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  • 101. Lal, Sreeyuth
    et al.
    Moonen, Peter
    Poulikakos, Lily D.
    Partl, Manfred N.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Swiss Federal Laboratories for Materials Science and Technology, Switzerland.
    Derome, Dominique
    Carmeliet, Jan
    Turbulent airflow above a full-scale macroporous material: Boundary layer characterization and conditional statistical analysis2016Ingår i: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 74, s. 390-403Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Convective drying of macroporous materials is governed by the complex interaction between airflow above and into the material, the roughness of the air material interface and the characteristics of the material pore system. In this study, we experimentally investigate this interplay in detail and at fullscale, using porous asphalt (PA) as a model material. The characteristics of the turbulent flow in the immediate vicinity of the material surface are studied with full-scale wind tunnel experiments at three flow speeds over two types of PA with different surface porosities and surface pore sizes, and are compared to similar measurements over a smooth and impermeable reference material. It is shown that, above a certain wall-normal distance, turbulence profiles can be scaled to make them independent of the flow speed. However, at low speed, the scaling breaks down due to a combination of organized turbulent structures of high intensity and a low turbulence background. No generally valid scaling applicable at all tested air speeds is found close to the surface, where drying occurs. Hence, realistic drying experiments must be performed at full scale and for the entire range of velocities of interest.

  • 102. Larsson Brelid, Pia
    et al.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Alfredsen, Gry
    Westin, Mats
    Wålinder, Magnus
    Trätek - Swedish Institute for Wood Technology Research, Stockholm, Sweden.
    Wood Plastic Composites with Improved Dimensional Stability and Biological Resistance2006Ingår i: 2nd International Conference on Environmentally-Compatible Forest Products, 2006Konferensbidrag (Övrigt vetenskapligt)
  • 103. Larsson Brelid, Pia
    et al.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Westin, Mats
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wood Plastic Composites from Modified Wood: Part 1 - Conceptual idea, mechanical and physical properties2006Ingår i: The 37th Annual Meeting of the International Research Group on Wood Preservation, 2006Konferensbidrag (Övrigt vetenskapligt)
  • 104.
    Larsson, Magnus
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Falk, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Teleodynamic timber façades2018Ingår i: Frontiers in Built Environment, ISSN 2297-3362, Vol. 4, artikel-id 37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates ways in which weathering-related site conditions can be allowed to inform the design process in order to improve a building's geometry and performance. Providing a building design with the capacity to remember past experiences and anticipate future events can provide substantial gains to the architectural configuration and engineering of a timber façade. A new theory of architecture is outlined based on recent “teleodynamic” theories—a hypothesis about the way far-from-equilibrium systems interact and combine to produce emergent patterns. The proposed explanation considers nested levels of thermodynamic systems applied to an architectural context: “homeodynamic” operations that involve equilibration and dissipation of constraint combine to produce self-organising “morphodynamic” procedures that amplify and regularise site-specific constraining data streams. A teleodynamic design reconstitutes itself by combining morphodynamic processes so as to optimise its relationship to the past, present, and future. A novel teleodynamic design tool called Contextual Optimisation Workspace (COW) is assembled within the Grasshopper visual programming environment. The tool is used to carry out four experiments that combine to produce the teleodynamic design of an urban wooden façade, exemplifying an alternative framework for the design of wood-based structures. The first experiment investigates a variegated grid combining two distinct subdivision methods (an orthogonal grid and a Voronoi tessellation), transmuting one system into another. The second and third experiments focus on durability aspects of a wooden façade and devise strategies for how the effects of photochemical degradation and wetting due to driving rain might be minimised using the COW tool. The fourth experiment optimises the building for daylight based on an illuminance simulation. Using simulation and anticipation to add the advantages of site- and time-specific data streams as a design strategy can effectively suspend an algorithm-driven design iteration in time and space in order to allow it to be parametrically influenced by past or future events such as unique site and project conditions. The COW tool can be used to produce such teleodynamic designs.

  • 105. Larsson-Brelid, P.
    et al.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Westin, M.
    Rowell, Roger
    Ecobuild a center for development of fully biobased material systems and furniture applications2008Ingår i: Molecular Crystals and Liquid Crystals, ISSN 1542-1406, Vol. 484, s. 623-630Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is a great incentive and motivation in the building and wood research communities as well as in the industry to develop more eco-efficient and durable wood-based products with better performances. In this context, eco-efficient products refer to "green" sustainable products where both economical and ecological aspects have to be balanced. This presentation will give the general strategies within the newly formed Swedish Institute Excellence Center, EcoBuild. The conceptual idea for this competence centre is a conversion of biomass into innovative, eco-efficient and durable wood based products. The vision is that EcoBuild will, through the formation of a university-institute-industry cooperation, act as an international leading innovation, research and technology development platform within the wood science and technology field. The research projects within the centre are guided by a group of about 30 industry partners and also by end-user demands (Fig. 1). Types of materials in focus are: modified solid wood such as heat treated, furfurylated and acetylated wood, biobased binders and coatings, and biocomposites. A top priority is to develop fully biobased products, i.e., all raw materials should preferably be biobased, including chemicals for modification, adhesives, and surface treatment. Aspects and initial results regarding some of the EcoBuild activities will also be presented. Examples of research projects already started are: 1) Novel bio-based board resins; 2) UV-resistant clear coatings for exterior use; 3) Highly durable WPCs for outdoor use based on modified wood particles; 4) Modification of hardwood for exterior applications; 5) Fundamental understanding of the mechanisms involved in the durability of modified wood.

  • 106. Li, T.
    et al.
    Cai, J. -B
    Avramidis, S.
    Cheng, D. -L
    Wålinder, Magnus E.P.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Zhou, D. -G
    Effect of conditioning history on the characterization of hardness of thermo-mechanical densified and heat treated poplar wood2017Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, nr 6, s. 515-520Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Poplar wood was modified by a combination of thermo-mechanical densification (TMD) and heat treatment (HT) process at five temperatures ranging from 170 to 210°C. A new two-step conditioning method (CM) is suggested, in the course of which the modified wood is submitted to 50°C/99% RH→25°C/65% RH, where RH means relative humidity in the climate chamber. The traditional one-step CM (25°C/65% RH) served as reference. The effects of conditioning history on hardness were observed and analyzed along with the change of dimensional stability. The hardness of the modified wood was lower in the case of the proposed CM due to more set-recovery release, but the extent of that decreased with the HT temperature. For a good hardness, HT200°C should be selected with the proposed CM, which is different from the optimization output of 180°C obtained from the traditional CM. In conclusion, a specific assessment method for the performance characterization of this type of modified wood would be beneficial for the combined TMD and HT processes.

  • 107.
    Li, Tao
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Nanjing Forestry University, China.
    Cheng, D. -L
    Wålinder, Magnus E. P.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Zhou, D. -G
    Wettability of oil heat-treated bamboo and bonding strength of laminated bamboo board2015Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 69, s. 15-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to improve the interface properties of bamboo in laminated board applications for severe outdoor environment, bamboo sheets were heat treated in soybean oil and post oil extracted in this paper. Following oil heat treatment at 180 degrees C for 2 h, bamboo specimens were either removed from the oil immediately or left in the oil until they were cooled to room temperature. Contact angle measurements before and after oil heat treatment showed a significant increase in the hydrophobicity of bamboo, and these changes differed based on the process parameters. Results from scanning electron microscopy and Fourier transform infrared spectroscopy indicated that these phenomena may be due to the combination effect of the change of chemical composition and the surplus oil on the surface of modified bamboo. Then, the ethanol extraction process was subsequently applied to remove the surplus oil. Finally, the results of bonding strength tests on laminated bamboo boards prepared from oil heat-treated samples which thereafter had been subjected to ethanol extraction showed acceptable interface properties, although lower than the reference.

