| 1. |
- de Frias Lopez, Ricardo, et al.
(författare)
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A Numerical Study on the Permanent Deformation of Gap-Graded Granular Mixtures
- 2016
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Ingår i: Proceedings of the Third International Conference on Railway Technology. - Stirlingshire, UK : Civil-Comp Press.
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Konferensbidrag (refereegranskat)abstract
- Permanent deformation accumulation of unbound granular layers under traffic plays a critical role in the performance and need for maintenance of pavements and railway structures. In this paper, the discrete element method is used to study the permanent strain behaviour of binary mixtures of elastic spheres, as an idealization of gap-graded mixtures, under triaxial monotonic loading. The effects of stress level and soil fabric structure, based on a recently proposed classification system founded on micromechanical considerations, are assessed by subjecting mixtures with varying fines contents to different stress levels. Additionally, mixtures are loaded to static failure to study the dependency of the permanent strains on the closeness of the applied stress to failure stress, in accordance with existing empirical models. Numerical results are also compared with the experimentally determined behaviour of granular materials. The findings indicate that numerical mixtures are able to reproduce some of the most significant features observed in laboratory tests on granular materials, further encouraging the use of numerical simulations to enhance the understanding of granular media behaviour. Additionally, a good correlation between fabric structure and performance is obtained, giving additional support to the use of the studied fabric classification system for performance characterization.
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| 2. |
- de Frias Lopez, Ricardo
(författare)
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Granular Materials for Transport Infrastructures : Mechanical performance of coarse–fine mixtures for unbound layers through DEM analysis
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Granular materials are widely used as unbound layers within the infrastructure system playing a significant role on performance and maintenance. However, fields like pavement and railway engineering still heavily rely on empirically-based models owing to the complex behaviour of these materials, which partly stems from their discrete nature. In this sense, the discrete element method (DEM) presents a numerical alternative to study the behaviour of discrete systems with explicit consideration of the processes at particulate level governing the macroscopic response. This thesis aims at providing micromechanical insight into the effect of different particle sizes on the load-bearing structure of granular materials and its influence on the resilient modulus and permanent deformation response, both of which are greatly influenced by the stress level. In order to accomplish this, binary mixtures of elastic spheres under axisymmetric stress are studied using DEM as the simplest expression for gap-graded materials, which in turn also can be seen as a simplification of more complex mixtures.First, the effect of the fines content on the force transmission at contact level was studied. Results were used to define a soil fabric classification system where the roles of the coarse and fine fractions were defined and quantified in terms of force transmission.A behavioural correspondence between numerical mixtures and granular materials was established, where the mixtures were able to reproduce some of the most significant features regarding the resilient modulus and permanent strain dependency on stress level for granular materials.A good correlation between soil fabric and performance was also found. Generally, higher resilient modulus and lower deformation values were observed for interactive fabrics, whereas the opposite held for instable fabrics.Mixtures of elastic spheres are far from granular materials, where numerous additional factors should be considered. Nevertheless, it is the author’s belief that this work provides insight into the soil fabric structure and its effect on the macroscopic response of granular materials.
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| 3. |
- de Frias Lopez, Ricardo, et al.
(författare)
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Resilient properties of binary granular mixtures: A numerical investigatio
- 2016
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Ingår i: Computers and geotechnics. - : Elsevier. - 0266-352X .- 1873-7633. ; 76, s. 222-233
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Tidskriftsartikel (refereegranskat)abstract
- The effect of stress level on the resilient modulus for binary mixtures of elastic spheres under triaxial loading is investigated using the discrete element method. The secant modulus during the first cycle of unloading is used as an estimate of the modulus after several load cycles due to computational time restrains. Later in the paper, its adequacy as an accurate and efficient estimator is shown. Numerical results are statistically compared with existing relations characterizing the stress dependency of the resilient modulus for real granular materials. It is concluded that the modulus prediction is significantly improved considering the effect of the deviator stress in addition to the confinement stress, obtaining a good correlation between the modulus and the confinement to deviator stress ratio for the numerical mixtures. The stress dependency of a recently proposed soil fabric classification system, based on force transmission considerations at particulate level, is also studied and its correlation with performance investigated. It is found that the relative load-bearing role of coarse and fine components is governed by the deviator to confinement stress ratio. However, the implemented fabric classification is fairly insensitive to changes in this ratio. Regarding resilient performance, interactive fabrics show the stiffest response whereas underfilled fabrics should be avoided due to a potential for instability.
