, using superposition to get the loads, since the model is axi-symmetric and thus limited to a single wheel load. Relative effect of any pavement is expressed in a damage factor. Much of his work is initiated in response to the 2002 CROW observation that CBR was unsuited to assess plane damage capacity. Calculations are stored is a database, which is used to assess relative damage capacities for various conditions COMPARISONS OF DIFFERENT SUMMATION MTHODS TO ACCOUNT FOR FATIGUE AND RUTTING DAAGE IN AC PAVEMENT SUBJECTED TO MULTIPLE AXLE LOADS ( ) ME design uses axle loads spectra rather than ESALS, requiring a summation method. This presentation reviews various ways to account for the interaction between multiple wheel loads in an axle, to arrive on axle damage factors. His story is very chaotic, maybe the paper is better. It appaears that he determines the factors via various superposition methods, peak-peak strain, dissipated energy etc and compares them to lab tests meant to represent fatigue and rutting respectively. But the link between any test and actual pavement response is unclear and the summation is based on the assumption of linear elasticity for the material response, without differences between tension and compression response, so it looks like a lot of energy spent in a rather useless direction EFFECTS OF AXLE LOAD, SUSPENSION SYSTEM, VEHICLE SPEED AND PAVEMENT CONDITION ( ) Detailed investigation on the influence of several aspects of truck geometry on the dynamic load. They use TRUCKSIM, a model that appears to originate from mechanical engineering. I wonder if this adds anything to a two-mass-spring system in assessing the effect on the pavement? They find that pavement roughness and vehicle speed are the most important parameters THE DEVELOPMENT OF A VEHICLE/PAVEMENT DYNAMIC INTERACTION MODEL FOR A TRUCK POPULATION ( ) They try to develop a representation of heavy vehicles based on previous WIM measurements. Generall they represent the vehicles as two-mass-spring systems, where mass is know from the WIM s. Pavement condition can also be obtained, but lateral position and spring stiffnesses are not known. They assume that the unknowns are normally distributed and use Bayesian statistics to determine them. First they assume a model, than based on the WIM data they fit the parameters. With the data they generate a fleet of trucks and check the result against the available data (or something like it?). Based on this they describe the measured impact factors by a mean and 95% limits of these factors. Based on this, they used the model to predict these factors also for stretches of raod that were not used as input and the lines are on top of those showing the measured data. As future work he mentiones using the Dutch WIM data as actual input (does that mean that the data he showed is not really measured?). 17

18 3.5 Low-volume road design 3.6 Accounting for frost action and seasonal effects 3.7 texte/ang-ptech-manu-2.htm Life-cycle cost analysis 4 Pavement Performance 4.1 Long-term performance studies SUPPORTING THE DEVELOPMENT OF PERFORMANCE MODELS WITH LONG- TERM PAVEMENT PERFORMANCE DATA (106) Discusses the Long-Term Pavement Performance (LTPP) program, a huge research program undertaken to provide data necessary to determine how and why pavements perform the way they do. In 2005 it consisted of 20GB of data. This kind of data is essential for any ME design code, because without the calibration component is not possible. Besides the distress inspections, the data set includes FWD data on test sections every 3 years, air temperature and precipitation data (can/should we combine GMS and winfrabase data?), sub-surface data build in pavement structures to assess base conditions. Furthermore, results from lab tests on HMA-mixtures are incorporated in the database. Currently, an effort to fill this in is underway as well as an effort to get traffic data, in order to couple material, structural, environmental and traffic data for response prediction and check it against the actual distress development. He stresses that I is important to use standardized definitions for distress, traffic loads etc in order obtain an objective database. In regards to the latter, WIM-techniques are mentioned. It is mentioned that over 100 reports are published based on the project and database, and that engineering students use actual data in their curriculum. It is not clear of this means the database is accessible for everyone? Might be interesting in order to decide on how we want to deal with our data? Future developments envisioned are focussed on the use of advancing material science in combination with the collected data to arrive at better models for both design and performance prediction (for maintenance). Discussion: The discussion at the end focuses on the necessity to sell these long-term, expensive data collection to politicians and the problems with it. Comercial firms are stated unwilling to invest in and contribute