  • 108. Li, Tao
    et al.
    Cheng, Da-li
    Avramidis, Stavros
    Wålinder, Magnus E. P.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Zhou, Ding-guo
    Response of hygroscopicity to heat treatment and its relation to durability of thermally modified wood2017Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 144, s. 671-676Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In an attempt to study the effect of heat treatment on hygroscopicity and durability of wood, Poplar (Populus spp.) wood was thermally modified using five different temperatures between 170 degrees C and 210 degrees C, for a fixed duration of 3 h. Moisture adsorption behavior and the resistance to soft rot fungi were investigated thereafter. Based on the Hailwood-Horrobin sorption model, the amount of available sorption sites within specimens for the different groups of Poplar wood were calculated from the model's m(0) parameter. Chemical analysis of the changes in wood components induced by heat treatment allows for a comparison between the easily obtained m(0) and the results of time-consuming wood decay tests. The proposed m(0)-based method for highly efficient evaluation and prediction of durability of thermally modified wood could optimize future research on the mechanisms of heat treatment processes.

  • 109.
    Lillqvist, Kristiina
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rohumaa, Anti
    LaBoMab - Ecole Nationale Supérieure d'Arts et Métiers.
    Källbom, Susanna
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Department of Bioproducts and Biosystems, Aalto University.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    The influence of thermal modification on veneer bond strength2017Konferensbidrag (Övrigt vetenskapligt)
  • 110.
    Linkosalmi, Lauri
    et al.
    Department of Forest Products Technology, Aalto University.
    Laine, Kristiina
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Life cycle impacts of modified wood products2015Konferensbidrag (Övrigt vetenskapligt)
  • 111.
    Lundberg, Joacim
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. VTI - Statens Väg- och Transportforskningsinstitut.
    Non-Exhaust PM10 and Road Dust2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Icke-avgasemissioner av PM10 är ett problem i urbana miljöer länkat till flera hälsoaspekter. Dessa emissioner kan relateras till beläggningars egenskaper. Även resuspension av vägdamm från ytor är av betydelse och beror på både trafiken och meterologin. Baserat på detta är syftet med denna avhandling att ge en översikt kring icke-avgas PM10 emissioner och vägdamm, begränsat till Sverige och de övriga nordiska länderna.

    Denna översikt inkluderar hur partiklar relaterar till människans hälsa. Annat som inkluderas är hur partiklarna emitteras från vägyta-däckinteraktionen, både direkt och genom resuspension av vägdamm. Avhandlingen inkluderar även en översikt kring hur användandet av dubbdäck inverkar på vägbeläggningar och hur dess egenskaper inverkar på nötningsslitage. Detta länkas därefter till partikelemissioner. Vidare beskrivs även hur mätningar kan genomföras av partiklar samt vägdamm vilket följs upp av beskrivningar kring två större modeller kring prediktion av nötningsslitage och prediktion av icke-avgasemissioner. Även hur driftåtgärder inverkar på emissionerna tillsammans med alternativ för att minska emissionerna tas upp.

    Ett särskilt problem som tas upp i avhandlingen är bristen på helhetssyn beträffande miljöproblem i den urbana miljön med fokus på partikel- och bulleremissioner från vägyta-däckinteraktionen. För närvarande brukar det värsta problemet prioriteras och lösningen till det detta problem kan i sin tur medföra att andra miljöproblem istället förvärras.

    Denna avhandling visar på att mycket kunskap existerar kring icke-avgasemissioner av PM10 och kring vägdamm, men även att flertalet kunskapsluckor existerar. Flertalet förslag på vidare studier ges tillsammans med en överblick kring det fortsatta arbetet.

  • 112.
    Lundberg, Joacim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. VTI - Statens Väg- och Transportforskningsinstitut.
    Blomqvist, Göran
    VTI - Statens Väg- och Transportforskningsinstitut.
    Gustafsson, Mats
    VTI - Statens Väg- och Transportforskningsinstitut.
    Janhäll, Sara
    VTI - Statens Väg- och Transportforskningsinstitut.
    Texture influence on road dust load2017Ingår i: Proceedings of the 22nd International Transportation and Air Pollution Conferens, 2017Konferensbidrag (Refereegranskat)
  • 113.
    Lundberg, Joacim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. VTI - Statens Väg- och Transportforskningsinstitut.
    Janhäll, Sara
    VTI - Statens Väg- och Transportforskningsinstitut.
    Gustafsson, Mats
    VTI - Statens Väg- och Transportforskningsinstitut.
    Erlingsson, Sigurdur
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap. VTI - Statens Väg- och Transportforskningsinstitut / Islands Universitet.
    Calibration of the Swedish Studded Tyre Abrasion Wear Prediction Model and the Implication for the NORTRIP Road Dust Emission Model2018Ingår i: Transportation Research Board 97th annual meeting, Washington, D.C., 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    An experimentally based prediction model of rut development due to studded tyres is available in 3 Sweden and which had been found to work well. However, since it has not been validated since 4 2007, during which traffic as well as road and tyre design have developed, the question has 5 arisen regarding the model’s current validity. Also, since the prediction model is used in the 6 NORTRIP (NOn-exhaust Road Traffic Induced Particle emission) emission model, a natural 7 question is how a change in the wear model will affect the emission model. In this paper, two 8 versions of the abrasion model are compared to measurements at several recently constructed 9 roads in Sweden to investigate the validity, while also proposing changes to allow for continued 10 use. In addition, the impact on NORTRIP is briefly investigated. The paper first describes the 11 abrasion models and their calibration, as well as the test sections for calibration. Both versions of 12 the model, as expected, overestimated the wear and an update was suggested. It was also found 13 that NORTRIP is indicatively affected by overestimating the contribution of pavement wear to 14 the emissions.

  • 114.
    Namutebi, May
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Bagampadde, Umaru
    Guarin, Alvaro
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    A review of some aspects for foamed bitumen technologyManuskript (preprint) (Övrigt vetenskapligt)
  • 115.
    Namutebi, May
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap. Makerere University, Uganda.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Guarin, Alvaro
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Exploratory study on bitumen content determination for foamed bitumen mixes based on porosity and indirect tensile strength2017Ingår i: International journal of traffic and transportation engineering, ISSN 2325-0062, E-ISSN 2325-0070, Vol. 4, nr 2, s. 131-144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optimum bitumen content determination is one of the major aims for foamed bitumen mix design. However, mix design procedures for foamed bitumen mixes are still under development. In this paper a method to determine the optimum bitumen content for given foamed bitumen mix based on primary aggregate structure porosity and indirect tensile strength criterion is proposed. Using packing theory concepts, the aggregate gradation is divided into three aggregate structures which are oversize, primary and secondary structures. Porosity for the primary aggregate structure is determined for given bitumen contents. A maximum value for porosity of 50% for the primary aggregate structure is used to choose initial bitumen content. Furthermore, a minimum indirect tensile strength criteria is suggested to refine this bitumen content. This method enables a bitumen content value to be chosen prior to the start of experimental work, as porosity is expressed in terms of physical parameters such as aggregate and binder specific gravity, and aggregate gradation which are known before the mix design process. The bitumen content is then later refined when the indirect tensile strength is determined in the laboratory. This method would reduce resources such as time and materials that may be required during the mix design procedure.

  • 116.
    Nilsson, Alexander
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Olsson, Matilda
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Trästommar på den svenska marknaden: En undersökning av leverantörer och den industriella byggprocessen2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I dagens samhälle är miljö- och hållbarhetsfrågor viktiga på grund av de pågående klimatförändringarna och detta har skapat en konkurrensfördel för användandet av trä som stommaterial då trä är det enda förnyelsebara materialet på marknaden. Trots detta byggs det idag främst med andra stommaterial, såsom stål och betong. Syftet med detta examensarbete är att få fler byggentreprenörer och byggherrar att uppföra fler byggnader i trä genom att sprida kunskap om trä och skapa en förståelse för materialet och dess fördelar. Målet med detta examensarbete är att göra en undersökning av användandet av trästommar på den svenska marknaden. Metoderna som använts till detta är litteraturstudie, undersökning av ett fallstudieobjekt, enkätstudie och en intervjustudie.