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| 4. |
- Edvardsson, Karin, et al.
(författare)
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Methods for Quantification of Lignosulphonate and Chloride in Gravel Wearing Courses
- 2010
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Ingår i: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 11:1, s. 171-185
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Tidskriftsartikel (refereegranskat)abstract
- Due to oxidation, breakdown, and leaching, dust suppressants will be lost from the gravel road surface. Methods for residual dust suppressant concentration supervision are a valuable tool for estimating life-length and optimal application rates, and, hence, efficiency of different products. The objective of this study was to identify methods for quantitative analyses of lignosulphonate and chloride, develop and adapt the methods for application on a gravel matrix, and validate the methods using samples collected in-situ. Results strongly suggest that the reliability and repeatability of the developed methods (23% for lignosulphonate and 30% for chloride, respectively) are acceptable for determination of relative variations in residual concentrations of dust suppressed gravel wearing courses.
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| 5. |
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| 6. |
- Ekblad, Jonas, et al.
(författare)
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Causes of rutting in flexible and semi-rigid test sections after 14 years of service
- 2018
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Ingår i: International Journal on Road Materials and Pavement Design. - : Taylor & Francis. - 1468-0629 .- 2164-7402. ; 19:4, s. 878-897
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Tidskriftsartikel (refereegranskat)abstract
- Rutting is a major distress and is commonly targeted in design-build contracts as a key requirement, but at the same time, contemporary design methods usually provide scarce information on evolution in absolute terms. The objective of this paper is to investigate and analyse rutting results from a large full-scale road test. The analyses concerned magnitudes and the causes of rutting with a main focus on flexible and semi-rigid structures: one Reference, one high-performance asphalt (HPA) and one asphalt on a lean concrete (LC) base. Field measurements and sampling for the current study comprised acquiring transversal profiles and coring pavement samples. The results suggest that for the HPA and the LC base pavements, rutting is mainly caused by studded tyre wear and densification of the asphalt layers. For the conventional reference pavement additional rutting, most likely in the lower layers, was noted.
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| 7. |
- Ekblad, Jonas, et al.
(författare)
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Creep of prestressed sulphur concrete
- 1996
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Ingår i: Proceedings of the 7th International Conference on Durability of Building Materials and Components, 7DBMC. - Stockholm.
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Konferensbidrag (refereegranskat)
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| 8. |
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| 9. |
- Ekblad, Jonas, et al.
(författare)
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Impact on rutting from introduction of increased axle loads in Finland
- 2020
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Ingår i: The international journal of pavement engineering. - : Taylor and Francis Ltd.. - 1029-8436 .- 1477-268X.
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Tidskriftsartikel (refereegranskat)abstract
- In 2013, Finland introduced legislation increasing gross vehicle weights (GVW) on a number of trucks. Since the actual impact on road damage is nearly impossible to quantify in advance, the present analysis of road surface measurements is intended to provide knowledge regarding the impact on road damage. Rutting is influenced by many conflated phenomena. To indicate and capture the effect on road damage due to the new maximum GVW for certain truck- and trailer combinations, the analysis follows two different but mutually supporting lines of reasoning, empirical and theoretical, respectively. Analysis of measured rut depth is supported by theoretical calculations. Theoretical findings clearly indicate that the relative increase in road damage induced by higher GVW is larger than the increase in relative payload capacity. There was a rapid fleet shift towards heavier trucks after 2013, and statistical (empirical) analysis of road surface measurements shows an increase in rutting after this introduction.
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| 10. |
- Ekblad, Jonas, et al.
(författare)
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Influence of mica content on time domain reflectometry and soil-water characteristic curve of coarse granular materials
- 2008
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Ingår i: ASTM geotechnical testing journal. - 0149-6115 .- 1945-7545. ; 31:4, s. 321-333
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Tidskriftsartikel (refereegranskat)abstract
- Elevated fractions of free mica particles in unbound granular materials, used in road constructions, are believed to reduce bearing capacity and influence the hydraulic behavior of the road structure. The objective of this investigation was to study the influence of mica content on the soil water characteristic curve and the dielectric response measured by time domain reflectometry, for coarse granular (maximum particle size 63 mm) materials. Increased fraction of mica was achieved by partly replacing the base crushed rock material smaller than 4 mm, by pure muscovite mica of similar grading, thereby keeping the overall particle size distribution unchanged. Acquired results indicated that, given equal matric suction, the water retention capacity increased with increased amount of mica. Concerning the time domain reflectometry measurements, no influence of mica content could be detected. Determined water contents required adjustment because of the nonlinear distribution of water in the sample.