sensitive data to something the competition will also use. (R: show the benefits!! & find the buttons to push, i.e. vision, courage, environment) 4.2 Full-scale and accelerated pavement testing THREE DECADES OF DEVELOPMENT AND ACHIEVEMENTS: THE HEAVY VEHICLE SIMULATOR IN ACCELERATED PAVEMENT TESTING (108) Presentation on South Africa s Accelerated Pavement Testing, started in 1970 to bridge he gap between design methods and actual performance, especially for heavy loads. Their long-term goal is to develop design procedures that accurately take the environmental and traffic data into account. He gives an historical overview of the developments. From local test sections they soon went into mobile heavy vehicle simulators, which could be used in various regions to include the environmental factors. Since the early 90 s some US organisations have adopted the HVS for their APT research. He goes on to present a long list of groups using the HVS in various projects. These groups are combined in a user group in order to facilitate data sharing, unfortunately, no resulting insights are presented. Stress in motion (SIM) as a component of pavement-vehicle interaction is presented, with examples of tyre foot prints. He mentions a sensor used for variable depth deflection measurements, but doesnot go into how it works and what it is used for (may be in the paper?). 18

19 He also presents the organizational form, stressing the involvement of industry (might be useful to see how they organize that) and shows a graph claiming that every rand invested in APT return between 2.4 and 6.3 rand. They developed design charts and design methods and are now in the proces of evaluating them, this has already shown that the material components and some other aspects need tob e adapted (especially the gap between lab and field data (Q: wasn t that the objectve of APT??), this is currently underway and in a few years they hope to have beteer design methods DYNAMIC WHEEL LOADS ON SUPERPAVE PAVEMENTS ( ) States that wheel loads are important for design, but users care only for smoothness. So that should be incorporated in the performance prediction. Smoothness in this case is expressed in the IRI, they registered the right wheel track longitudinal profile yearly for asset of test sections. They use the profiles to asses correction factors for the dynamic effect the roughness would ad to a static wheel load. Most dynamically corrected loads are within 20% of the static value, with exceptions to over 30% difference. At higher speeds, the dynamic load increased further (R: sound logical, but it is probably dependent on the model used to get from profile and speed to load factor, so should betreated carefully) RECONSIDERATION OF TIRE-PAVEMENT INPUT PARAMETERS FOR THE STRUCTURAL DESIGN OF FLEXIBLE PAVEMENTS ( ) He pleads for more realistic wheel loads, instead of limiting ourselves to uniform circular loads because that is all our software can handle. Shows some complex tyre models and the Stress In Motion system where slow moving wheels pass over steel pins and the corresponding vertical, lateral and longitudinal stresses are registered (R: essential for top-damage, like ravelling, surface cracking and to a lesser extend, rutting). He shows tat low loads (800kPa and 30kN) the contact surface is roughly circular, if the load increases the shape becomes rectangular, about twice as long in the longitudinal than the transverse direction. Measurement on actual trucks driving over SIM s (and loading bridge) shows that the assumption of equal and symmetric distribution between the various tyres is very often incorrect, leading to wheel loads higher than assumed, with the stresses even higher because of the non-uniform distribution. Generally, the steering axle is the heaviest loaded. Based on the data, FEM simulations of multi-layer constructions using schematic wheel stress profiles (n vs m shape) (R: unfortunately with isotropic, linear elastic material properties!) and these analysis indicated that near-surface Strain Energy of Distortion (SED) may be utilised for pavement rutting studies in this asphalt layer. 4.3 Measuring pavement performance CORRELATION OF SMALL STRAIN STIFFNESS AND STRENGTH OF HOT MIX ASPHALT (3.3 98) Presentation about a search for a new simple performance test, the Marshall test of this century. She looks at the Dynamic Modulus test and claims that where Marshall is a strength indicator, this test is representative for the small strain region. Unless there is a relation between this small strain stiffness and the strength, you cannot predict stress related damage by means of the stiffness results. She looks at the test as an rutting indicator, proposing that this damage is stress related. She also proposes that although rutting involves shear, it must initiate by densification in the wheel path (R: similar to what Arthur & I postulated in 2003, if shear is dominant PA would rut, son densification plays a key role in some way). She runs