    Litteraturstudien visar att de byggprodukter som främst används i trästommar är konstruktionsvirke, KL-träskivor, limträ, LVL och lättbalkar samt att flervåningshus i trä främst uppförs med stomsystemen massiv trästomme, pelar-balksstomme och regelstomme. Den visar även att trä lämpar sig väl till den industriella byggprocessen då träets låga densitet möjliggör transport av stora plan- och volymelement som prefabriceras. Leverantörer av trästommar kan arbeta med olika affärssystem, vilket leder till att de fungerar som komponentleverantör, delsystemleverantör och/eller systemleverantör. Erfarenheter från fallstudieobjektet visar att det vid uppförandet av en trästomme förekommer flertalet miljö- och kostnadsfördelar samtidigt som de mest kritiska aspekterna är akustik, brand och fukt.

    Resultatet av enkätstudien visar att det på den svenska marknaden idag finns en variation bland leverantörerna gällande affärssystem, uppdelningen av projektering och montage samt hur högt de byggt, vilket i de aktuella fallen handlar om mellan 2 och 8 våningar. Resultatet visar även att leverantörerna arbetar med lean-produktion för att förstärka fördelen som trä har i ett industriellt byggande.

    Resultatet av intervjustudien visar att det i dagsläget är vanligast att leverantören projekterar och att byggentreprenören utför montaget av stommen. Resultatet visar även att leverantörer av trästommar har erfarenhet och lösningar för att uppfylla krav på akustik, brand och fukt, men att det är av vikt att montaget utförs korrekt för att kraven ska uppfyllas. Vidare visar resultat att byggentreprenörens roll kan anpassas beroende på kunskap och erfarenhet gällande projektering och montage. Till sist visar resultatet att leverantörer bedriver forskning och utveckling för att träet ska vara ännu mera konkurrenskraftigt i framtiden.

    Slutsatsen av de utförda studierna är att trä erbjuder flexibilitet genom olika stomsystem och genom möjligheten att kombinera stomsystem, att en beställare, med lite erfarenhet, kan utnyttja leverantörers kunskaper kring trästommar, att trä är konkurrenskraftigt på grund av miljövänlighet och applicerbarhet i den industriella byggprocessen samt att forskning pågår för att göra träet mer konkurrenskraftigt i framtiden.

  • 117.
    Nordlöf, Jennifer
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Stenberg, Linda
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Vinklade lättbalkar i bjälklag: - En lösning till minskad bjälklagshöjd2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 118.
    Olsson, Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.). KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    A contact model for the normal force between viscoelastic particles in discrete element simulations2019Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 342, s. 985-991Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    DEM modeling of granular materials composed of viscoelastic particles can provide valuable insights into the mechanical behavior of a wide range of engineering materials. In this paper, a new model for calculating the normal contact force between visoelastic spheres is presented based on contact mechanics that takes the mechanical behavior of the DEM particles into account. The model relies on an application of the viscoelastic correspondence principle to elastic Hertz contact. A viscoelastic relaxation function for the contact is defined and a generalized Maxwell material is used for describing this function. An analytical expression for the increment in contact force given an increment in overlap is derived leading to a computationally efficient model. The proposed model provides the analytical small deformation solution upon loading but provides an approximate solution at unloading. Comparisons are made with FEM simulations of contact between spheres of different sizes of equal and dissimilar materials. An excellent agreement is found between the model and the FEM simulations for almost all cases except at cyclic loading where the characteristic times of the viscoelastic behavior and the loading are similar.

  • 119.
    Olsson, Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Forquin, P. A.
    Computational framework for analysis of contact-induced damage in brittle rocks2019Ingår i: International Journal of Solids and StructuresArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a numerical approach for predicting damage in rock materials caused by contact loading. The rock material is modelled using a constitutive description that combines pressure dependent plasticity, for capturing shear deformation under high confining pressure, with an anisotropic damage model for capturing mode I cracking in tension. Material parameters for the model are taken from a recently performed investigation on a granite material. The model has been used to simulate two types of contact loading experiments from the literature, cyclic loading and monotonic loading up to fracture. In order to achieve accurate predictions, the model has been extended to account for small loaded volumes which occur at contact loading. The results show that the main damage mechanism at cyclic loading is crack propagation due to Hertzian stresses whereas in the monotonic experiments sub-surface cracks could initiate. All features measured in the contact loading experiments are captured by the model and hence, the modelling framework is judged to be able to capture contact damage if real stone geometries are studied in FEM.

  • 120.
    Olsson, Erik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Jelagin, Denis
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.).
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    New discrete element framework for modelling asphalt compaction2019Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During asphalt mixture compaction, loads in the material are mainly transferred through contact between the stones and the interaction between the stones and the binder. The behaviour of such materials is suitable to model using the Discrete Element Method (DEM). In this study, a new DEM modelling approach has been developed for studying the asphalt compaction process, incorporating contact and damage laws based on granular mechanics. In the simulations, aggregate fracture is handled by a recently developed method of incorporating particle fracture in DEM, based on previously performed fracture experiments on granite specimens. The binder phase is modelled by adding a viscoelastic film around each DEM particle. This surface layer has a thickness that obtains the correct volume of the binder phase and has mechanical properties representative for the binder at different temperatures. The ability of the model to capture the influence of mixture parameters on the compactability and the eventual stone damage during compaction is examined for the cases of compaction flow test and gyratory compaction. Explicitly, the influence of different aggregate gradations, mixture temperatures and binder properties are studied. The results show that the proposed DEM approach is able to capture qualitatively and quantitatively responses in both cases and also provide predictions of aggregate damage. One large benefit with the developed modelling approach is that the influence of different asphalt mixture parameters could be studied without re-calibration of model parameters. Furthermore, based on comparative DEM simulations, it is shown that the proposed approach provides more realistic force distribution networks in the material.

  • 121. Olsson, Sara
    et al.
    Östmark, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ibach, Rebecca E.
    Clemons, Craig M.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Englund, Finn
    The use of esterified lignin for synthesis of durable composites2011Ingår i: Proceedings of the 7th meeting of the Nordic-Baltic Network in Wood Material Science and Engineering (WSE), 2011, s. 173-178Konferensbidrag (Refereegranskat)
  • 122.
    Onifade, Ibrahim
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Continuum Plasticity Mechanics (CPM) - An energy-based plasticity model - Application to asphalt concrete mixtures.Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new generalized energy-based elasto-plastic constitutive model for both pressure-sensitive and pressure insensitive materials is developed and presented in this paper. The model is developed with the energy formulation which inherently captures the rate-sensitivity and can be used to model a wide range of materials ranging from rate-dependent materials such as polymers and asphalt concrete to rate-independent materials such as steel. No additional rate-dependency parameters is required to model rate dependent behaviour at different strain-rates. The new energy-based plasticity formulation takes a similar form as the conceptsused in continuum damage mechanics with the plastic strain transformed into a plasticity variable whichenters into the formulation to obtain the corresponding stress and strain due to the applied or subjected load conditions. The new energy-based plasticity formulation fits nicely into the thermodynamics framework thereby providing a true unifying framework for coupling damage and plasticity

  • 123.
    Onifade, Ibrahim
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Damage and Fracture Characterization of Asphalt Concrete Mixtures using the Equivalent Micro-crack Stress ApproacIngår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a new parameter termed ”equivalent micro-crack stress” (σmc) is proposed for characterizingthe cracking performance of asphalt mixtures. The ”equivalent micro-crack stress” (σmc) is a function ofthe material stiffness and a critical micro-crack initiation threshold (MCIT). The ”equivalent micro-crackstress” (σmc) takes a similar form as the failure stress obtained from the Griffith energy balance equation.The MCIT incorporates the influence of the fracture work and the size and spatial distribution of the airvoids in the determination of the material cracking performance. Experimental tests are carried out toobtain the (σmc) to characterize the cracking performance of unmodified and wax modified mixtures usingthe Superpave IDT tests at low temperature range (i.e. -20oC, -10oC and 0oC). The result shows that the ”equivalent micro-crack stress” (σmc) gives a good indication of the material cracking performance ofthe unmodified and wax modified mixtures. The result of numerical simulations of the fatigue behaviouralso shows that the relationship between the number of cycles to micro-crack formation (Nmc) and σmc can be used to distinguish the wax modified mixtures from the unmodified mixture.