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| 11. |
- Ekblad, Jonas, et al.
(författare)
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Influence of water and mica content on resilient properties of coarse granular materials
- 2008
-
Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 9:3, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- Elevated amounts of free mica particles in unbound granular materials used in road construction are believed to detrimentally influence bearing capacity. The objective of presented work was to investigate the influence of mica content on resilient properties of coarse granular material (maximum particle size 63mm) under varying water contents. The test scheme comprised triaxial tests, using constant confining pressures, at incrementally raised water contents up to practically full saturation. Increased mica content was achieved by replacing a part of the base material grading smaller than 4mm, with an equal amount of pure muscovite mica of similar grading, hence keeping the overall particle size distribution unchanged. Generally, resilient modulus decreased with increased mica content and elevated water contents caused reduction in stiffness. In relative terms, the reduction in resilient modulus caused by water decreased with increased mica content.
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| 12. |
- Ekblad, Jonas, 1966-
(författare)
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Influence of Water on Coarse Granular Road Material Properties
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Even though the practical experience of using coarse unbound granular materials is extensive, detailed knowledge on the mechanical and hydraulic behavior is to a large extent lacking. Regarding influence of water on mechanical properties, this is even more pronounced. The main objective of this work was to investigate the influence of water on behavior and properties of coarse granular materials. The study comprises measurements of resilient properties, soil-water characteristic curve and influence of water content on dielectric properties measured by the use of time domain reflectometry (TDR). The work described herein comprised two test series in terms of materials: firstly, a series where the grading was changed and secondly, a series where the influence of increased contents of free mica was studied. To measure resilient response, triaxial testing, using sample size of 500 mm diameter and 1000 mm height, was performed mainly using constant confining pressures. Tests were performed at incrementally varying water contents up to almost full saturation. Dielectric response and matric suction of compacted specimens were measured in a steel box at varying water content. Results from the first series indicated that the influence of water content on resilient properties depends on the material grading. The coarsest grading, containing least fines, experienced only a small reduction when brought close to saturation. Specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared as water content increased, the specimens became more dilative. From the second series, generally, resilient modulus decreased with increased mica content and furthermore, elevated water contents caused reduction in stiffness. However, in relative terms, the reduction in resilient modulus caused by water decreased with increased mica content. The soil-water characteristic curves are influenced by grading coefficient and mica content; retentive capacity increases with decreased grading coefficient and increases with increased amount of mica. Volumetric water content as a function of apparent relative permittivity was fitted using a third-degree polynomial. Although, determined relationships deviated from Topp's (1980) relationship. Detailed information on the work is given in five enclosed papers.
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| 13. |
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| 14. |
- Ekblad, Jonas, et al.
(författare)
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Influence of water on resilient properties of coarse granular materials
- 2006
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Ingår i: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 7:3, s. 369-404
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to investigate influence of water on resilient properties of a coarse (maximum particle size 90 mm) granular material using various gradings. Triaxial testing, using large-size samples (diameter 500 mm and height 1000 mm) and constant confining pressures, was performed at varying water content up to practically full saturation. Time Domain Reflectometry (TDR) was used to monitor transient in-sample water contents. Evaluation comprised resilient modulus and Poisson ratio in terms of total stresses, although the results were also discussed in the context of effective stresses. The coarsest grading experienced only a small reduction in resilient modulus when brought close to saturation, while specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared that, as water content increased, the specimens became more dilative (increase in Poisson ratio).
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| 15. |
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| 16. |
- Ekblad, Jonas, et al.
(författare)
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Precision of method for determining resistance of bituminous mixtures to de-icing fluids
- 2008
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 41:9, s. 1551-1562
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of a Round-Robin test to estimate the precision of European method EN-12697-41 "Test methods for hot mix asphalt-Resistance to de-icing fluids". The purpose of the project was to determine precision data according to ISO 5725, ASTM E691 and ASTM C802. The examined test method is intended for use in requirements specifications for airfield de-icing chemicals and/or as a tool for development of such products. Precision statistics, repeatability and reproducibility standard deviations, are based on observed values from six laboratories and six levels, each level comprising four samples. From a general statistical analysis, which was conducted in addition to precision determination, it could be concluded that the most damaging de-icing agents (treatments) were identified by all participating laboratories both in terms of absolute values and by ranks.
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| 17. |
- Ekblad, Jonas, et al.