dynamic modulus E* and Simple Shear Tester (SST) shear modulus G* tests, adapting deformation rates in order to arrive at similar strain rates when you compensate for the geometry. Both dense and gap grade mixtures are investigated and aging protocols are applied. For young and aged specimens no correlation between stiffness and strength was found, especially for the SMA mixes. Also, the additives (cellulose fiber and fine mineral filler) used in the SMA mixtures had more effect on stiffness than on strength properties. The dynamic modulus and SST shear modulus did not rank mixtures in a similar manner, but both test methods were able to identify the same mixtures as being the softest and stiffest among the 11 studied mixtures. The same applied to the strength parameters, cohesion and indirect tensile strength. 19

20 She suggests that the different material responses to mechanical loading in the compressive modulus E* and SST shear modulus G* are due to different loading and orientation. Generally she concludes that the tests seem able to rank mixes of similar composition, but if the composition changes the ranking doesnot work. Also field cores versus lab cores result in different result, be it due to compaction/composition differences or different ageing patterns. As a suggestion she sates that maybe both stiffness and strength are needed to characterize all AC mixtures, so two tests instead of one. 4.4 Pavement instrumentation 4.5 Modeling pavement deterioration MODELING OF RUTTING IN ASPHALT FLEXIBLE PAVEMENT (3.5 10) Goal was to understand rutting and to develop a usefull countering strategy. Asphalt was modelled viso-elasto-plastic with von Mises as bounding surface (R:means tensile strength equals compressive strength!). Mohr-Coulomb was used for the sub-layers. Parameters were determined by back calculation from strain measurements at the bottom of the AC layer in full scale rut tests. They model rutting in 2D with ABAQUS. They found that a super single cuases morelk rutting than dual wheels (how schematised?). This paper presents a finite element analysis modeling of rutting. The behavior of the asphalt concrete is described using an elasto-viscoplastic constitutive relation, while an elastoplastic constitutive relation is used for the lower layers. The model allows for taking into consideration the influence of both the loading period and the temperature. The numerical model is validated on accelerated pavement tests realized at LAVOC laboratory. Results show that rutting increases with the increase in the contact pressure and in axle load with a dominant role for the axle load. Wheel wander significantly affects the development and profile of rutting. Rutting due to the asphalt layer is generally accompanied by a pavement uplift A SIMPLE APPROACH FOR DESIGN AGAINST REFLECTIVE CRACKING IN ASPHALT CONCRETE OVERLAYS ( ) Very fast, complex story that is supposed to explain a very simple method. It is meant to replace the current Californian design method for AC overlays on concrete, which is a fixed thickness irrespective of conditions. So it s clearly an improvement. They did fem analysis and couple the results to N-values using an elaborate regression relation (Read paper) TOP-DOWN CRACKING ANALYSIS AND CONTROL FOR ASPHALT PAVEMENTS ( ) Presentation based on the proposition that longitudinal cracks are load-induced. \they build a lab set up to measure the tyre stresses, by mounting a wheel in a frame under an actuator and pressing it down on an instrumented AC slab (R: static!). He presented a shear stress analysis, but it was unclear (bad English) if it was measured (how do you measure shear stress??) or calculated, it looked like typical multi layer output, but could be linear FEM with the stresses from the tyre experiments imposed. He postulates that shear stress is the cause of any top-down cracking and that to avoid it the stress has to decrease or the strength increased. (R: I wonder how he wants to do the former..?) A VISCOELASTOPLASTIC CONTINUUM DAMAGE MODEL OF ASPHALT CONCRETE IN TENSION ( ) They use a Schapery-modified approach, with input from frequency sweep data from the unixial tension test in frequency sweep and monotonic failure tests. They validate the model with tension tests at other conditions, among which random cyclic signal tension tests. They found very different rankings of tests on mixes with various binders when compared to ALF full scale results (concerning fatigue), they tried various tests and eventually found a reasonable ranking with strain controlled tests. They couple this to the relatively thin ALF pavement, which they motivate with thin and thick pavement simulations like we did for ACRe, where it shows damage initiating at both top and bottom for thick and purely at the bottom for thin pavements. R: potential problem is that their model is calibrated solely in tension, so predominantly non-tension states of stress in the 20

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