  • 124.
    Onifade, Ibrahim
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Development of a Morphology-based Analysis Framework for Asphalt Pavements2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Asfaltblandningars morfologi har en avgörande betydelse för deras egenskaper och beteenden. Arbetet i denna avhandling syftar till att utveckla en grundläggande förståelse för effekten av asfaltsmorfologin för deras hållfasthetsegenskaper och deformationsmekanismer och utveckling av ramverksanalysmorfologi baserat på långsiktig förutsägelse. Experimentella beräkningsmetoder används för att fastställa sambandet mellan blandningens morfologi och respons. Mikromekanisk modellering används för att förstå det komplexa samspelet mellan asfaltmassans beståndsdelar som resulterar i spänningslokalisering och spänningskoncentrationer som är föregångare till initiering av skador och ackumulation. Morfologibaserade materialmodeller beaktar påverkan av morfologin på de långsiktiga materialegenskaperna med avseende på skademotstånd, helande samt åldrande, och är utvecklade från data hos verkliga asfaltsfältskärnor. Morfologinbaserade materialmodeller är implementerade i en varmblandad asfalt-( HMA )-brottmekanik-ramverk för förutsägelse av beläggningsprestanda. Ramverket kan i rimlig utsträckning förutspå variationen i ingångsparametrarna ’top-down’ sprickbildningsinitiering. En termodynamiskbaserat ramverk föreslås för skador och brott. Resultaten från studien visar att morfologin är en viktig faktor som bör beaktas för att bestämma respons av asfaltblandningar på kort och lång sikt. Ytterligare förståelse av inverkan av morfologin kommer att leda till utvecklingen av grundläggande analytiska tekniker i design för fastställning av materialegenskaper och belastningars respons. Detta kommer att minska empirism som förknippas med beläggningskonstruktionen, minska behovet av omfattande kalibrering och validering, öka förutsägelseförmågan av designverktyg för beläggningen, samt avancera beläggningsdesign till en ny vetenskaplig nivå och ingenjörskonst.

  • 125.
    Onifade, Ibrahim
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Development of Energy-based Damage and Plasticity Models for Asphalt Concrete Mixtures2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    En heltäckande karakterisering av skador och plastiska beteende hos asfaltblandningar under varierande belastningshastighet och spänningstillstånd är en komplex och svår uppgift. En orsak till detta är relaterat till materialets belastningshastighet- och temperaturberoende, såväl som variationen i materialegenskaperna hos de ingående komponenterna i den sammansatta asfaltblandningen. Befintliga spänningsbaserade modeller för asfaltbetongmaterial är utvecklade baserade på mekanikprinciper, men dessa modeller är begränsade när det gäller analys och design av verkliga asfaltsbeläggningar eftersom hastighetsberoende parametrar behövs i den konstitutiva modellen även med hänsyn till töjningshastighetens inverkan på kriterier för gränser och utveckling av spänningstillstånd. Det finns därför behov av att utveckla enkla men ändå heltäckande konstitutiva modeller som kan användas för att modellera beteendet hos asfaltmassan över ett brett spektrum av belastningshastigheter för olika av sektioner asfaltsbeläggningar. Syftet med denna avhandling är att öka förståelsen av hållfasthets- och deformationsmekanismer för asfaltblandningar genom multi-modellering. Målet är att utveckla enkla och heltäckande kontinuummodeller som karakteriserar materialets olinjära beteende under varierande spänningstillstånd och betingelser. Ett analysramverk har utvecklats för utvärdering av påverkan av asfaltmassans morfologi på dess mekaniska egenskaper och beteende med hjälp av röntgendatortomografi och digital bildbehandlingsteknik. Detta förfarande har sedan använts för att undersöka förekomsten av inneboende kritiska tröskelvärden för brottenergin för mesosprickinitiering vilket i sin tur ligger till grund för utvecklingen av en teori för modellering av energibaserade skador och plastisk deformation hos asfaltblandningar. En ny energidensitet baserad viskoelastisk skademodell utvecklas och föreslås utgå från kontinuum-skade-mekanik (CDM) och termodynamik för irreversibla processer. En andra ordningens skadevariabeltensor införs för att ta hänsyn till  skadedistributionen i materialen i de olika principiella skaderiktningarna. På detta sätt kan materialets respons i drag- och tryckbelastning separeras och effekterna av spänningstillstånd i både drag och tryck kan beaktas på ett adekvat sätt. Baserat på resultaten från den energibaserade skademodellen utvecklas och föreslås en motsvarande metod för mikrosprickspänning gällande skade- och brottkarakteriseringen av asfaltblandningar. Metoden för den effektiva mikrosprickspänningen tar hänsyn till materialets styvhet och en kritisk tröskelenergi för mikrosprickinitiering för karakteriseringen av skador och brottegenskaper hos blandningen. Denna metod är utvecklad baserat på grundläggande mekanikprinciper och kan för rent elastiska material reduceras till Griffiths energibalanskriterium utan hänsyn till ytenergi och sprickstorlek vid bestämningen av brottspänningen. En ny termodynamikbaserad modell för kontinuumplasticitetsmekanik (CPM) utvecklas för att beskriva det plastiska beteendet hos asfaltbetongmaterial med energibaserade kriterier härledda för initiering och progression av plastisk deformation. En intern tillståndsvariabel kallad "plasticitetvariabeln" införs för att beskriva den fördelade dislokationsrörelsen i mikrostrukturen. CPM-modellen förenar befintliga elasto-plastiska och visko-plastiska teorier i en teori och visar sig vara särskilt effektiv i modelleringen av hastighetsberoende plastiskt beteende hos material utan att behöva beakta hastighetsberoende parametrar i de konstitutiva sambanden. CPM-modellen utvidgas ytterligare för att kunna beakta reduktionen av styvheten med stegvis ökad belastning och för att utveckla en enhetlig energibaserad skade- och plasticitetmodell. Modellerna är implementerade i ett finit element (FE)-analysprogram för validering av modellerna. Resultatet visar att de energibaserade modellerna för skador och plastisk deformation kan förutsäga beteendet hos asfaltbetongblandningar under varierande spänningstillstånd och töjningshastighetsförhållanden. Arbetet i denna avhandling utgör grunden för utvecklingen av mer grundläggande förståelse av asfaltbetongmaterialets respons och tillämpningen av sunda och robusta mekanikprinciper i analys och design av asfaltstrukturer.

  • 126.
    Onifade, Ibrahim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Balieu, Romain
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Birgisson, B.
    Interpretation of the Superpave IDT strength test using a viscoelastic-damage constitutive model2016Ingår i: Mechanics of time-dependant materials, ISSN 1385-2000, E-ISSN 1573-2738, s. 1-19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a new interpretation for the Superpave IDT strength test based on a viscoelastic-damage framework. The framework is based on continuum damage mechanics and the thermodynamics of irreversible processes with an anisotropic damage representation. The new approach introduces considerations for the viscoelastic effects and the damage accumulation that accompanies the fracture process in the interpretation of the Superpave IDT strength test for the identification of the Dissipated Creep Strain Energy (DCSE) limit from the test result. The viscoelastic model is implemented in a Finite Element Method (FEM) program for the simulation of the Superpave IDT strength test. The DCSE values obtained using the new approach is compared with the values obtained using the conventional approach to evaluate the validity of the assumptions made in the conventional interpretation of the test results. The result shows that the conventional approach over-estimates the DCSE value with increasing estimation error at higher deformation rates.