(författare)
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Provväg Riksväg 40 efter 6 år
- 2024
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Ingår i: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 415-416
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Provvägen byggdes för att undersöka effekten av att använda hårdare bitumensorter eller högpresterande modifierade bindemedel, jämfört med traditionella val. Undersökningen redovisar vägens och asfaltens egenskaper efter 6 års användning. Till detta hör även en analys av asfalteringsarbetets klimatpåverkan vid byggandet. 6-årsuppföljningen har utförts och finansierats av PEAB Asfalt och NCC Industry gemensamt med delstöd från Svenska Byggbranschens Utvecklingsfond (SBUF).Provvägen består av 5 delsträckor där referensen är traditionellt uppbyggd. De 4 övriga har ett asfaltlagers reducerad tjocklek och varierade bindemedel i de olika beläggningslagren. Vägytemätningar har utförts 2 gånger om året, vår och höst, och omfattat längsgående jämnhet (IRI, International Roughness Index) och spårdjup. Sträckornas bärighet har mätts med fallvikt och s.k. rullande fallvikt. Vid fallviktsmätningarna mättes även asfalttöjning från givare installerade vid byggnation. För att undersöka asfaltens egenskaper borrades prover från vägen och analyserades med avseende på permanenta deformationer samt återvunnet bindemedels egenskaper. För klimatpåverkansberäkningar används Trafikverkets modell Klimatkalkyl och asfaltproduktionens påverkan bestämdes genom s.k. miljövarudeklarationer. Resultaten visar att provvägen har mycket låg skadeutveckling. Det finns inga tecken på att tjockleksreduceringen, 1 lager asfalt borttaget, påverkar vägens jämnhet varken för spårdjup eller IRI. Det finns inga statistiskt säkerställda skillnader mellan provsträckorna, dock visar sträckan med lägre grad av polymermodifiering lägst spårdjupsutveckling. Bärighetsmätningarna visar högre bärighet för referensprovsträckan med tjockare asfaltlager medan övriga inte kan skiljas åt. Laboratorieprovning av asfaltbeläggning och återvunnet bindemedel visar klara skillnader mellan använda material. Främst är det de polymermodifierade bindemedlen som visar förbättrade egenskaper. Det finns dock ingen korrelation mellan funktionsrelaterad provning och uppmätt spårdjupsutveckling. Tjockleksreduktion leder naturligt till lägre klimatpåverkande utsläpp medan ökande grad av polymermodifiering ökar utsläppen. Baserat på undersökningar redovisade i rapporterna kan följande slutsatser dras:provvägen är välbyggd med hög teknisk prestanda d.v.s. den visar mycket låg skadeutveckling under uppföljningsperiodendet finns inga tecken på att tjockleksreduceringen, 1 lager asfalt (5 cm) borttaget, påverkar vägens jämnhet varken spårdjup eller IRI tjockleksreduktion leder naturligt till lägre klimatpåverkande utsläpp medan ökande grad av polymermodifiering ökar utsläppensträckan med lägre grad av polymermodifiering visar lägst spårdjupsutveckling, dock inte statistiskt signifikant vid en sammantagen analys av samtliga provsträckor bärighetsmätning, FWD och TSD, visar högre bärighet för provsträckan med tjockare asfaltlager (Referens +5 cm asfalt); övriga kan inte skiljas åtdet finns ingen korrelation mellan funktionsrelaterad provning och uppmätt spårdjupsutveckling.
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| 18. |
- Ekblad, Jonas, et al.
(författare)
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Soft bitumen asphalt produced using RAP
- 2017
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Ingår i: Materials and Structures. - : Springer. - 1359-5997 .- 1871-6873. ; 50:1
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Tidskriftsartikel (refereegranskat)abstract
- Soft bitumen asphalt concrete is a common paving material in Scandinavia. The purpose of this investigation was to indicate the possibility to compensate for the stiff binder of reclaimed asphalt pavement (RAP) by using softer binders compared to the mix design. Characterization of binder mixing and diffusion were carried out using viscosity measurements and tests on asphalt concrete comprised stiffness modulus and cyclic compression testing. Acquired results suggest that virgin and reclaimed binders mix and the viscosity can be predicted using simple mixing models. In the case of asphalt made from mixing virgin and recycled material, the mechanical properties indicates fully mixed binders and mixing occurs during sample manufacturing. In general, this study suggests that soft asphalt mixtures can be produced using RAP and that nominal binder viscosity of the final product can be obtained by compensating the stiff binder of the RAP by virgin bitumen of a softer grade.