  • 127.
    Onifade, Ibrahim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Birgisson, B.
    Damage and fracture characterization of asphalt concrete mixtures using the equivalent micro-crack stress approach2017Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 148, s. 521-530Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a new parameter termed “equivalent micro-crack stress” (σmc) is proposed for the evaluation of the cracking performance of asphalt mixtures with respect to their resistance to the initiation of micro-crack. The “equivalent micro-crack stress” (σmc) is a function of the material stiffness and the “micro-crack initiation threshold” (MCIT). The MCIT is a critical strain energy density at the instance of initiation of micro-crack. Experimental testing is carried out for the evaluation of the cracking performance of unmodified and wax modified asphalt mixtures using the Superpave IDT tests at −20 °C, −10 °C and 0 °C. The low temperature range is used in the study to minimize the effect of viscoplastic dissipation on the material cracking behaviour. The result shows that the “equivalent micro-crack stress” (σmc) gives a good indication of the material cracking performance of the unmodified and wax modified mixtures. A Finite Element Analysis is performed to assess the validity of the proposed approach under cyclic loading condition in the controlled-stress mode. The result shows that there is a good agreement between the material cracking performance in both monotonic and cyclic loading conditions using the proposed approach. The higher the “effective micro-crack stress” (σmc), the better the fracture performance of the mixture.

  • 128.
    Onifade, Ibrahim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE). Aston University, UK .
    Investigation of Energy-Based Crack Initiation Threshold from Meso-Scale Asphalt Concrete Response2016Ingår i: 8th RILEM International Conference on Mechanisms of Cracking and Debonding in Pavements, Springer Netherlands, 2016, s. 679-685Konferensbidrag (Refereegranskat)
    Abstract [en]

    The existence of a fundamental energy threshold for meso-scale crackinitiation is investigated using micromechanical modeling techniques. X-rayComputed Tomography (CT) is used to acquire the internal structure of an asphaltconcrete mixture while Digital Image Processing (DIP) techniques is used to segment and analyze the different phases present in the mixture. Finite Element (FE)modeling is used to simulate a tensile loading condition to establish a critical micromechanical criterion for meso-scale crack initiation. The meso-scale asphaltconcrete mixture is subjected to different loading rates to obtain the global strainenergy density at the instance when the critical micromechanical crack-initiationcriterion threshold is attained at different deformation rates. The result from thestudy shows that there exists a fundamental global strain energy density thresholdthat is invariant of the rate of loading at the instance of meso-scale crack initiation.The result of this study also shows the potential of the use of X-Ray computedtomography in understanding the cracking phenomenon in asphalt mixture.

  • 129.
    Onifade, Ibrahim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Birgisson, Björn
    Balieu, Romain
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Energy-Based Damage and Fracture Framework for Viscoelastic Asphalt Concrete2015Ingår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 145, s. 67-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A framework based on the continuum damage mechanics and thermodynamics of irreversible processes using internal state variables is used to characterize the distributed damage in viscoelastic asphalt materials in the form of micro-crack initiation and accumulation. At low temperatures and high deformation rates, micro-cracking is considered as the source of nonlinearity and thus the cause of deviation from linear viscoelastic response. Using a non-associated damage evolution law, the proposed model shows the ability to describe the temperature-dependent processes of micro-crack initiation, evolution and macro-crack formation with good comparison to the material response in the Superpave indirect tensile (IDT) strength test.

  • 130.
    Onifade, Ibrahim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Vägtekniks laboratorium.
    Dinegdae, Yared H.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Birgisson, Björn
    Hierarchical approach for fatigue cracking performance evaluation in asphalt pavements2017Ingår i: Frontiers of Structural and Civil Engineering, ISSN 2095-2430, E-ISSN 2095-2449, Vol. 11, nr 3, s. 257-269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a hierarchical approach is proposed for the evaluation of fatigue cracking in asphalt concrete pavements considering three different levels of complexities in the representation of the material behaviour, design parameters characterization and the determination of the pavement response as well as damage computation. Based on the developed hierarchical approach, three damage computation levels are identified and proposed. The levels of fatigue damage analysis provides pavement engineers a variety of tools that can be used for pavement analysis depending on the availability of data, required level of prediction accuracy and computational power at their disposal. The hierarchical approach also provides a systematic approach for the understanding of the fundamental mechanisms of pavement deterioration, the elimination of the empiricism associated with pavement design today and the transition towards the use of sound principles of mechanics in pavement analysis and design.

  • 131.
    Onifade, Ibrahim
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jelagin, Denis
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Birgisson, Björn
    Kringos, Nicole
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Bro- och stålbyggnad.
    Towards Asphalt Mixture Morphology Evaluation with the Virtual Specimen Approach2015Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The morphology of asphalt mixture can be defined as a set of parameters describing the geo-metrical characteristics of its constituent materials, their relative proportions as well as spatialarrangement in the mixture. The present study is carried out to investigate the effect of themorphology on its meso- and macro-mechanical response. An analysis approach is used forthe meso-structural characterisation based on the X-ray computed tomography (CT) data.Image processing techniques are used to systematically vary the internal structure to obtaindifferent morphology structures. A morphology framework is used to characterise the aver-age mastic coating thickness around the main load carrying structure in the structures. Theuniaxial tension simulation shows that the mixtures with the lowest coating thickness exhibitbetter inter-particle interaction with more continuous load distribution chains between adja-cent aggregate particles, less stress concentrations and less strain localisation in the masticphase.

  • 132. Ormondroyd, G. A.
    et al.
    Källbom, Susanna
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Curling, S. F.
    Stefanowski, B. K.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Jones, D.
    Water sorption, surface structure and surface energy characteristics of wood composite fibres refined at different pressures2016Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, s. 1-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During fibre processing, wood fibres are subjected to a range of physical and chemical conditions sufficient to slightly alter their chemical composition and hence their ultimate performance when used in the manufacture of wood fibre-based composites. In order to better understand the effects of refiner conditions on material performance, wood fibres were subjected to processing at different refiner pressures (4, 6, 8 and 10 bar) and subsequently dried in a flash drier. The fibres were analysed for changes in surface area, surface energy, surface structure and water vapour sorption characteristics. The methods applied were nitrogen adsorption utilising the Brunauer–Emmett–Teller theory, inverse gas chromatography, scanning electron microscopy and dynamic vapour sorption. It was found that increasing refiner pressure resulted in fibres of lower surface area, accompanied by increasing dispersive surface energies up to operating refiner pressures of 8 bar. It was found with fibres refined at different pressures that as the refiner pressure increased the equilibrium moisture content of the fibre decreased at the set relative humidities. However, it was also noted that the hysteresis was not significantly different between each of the refiner pressures. The results suggest that different refiner pressures can be used to tune the surface characteristics which may be beneficial to product development and the improvement of the environmental profile of the wood fibre composites.

  • 133.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. Carleton University, Canada.
    Editorial2017Ingår i: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 18, s. 1-1Artikel i tidskrift (Refereegranskat)
  • 134.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Introduction2018Ingår i: RILEM State-of-the-Art Reports, Springer Netherlands , 2018, s. 1-14Konferensbidrag (Refereegranskat)
    Abstract [en]

    An overview on the background and motivation for this report on the achievements of the technical committee RILEM TC 237-SIB on Testing and Characterization of Sustainable Innovative Bituminous Materials and Systems is presented, together with a short summary on the scope of this voluntary international team effort. Challenges and key research paths towards modern “green” asphalt pavements are addressed, focusing on general aspects associated with the increasing variety of approaches and their implication on testing and characterization of innovative asphalt pavement materials. As example for the complexity of the experimental challenges and the potential necessity to break free from traditional testing patterns, selected specific aspects of reinforced asphalt pavements are considered and discussed. It is emphasized that testing must be consistent with the purpose of the reinforcement, answering the key questions in what respect, under what conditions and in what loading direction reinforcement should be achieved and tested. This “garbage-in-garbage-out” awareness is also valid for all other fields dealing with testing and characterization of innovative bituminous materials and systems, of course. 

  • 135.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Towards improved testing of modern asphalt pavements2018Ingår i: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 51, nr 6, artikel-id 166Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During the last 50 years, Rilem was continuously active in pre-standardization efforts aiming at gradually improving scientific and technological testing and analysis methods for refined understanding and characterization of bituminous binders and asphalt, both under well-defined laboratory and performance driven in-field conditions. This paper intends to highlight and provide a short overview on the international activities of Rilem’s to date 18 technical committees (TC) on asphalt and bituminous binders. After some general background information, underlining the specific complexity of asphalt pavement materials in terms of rheological behavior and basic structural functioning, it is shown that these activities resulted in numerous recommendations, state of the art reports and conference proceedings, all produced on a voluntary basis by scientific and technical commitment of individual experts. This wealth of results was created by the TCs following an own systematic methodology for many years which, at the end of the day, allowed building up activities through the new TCs of today in a much more specialized but at the same time also more diverse way. In view of this new flexibility and keeping in mind the previous success story of Rilem towards improved testing of asphalt pavements, future developments, challenges and interdisciplinary issues regarding bituminous road materials are outlined as potential starting point for future TC initiatives.

  • 136.
    Penaloza, Diego
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Royne, Frida
    RISE Res Inst Sweden, Gothenburg, Sweden..
    Sandin, Gustav
    RISE Res Inst Sweden, Gothenburg, Sweden..
    Svanstrom, Magdalena
    Chalmers Univ Technol, Div Environm Syst Anal, Gothenburg, Sweden..
    Erlandsson, Martin
    IVL Swedish Environm Res Inst, Stockholm, Sweden..
    The influence of system boundaries and baseline in climate impact assessment of forest products2019Ingår i: The International Journal of Life Cycle Assessment, ISSN 0948-3349, E-ISSN 1614-7502, Vol. 24, nr 1, s. 160-176Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    PurposeThis article aims to explore how different assumptions about system boundaries and setting of baselines for forest growth affect the outcome of climate impact assessments of forest products using life cycle assessment (LCA), regarding the potential for climate impact mitigation from replacing non-forest benchmarks. This article attempts to explore how several assumptions interact and influence results for different products with different service life lengths.MethodsFour products made from forest biomass were analysed and compared to non-forest benchmarks using dynamic LCA with time horizons between 0 and 300years. The studied products have different service lives: butanol automotive fuel (0years), viscose textile fibres (2years), a cross-laminated timber building structure (50years) and methanol used to produce short-lived (0years) and long-lived (20years) products. Five calculation setups were tested featuring different assumptions about how to account for the carbon uptake during forest growth or regrowth. These assumptions relate to the timing of the uptake (before or after harvest), the spatial system boundaries (national, landscape or single stand) and the land-use baseline (zero baseline or natural regeneration).Results and discussionThe implications of using different assumptions depend on the type of product. The choice of time horizon for dynamic LCA and the timing of forest carbon uptake are important for all products, especially long-lived ones where end-of-life biogenic emissions take place in the relatively distant future. The choice of time horizon is less influential when using landscape- or national-level system boundaries than when using stand-level system boundaries and has greater influence on the results for long-lived products. Short-lived products perform worse than their benchmarks with short time horizons whatever spatial system boundaries are chosen, while long-lived products outperform their benchmarks with all methods tested. The approach and data used to model the forest carbon uptake can significantly influence the outcome of the assessment for all products.ConclusionsThe choices of spatial system boundaries, temporal system boundaries and land-use baseline have a large influence on the results, and this influence decreases for longer time horizons. Short-lived products are more sensitive to the choice of time horizon than long-lived products. Recommendations are given for LCA practitioners: to be aware of the influence of method choice when carrying out studies, to use case-specific data (for the forest growth) and to communicate clearly how results can be used.

  • 137.
    Peñaloza, Diego
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Exploring climate impacts of timber buildings: The effects from including non-traditional aspects in life cycle impact assessment2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    There is an urgency within the building sector to reduce its greenhouse gas emissions and mitigate climate change. An increased proportion of biobased building materials in construction is a potential measure to reduce these emissions. Life cycle assessment (LCA) has often been applied to compare the climate impact from biobased materials with that from e.g. mineral based materials, mostly favouring biobased materials. Contradicting results have however been reported due to differences in methodology, as there is not yet consensus regarding certain aspects. The aim of this thesis is to study the implications from non-traditional practices in climate impact assessment of timber buildings, and to discuss the shortcomings of current practices when assessing such products and comparing them with non-renewable alternatives.

    The traditional practices for climate impact assessment of biobased materials have been identified, and then applied to a case study of a building with different timber frame designs and an alternative building with a concrete frame. Then, non-traditional practices were explored by calculating climate impact results using alternative methods to handle certain methodological aspects, which have been found relevant for forest products in previous research such as the timing of emissions, biogenic emissions, carbon storage in the products, end-of-life substitution credits, soil carbon disturbances and change in albedo. These alternative practices and their implications were also studied for low-carbon buildings.

    The use of non-traditional practices can affect the climate impact assessment results of timber buildings, and to some extent the comparison with buildings with lower content of biobased building materials. This effect is especially evident for energy-efficient buildings. Current normal practices tend to account separately for forest-related carbon flows and aspects such as biogenic carbon emissions and sequestration or effects from carbon storage in the products, missing to capture the forest carbon cycle as a whole. Climate neutrality of wood-based construction materials seems like a valid assumption for studies which require methodological simplification, while other aspects such as end-of-life substitution credits, soil carbon disturbances or changes in albedo should be studied carefully due to their potentially high implications and the uncertainties around the methods used to account for them. If forest phenomena are to be included in LCA studies, a robust and complete model of the forest carbon cycle should be used. Another shortcoming is the lack of clear communication of the way some important aspects were handled.

  • 138.
    Peñaloza, Diego
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. RISE - Research Institutes of Sweden.
    Future scenarios for climate change mitigation of new building construction in Sweden: Effects of different technological pathwaysManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Climate mitigation strategies are required with urgency. The Swedish construction sector contributes to a significant share of the country’s yearly greenhouse gas (GHG) emissions. A variety of alternative climate mitigation strategies is available aimed to different processes and activities related to production and operation of buildings. Several studies evaluating the effectiveness of these strategies have been performed at the building stock level. These studies however do not consider the technological change in manufacturing of building materials. The objective of this study is to evaluate the climate change mitigation effects of increasing the use of biobased materials in the construction of new residential buildings in Sweden under different scenarios related to technological change in material manufacturing. For this, the climate impact from Swedish new buildings has been assessed for the coming one hundred years using a model that combines scenario analysis based on official statistics and life cycle assessment of seven different building typologies. Eight different scenarios for increased use of low-impact building typologies such as timber buildings and low-impact concrete are explored under different pathways for growth of their market share and changes in energy production. The results show that the benefits from an increased use of biobased materials are significant in all scenarios evaluated, but decrease if the use of low-impact concrete expands more rapidly or under optimistic scenarios for energy production. Results are also highly sensitive to the choice of climate impact metric. Results also show that the Swedish construction sector can only reach maximum climate change mitigation scenarios if all the low-impact typologies are implemented together and rapidly, including a rapid switch to cleaner energy.

  • 139.
    Peñaloza, Diego
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. RISE - Research Institutes of Sweden.
    The influence of system boundaries and baseline in climate impact assessment of forest productsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Purpose

    This article aims to explore how different assumptions about system boundaries and setting of baselines for forest growth affect the outcome of climate impact assessments of forest products during life cycle assessment (LCA), including potential climate impact mitigation from replacing non-forest benchmarks. This article attempts to explore how several assumptions interact and influence results for different products with different service life lengths.

    Methods

    Four products made from forest biomass were analysed and compared to non-forest benchmarks using dynamic LCA with time horizons between 0 and 300 years. The studied products have different service lives: butanol automotive fuel (0 years), viscose textile fibres (2 years), a cross-laminated timber building structure (50 years) and methanol used to produce short-lived (0 years) and long-lived (20 years) products. Five calculation setups were tested featuring different assumptions about how to account for the carbon uptake during forest growth or regrowth. These assumptions relate to the timing of the uptake (before or after harvest), the spatial system boundaries (national, landscape and single stand approaches) and the land use baseline (zero baseline and natural regeneration).