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| 19. |
- Ekblad, Jonas
(författare)
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Statistical evaluation of resilient models for characterizing coarse granular materials
- 2008
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 41:3, s. 509-525
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Tidskriftsartikel (refereegranskat)abstract
- Consistent material modeling is a prerequisite for a mechanistic approach to pavement design. The scope of this investigation was to statistically evaluate the efficiency of various resilient models commonly encountered in highway engineering. These models were categorized as describing either resilient modulus or shear and volumetric strains. Triaxial tests using constant and cyclic confining pressure were performed on coarse granular materials of various gradings (maximum particle size 90 mm). Two statistical methods, the extra sum of squares F-test and the Akaike information criterion, were used for model comparison. Concerning resilient modulus, the Uzan model provided, in general, a statistically significant improvement compared to the k-theta model. However, this improvement is lost if a constant Poisson ratio is used to predict shear and volumetric strains. In case of the shear-volumetric approach, no single model was most likely to be the best model for all gradings studied.
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| 20. |
- Ekblad, Jonas, et al.
(författare)
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Texturmätning med vägytemätbil, som indikator för beläggningens friktion
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Tillräcklig friktion är en viktig egenskap hos en vägyta. Normal friktionsmätning är omständlig och resurskrävande. Vägytans makrotextur mäts varje år för den större delen av vägnätet. Det skulle därför vara effektivt att använda makrotextur som indikator för nedsatt friktion. I denna rapport studeras sambandet mellan makrotextur och friktion.Mätningar utfördes på ett riktat urval av sträckor i Östergötland. Urvalet riktades mot låga makrotextur-värden. På identifierade sträckor mättes friktion (SAAB Friction Tester) och makrotextur (MPD, Mean Profile Depth med vägytemätbil). Makrotextur mättes av 2 olika mätare.Resultaten tyder på att det inte finns något tillräckligt starkt samband mellan friktion och MPD för att användas som indikator. Några generella mönster kan dock skönjas. Låg friktion uppträder främst vid låg makrotextur dock är det samtidigt endast en mycket liten del av sträckor med låga MPD som uppvisar nedsatt friktion.
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| 21. |
- Ekblad, Jonas, et al.
(författare)
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Time domain reflectometry measurements and soil-water characteristic curves of coarse granular materials used in road pavements
- 2007
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Ingår i: Canadian geotechnical journal (Print). - 0008-3674 .- 1208-6010. ; 44:7, s. 858-872
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Tidskriftsartikel (refereegranskat)abstract
- Coarse granular materials are used extensively in road construction. Bearing capacity can be affected by the water content in the layers of these materials. The ability to estimate water content and to infer water movements is therefore important. The purpose of the work described herein was to determine soil-water characteristic curves and the relationship between relative apparent permittivity and volumetric water content for coarse (maximum particle size 90 mm) granular materials having various gradations. The relative apparent permittivity was measured with the aid of time-domain reflectometry (TDR), and the concurrent matric suction was measured with a tensiometer. Samples were prepared in a steel box and were heavily compacted, and TDR probes and a tensiometer cup were buried within the matrix. The variation in volumetric water content with apparent relative permittivity was found to deviate from the Topp et al. relationship. Soil-water characteristic curves were described using the Brooks-Corey and van Genuchten models. A pronounced hysteresis between wetting and drying paths was observed. For the low water retention coarse materials, measurements of water content might, in general, require correction because of the nonlinear distribution of water in the sample.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Ekblad, Jonas, et al.
(författare)
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Water in coarse granular materials : Resilient and retentive properties
- 2008
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Ingår i: Adv. Transp. Geotech. - Proc. Int. Conf. Transp. Geotech.. - : CRC PRESS-TAYLOR & FRANCIS GROUP. - 9780415475907 ; , s. 117-123, s. 117-
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Konferensbidrag (refereegranskat)abstract
- Granular material is, perhaps the most common construction material used in civil engineering, being an important constituent in road constructions, railways, embankments, foundations, buildings etc. This paper presents results from triaxial testing, at various water contents using constant confining pressure, of two different continuously graded granular materials with maximum particle size 90 mm and 63 mm, respectively. Furthermore, water retention properties of the unbound materials are presented and examples of water distributions in a common construction are shown. From the results presented, it can be concluded that increased water contents cause a reduction in resilient modulus and an increase in strain ratio. The distribution of water content in the vertical direction is highly nonlinear and the degree of saturation in the unbound layers of a road construction depends to a large degree on the level of the water table.