    Results and discussion

    The implications of using different assumptions depend on the type of product. The choice of time horizon for dynamic LCA and the timing of forest carbon uptake are important for all products, especially long-lived ones where end-of-life biogenic emissions take place in the relatively distant future. The choice of time horizon is less influential when using landscape or national spatial boundaries than when using a stand approach, but has great influence on the results for long-lived products. The influence of the methodological choices studied in the comparison of the products with their benchmarks has divergent outcomes. Short-lived products perform worse than their benchmarks with short time horizons whatever spatial boundaries are chosen, while long-lived products outperform their benchmarks with all methods tested.

    Conclusions

    The choices of spatial boundaries, temporal boundaries and land use baseline have a large influence on the results, but this influence decreases for longer time horizons. Short-lived products are more sensitive to the choice of time horizon than long-lived products. Recommendations are given for LCA practitioners: to be aware of the influence of method choice when carrying out studies, to prioritise case-specific data for forest growth and to communicate clearly how results should be used and interpreted.

  • 140.
    Peñaloza, Diego
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. RISE - Research Institutes of Sweden.
    The role of biobased building materials in the climate impacts of construction: Effects of increased use of biobased materials in the Swedish building sector2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Irreversibel global påverkan på klimat och miljö måste undvikas och olika strategier som begränsar klimatförändringarna kan utnyttjas för att hantera denna utmaning. En betydande andel av de globala utsläppen av växthusgaser kan hänföras till byggsektorn i allmänhet och cementproduktion i synnerhet, och begränsningsstrategier söker alternativ till fossil- och mineralbaserade resurser, med mindre påverkan, som exempelvis en ökad användning av biobaserade material i byggandet. Livscykelanalys (LCA) har använts för att demonstrera klimatnyttan av denna ökning, men skogens komplexiteter i samband med biogent koldioxid skapar osäkerhet i resultaten då de som genomför LCA-studier traditionellt utelämnar viktiga nyckelaspekter.

    Denna avhandling syftar till att öka förståelsen för effekterna av en ökad användning av biobaserade material för begränsning av byggandets klimatpåverkan i ett livscykelperspektiv. Forskningsfrågorna formulerades med fokus på att identifiera icke-traditionell LCA-metodik, samt att bedöma miljöeffekterna av en ökad användning av biobaserade material med redovisning av dessa aspekter på olika nivåer, gällande enstaka konstruktioner och byggnadsbeståndet som helhet. Den metodik som används är dynamisk LCA i kombination med data om skogskolbalans, med analyser av flera scenarier med olika metodologiska antaganden. Fallstudier med olika kännetecken användes, nämligen en byggnad, en bilvägsbro och en uppskattning av det svenska byggnadsbeståndet på lång sikt.

    Resultaten bekräftar att en ökad användning av biobaserade material minskar klimatpåverkan av byggandet – en tydlig majoritet av de scenarier som analyserats för alla fallstudier resulterar i sänkt klimatpåverkan. Införandet av icke-traditionella LCA-aspekter påverkar resultatet, men förändrar inte att en ökad användning av biobaserade material resulterar i lägre långsiktig och kumulativ klimatpåverkan. Resultaten visar också att den maximala klimatbegränsningspotentialen endast nås genom att samtidigt införa andra tekniska lösningar med lägre klimatpåverkan. När det gäller LCA-metodik visar resultaten att antagandet att biobaserade byggnadsmaterial är klimatneutrala är en överförenkling eftersom deras klimatpåverkan beror på fallspecifika faktorer och därför bör inga generaliseringar göras. Några av dessa klimatpåverkande faktorer beror på modellering av skogssystemet i en dynamisk LCA; såsom när skogstillväxten antas börja i förhållande till avverkningen, den geografiska upplösningen för att analysera de biogena kolflödena dvs. som ett avverkningsbestånd eller på landskapsnivå och vad utgångsläget sätts till vid analys av skogens markanvändning. Andra faktorer beror på LCA-modellering, nämligen valet av integrerad tidshorisont för beräkning av klimatpåverkan, det antagna scenariot för avfallshantering och lagringsperioden för det biogena kolet i tillverkade produkter.

    För att minska osäkerheten i bedömning av klimatpåverkan av biobaserade byggmaterial rekommenderas användning av minst en mätmetod som gör det möjligt att bedöma koldioxidutsläppen baserat på tidpunkten på dessa, samt att tillämpa mätvärden med långa tidsperspektiv. Redovisning av icke-traditionella aspekter har en betydande effekt på klimatpåverkan av biobaserade byggmaterial. Utförare av analyser rekommenderas därför även att redovisa hur dessa aspekter hanteras och att ställa upp flera olika scenarier och analysera dessa med flera olika metodologiska inställningar. Slutligen rekommenderas att ta hänsyn till den tekniska utvecklingen vid analyser av långsiktig klimatpåverkan av byggnadsbeståndet som genomförs med dynamiska värden för processer som äger rum i framtiden.

  • 141.
    Peñaloza, Diego
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Erlandsson, Martin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Falk, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Exploring the climate impact effects of increased use of bio-based materials in buildings2016Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 125, s. 219-226Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Whenever Life Cycle Assessment (LCA) is used to assess the climate impact of buildings, those with high content of biobased materials result with the lowest impact. Traditional approaches to LCA fail to capture aspects such as biogenic carbon exchanges, their timing and the effects from carbon storage. This paper explores a prospective increase of biobased materials in Swedish buildings, using traditional and dynamic LCA to assess the climate impact effects of this increase. Three alternative designs are analysed; one without biobased material content, a CLT building and an alternative timber design with “increased bio”. Different scenario setups explore the sensitivity to key assumptions such as the building's service life, end-of-life scenario, setting of forest sequestration before (growth) or after (regrowth) harvesting and time horizon of the dynamic LCA. Results show that increasing the biobased material content in a building reduces its climate impact when biogenic sequestration and emissions are accounted for using traditional or dynamic LCA in all the scenarios explored. The extent of these reductions is significantly sensitive to the end-of-life scenario assumed, the timing of the forest growth or regrowth and the time horizon of the integrated global warming impact in a dynamic LCA. A time horizon longer than one hundred years is necessary if biogenic flows from forest carbon sequestration and the building's life cycle are accounted for. Further climate impact reductions can be obtained by keeping the biogenic carbon dioxide stored after end-of-life or by extending the building's service life, but the time horizon and impact allocation among different life cycles must be properly addressed.

  • 142.
    Peñaloza, Diego
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. RISE - Research Institutes of Sweden.
    Erlandsson, Martin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Pousette, Anna
    Climate impacts from road bridges: effects of introducing concrete carbonation and biogenic carbon storage in wood2018Ingår i: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 14, nr 1, s. 56-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The construction sector faces the challenge of mitigating climate change with urgency. Life cycle assessment(LCA), a widely used tool to assess the climate impacts of buildings, is seldom used for bridges. Materialspecificphenomena such as concrete carbonation and biogenic carbon storage are usually unaccountedfor when assessing the climate impacts from infrastructure. The purpose of this article is to explore theeffects these phenomena could have on climate impact assessment of road bridges and comparisonsbetween bridge designs. For this, a case study is used of two functionally equivalent design alternativesfor a small road bridge in Sweden. Dynamic LCA is used to calculate the effects of biogenic carbon storage,while the Lagerblad method and literature values are used to estimate concrete carbonation. The resultsshow that the climate impact of the bridge is influenced by both phenomena, and that the gap betweenthe impacts from both designs increases if the phenomena are accounted for. The outcome is influencedby the time occurrence assumed for the forest carbon uptake and the end-of-life scenario for the concrete.An equilibrium or 50/50 approach for accounting for the forest carbon uptake is proposed as a middlevalue compromise to handle this issue.

  • 143. Piber, H.
    et al.
    Partl, Manfred
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Raab, Christiane
    Interlaboratory tests on pavement performance prediction and evaluation-rutting2013Ingår i: RILEM State-of-the-Art Reports, Springer Netherlands, 2013, Vol. 9, s. 257-302Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The former RILEM TC 182 PEB organized 1997 an international interlaboratory test on pavement performance, prediction and evaluation. The aim was to predict the expected damages after 10 years on the basis of traffic and climatic data by testing samples that were cut from the newly constructed road. On esection in Austria was monitored as planned until 2007. Thirteen laboratories from 12 countries participated in the study and provided performance predictions for both sections according to their own methods and standards. This chapter summarises the road condition after this long term performance observation and compares it to the rutting results from those laboratories which performed dynamic rutting tests on more than one pavement layer and based their prediction on their own test results and models without relying on national requirements. © RILEM 2013.

  • 144.
    Rask, Fredrik
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Life Cycle Assessment and comparison of the climate impact of structural members and floor systems constructed in concrete, steel and timber2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this report the climate impact is determined for some basic structural elements made in steel,>mber and concrete. The aim is to compare the climate impact of these three building materials byquan>fying the emissions related to the produc>on and construc>on of some typical structures.The comparison comprise two parts, were one is the comparison of members in bending,compression and tension and the other part is the comparison of a couple of floor structures.The emissions are determined through a Life Cycle Assessment, LCA. The members are comparedwith respect to their load bearing resistance and the floor structures is compared per square meter.The mo>va>on for this inves>ga>on is that the construc>on industry is a large contributor to the totalamount of greenhouse gas emissions and in order to reduce these emissions new solu>ons andprac>ses must be adopted. A more thoughVul choice of the materials used in structures has thepoten>al of reducing the emissions.The method of determining the climate impact is based on first determining the material quan>>esfor all the inves>gated structures and then calcula>ng the amount of carbon dioxide equivalentsrelated to the produc>on of these materials with the help of a Life Cycle Assessment.The material quan>>es of the structural members is determined based on the load. The dimensionsof the cross sec>on is determined with respect to the required load resistance. The materialquan>>es of the floor structures is based on some exis>ng solu>ons from manufacturers.The study show that the >mber based design solu>ons almost always has a smaller climate impactand that the differences can be considerable. Members made in steel oZen result in very largeamount of greenhouse gas emissions but the sca[er in the results indicate that the origin of the steelhas great importance. Primary steel has a much larger impact as opposed to recycled steel.The comparison of the floor designs show that beyond the material choice itself, also the materialefficiency is important. The hollow core slab made in concrete is a very material efficient design andmay in some cases be on par with >mber based designs.The massive >mber floors made of Cross Laminated Timber, CLT, has a fairly large climate impactbecause of the sheer volume of material and may be on the same level as the floor made in concretefor some scenarios. There is however a wide range in the result based on whether the material istransported a long distance and depending on the choice of insula>on material. If these choices isop>mised, the emissions of the CLT floor is instead on a much lower level, closer to that of the otherlightweight floors inves>gated.The process of evalua>ng and comparing the material choices and structural designs form a lifecycleperspec>ve can be u>lised during the design in order to reduce the emissions. With a be[erknowledge of the climate impact of the design, be[er choices can be made in order to reduce theemissions.

  • 145. Ritter, E.
    et al.
    De Rosa, M.
    Falk, Andreas
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Christensen, P.
    Løkke, S.
    Wood as construction material: A "common" choice for carbon management?2013Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, nr 21, s. 11930-11931Artikel i tidskrift (Refereegranskat)
  • 146. Royne, Frida
    et al.
    Penaloza, Diego
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial. SP Technical Research Institute of Sweden, Sweden.
    Sandin, Gustav
    Berlin, Johanna
    Svanström, Magdalena
    Climate impact assessment in life cycle assessments of forest products: implications of method choice for results and decision making2016Ingår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 116, s. 90-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As life cycle assessments are often conducted to provide decision support, it is important that impact assessment methodology is consistent with the intended decision context. The currently most used climate impact assessment metric, the global warming potential, and how it is applied in life cycle assessments, has for example been criticised for insufficiently accounting for carbon sequestration, carbon stored in long-lived products and timing of emission. The aim of this study is to evaluate how practitioners assess the climate impact of forest products and the implications of method choice for results and decision-making. To identify current common practices, we reviewed climate impact assessment practices in 101 life cycle assessments of forest products. We then applied identified common practices in case studies comparing the climate impact of a forest-based and a non-forest-based fuel and building, respectively, and compared the outcomes with outcomes of applying alternative, non-established practices. Results indicate that current common practices exclude most of the dynamic features of carbon uptake and storage as well as the climate impact from indirect land use change, aerosols and changed albedo. The case studies demonstrate that the inclusion of such aspects could influence results considerably, both positively and negatively. Ignoring aspects could thus have important implications for the decision support. The product life cycle stages with greatest climate impact reduction potential might not be identified, product comparisons might favour the less preferable product and policy instruments might support the development and use of inefficient climate impact reduction strategies.

  • 147. Ruponen, J.
    et al.
    Kimpimäki, S.
    Rohumaa, A.
    Laine, K.
    KTH.
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wålinder, Magnus
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Rautkari, L.
    Hughes, M.
    Tensile-shear strength studies on self-bonded 2-ply birch veneer joint manufactured and tested by applying Automated Bonding Evaluation System (ABES) hot press2016Ingår i: WCTE 2016 - World Conference on Timber Engineering, Vienna University of Technology , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    An Automatic Bond Evaluation System (ABES) hot press was employed to manufacture a self-bonded joint between two veneers of rotary-cut birch (Betula pendula Roth). The hot-pressing conditions were 220 °C and 5.0 MPa, with press times ranging from 180 s to 600 s with 60 s intervals. Additionally, the log-soaking temperature (20 °C and 70 °C) and the veneer initial MC (6% and 11%) were varied to study the effect on the tensile-shear strength of the joints. For one set, the surface properties were altered by acetone extraction. The samples were tested at 11% MC. However, one set was partly duplicated and tested at 6% MC, to study how the testing conditions influenced the bond strength. The maximum average tensile-shear strength was 3.3 MPa, observed after 600 s hot pressing. The studies also included bond-line micromorphology analysis by applying SEM combined with a micromachining surface preparation technique based on UV excimer laser ablation. It was also indicated that longer hot-pressing times, lower veneer initial MC and a lower testing MC resulted in increased tensile-shear strength. Acetone extraction decreased the bond strength with increased standard deviation. Finally, the highest single and average strengths were observed for veneers from higher soaking temperature.

  • 148. Sandberg, Dick
    et al.
    Söderström, Ove
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Crack formation due to weathering of radial and tangential sections of pine and spruce2006Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 1, nr 1, s. 12-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of cracks and changes in appearance have been investigated on radial and tangential sections of pine (Pinus sylvestris L.) and spruce (Picea abies Karst.) after exposure outdoors for 61 months. The degradation of the sections has also been studied at the micro-level. The annual ring orientation was the most important factor affecting crack development on weathering. After 61 months of outdoor exposure, the tangential sections of spruce had 1.7–2.2 times greater mean total crack length per area unit than the corresponding radial sections. In pine, the total crack length per area unit on the tangential sections was 2.2–2.6 times greater than that on the radial sections. Tangential and radial sections show the same colour change as a result of weathering. Tangential sections have more and deeper cracks than radial surfaces. The cracks on the tangential sections occur frequently in both earlywood and latewood. On radial sections, cracks occur primarily at the annual ring borders, but to a certain extent also in the earlywood. Decomposition of the cell wall takes place in both radial and tangential cell walls, and cracks tend to follow the fibril orientation in the S2-layer of the cell wall. The radial cell wall of the earlywood has a large number of pits which are degraded at an early stage.

  • 149. Sandberg, Dick
    et al.
    Söderström, Ove
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Environmental Friendly Wood Linings for Outdoor Exposure2005Ingår i: In: Proceedings of the 10th International Conference on Durability of Building Materials and Components in Lyon, 2005Konferensbidrag (Refereegranskat)
  • 150. Sandberg, Dick
    et al.
    Söderström, OveKTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Wood Material Science, advanced PhD-course2007Samlingsverk (redaktörskap) (Refereegranskat)
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