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| 26. |
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| 27. |
- Jönsson, Daniel, et al.
(författare)
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Demonstration of mitochondrial oestrogen receptor beta and oestrogen-induced attenuation of cytochrome c oxidase subunit I expression in human periodontal ligament cells.
- 2007
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Ingår i: Archives of Oral Biology. - : Elsevier BV. - 1879-1506 .- 0003-9969. ; 52:7, s. 669-676
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Periodontal ligament (PDL) cells express oestrogen receptor beta (ERbeta) protein, but cellular functions regulated by ERbeta in these cells have not been identified. In this study we determine if ERbeta is localised to mitochondria and if oestrogen regulates mitochondrial function in human PDL cells obtained from teeth extracted for orthodontic reasons. DESIGN: Subcellular distribution of ERbeta was determined by confocal microscopy of cells co-stained with ERbeta antibody and the mitochondrion-selective probe MitoTracker and by immunogold electron microscopy. Expression of the mitochondrial enzyme cytochrome c oxidase subunit I, involved in oxidative phosphorylation, was determined by Western blotting in cells treated with or without physiological concentrations of the endogenous oestrogen 17beta-oestradiol. RESULTS: ERbeta immunoreactivity was observed both in the nuclei and the cytoplasm. MitoTracker-labelling was observed in the cytoplasm, especially in the perinuclear region, but not in the nuclei. Co-localisation of ERbeta and MitoTracker was observed in cells derived from both male and female subjects. Mitochondrial localisation of ERbeta was confirmed by immunogold electron microscopy. Cells treated with or without 17beta-oestradiol (100 nM) displayed an identical pattern of staining for mitochondria. Treatment with 100 nM 17beta-oestradiol attenuated cytochrome c oxidase subunit I expression by about 30%, while combined treatment with 17beta-oestradiol and the ER blocker ICI 182780 (10 microM) had no effect. CONCLUSION: This study demonstrates mitochondrial localisation of ERbeta and oestrogen-induced decrease in the expression of cytochrome c oxidase subunit I in human PDL cells, suggesting that oestrogen probably via ERbeta influences mitochondrial function and PDL cell energy
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| 28. |
- Karlsson, Robert, et al.
(författare)
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Rheological characterisation of bitumen diffusion
- 2007
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 42:1, s. 101-108
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion is considered important in the process of mixing old and new binders during asphalt recycling. The degree of mixing is presumed to greatly influence the final properties of recycled asphalt concrete. Previously, studies have been undertaken to investigate diffusion using FTIR-ATR (Fourier Transform Infrared Spectroscopy using Attenuated Total Reflectance). A need was identified to verify, if the rates of diffusion detected using FTIR-ATR were accompanied by changes in rheological properties. In this paper, a dynamic shear rheometer (DSR) with parallel plates is used for monitoring diffusion. Diffusion coefficients obtained at 60, 80 and 100 degrees C from tests of a soft bitumen (rejuvenator) diffusing into a stiff one are presented. The diffusion coefficients determined are compared with the corresponding diffusion coefficients obtained using FTIR-ATR. The comparison shows that the rates of diffusion detected by the DSR are of the same magnitude, but somewhat higher than the ones detected by FTIR-ATR.
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| 29. |
- Larsson, Andreas, et al.
(författare)
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A Comparative UX Analysis between Tabletop Games and their Digital Counterparts
- 2020
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Ingår i: Extended Abstracts of the 2020 Annual Symposium on Computer-Human Interaction in Play. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450375870 ; , s. 301-305
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Konferensbidrag (refereegranskat)abstract
- As tabletop games are ported to digital versions to increase their accessibility, the expected User Experience (UX) might be degraded in the transition. This paper aims to understand how and why playing tabletop games differentiates depending on the platform. Seven tabletop games have been chosen from different genres with an official digital adaptation. Our approach has been to do a comparative analysis of both versions followed by a user study to analyze and measure the UX differences, measuring five key factors, Usability, Engagement, Social Connectivity, Aesthetics, and Enjoyment. Our results indicate that games that rely on imperfect information offer a much higher social connectivity and engagement when played around a table. Meanwhile, games relying on tile-placement offers higher usability and engagement when played digitally due to the assistance provided by the game. However, the physical versions got, in general, a higher rating than the digital versions in all key factors except slightly in the usability. Physical versions are the preferred options, but the digital versions' benefits, such as accessibility and in-game assistance, makes them relevant for further analysis.
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| 30. |
- Lira, Bernardita, et al.
(författare)
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Evaluation of asphalt rutting based on mixture aggregate gradation
- 2019
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Ingår i: Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; , s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- Aggregate gradation is fundamental concerning asphalt pavement response to loading, especially regarding resistance to permanent deformation. This study assess, in an empirical way, the capability of a gradation-based framework to evaluate the susceptibility to permanent deformation of asphalt mixtures with varying aggregate gradation. The laboratory study was planned to isolate the effect of aggregate gradation by keeping the source of both the aggregates and the binder constant. The work consisted of testing six different asphalt mixtures with varying aggregate gradations using two different methods: wheel tracking and cyclic compression test. Results show that the testing method influences the asphalt mixtures response to loading. The combined normalised result shows a non-significant relationship between the gradation-based framework parameters and resistance to permanent deformation. Additionally, it was observed that the total amount of coarse material have an influence on mixture resistance to permanent deformation.
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| 31. |
- Lira, Bernardita, et al.
(författare)
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Influence of Aggregate Gradation on the Permanent Deformation of Asphalt Mixtures
- 2022
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Ingår i: RILEM Bookseries. - Cham : Springer Nature. ; , s. 1063-1069
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Konferensbidrag (refereegranskat)abstract
- The following study aims to measure the resistance to permanent deformation of mixtures with varying aggregate gradation and correlate these results to the performance predicted by the Marshall stability test. The experimental study is performed on 6 mixtures designed with the Marshall mix design method and measured using the wheel tracking test. The total rut depth obtained with the wheel tracking test shows a high correlation to the Marshall flow values, as higher rutting corresponds to mixtures with higher flow. The study has shown the ability of Marshall flow value to predict the resistance to permanent deformation, independent of asphalt mixture type, as well as a close correlation between aggregate gradation and stability.
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| 32. |
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| 33. |
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| 34. |
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Lundberg, Thomas, 1965-, et al.
(författare)
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Makrotexturens möjlighet att identifiera låg friktion : tillståndsmätning av vägytan
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Trafikverket vill kunna beskriva friktionen för hela det statliga vägnätet. En rikstäckande friktionsmätning är praktiskt svår att hantera och mycket kostsam medan vi redan idag mäter vägytans makrotextur. I projektet testar vi om makrotexturen (MPD, Mean Profile Depth) kan användas för att beskriva friktionstillståndet på vägnätet. Vi har inte kunnat visa på detta samband men vi redovisar andra intressanta iakttagelser som ger en pusselbit till hur Trafikverket kan och bör hantera friktionsfrågan. Vi ser bland annat att risken för låg friktion är större på vägavsnitt som har låga MPD-värden speciellt på lappade ytbehandlade vägar med blödningar. Vidare beskriver vi vilka friktionsrisker det finns med olika beläggningar och hur dessa kan hanteras.
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| 39. |
- Lundström, Robert, et al.
(författare)
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Fatigue characterization of asphalt concrete using Schapery's work potential model
- 2006
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Ingår i: Nordic Rheology Society.
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Konferensbidrag (refereegranskat)abstract
- This paper presents an investigation ofSchapery´s work potential theory (WPT), aconstitutive viscoelastic continuum damagemodel, applied to characterize fatigue behaviorof asphalt concrete. Although someanomalies were noted, results indicate thatthe model is applicable to characterizefatigue-related damage growth at differentloading modes, excitation amplitudes andtemperatures.
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| 40. |
- Lundström, Robert, et al.
(författare)
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Fatigue modeling as related to flexible pavement design - State of the art
- 2007
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Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 8:2, s. 165-205
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Forskningsöversikt (refereegranskat)abstract
- A literature study of rheological and fatigue modeling of asphalt mixtures is presented. Theoretical aspects on structural modeling, rheological behavior and the fatigue integration in design procedures are reviewed In principle, pavement design methods can be categorized in three broad groups: empirical, semi-mechanistic and fully mechanistic methods. Pavement design is generally performed using semi-mechanistic methods comprising analytical or numerical structural response models and deterioration modeling based on transfer functions and shift factors. In the case of fatigue deterioration, several approaches have been elaborated e.g. classical models, fracture mechanics and damage mechanics. The approaches differ regarding theoretical foundation and evaluation methods used. Recognizing significant limitations concerning theoretical basis as well as lack of empirical support for current design methods, a shift in paradigm from semi-empirical methods towards more advanced fully mechanistic methods have been initiated. According to this approach, improved pavements are achieved by appropriate design methods which are capable of predicting fatigue resistance in the actual pavement environment, and thus taking into account complex stress conditions, influence of temperature and material characteristics, such as aging and healing.
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| 41. |
- Lundström, Robert, et al.
(författare)
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Influence of hysteretic heating on asphalt fatigue characterization
- 2004
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Ingår i: Journal of Testing and Evaluation. - 0090-3973 .- 1945-7553. ; 32:6, s. 484-493
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study focusing on the influence of hysteretic heating on asphalt samples during laboratory fatigue testing. The experimental test setup for material characterization and temperature measurements, including its effect on fatigue test results, as well as theoretical aspects on hysteretic heating, are described. The experimental part of the investigation concerns linear viscoelastic and cyclic fatigue characterization of six asphalt concrete mixtures using uniaxial testing. All the mixtures show nominally identical volumetric properties (aggregate size distribution, binder and air void content) but different binder properties. Three base bitumens and three polymer modified binders were used. The cyclic fatigue tests were carried out at 0, 10, and 20 C using controlled strain and stress modes and different excitation amplitudes. In order to acquire knowledge regarding temperature changes during fatigue testing, several experimental techniques were used. The main thermal study was performed using thermocouples attached to the midheight envelope surface of each sample. The sample surface temperature distribution and its evolution during fatigue testing were investigated using an infrared thermal camera. Furthermore, a limited study of the magnitude of difference between surface and maximum temperature inside the sample was carried out using thermocouples embedded during gyratory compaction. When compared, each method shows advantages and disadvantages regarding simplicity and reliability. In principle, the three methods provide similar results, but the type of information obtained differs among the methods. The use of thermocouples attached to the envelope surface during fatigue testing provides accurate and consistent results of global temperature that can be used to investigate the influence of heating on asphalt fatigue characteristics. By use of thermal measurements and a continuum damage model, it was possible to show a pronounced effect of heating on fatigue behavior. The influence of heating was especially obvious at high excitation amplitudes and elevated temperatures, i.e., conditions where the material produces high amounts of viscoelastic dissipated energy as well as temperature sensitive material behavior.
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| 42. |
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| 43. |
- Namutebi, May
(författare)
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Some Aspects of Foamed Bitumen Technology
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Although foamed bitumen has been widely applied in pavement construction some of its aspects are still not yet understood. In this study, some of these aspects including: effects of the foaming process on binder chemistry, characterization of foamed bitumen and development of a rational method to optimize foam characteristics, evaluation of aggregate particle coating within foamed bitumen treated materials, and development of a gyratory compaction procedure for laterite gravels treated with foamed bitumen were addressed. The effects of the foaming process on bitumen chemistry were investigated using Fourier transform infrared spectroscopy techniques. Also, foam characteristics of three binders were established and a rational method to optimize foam characteristics proposed. Aggregate particle coating with foamed bitumen was studied using the concepts of surface energy and Rice density. In addition a gyratory laboratory compaction procedure for laterite gravels treated with foamed bitumen was established using the modified locking concept. Infrared techniques have shown that foaming does not cause any changes in the binder chemistry, suggesting that foaming may be a physical process. Further, foam characteristics are greatly influenced by binder viscosity. Also, the equiviscous temperature seems to produce foam with optimum foam characteristics. Rice density results showed that aggregate size fraction, binder expansion ratio and viscosity influenced aggregate particle coating. Surface energy results revealed that foamed bitumen exhibited better coating attributes than neat bitumen. A new compaction procedure for laterite gravels treated with foamed bitumen based on the modified locking point was developed.
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| 44. |
- Oscarsson, Karin, et al.
(författare)
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Methods for quantification of lignosulphonate and chloride in gravel wearing courses
- 2010
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Ingår i: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 11:1, s. 171-185
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Tidskriftsartikel (refereegranskat)abstract
- Due to oxidation, breakdown, and leaching, dust suppressants will be lost from the gravel road surface. Methods for residual dust suppressant concentration supervision are a valuable tool for estimating life-length and optimal application rates, and, hence, efficiency of different products. The objective of this study was to identify methods for quantitative analyses of lignosulphonate and chloride, develop and adapt the methods for application on a gravel matrix, and validate the methods using samples collected in-situ. Results strongly suggest that the reliability and repeatability of the developed methods (23 % for lignosulphonate and 30 % for chloride, respectively) are acceptable for determination of relative variations in residual concentrations of dust suppressed gravel wearing courses.
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